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Technical Low compression on all cylinders

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Technical Low compression on all cylinders

nitro_warrior

nitro_warrior

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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??? :confused:

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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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.
 
panda1408 said:
I'd verify the compression tester is reading correctly first!
Click to expand...
:yeahthat:
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.
 
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?
 
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?
 
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.
 
Might be on to something here. See pictures. Timing is a long way out. A surprising amount. I would have thought one or two teeth at most, but the cam shaft is a good quarter turn out of position! :eek: Is that normal for a timing belt slipping?

I will order a new belt install and check the pressure again. Thanks for steering me in presumably the right direction!

AKBeXqj.jpg


p13YuQ5.jpg


***EDIT***
When cleaning the timing cover I spotted there was wear on the inside. Definitly some untoward timing belt action been happening!

dpRAPqq.jpg
 
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Timing belt will slip if belt becomes slack. Tensioner might be failing, or more common, water pump bearings. A failing water pump will slacken the belt tension.

Whilst the belt is off it is a false economy not to replace the pump.
 
I replaced the water pump not so long ago - couple of years (and didn't replace the belt! :eek:) so hopefully the pump is still ok. Very much the school of thought of non-interference no problem!
Will take a look at the pump and the tensioner whilst i'm replaceing the belt.
 
Got a chance to replace the belt and fix the timing yesterday.

Changed the tensioner bearing too - it was knackered, and running dry. I left the water pump as it is actually quite new.

Ran the vacuum test again. 100 psi on cylinder 1, good. 15 psi cylinder 2 and 3, not so good. Back to 100 psi on cylinder 4. Headgasket then.

A quick strip down revealed the gasket had blown between 2 and 3.

ptFSLZd.jpg


Good double whammy of issues. I suspect the engine was running for a while with the blown gasket, I imagine a blow between 2 and 3 doesn't make a huge difference as the cylinders are in phase. Then a combo of lumpy firing and a worn tension bearing threw the timing.

Hoping I've got away with with just a new gasket, the head and block look like they should be ok after a clean up.

Also got a slight crack on the exhaust manifold - just the flange for one of bolts to connect to the exhaust. Take it 4wd manifolds are the same as 2wd?
 
Just been looking at exhaust manifolds and spotted this on ebay

STAINLESS STEEL RACE DECAT DE CAT EXHAUST MANIFOLD FOR FIAT 500 PANDA 1.2 09-13
G4uYAAb.jpg



Aside from the difference in the down pipe. Would this fit to the head? The bolt pattern and gasket look the same. Looks like quite a tempting option to make fit, or spur me on to my often contemplated stainless exhaust...
 
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It is a long time since I had to remove the head from one of these.
It appears that the manifold gasket is actually four separate gaskets, one for each cylinder, just an oval gasket, a round hole in the middle for the exhaust, and two bolt holes.

Payen, oneof the oldest gasket brands list the same part nmber for 1.0, 1.1 and 1.2 FIRE engines, so at least the port and bolt holes should be ok.

BUT!
As these are separate gaskets, spacing apart might change.
The 1.2 engine is taller, to allow the longer stroke, so the exhaust downpipe is longer for the exhaust to pass under the sump. Fitting this manifold to a 1.0 or 1.1 is likely to put the exhaust lower to the ground, giving initially clearance issues, but will also destroy the rubber mountings quickly.
The exhaust is designed to sit horizontally along under the car, hanging gently on its rubber mountings. If the downpipe is longer, the rest of the exhaust will slope gently upwards towards the rear. The first mountings (centre), will take all the weight, as the rear mountings will do nothing except inhibit sideways movement. The centre mountings will give up under the strain fairly quickly, requiring regular replacement. The rear of the exhaust is also likely to hit the underside of the car.

I had this problem many years ago, with a Fiat Argenta. An aftermarket exhaust had a downpipe 5mm too long. The cente mountings lasted around a fortnight each until the pipe was replaced.
 
portland_bill said:
It is a long time since I had to remove the head from one of these.
It appears that the manifold gasket is actually four separate gaskets, one for each cylinder, just an oval gasket, a round hole in the middle for the exhaust, and two bolt holes.

Payen, oneof the oldest gasket brands list the same part nmber for 1.0, 1.1 and 1.2 FIRE engines, so at least the port and bolt holes should be ok.

BUT!
As these are separate gaskets, spacing apart might change.
The 1.2 engine is taller, to allow the longer stroke, so the exhaust downpipe is longer for the exhaust to pass under the sump. Fitting this manifold to a 1.0 or 1.1 is likely to put the exhaust lower to the ground, giving initially clearance issues, but will also destroy the rubber mountings quickly.
The exhaust is designed to sit horizontally along under the car, hanging gently on its rubber mountings. If the downpipe is longer, the rest of the exhaust will slope gently upwards towards the rear. The first mountings (centre), will take all the weight, as the rear mountings will do nothing except inhibit sideways movement. The centre mountings will give up under the strain fairly quickly, requiring regular replacement. The rear of the exhaust is also likely to hit the underside of the car.

I had this problem many years ago, with a Fiat Argenta. An aftermarket exhaust had a downpipe 5mm too long. The cente mountings lasted around a fortnight each until the pipe was replaced.
Click to expand...

Thanks. Yes, I suspect it would be too long. It is also quite a different to the stock exhaust manifold which doesn't have a long "tail" and rather bolts to the exhaust near the top of the engine. If I were to go for it I would be cutting the downpipe shorter and fabricating a new coupling to the rest of the exhaust.
 
Decided to go for it and order the stainless manifold. I have actually welded the tab back on the old manifold and will use that for now. However, the stainless one fits the stud pattern and looks good. 2" diameter rather than the stock 1-1/2". I will check how low to the ground it is. Ultimately I will probably take it to get a custom stainless system put on using this as a starting point.

LWPSCrI.jpg
 
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