NO COMPRESSION ON ALL CYLINDERS - TESTER GAUGE GOES UP THEN DOWN
Hi, while conducting a compression test on my 2.2 four cylinder vehicle, the compression tester gauge goes up to around 165 psi on all cylinders but the value does not freeze/register, the gauge rather rapidly goes back down to literally 0 on every cylinder. This vehicle is currently not starting, all vehicle start check-ups have been made, including, fuel, air, spark plugs, battery, etc... It is now down to compression. 1) Am I right in thinking that I indeed have no compression - rather than hoping the fault is with the tester? 2) If it is true that I have no compression, is this more of a case of mis-timing/bent valves - or, could a cylinder/gasket crack indeed cause no compression on all cylinders? 3) Is there any other crack or leak anywhere in the engine that could cause no compression on all cylinders?
Note: This vehicle was starting and driving fine (even after it's had been diagnosed with a head gasket issue)... the vehicle suddenly lost power on the freeway and ultimately shut off - did not overheat, as gauge was still below half. Please help!
All 4 of them got up the around the same value (165) on a cold engine. I looked inside the belt cover and belt seemed on and tight. I will do as you suggest, getting another tester. But my question now is, if there is compression... I've done all the tricks in the books to get this thing to start with no success. It's a breath of fresh air to get the re-assurance that the tester my be faulty - I was getting ready to garbage the car. By the way, it's a 1999 Olds Alero DOHC with 152k automatic. Thanks for you insight; I'll do the test again and repost.All 4 of them got up the around the same value (165) on a cold engine. I looked inside the belt cover and belt seemed on and tight. I will do as you suggest, getting another tester. But my question now is, if there is compression... I've done all the tricks in the books to get this thing to start with no success. It's a breath of fresh air to get the re-assurance that the tester my be faulty - I was getting ready to garbage the car. By the way, it's a 1999 Olds Alero DOHC with 152k automatic. Thanks for you insight; I'll do the test again and repost.
hansola, I hope you're still around to advise me on this. Okay, the new test tester held the compression at 153, 153, 153, 135 on the cylinders. The vehicle practically starts (a little rough for 1 second) then shuts off. Here's what I notice: When I keep my fuel pump relay in and turn the key to ignition (without starting) about 3 times and then floor the accelerator, the vehicle starts pretty good at times then die after a second. After that it won't try to start again (good cranking though) unless I repeat the same sequence.
Should I be thinking fuel injectors, or fuel pressure, or could it be air intake? Keep in mind that I did a code reading that output P-0107 MAP/BARO circuit low input - which referred to the MAP sensor being bad... well, I changed that and the vehicle still didn't start. Thanks for your willingness to help so far!hansola, I hope you're still around to advise me on this. Okay, the new test tester held the compression at 153, 153, 153, 135 on the cylinders. The vehicle practically starts (a little rough for 1 second) then shuts off. Here's what I notice: When I keep my fuel pump relay in and turn the key to ignition (without starting) about 3 times and then floor the accelerator, the vehicle starts pretty good at times then die after a second. After that it won't try to start again (good cranking though) unless I repeat the same sequence.
Should I be thinking fuel injectors, or fuel pressure, or could it be air intake? Keep in mind that I did a code reading that output P-0107 MAP/BARO circuit low input - which referred to the MAP sensor being bad... well, I changed that and the vehicle still didn't start. Thanks for your willingness to help so far!
hansola, I hope you're still around to advise me on this. Okay, the new test tester held the compression at 153, 153, 153, 135 on the cylinders. The vehicle practically starts (a little rough for 1 second) then shuts off. Here's what I notice: When I keep my fuel pump relay in and turn the key to ignition (without starting) about 3 times and then floor the accelerator, the vehicle starts pretty good at times then die after a second. After that it won't try to start again (good cranking though) unless I repeat the same sequence.
Should I be thinking fuel injectors, or fuel pressure, or could it be air intake? Keep in mind that I did a code reading that output P-0107 MAP/BARO circuit low input - which referred to the MAP sensor being bad... well, I changed that and the vehicle still didn't start. Thanks for your willingness to help so far!hansola, I hope you're still around to advise me on this. Okay, the new test tester held the compression at 153, 153, 153, 135 on the cylinders. The vehicle practically starts (a little rough for 1 second) then shuts off. Here's what I notice: When I keep my fuel pump relay in and turn the key to ignition (without starting) about 3 times and then floor the accelerator, the vehicle starts pretty good at times then die after a second. After that it won't try to start again (good cranking though) unless I repeat the same sequence.
Should I be thinking fuel injectors, or fuel pressure, or could it be air intake? Keep in mind that I did a code reading that output P-0107 MAP/BARO circuit low input - which referred to the MAP sensor being bad... well, I changed that and the vehicle still didn't start. Thanks for your willingness to help so far!
Great, great, great stuff... OK, soon after the car starts for one second, I will pull the plugs and check for evidence of fuel on their tips. I should say, I have noticed fuel on them before. But in contrast, I have done a check for spark on all the coils (as you know this vehicle uses a COP system) and I had spark on each one, though, I couldn't tell you if it is enough spark. So if there is fuel on the plugs as you point out (and I'm sure there will be) - and I have spark - are we going with a timing issue then?
I will also do the fuel pressure check if there is no sign of fuel on the plugs (well, I will regardless). If there is no fuel deposit and I have pressure, is the fuel filter then exempt, and should I then focus on the injectors.
Thank you so much, man; you've great help!Great, great, great stuff... OK, soon after the car starts for one second, I will pull the plugs and check for evidence of fuel on their tips. I should say, I have noticed fuel on them before. But in contrast, I have done a check for spark on all the coils (as you know this vehicle uses a COP system) and I had spark on each one, though, I couldn't tell you if it is enough spark. So if there is fuel on the plugs as you point out (and I'm sure there will be) - and I have spark - are we going with a timing issue then?
I will also do the fuel pressure check if there is no sign of fuel on the plugs (well, I will regardless). If there is no fuel deposit and I have pressure, is the fuel filter then exempt, and should I then focus on the injectors.
Thank you so much, man; you've great help!
Great, great, great stuff... OK, soon after the car starts for one second, I will pull the plugs and check for evidence of fuel on their tips. I should say, I have noticed fuel on them before. But in contrast, I have done a check for spark on all the coils (as you know this vehicle uses a COP system) and I had spark on each one, though, I couldn't tell you if it is enough spark. So if there is fuel on the plugs as you point out (and I'm sure there will be) - and I have spark - are we going with a timing issue then?
I will also do the fuel pressure check if there is no sign of fuel on the plugs (well, I will regardless). If there is no fuel deposit and I have pressure, is the fuel filter then exempt, and should I then focus on the injectors.
Thank you so much, man; you've great help!Great, great, great stuff... OK, soon after the car starts for one second, I will pull the plugs and check for evidence of fuel on their tips. I should say, I have noticed fuel on them before. But in contrast, I have done a check for spark on all the coils (as you know this vehicle uses a COP system) and I had spark on each one, though, I couldn't tell you if it is enough spark. So if there is fuel on the plugs as you point out (and I'm sure there will be) - and I have spark - are we going with a timing issue then?
I will also do the fuel pressure check if there is no sign of fuel on the plugs (well, I will regardless). If there is no fuel deposit and I have pressure, is the fuel filter then exempt, and should I then focus on the injectors.
Thank you so much, man; you've great help!
Well, I see a knob that looks like a tire valve cap, and it's green, it has a plastic tag around it reading EVAP service port. I'm not sure this is where you suggested that I check for fuel realease - as when I remove the cap and push on the valve with a screwdriver, absolutely nothing happens, not even a sound. There seems to be nothing else resembling a fuel port; there are two other bigger knobs, but I'm almost certain those are on the AC lines.Well, I see a knob that looks like a tire valve cap, and it's green, it has a plastic tag around it reading EVAP service port. I'm not sure this is where you suggested that I check for fuel realease - as when I remove the cap and push on the valve with a screwdriver, absolutely nothing happens, not even a sound. There seems to be nothing else resembling a fuel port; there are two other bigger knobs, but I'm almost certain those are on the AC lines.
OK, disregard the previous comment. I pulled the plugs and they all had fuel residue on them. I also did a check for spark, each one of them did a rhythmic little sparkle (which I thought seemed very weak). So this is where I'm at, at this point.OK, disregard the previous comment. I pulled the plugs and they all had fuel residue on them. I also did a check for spark, each one of them did a rhythmic little sparkle (which I thought seemed very weak). So this is where I'm at, at this point.
OK, disregard the previous comment. I pulled the plugs and they all had fuel residue on them. I also did a check for spark, each one of them did a rhythmic little sparkle (which I thought seemed very weak). So this is where I'm at, at this point.OK, disregard the previous comment. I pulled the plugs and they all had fuel residue on them. I also did a check for spark, each one of them did a rhythmic little sparkle (which I thought seemed very weak). So this is where I'm at, at this point.
Thanks hansola, you've been a lot of help... I'm thinking you're right, it's likely the ignition module... because my sparks look weak and yellow-ish instead of bright blue (btw, I did chance all spark plugs). For my car, an entire unit that comprises the coil, coil boots, the ignition module, and metal cover is inserted face-down on top of the spark plugs onto the engine (Yes, it is DIS). So, from that unit, either the coil which is inside of it or the ignition module which is readily accessible could be the problem - I can't determine which one, but I'll start with the module first and see what happens! eewwfh!
I think we're making progress at this... It'll be a relief if/when I finally turn the key and hear that engine run. I plan to replace the part(s) tomorrow and will keep you posted! Thanks a million!Thanks hansola, you've been a lot of help... I'm thinking you're right, it's likely the ignition module... because my sparks look weak and yellow-ish instead of bright blue (btw, I did chance all spark plugs). For my car, an entire unit that comprises the coil, coil boots, the ignition module, and metal cover is inserted face-down on top of the spark plugs onto the engine (Yes, it is DIS). So, from that unit, either the coil which is inside of it or the ignition module which is readily accessible could be the problem - I can't determine which one, but I'll start with the module first and see what happens! eewwfh!
I think we're making progress at this... It'll be a relief if/when I finally turn the key and hear that engine run. I plan to replace the part(s) tomorrow and will keep you posted! Thanks a million!
Just this afternoon I grabbed the complete compartment (DIS ignition) that includes the icu, the coil, and the boots from another vehicle at a junk yard, and did a replacement with my car, and I'm getting the same, what is to me, weak spark. Could it be that the part from the yard is also no good?
I'm ruling out timing because my compression seems pretty good on a cold engine not start for a month now. I'm ruling out fuel, because fuel is being deposited on the plugs, and the car acts like it wants to start (and technically does very shortly). I have new spark plugs in there and gapped appropriately - so it couldn't be them.... Man, I'm tired of this car, it's been a month now. Could it possibly the the f*cking passlock bs, causing this? I ruled that out way earlier in my quest since I did the 20 min. wait procedure and still no go - but my ignition is sorta broken and the key hardly turn... Is the darn computer thinking that the car is being broken into each and every time I turn the darn key. Pardon my French... but you can see my frustration!
Should I resort to buying a pair of coils for $129?Just this afternoon I grabbed the complete compartment (DIS ignition) that includes the icu, the coil, and the boots from another vehicle at a junk yard, and did a replacement with my car, and I'm getting the same, what is to me, weak spark. Could it be that the part from the yard is also no good?
I'm ruling out timing because my compression seems pretty good on a cold engine not start for a month now. I'm ruling out fuel, because fuel is being deposited on the plugs, and the car acts like it wants to start (and technically does very shortly). I have new spark plugs in there and gapped appropriately - so it couldn't be them.... Man, I'm tired of this car, it's been a month now. Could it possibly the the f*cking passlock bs, causing this? I ruled that out way earlier in my quest since I did the 20 min. wait procedure and still no go - but my ignition is sorta broken and the key hardly turn... Is the darn computer thinking that the car is being broken into each and every time I turn the darn key. Pardon my French... but you can see my frustration!
Should I resort to buying a pair of coils for $129?
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Re: NO COMPRESSION ON ALL CYLINDERS - TESTER GAUGE GOES...
The fault may very well be with the tester itself: The compression tester should have a check or "HOLD" valve which causes the needle on the gauge to REMAIN at it's highest recorded point. For example, my 1993 Isuzu Rodeo had a compression of 160 psi. The gauge "holds" the needle at the measurement UNTIL THE VALVE IS RELEASED-(mine had a button that needed to be pressed to release the pressure) then there will be a slight discharge of the pressure contained within, the needle should drop back to zero, and THEN you should be able to remove the tester. What I am getting at is if the pressure drops that fast, I think the "HOLD" valve on it may be defective, OR the tester is not properly sealing on the combustion chamber (stripped threads?). Might be worth buying another one for 20$ just to be sure.
A four cylinder engine, you say? Very rarely will you have ALL of your cylinders exhibit the same pressure loss symptoms. How did the other three cylinders test?
Here are the components required for a running engine to fire:
1-good spark (adequate voltage, good plugs/wires)
2-dedicated fuel supply (fuel pump with adequate pressure)
3-timing (slack in timing chain/belt?)
If the timing belt broke or maybe even jumped a tooth or two, it COULD cause DAMAGE to your engine-pistons hitting valves-if it IS what they call an "INTERFERENCE" engine.
If it WAS a faulty tester, and the new tester holds good combustion, and the car STILL won't start:
Make sure you have good spark-all the way to the plugs.
Make sure you have FUEL (and pressure)-all the way to the plugs.
**Fuel injected?-hit the schroeder valve on the fuel rail-fuel should spurt out-that way you know you've got fuel psi all the way to the injectors (Bad injectors?-check for gas on the plugs). (Spark plugs have fuel on them? Fouling plugs? Plugs are ALSO a cheap double check area.)
It's GOT to be timing or possibly computer if both areas check okay-Try checking for any OBD stored trouble codes?
Good luck!If it WAS a faulty tester, and the new tester holds good combustion, and the car STILL won't start:
Make sure you have good spark-all the way to the plugs.
Make sure you have FUEL (and pressure)-all the way to the plugs.
**Fuel injected?-hit the schroeder valve on the fuel rail-fuel should spurt out-that way you know you've got fuel psi all the way to the injectors (Bad injectors?-check for gas on the plugs). (Spark plugs have fuel on them? Fouling plugs? Plugs are ALSO a cheap double check area.)
It's GOT to be timing or possibly computer if both areas check okay-Try checking for any OBD stored trouble codes?
Okay, after the car was able to start, does it idle roughly? Do you have to keep giving it gas to stay running? Pull the spark plugs after this sequence and see if they are all dry, as they should be, or, if any of them have gas and/or are wet. If it is idling rough I think it is the timing. Then again, if only 2 or 3 cylinders are firing, it will run rough, even with accurate timing. Faulty Ignition module, plug wires, distributor, spark plugs, coil, not letting spark get to all cylinders?-This will be evident if there is any unburnt gas on any plugs. If there is no evidence of this syndrome, then it could be fuel pressure: check the fuel pressure at the schroeder valve (looks like a tire valve) on the metal fuel rail-locate your injectors and then follow the common fuel supply line backward just a short bit. If you push this valve very briefly, fuel should spurt out, indicating pressure. If fuel pressure is okay, and no unburnt fuel on plugs-probably injectors.
Will check back later.Okay, after the car was able to start, does it idle roughly? Do you have to keep giving it gas to stay running? Pull the spark plugs after this sequence and see if they are all dry, as they should be, or, if any of them have gas and/or are wet. If it is idling rough I think it is the timing. Then again, if only 2 or 3 cylinders are firing, it will run rough, even with accurate timing. Faulty Ignition module, plug wires, distributor, spark plugs, coil, not letting spark get to all cylinders?-This will be evident if there is any unburnt gas on any plugs. If there is no evidence of this syndrome, then it could be fuel pressure: check the fuel pressure at the schroeder valve (looks like a tire valve) on the metal fuel rail-locate your injectors and then follow the common fuel supply line backward just a short bit. If you push this valve very briefly, fuel should spurt out, indicating pressure. If fuel pressure is okay, and no unburnt fuel on plugs-probably injectors.
So, it looks like a weak spark, then. I had this symptom once, which ended up being a defective ignition module (electronic). It could also be coil, distributor, plug wires, or even all 4 plugs could be fouled. On the other hand, it's doubtful that all 4 cylinder plugs would have fouled while on the freeway. Is this a distributorless ignition? You need to determine why your spark is weak. More than likely it is an electrical component that failed while on the freeway. It's NOT timing if the spark is weak. Spark should be strong, bright blue. You have fuel delivery.
What I did (my ignition module would not produce spark at cylinder #4), was use an inductive (has a clip that you connect to a plug wire) timing light to make sure each one of my plug wires was firing. #4 cylinder would not fire, so, after switching plugs and wires and coils, retrying, getting same results, I determined that the ignition module was bad, as I have distributorless ignition. Your ignition module will probably run about $150 at most auto parts stores. I don't know of any way to test an ignition module, so eliminate everything else before buying the expensive part! Hope it's as simple as this for you. Good luck!So, it looks like a weak spark, then. I had this symptom once, which ended up being a defective ignition module (electronic). It could also be coil, distributor, plug wires, or even all 4 plugs could be fouled. On the other hand, it's doubtful that all 4 cylinder plugs would have fouled while on the freeway. Is this a distributorless ignition? You need to determine why your spark is weak. More than likely it is an electrical component that failed while on the freeway. It's NOT timing if the spark is weak. Spark should be strong, bright blue. You have fuel delivery.
What I did (my ignition module would not produce spark at cylinder #4), was use an inductive (has a clip that you connect to a plug wire) timing light to make sure each one of my plug wires was firing. #4 cylinder would not fire, so, after switching plugs and wires and coils, retrying, getting same results, I determined that the ignition module was bad, as I have distributorless ignition. Your ignition module will probably run about $150 at most auto parts stores. I don't know of any way to test an ignition module, so eliminate everything else before buying the expensive part! Hope it's as simple as this for you. Good luck!
Yeah, I don't know much about that passlock stuff, I'm mostly old school when it comes to cars. However, I don't know if buying a pair of coils is going to do anything for you if the passlock IS your trouble. Maybe you need to install a new key switch first to rule THAT out; I wasn't aware you had a key switch problem also. I did some checking and (in my area) I could by a new aftermarket ignition key switch for $80. See here:
Don't know how much is involved in replacing the switch but usually there's (ugh) steering column work involved. There's also usually anti theft stuff (tamperproof screws, difficult shields, etc.) guarding it so not just anyone can change your key switch.
Hope I've been some help.Yeah, I don't know much about that passlock stuff, I'm mostly old school when it comes to cars. However, I don't know if buying a pair of coils is going to do anything for you if the passlock IS your trouble. Maybe you need to install a new key switch first to rule THAT out; I wasn't aware you had a key switch problem also. I did some checking and (in my area) I could by a new aftermarket ignition key switch for $80. See here:
Don't know how much is involved in replacing the switch but usually there's (ugh) steering column work involved. There's also usually anti theft stuff (tamperproof screws, difficult shields, etc.) guarding it so not just anyone can change your key switch.
Hope I've been some help.
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Are you sure it's actually a plug?
Are you getting oil on the plug?
The plug may be firing but you may be losing compression which gives the symptoms of a misfire. As you've changed the plug, lead and coil this points to to a problem elsewhere.
Your first course of action should be to get a mobile mechanic carry out a diagnostic check for you.
To put your mind at rest, do a 2nd compression test using a light oil squirted into the bores:
Doing a Compression Test
Warm the engine. Remove all the spark plugs.
Get a pencil and piece of paper to note down the readings.
Put the compression tester into the No1 cylinder and crank the engine for 10 seconds.
Note down the compression reading.
Repeat process for all cylinders.
Here's an illustration of what you may expect on a 4 cylinder engine:
Cylinder 1 2 3 4 psi 125 122 120 124
125 is the uppermost figure for that engine. Here, this engine is fine. There's a slight variation in psi figures, but that's perfectly normal.
Here's the same engine:
Cylinder 1 2 3 4 psi 110 112 114 112
The psi reading is down. However, as all the figures are pretty much equal it doesn't indicate head /gasket problems. It may point towards worn pistons or burnt valves.
Now consider these psi readings:
Cylinder 1 2 3 4 psi 125 84 86 124
There's more than a 10% drop - a difference - between cylinder 1 and 2, and cylinders 3 and 4.
The compression readings for cylinders 2 and 3 is down; low. There's something clearly wrong.
It suggests that there is a defective head gasket between cylinders 2 and 3 or a crack in the cylinder head. The rising piston compresses the gases which escape into the adjoining cylinder via the defective gasket or cracked head.
However, it could also mean that there is a problem with the valves (burnt/not seating properly) or perhaps piston / ring problems.
A burnt valve - it's usually the exhaust valve as they bear the brunt of the combustion - can cause a reduction in engine power simply because the combustion process isn't occurring properly. Compressed air/fuel gets squeezed out of that cylinder because of the damaged valve . There even may be a misfire - a surge as the car runs.
Worn or broken piston rings allow compressed gases to leak past into the crankcase. A compressed crankcase can force oil out of the dipstick tube. The pressure in the crankcase will leak to atmosphere anywhere it can find an outlet.
The 2nd Compression Test
The second compression test is known as a 'wet test'. The first compression test was the dry test because no oil was added to the bores. The second 'wet' test can give an indication of whether it is the rings or valves at fault (though bear in mind rings and valves do not cause overheating or water in the coolant symptoms).
Spray a liberal amount of light penetrating oil into each cylinder - aim for the cylinder walls, not the centre of the piston. You want the oil to run down the cylinder wall and around the piston to form a seal.
Place a rag over each spark plug hole and spin the engine to eject the surplus oil.
Then carry out a full compression test noting down the results.
Here's the previous results with the 2nd compression readings added:
Cylinder 1 2 3 4 psi 125 84 86 124 Wet 128 112 110 126
The readings have increased. This because the oil sprayed into the bores has formed a temporary seal around the piston, thereby enabling the compression to be raised. It also indicates that the bores/rings are worn on cylinder 2 and 3 - the 'oil seal' has increased the readings but is still low in comparison with cylinders 1 and 2.
This could also indicate that in addition to worn rings there is also burnt valves. Oil cannot form a seal around a valve. A worn or split valve will cause a low compression reading and misfiring symptoms.
Compressions readings should be taken in conjunction with other symptoms. It will help you identify the problem:
Low compression readings between two adjoining cylinders point towards a head gasket/head fault if your vehicle has shown signs of coolant loss, coolant in the oil system - mayonnaise, overheating, rough running and lack of power.
If those symptoms are not present it points towards burnt valves/piston rings. A worn engine may be difficult to start and pressurise the crankcase, but it doesn't cause overheating problems.
You have to buy or borrow a compression gauge tester. It threads into the spark plug hole; so you pull all the plugs out, then check each cylinder's compression. The proper way is to first disable gas and spark, put the tester into the first cylinder, then crank the engine over a set number of times- the same amount of cranking for each cylinder, so all get a balanced test. While cranking, hold the accelerator pedal all the way to the floor-this lets the engine breathe normally, getting all the air available. then compare your compression readings: a good healthy engine will have all cylinders pretty even, in the range of somewhere between 150 psi-200 psi. Low compression readings means compression is being lost somewhere, like worn piston rings, bad head gasket seal, or valves not sealing.
Wondering if you have any compression at all? Hold your finger over a spark plug hole while someone briefly cranks the engine over. You can tell if there's any compression at all-you will feel the pressure build up under your finger. Rent or buy the gauge tester to get a true reading of your compression.
Have you put each cylinder at top dead center on compression
stroke & done a cylinder leak down test BEFORE ever starting
the motor,& is the timing belt still on & timed correctly?
Compression is relative to many things & not much use these
days,you got it or you don't
A simple compression check will tell you what cylinder is the culprit. Remove the fuel pump relay or fuse to disable the injectors and fuel system, then remove one spark plug at a time to perform the test on the vehicle. Install the compression tester to each cylinder individually and record the readings for each after cranking the engine for at least 10 seconds till the gauge on the compression tester reaches it's "peak". Use caution while performing the compression test. Good luck !!
Get a compression tester, remove all the spark plugs, unplug ignition module and injectors. Now screw in tester hose to cylinder #1, attach guage and crank engine for 3 seconds. Record reading on gauge and move to next cylinder. Repeat this on all cylinders. Compression should be around 90-100 psi and should not vary more than 20% between cylinders.
Auto parts stores sell a compression testing tool which is a gauge and hose attachment. Remove the park plugs, make sure you mark the spark plug wires so that you can replace the wires in the correct location and keep the firing order correct. You attach the tester by screwing it into the spark plug hole and then crank the motor over several times. This has to be done for each cylinder. I recommend you get the Haynes repair manual on your vehicle so you have the proper ranges for compression for the cylinders and further instructions on doing this test.
First go to a different Mechanic, second,, if you have no compression in 3 cylinders, sounds like you have three dead cylinders or bad valves, either way it is not a cheap fix, unless you absolutely adore your trooper... it may be time to give her up.
FIRST OF ALL YOU NEED TO RUN ENGINE FEW MINUTES DONT GET IT TOO HOT. TURN OFF ENGINE. THEN PUT ON SAFETY GLASSES. USE COMPRESS AIR BLOW DEBRI AWAY FROM SPARKS PLUGS.TO KEEP FROM GETTING INTO CYLINDERS.DISABLE YOUR SPARK IGNITION.AND DISABLE FUEL PUMP.BY REMOVING FUSE.NUMBER AND TAG SPARK PLUG WIRES.REMOVE ALL PLUG WIRES AND SPARK PLUGS.BESURE YOU NUMBER THEM AND TAG THEM SO THEY GO BACK IN THE ORIGINAL PLACE.THEN GET COMPRESSION GAUGE TESTER SCREW IT IN SPARK PLUG HOLE TO CYLINDER 1 FIRST.TAKE YOUR FOOT PRESS ACCELERATOR PEDAL TO FLOOR.PUT KEY IN IGNITION SWITCH CRANK ENGINE AROUND A FIVE TURNS.THEN CHECK COMPRESSION ON GAUGE.IT SHOULD BE NO LOWER THAN 100 PSI.IF SO SQUIRT SOME OIL IN THAT CYLINDER. IF COMPRESSION INCREASES.THAT CYLINDER HAS BAD RINGS IF OIL SQUIRT DONT INCREASE COMPRESSION. VALVES IS LEAKING. YOU DO ALL CYLINDER THE SAME.SCREW COMPRESSION IN PLUG HOLES.TURN ENGINE OVER 5 ROUNDS. WRITE DOWN ALL READINGS.
Leak down tester, swap the spark plug for the tester, have the motor set where both valves are closed, that means taking off the valve cover, inject the air and watch the gauge.
If it leaks quickly then suspect valves, squirt in a bit of oil and try again, if no change you have a suspect. If you have good compression on the other cylinders then I would agree on the rings.
How to Test Engine CompressionAn engine depends on an equal compression reading in each cylinder to run smoothly. If poor compression exits in one or more cylinders it can cause a rough idle condition and low power. A compression test can be performed to check wear or internal damage. To start a engine compression test gauge is needed. There are two types of gauge styles, one threads into the spark plug hole which is more accurate. The other style of gauge is constructed with a rubber plug that is meant to be pressed against the spark plug hole, this style of gauge is difficult to use. To perform a engine cylinder compression test follow the steps below.
Remove ignition coil connector or ignition system fuse to disable power to the ignition system
Test ignition system to ensure that the power to the system has been disabled
Remove #1 cylinder spark plug and insert compression gauge, most gauges have a hose attachment that is installed into the spark plug hole with the gauge connecting to the gauge hose.
Engine Cylinder Compression Gauge
After the compression gauge has been inserted, use the starter to crank the engine over for about five seconds. Use about the same five seconds to test the remaining cylinders.
Record the compression reading as each cylinder is tested
Remove the compression gauge and reinsert the spark plug
Follow this procedure until all cylinders have been tested
Compare cylinders compression reading, all readings should be within about 5% of each other
If low compression exists a cylinder malfunction exits and further inspection is required. Possible causes for a low compression condition are: burned intake or exhaust valve, broken piston or piston ring, broken valve spring or a blown head gasket.
All 4 of them got up the around the same value (165) on a cold engine. I looked inside the belt cover and belt seemed on and tight. I will do as you suggest, getting another tester. But my question now is, if there is compression... I've done all the tricks in the books to get this thing to start with no success. It's a breath of fresh air to get the re-assurance that the tester my be faulty - I was getting ready to garbage the car. By the way, it's a 1999 Olds Alero DOHC with 152k automatic. Thanks for you insight; I'll do the test again and repost.
hansola, I hope you're still around to advise me on this. Okay, the new test tester held the compression at 153, 153, 153, 135 on the cylinders. The vehicle practically starts (a little rough for 1 second) then shuts off. Here's what I notice: When I keep my fuel pump relay in and turn the key to ignition (without starting) about 3 times and then floor the accelerator, the vehicle starts pretty good at times then die after a second. After that it won't try to start again (good cranking though) unless I repeat the same sequence.
Should I be thinking fuel injectors, or fuel pressure, or could it be air intake? Keep in mind that I did a code reading that output P-0107 MAP/BARO circuit low input - which referred to the MAP sensor being bad... well, I changed that and the vehicle still didn't start. Thanks for your willingness to help so far!
hansola, I hope you're still around to advise me on this. Okay, the new test tester held the compression at 153, 153, 153, 135 on the cylinders. The vehicle practically starts (a little rough for 1 second) then shuts off. Here's what I notice: When I keep my fuel pump relay in and turn the key to ignition (without starting) about 3 times and then floor the accelerator, the vehicle starts pretty good at times then die after a second. After that it won't try to start again (good cranking though) unless I repeat the same sequence.
Should I be thinking fuel injectors, or fuel pressure, or could it be air intake? Keep in mind that I did a code reading that output P-0107 MAP/BARO circuit low input - which referred to the MAP sensor being bad... well, I changed that and the vehicle still didn't start. Thanks for your willingness to help so far!
Great, great, great stuff... OK, soon after the car starts for one second, I will pull the plugs and check for evidence of fuel on their tips. I should say, I have noticed fuel on them before. But in contrast, I have done a check for spark on all the coils (as you know this vehicle uses a COP system) and I had spark on each one, though, I couldn't tell you if it is enough spark. So if there is fuel on the plugs as you point out (and I'm sure there will be) - and I have spark - are we going with a timing issue then?
I will also do the fuel pressure check if there is no sign of fuel on the plugs (well, I will regardless). If there is no fuel deposit and I have pressure, is the fuel filter then exempt, and should I then focus on the injectors.
Thank you so much, man; you've great help!
Great, great, great stuff... OK, soon after the car starts for one second, I will pull the plugs and check for evidence of fuel on their tips. I should say, I have noticed fuel on them before. But in contrast, I have done a check for spark on all the coils (as you know this vehicle uses a COP system) and I had spark on each one, though, I couldn't tell you if it is enough spark. So if there is fuel on the plugs as you point out (and I'm sure there will be) - and I have spark - are we going with a timing issue then?
I will also do the fuel pressure check if there is no sign of fuel on the plugs (well, I will regardless). If there is no fuel deposit and I have pressure, is the fuel filter then exempt, and should I then focus on the injectors.
Thank you so much, man; you've great help!
Well, I see a knob that looks like a tire valve cap, and it's green, it has a plastic tag around it reading EVAP service port. I'm not sure this is where you suggested that I check for fuel realease - as when I remove the cap and push on the valve with a screwdriver, absolutely nothing happens, not even a sound. There seems to be nothing else resembling a fuel port; there are two other bigger knobs, but I'm almost certain those are on the AC lines.
OK, disregard the previous comment. I pulled the plugs and they all had fuel residue on them. I also did a check for spark, each one of them did a rhythmic little sparkle (which I thought seemed very weak). So this is where I'm at, at this point.
OK, disregard the previous comment. I pulled the plugs and they all had fuel residue on them. I also did a check for spark, each one of them did a rhythmic little sparkle (which I thought seemed very weak). So this is where I'm at, at this point.
Thanks hansola, you've been a lot of help... I'm thinking you're right, it's likely the ignition module... because my sparks look weak and yellow-ish instead of bright blue (btw, I did chance all spark plugs). For my car, an entire unit that comprises the coil, coil boots, the ignition module, and metal cover is inserted face-down on top of the spark plugs onto the engine (Yes, it is DIS). So, from that unit, either the coil which is inside of it or the ignition module which is readily accessible could be the problem - I can't determine which one, but I'll start with the module first and see what happens! eewwfh!
I think we're making progress at this... It'll be a relief if/when I finally turn the key and hear that engine run. I plan to replace the part(s) tomorrow and will keep you posted! Thanks a million!
Just this afternoon I grabbed the complete compartment (DIS ignition) that includes the icu, the coil, and the boots from another vehicle at a junk yard, and did a replacement with my car, and I'm getting the same, what is to me, weak spark. Could it be that the part from the yard is also no good?
I'm ruling out timing because my compression seems pretty good on a cold engine not start for a month now. I'm ruling out fuel, because fuel is being deposited on the plugs, and the car acts like it wants to start (and technically does very shortly). I have new spark plugs in there and gapped appropriately - so it couldn't be them.... Man, I'm tired of this car, it's been a month now. Could it possibly the the f*cking passlock bs, causing this? I ruled that out way earlier in my quest since I did the 20 min. wait procedure and still no go - but my ignition is sorta broken and the key hardly turn... Is the darn computer thinking that the car is being broken into each and every time I turn the darn key. Pardon my French... but you can see my frustration!
Should I resort to buying a pair of coils for $129?
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