Failed compression test and misfire

[amorlv70]

Originally Posted by classicswede

You have still not said what the engine is
If the engine is a type that needs a oiling system then that can be the problem
A failed injector, poor tune, failed sensor and a number of other things could have caused it

Spark plugs the Volvo 3 prong plugs are not the best choice, I convert to NGK single prong plugs

Sorry, I did in the below message but it was probably lost in my nonsense..

Originally Posted by amorlv70

The car is a 2004 pre-facelift (2004 my) v70 with the 2.4 170 B5244S 2435cc.

Thanks very much for your reply, much appreciated.

I will get a set of NGK plugs when I have sorted these issues out. Thanks

[classicswede]

Should not need the oiling system on that so that suggests something else has caused the problem

[amorlv70]

Originally Posted by classicswede

Should not need the oiling system on that so that suggests something else has caused the problem

OK, thanks very much Classic
I didn't think it did..
I'll get the head off when there is time to see what is going on.

[dikidera]

Very sad I was not here when the thread was made. If the car is a factory CNG or LPG I would also suspect the head gasket.

And if so, it is very likely the block is warped too. I've heard horror stories of our S,S2,SG and SG2 engines. Especially CNG and LPG. Tomorrow after cleaning my head gasket material as well as carbon ring from the block I will test for warpage with a Straight Edge, flat 8mm thick with an accuracy of 12 micrometers.

I suspect it will be.

[amorlv70]

Originally Posted by dikidera

Very sad I was not here when the thread was made. If the car is a factory CNG or LPG I would also suspect the head gasket.

And if so, it is very likely the block is warped too. I've heard horror stories of our S,S2,SG and SG2 engines. Especially CNG and LPG. Tomorrow after cleaning my head gasket material as well as carbon ring from the block I will test for warpage with a Straight Edge, flat 8mm thick with an accuracy of 12 micrometers.

I suspect it will be.

The car is not factory LPG, it's an aftermarket conversion - when I remove the head (next week) I will also check for warpage, but there are no signs of headgasket failure other than the loss of compression, leading me to believe it's a valve issue.. I'll update when I have the engine apart
Hope yours went ok

[dikidera]

Very nice if it's simply a valve. I however measured 0.05mm or 0.002 inch of warping at least in several places of my block. I suspect it could be as high as 0.003 in some.

Unfortunately there is no information if this is within tolerance or not. Some have said it should be lower than this, others have said up to 0.08mm is fine and the head gasket will help seal this.

Basically it's a trial and error type of thing. Some will not risk it and machine the block, I plan to test it as-is.

What I find odd is that some people say Volvo blocks are tough to warp. In my opinion, not so. It's aluminum, it's a malleable metal. I agree with some that if the head is warped, so is the block.

[amorlv70]

Head is off and at engine shop. Very dark oil deposits on and around camshaft lobes in the cylinders that lost compression. Gets progressively worse from cyl1-5.

[classicswede]

Any visable valve or gasket damage?

[dikidera]

Originally Posted by amorlv70

Head is off and at engine shop. Very dark oil deposits on and around camshaft lobes in the cylinders that lost compression. Gets progressively worse from cyl1-5.

I've heard...and this is only something I've heard from mechanics. Is that the black deposits are not problematic. Whether this is because it's true or they don't know, that's a different story.

Point being, it may not be such an issue. Let them measure the clearances between the lobes and lifters, if they are within spec I would imagine there should be no issue.

[amorlv70]

Originally Posted by classicswede

Any visable valve or gasket damage?

Gasket was absolutely fine, valves got progressively more brown towards cyl5, and there was dark deposit on the cam lobes of the cylinders that lost compression as well as on the underside of the valve cover. No visible valve recession to the eye, and my engine seems to have solid tappets, not hydraulic as most seem to suggest. I have a theory that I did not replace the vapour filter soon enough and it has got dirty and starved the latter cylinders of gas and leaned out, not sure if this is possible, but would make sense if injector 1 recieves the gas first.

Edit: ClassicSwede, which NGK plugs would you recommend I get? They seem to do multiple types and GSF has different plugs as well for LPG/CNG. I was just after basic standard ones that I will replace every 10k or something.


Cyl1
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Cyl2
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Cyl3
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Cyl4
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Cyl5
5.jpg