Compression test results

[minxgirl]

OK I put this in my other thread - but Im resposting to get some opinions on my interpretation of the results...

dry test:
135
140
140
140

wet test
170
170
210
170

OK so Google tells me the petrol getting into the sump is the compression rings, and the oil burning (smoke from exhaust w/e) is the oil rings....
Does that sound about right?

[slide86]

if you are getting petrol in the sump then i would say your rings are definetly shot. but it would be really bad, ie the engine wouldnt run on one/all cylinders.

the oil burning is either the rings or your valve stem seals.

the dry test looks ok, pretty even, although the pressures may be low???

[Negative Boost]

What engine are we looking at here?

[minxgirl]

2tg-eu but without the efi on it

[Dale]

The figures are a little low, not catastrophic though.. I think they're meant to be about 180psi?

The rings probably aren't too bad considering the fluctuations between wet/dry.. I doubt they'd be bad enough to be letting fuel into the oil, I'd say that would be from a leak in the carby dripping into the intake manifold then pooling in the sump or something along those lines

[minxgirl]

Would the carbies be leaking 2 weeks after having them rebuilt though? (the fuel in the oil prob was there before and after too)

[Dale]

Well you'd hope they wouldn't be, but you never know!
Realistically with those compression results most of the fuel going in, should be igniting and what doesn't should come out the exhaust so I'd tend to think the fuel is coming from somewhere else.. when the engine isn't running

[minxgirl]

How do I find out where the fuel is getting into the sump? If I take it back to the mechanics it will be there 3 weeks I need my car!

[gianttomato]

As for the comp results, sounds like motor is probably a bit tired. All the cylinders are even but seems like 140 is a little on the low side for a 2TG (maybe someone with a manual would like to chime in?). A wet test will always result in slightly higher numbers than a dry test however you would expect there to be a big increase in compression (30 psi or more) with the wet test if there is a ring problem - which I suspect you have.

You can have a sample of your oil analysed to see if there is fuel in the oil - easy enough to do. However, given the comp test results, I think you could better redirect funds.

The usual suspects for fuel getting into the oil are torn mechanical fuel pump diaphragm (perhaps it might have a small enough hole such that it still pumps enough fuel to the carbs but leaks into the block and oil) or from excess fuel via the carbs (however the engine would be running mighty rich - clouds of black smoke). However, given the results of your comp test, I would say your rings are worn.

Maybe time for a freshen up? Motor is 30 years old after all.....

[TheToyman75]

Jill,

Being a 2T-GEU you have a low compression engine. As such those compression results you have are actually quite good.

Have you changed your engine oil since the carbies were rebuilt ? If not change the engine oil and checkthe oil level after a restart and let it settle. Then check the oil level again in a week. If its rising up the dipstick then you are most likely washing the bores with fuel as a result of it running much to rich. If that is the case you will find your spark plugs are black on the electrodes too.

[minxgirl]

I changed the oil on friday, I cleaned the plugs on friday. (mobil super hp 20w-50) Rechecked oil on Sunday and there was definitely petrol in it which was easy to smell, and yes the level had risen on the dipstick. Plugs extremely fouled again black carbon fouling (since friday and just a drive around the block - and oil on plug no. 3 but thats not a new thing either) My carbs were rebuilt like less than $15 fuels worth of driving ago *LOL* if that makes sense...so what could be making it run rich then? I do have an electric fuel pump on it too btw.

[gianttomato]

That's a BIG increase in compression for the wet test Rod.

[minxgirl]

*tears hair out* *LOL*
OMFG can someone tell me what the results mean?? *LOL*
Everyone interprets this differently...
Im confused

[Grega]

minxgirl what sort of fuel pump are you running?
and how many PSI is it pushing to your mikunis?
if you're pushing too much fuel to the carbs they may be having issues with getting too much fuel supplied to them which may be upsetting the balance.. easiest way to check is get a fuel pressure pressure gauge and put it on the furthest from the supply of fuel in to check how much fuel pressure is delivered.
it may just be a case of a regulator in the way to drop the pressure back a bit
when your carbs were rebuilt did you take em somewhere, get em built, then put em back on?
or did these dudes fit them back to the car after rebuild?

[gianttomato]

I'm no 2T expert but I'd be concerned at the size of the increase in compression with the wet test.

From memory, that increase with the wet test should be less than 10 percent (maybe 15) of the original value (irrespective of engine).

Worth refering to a manual re compression test limits.