4 replies to this topic

[Otto’s Garage]

Good day all,

I have an 88 998cc.  I recently started having an issue with my engine just suddenly started running very rich. I’ve gone through the carb (float appears to be working fine), and ignition system, annd timing everything seems fine but no luck correcting the issue. I did a compression check and it appears very low at 90-92 psi across all cylinders.  I added a teaspoon of oil and it jumped a couple pounds but still below 95. Based on that I assume the rings at the very least are probably pretty tired.  I borescoped the engine, the pistons and cylinder walls look ok at least visually. Budget is tight right now, is it possible I can get away with a hone and rings with that low psi or will I likely need to punch out the block. I know it’s tough to answer without more info, I don’t know the history of the engine but it has just over 50k on the clock, Trying figure out the best option prior to tearing into it.

[Spider]

You really won't know until its stripped and measured, but I'd almost certainly say given the mileage and that it's been running rich, it'll have wear in it.

[Otto’s Garage]

You really won't know until it’s stripped and measured, but I'd almost certainly say given the mileage and that it's been running rich, it'll have wear in it.

I kinda figured it wouldn’t likely be that easy.  Guess I better just tear into it and hope for the best!

[MiniMadRacer]

Those figures do seem very low, but also very even across the cylinders, (which is good), and when you added the oil you said it only jumped up by a few pounds. I would expect it to jump up significantly if there was bore / ring wear. As Spider has intimated it may well need a strip down and rebuild, but what are the symptoms you are having in normal running.

 

I would be tempted to maybe get / borrow another guage, and test as follows:-

 

1) Fully charge battery

2) All plugs out (label the leads first)

3) Adjust the valve clearances correctly

4) Throttle fully open

5) Install the guage in each cylinder in turn and test

 

As a side note, I always do a compression check on a hot engine, up to its normal working temparature

[weef]

A compression test is all well and good but there are too many variables as mentioned above.

A cylinder leak down test using a quality set up that operates at 100PSI is a more accurate procedure and helps identify/ pinpiont any problems.