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Old 1 Week Ago   #1
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Low compression on all cylinders

This actually happened months ago, but only had a chance to look into it now.

My '91 Panda 4x4 was running a bit poorly then it stalled and wouldn't start. It was getting fuel, it had a spark, and and was turning over well - so I was confused.

At last I had a chance to look at it today and so I started with a compression test. All the cylinders were around 20 to 30 psi. After a google, I thought it was maybe fuel washed. So I added a little engine oil to each cylinder and disconnected the fuel. Compression remains low, maybe 5psi more with the oil. Surely oil would have revived the compression a little more?

Any ideas what is wrong? The engine has been idling poorly for sometime so I quite often run with a little choke to stop stalling at lights is town. Could I have flooded, fuel washed the cylinders and worn out the piston rings? On all 4 cylinders???

I'm also thinking the carb might be at fault for the not starting and may need a service, but that doesn't help the compression problem.
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Last edited by nitro_warrior; 1 Week Ago at 23:28.
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Old 1 Week Ago   #2
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Re: Low compression on all cylinders

Hey Nitro. Been a while. The HG was my 1st thought but again you'd expect some difference between cylinders. Has it overheated at all.
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Old 6 Days Ago   #3
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Re: Low compression on all cylinders

I'd verify the compression tester is reading correctly first!
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Old 6 Days Ago   #4
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Re: Low compression on all cylinders

Quote Originally Posted by panda1408 View Post
I'd verify the compression tester is reading correctly first!

Most things that'll cause a loss of compression are unlikely to affect all the cylinders simultaneously. even reading usually means you're OK. Maybe cam timing? belt slipped a couple of teeth?
Or wildly speculating - cam lobes worn. Didn't you have an issue with wear on the fuel pump drive? maybe that's not the only bit that wasn't getting properly lubed.
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Old 5 Days Ago   #5
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Re: Low compression on all cylinders

Hi guys, good to be back on the forum, been a while! Thanks for the suggestions.

A bit more info. I actually did question the compression tester and replaced it for a better one. I checked it on my air compressor too and the readings matched so I think the compression tester is good.

A few years ago (er at least 7...) I replaced all the valve stem seals, ground the valve seats and replaced the head gasket. It ran ok after that. Though I don't think compression has ever been that great (I hazily recall 70-90 from the last time)

Thinking aloud. For there not to be compression it has to be either
  1. Head gasket
  2. Piston Rings
  3. Valve seats

Have I missed anything? Any other ways of checking the above items?
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Old 5 Days Ago   #6
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Re: Low compression on all cylinders

Or cam timing. If you've got valves opening out of time you could finish up with less of an inlet charge or exhaust valves opening early, either of which might give you less, but even compression as it will affect all cylinders. Your oil in the bores check would make no difference in that case either. Did you check the cam timing as part of your initial fault finding?
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Old 4 Days Ago   #7
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Re: Low compression on all cylinders

Cam timing, yes missed that in your first post. That is a good call. My timing belt is embarrassingly old too.

Another piece of the jigsaw... at the time I was getting spark, getting fuel but the engine was turning over really easily. I remember thinking it didn't feel right, which supports to the low compression readings and the sudden change would give weight to the timing belt jumping... might be on to something...

I have a late summer holiday next week but will take a look at the cam timing when I get back.
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