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What are the cylinder compression figures for a 1098cc mini

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Around 120 psi with no more than 10% difference between adjacent cylinders 120--120--110-110 indicates a head gasket or 120-100-100-120 is head gasket. test is done cold with the throttle held wide open and all plugs out.. Next squirt oil from an oil can (3to 4 pumps) into each cylinder and retest Pressure should go up indicating good rings. If it doesn't change up in each cylinder the cylinder will have possibly a broken ring or scored bore allowing the oil to be blown into the sump

Posted on Nov 22, 2013

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My 1993 camry is now high on fuel consumption after engine haul. what could be the cause?


Check cylinder compression.
Any applicable trouble codes?
What about a tune-up?
With any problems after engine over-haul, I always check cylinder compression.

Apr 15, 2016 | Cars & Trucks

2 Answers

Have a spark plug not firing.


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.

Feb 09, 2016 | Cars & Trucks

1 Answer

Cylinder 2 misfire and low fuel detected again and again seems there are issues with minis and this problem? I am reading thru other posts is there any quick fix?


Usually the mystery misfire on a single cylinder is a bad distributor wire. It can sometimes be seen arcing to ground at night & sometimes you can see a small pin head sized discoloration on the wire. It could also be oil around a spark plug needing the surrounding rubber seals replaced. Take it apart & figure it out. Good luck

Oct 29, 2015 | 2005 Mini Cooper S

2 Answers

Bad misfire and no compression on cylinder 1


it possibly has a hole burnt in the top of piston . take to a good mechanic

May 12, 2015 | Mini Cooper Clubman Cars & Trucks

1 Answer

2005 mini cooper cy;inder 2 dead


Have you done a cylinder compression test. If so what pressures?

Apr 20, 2013 | 2005 Mini Cooper S

1 Answer

How can I recover the power (performance/horse power) of 1990 JEEP CHEROKEE LIMITED? this jeep has been stopped for long time and i want to make back powerful as as close to manufacturer state as...


First thing to do is have a compression test of the engine, to determine its internal condition and worthiness. Go from there. Low compression in any cylinders from worn rings or poorly sealing valves translates into poor performance and horsepower. What you want is good compression (about 140 psi minimum) across all cylinders, and near evenly balanced-all with nearly even figures. As a rule of thumb, all cylinders should be within 75% of the highest reading cylinder

Oct 25, 2012 | 1990 Jeep Cherokee Limited

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2002 mazda millenia 2.5 v6 just replaced timing belt that was broken...double and triple checked t belt alignment is correct put it all back together....now no start...compression is 50% suposed to...


Can stop cranking. With compression figures that low, it will never start. Are you sure the figures are accurate? Throttle wide open when cranking up pressure? Compression has to be at least 100 psi for the spark to ignite the mixture.
If the belt broke while engine was running, and if it is an interference engine, you may have sustained some bent valves, internal damage to one or more cylinders, but not, I don't think, to all cylinders. I don't understand how you are getting such low compression on all cylinders Those figures sound like both head gaskets are failed, or the timing is way off.
Review your timing procedure and recheck compression. Something is definitely wrong. Hope you can figure it out. Good luck.

May 31, 2012 | Mazda Millenia Cars & Trucks

1 Answer

1998 dodge 318 5.2L compression


when you do your compression test squirt some oil in the cylinder through the spark plug hole first then check compression if you have compression then its rings. If still no compress you might have worn off cam lobes.

Feb 04, 2012 | 1998 Dodge Dakota

2 Answers

How do you check compression


A compression test will tell you if your engine has good compression. An engine is essentially a self-powered air pump, so it needs good compression to run efficiently, cleanly and to start easily.

As a rule, most engines should have 140 to 160 lbs. Of cranking compression with no more than 10% difference between any of the cylinders.

Low compression in one cylinder usually indicates a bad exhaust valve. Low compression in two adjacent cylinders typically means you have a bad head gasket. Low compression in all cylinders would tell you the rings and cylinders are worn and the engine needs to be overhauled.

HOW TO CHECK COMPRESSION
Compression can be checked two ways: manually with a compression gauge, or electronically with an engine analyzer the measures cranking compression. With electronic testing, a computer analyzer estimates compression in each of the engine's cylinders by measuring slight variations in engine cranking speed.

The results correlate well with actual gauge readings, and can be completed in a matter of minutes without having to remove any spark plugs. What's more, the analyzer prints out the results of the compression test making it easy to see and compare the actual numbers.

To check compression manually with a gauge, all the spark plugs must be removed. The ignition coil must then disabled or the high tension lead grounded. If the engine has a distributorless ignition, the ignition coils must be disabled to prevent them from firing. The throttle must also be held open.

The engine is then cranked for a few seconds using a remote starter switch or a helper while a compression gauge is held in a spark plug hole.

The maximum compression reading is noted, then the process is repeated for each of the remaining cylinders.

The individual cylinder readings are then compared to see if the results are within specifications (always refer to a manual for the exact compression figures for your engine because they do vary from the ballpark figures quoted earlier).

IS IT THE RINGS OR THE VALVES?
If compression is low in one or more cylinders, you can isolate the problem to the valves or rings by squirting a little 30 weight motor oil into the cylinder through the spark plug hole and repeating the compression test. The oil temporarily seals the rings.

If the compression readings are higher the second time around, it means the rings and/or cylinder is worn. No change in the compression readings would tell you the cylinder has a bad valve.

Hope this help (remember comment and rated this).

Apr 20, 2010 | 1998 Ford Contour

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