Question about Chevrolet Corvette

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Have replaced whole ignition system and spark plugs except magnetic pickups and compression is good 150PSI per cylinder on a chevy v8 smallblock gen 1 #2 cylinder exhaust header is cold fuel pump has been replaced carburetor has been rebuilt any suggestions???

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  • skiinian Jul 26, 2008

    ya i did that and all the valves are moving the same amount as the other valves using a dial indicator

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  • 21 Answers

Have you taken the passanger side valve cover off while the cars running? Doing this you will see if the valve is opening at the intake valve allowing gas vapors to fill the cylinders so as to ignite and exit out the exhaust. No fuel from intake valve no heat from exhaust. I have another idea as well but this is the quickest and most simple.

Posted on Jul 26, 2008

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No spark to distrubter


you meant no spark from distributor.? if its TO that means the ignition coil is dead. (or pcm not seeing cmp/ckp sensor signals)
PCM is the Engine injection and spark creating system EFI.
power train control module it is.
which engine of the 4?
try the correct order. this time...... and checks.... and win....
battery charged, fully to 12.6vdc rested
did you do the 60,000 mile tune up yet? if not why not?

  1. it must crank fast. if not fix that first.
  2. the spark plugs all 4 must spark, not just one.
  3. the CEL lamp must turn on key on or fuses are blown.
  4. connect scan tool,
  5. crank for 5 seconds, release key , do not turn off key yet.
  6. behold, scan tool shows why there is no spark or shows cmp/ckp ok but spark is bad (primary side) , end riddle. now.
  7. ok 6 passes muster, so is engine compression over 150psi on all 4 cylinders. sure. next
  8. we check spark at all spark plugs and use new spark plugs, and see one is oil soaked, or green antifreezes soaked or black or very odd locking tips (this is called gathering evidence, never to be skipped
  9. did you replace the timing belt if in fact you have one, CAM at the 60k service point (if not it slips and compression will be like 1/2 the normal 150psi + compression.
  10. did you do the tuneup
  11. ok all above is ok, and i do test fuel test, it runs for 3 seconds, and sounds real good, that 3 seconds, and repeats as i repeat
  12. ok that means you lost fueling or its flooding per #8 check.
  13. ill stop at fueling,,, you need a fuel pressure gauge next..
  14. btw, wide open cranking clears floods.

Mar 13, 2015 | 2006 Suzuki Forenza

2 Answers

I need help with my 1999 chevy silverado 1500 5.3 4x4 I have a rough idle like its only running on 7 cylinders here are some of the things I've done to try and resolve this issue, changed fuel filter


you need to isolate which cylinder it is first may help.
while running use insulated pliers to pull each plug wire off plug or cap separately, you will hear idle change/drop when a good cylinder is pulled. it will not change when not firing cylinder is pulled. now u got the cylinder and can double check plug, wire connections there. see if that wire sparks on a ground or plug to check spark and eliminate that issue. if you get a zap you need a better insulated pliers, but you know that wire is good. Remember the 3 things needed on all engines- Spark, Fuel, Air. oh yes and Compression. if you have spark, then have cylinder compression tested 120-150psi is still good. 80psi sucks and you have bad rings or valves., fuel cleaner may help in that situation, rare fix, but cheaper than a new engine.

Aug 28, 2014 | 1999 Chevrolet Silverado 1500

2 Answers

Free ford troubleshooting


You need 3 things for a cylinder to fire; spark, fuel and compression. You have to check for all 3. The easiest order is the order I stated them.

Apr 17, 2014 | 2002 Ford Ranger Regular Cab

1 Answer

Chevy troubleshooting


Spark, gas, and compression. And check timing. You've done the major work. Now you have to make sure you have done it right. By getting it running, you know. I'm pretty sure you can rent a fuel pressure tester and a cylinder compression tester at some national parts stores, Autozone or O'reillys, maybe others.
I don't understand your expression "...a little miss from bottom end" -an ignition miss, or a bottom skip or noise?

Start with checking ignition-a blue snapping spark-what you want to see at all cylinders. Then check that gas is getting into the cylinders. Fuel pressure and injector solenoid pulse. Then all you need after that is compression -good even compression in all cylinders-. Timing is right, spark timing is right, it should crank, er start.
Just one thing about compression, on a cold engine you're just looking for gross irregularities, you can't depend on the readings to be very accurate. A good compression test should be done on an engine at normal operating temperature. It gives a more accurate picture of your engine condition. As long as compression is over 100 psi per cylinder on a cold engine might be a general guideline, I suppose, but take that as only opinion, not fact..

Feb 19, 2014 | Chevrolet 1500 Cars & Trucks

2 Answers

2002 kia spectra misfire


bad senser or computer

Dec 11, 2013 | 2002 Kia Spectra

1 Answer

Cylinder 6 is misfiring. What was will fix this problem? It's a 5.7L v8 in a Chevy 1500.


You don't say what year the truck is, so I will guess on the fuel system.
You need spark, fuel, and compression for the cylinder to produce power. One of the three is missing.
If the engine has multi-port fuel injection the injector for that cylinder could have failed.
Could also be a plug, plug wire, or something mechanical.

Aug 12, 2013 | Cars & Trucks

2 Answers

Enging code came up on my 2004 dodge ram 1500 5.7 Hemi. Said ignition coil E was bad and that I had a misfire in cylinder 3. Replaced coil at cylinder 3 but it's still running rough. Is coil E somewhere...


Have you checked the spark plug itself? --- 5.7L Engine To Remove:
NOTE: Note spark plug cable original positions before removing.
dod_ram15_57_ign_coil.gif

dod_ram15_57_ign_coil_loc.gif

  1. Before servicing the vehicle, refer to the precautions at the beginning of this section.
  2. Clean the area around the coil with compressed air.
  3. Remove or disconnect the following:
    • Battery negative cable
    • Throttle body air intake tube and intake box (if necessary)
    • Coil electrical connector by moving slide lock and pressing on release lock
    • Secondary high-voltage cable from coil
    • Mounting bolts
    • Coil from cylinder head opening by twisting
To Install:
  1. Clean area around spark plugs with compressed air.
  2. Apply dielectric grease to inside of boots.
  3. Install or connect the following:
    • Ignition coil to cylinder head opening
    • 2 mounting bolts
      1. Torque to: 106 inch lbs. (12 Nm)
    • Coil electrical connector
    • Cable to coil
    • Throttle body air tube and intake box (if necessary)
    • Battery negative cable
---
Distributorless Ignition System General Information This vehicle uses two different types of ignition systems. The 3.7L, 4.7L, and 5.7L engines do not use a conventional distributor. The 5.9L engine uses a conventional distributor. The ignition system is controlled by the Powertrain Control Module (PCM) on all engines. Procedures in this section are for the 3.7L, 4.7L, and 5.7L engines; please see the section on Distributor Ignition Systems for procedures for the 5.9L engine.
Distributorless ignition systems (EI) are used on many current engines. This system uses the waste spark method for distributing secondary voltage. In a waste spark system, an individual coil is used to fire one pair of engine cylinders simultaneously. These cylinders are known as companions, since each of their pistons is at TDC at the same time. On a typical V6 engine for example, cylinder 1 is at TDC compression while cylinder 4 is at TDC exhaust. This is also true of cylinders 2 and 5 as well as cylinder 3 and 6.
The cylinder on the compression stroke is known as the event cylinder, while the cylinder on the exhaust stroke is called the waste cylinder. Since secondary resistance is very low in the cylinder on the exhaust stroke, little voltage is required to fire the plug. For this reason, the majority of available voltage is consumed by the cylinder on the compression stroke.
One spark plug is attached to each end of the secondary coil winding via the spark plug wires. This series circuit arrangement causes one of the plugs to fire in a forward direction (center electrode to outer electrode), and the other spark plug to fire in a reverse direction (outer electrode to center electrode). The firing voltage requirements on the waste spark ignition are significantly greater than a traditional ignition system primarily because it takes 30% more energy to fire a plug reverse polarity. When a spark plug is fired backwards, it fires from the outer electrode to the center electrode. This is a high resistance path since the electrons do not flow as easily from a cold, dull surface such as the outer electrode to a hot, sharp surface like the center electrode.
Since the coil and plugs are arranged in a series circuit, a typical plug gap of .050" results in a total gap of .100" for the whole circuit that includes two spark plugs for the companion cylinders. The waste spark can overcome this added resistance by producing high secondary output voltages due to low resistance in the primary winding. Another reason higher secondary ignition voltage is required is cylinder pressure; specifically, the lack of it. Generally, event cylinders require 10 to 12-kV to initiate current flow across the spark plug gap, while only 2 - 3-kV is needed to fire the waste cylinder. Therefore, the air gap in the waste cylinder creates no more resistance than the rotor gap does in a conventional ignition system.
There are two different methods used for coil trigger. One method sends the crankshaft sensor signal directly to the ignition module to activate the coils, while the other sends the crankshaft sensor signal to the PCM and the PCM controls ignition operation either directly or through a separate ignition module.
Waste spark ignition advantages
  • It has fewer components than conventional distributor-type ignition systems.
  • No mechanical adjustments to set ignition timing.
  • No mechanical load (turning the distributor shaft).
  • No unwanted timing variations caused by gear lash or other worn distributor components.
Another advantage of waste spark is longer coil life. To illustrate this point, consider a six-cylinder engine with conventional ignition. At 3000 RPM, the coil must fire 9000 times per minute. This is calculated by dividing the engine speed by 2, since the cam turns at half crank speed, and then multiplying the distributor RPM by the total number of engine cylinders.
In contrast, the coils on a six-cylinder engine with waste spark only work a third as hard. This is because there's a coil for every two cylinders and each coil fires every crankshaft revolution. This means that at 3000 RPM, the coils only fire 3000 times per minute. This allows each coil to operate with less dwell (time that the coil is energized), resulting in less heat buildup and longer life.
Coil Over Plug System The coil over plug system was developed so that spark and spark timing could be better controlled on an individual cylinder basis. Each cylinder has an ignition coil mounted directly above the spark plug on the cylinder head cover. A short suppresser/connector replaces the spark plug wire and links the coil to the plug. There are different methods used for primary triggering. Some manufacturers use a combination coil/module, which means each coil has its own control circuit that is activated by the PCM. Others use remote mounted modules to trigger the coils.
Each individual coil is allowed to saturate while all other cylinders fire. For a V-8 engine, this allows a period of seven firing events for coil saturation, compared to three events for the same V-8 engine with a waste spark system. The coil over plug system also benefits from a minimum amount of energy lost, due to the resistance of spark plug wires.
Coil Near Plug System The coil near plug system also features multiple ignition coils. An ignition coil/module is mounted in proximity of each cylinder. There is a short length of spark plug wire between the coil and the spark plug.
Each ignition coil/module has its own control circuit and is activated sequentially by the PCM. All timing decisions are made by the PCM. This includes both ignition timing and duration of the spark.

Nov 03, 2010 | 2004 Dodge Ram 1500

3 Answers

After replacing plugs, wires, coil, ignition modual, and computer, I still don't have spark.


take the cap off the distributor and have someone crank if over, it rotor doesnt turn, distributor is bad.

Aug 18, 2010 | 1991 Chevrolet Suburban

4 Answers

Whats the correct way 2 perform a compression test on a chevy v8 small block


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.

Sep 13, 2009 | 1985 Chevrolet Suburban

2 Answers

Engine won't start


even if you have spark, it may not be "good spark"

Try cleaning the contacts to the coil, or replace the coil itself.

May have pinched or cut a wire by mistake during the work you have done. Check all for proper grounding as well

Feb 27, 2009 | 1996 GMC Sierra

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