13b, 1986. Unknown mileage believed to be 50k-60k ish.

When I first got this motor, I tested it and I believe the results came back ~100psi each rotor. I had it in a car that ran great, got 22mpg-ish, decent power for N/A, ran strong. I pulled it out, transplanted it into a GXL and it's sat for a couple of months. I got it running, ran some water through it to clean it out and now I get 6 strong exhaust pulses, not 5. A seal must have been stuck or something.

I've had the car around the block once or twice and it seems to still be in good condition, albeit a large vacuum leak preventing it from idling.

I tested the compression last night and I dunno if it's my $7 harbor freight tester or what, but I got 90 front/65 rear While holding the pressure release button, the needle didn't even really move.

Would the car even run with compression that low? What's going on?

 

Yeah it'll run. just not well at all. Where's your vacuum leak at? If it's at an injector or something on the rotor housing you could be loosing compression through the leak.
Did ou use the same tester for both times?

 

You are either going to get 6 consistent pulses or 4. You will never get 5.

 

That sounds like an issue with your gauge. You should take the valve out of the gauge by the way. Don't just hold down the release button. Fix your vacuum leak and just drive it. If it runs well, that should be what matters. It will probably start and run all the way down to 60psi per face. It will just get hot start problems the weaker it is.

Josh

 

I didn't think 5 pulses would make sense either, but I'm positive it did make 5 pulses at one point. I have video of it somewhere. Perhaps it was a side seal or something.

It's very possible that the injectors are leaking (probable, actually) and that makes alot of sense, I don't know why I didn't think about it. Thanks for the help.

 

Oh, yes, it's the same compression tester. I don't think I can remove the valve, it's really cheap.

I'm looking to sell this motor which is why I want concrete numbers. Motor runs great and pulls strong but I don't want to mislead anybody.

 

Low compression makes me cry

 

put some oil into the spark plug holes, and try again. no oil will not make a very good seal.

 

By 5 pulses I assume you mean 3 pulses for the front and 2 for the rear. That is possible, because if a side seal is stuck or blown you will still see compression on the other two faces.

 

dont hold down the release valve. that'll give incorrect readings. if u cant remove the valve then just do the test without holding it down and at least u will get an accurate reading of the strongest side.

 

I can try that I suppose. That would be a wet compression test.

Several sites have mentioned doing this to measure each individual face. The needle didn't move with the button held down so the numbers I have are from doing it normally.

I believe so, and I agree with you.

I'll pull off the intake manifold and see if I can find another vacuum leak and wet test it and post the results.

 

oh my bad. well considering how much the numbers have dropped, that sucks. well a wet test will always return back stronger numbers so dont be surprised if ur back up to 100. how is the charge in ur battery? if the battery was at full charge when u first tested it then that could explain the stronger numbers. battery voltage will also change readings but that doesnt explain the difference between the front and rear. best of luck.

 

ah, haven't charged the battery in awhile either, I'll throw it on there right now and report back when I test it tonight or tomorrow.


Should I pull both trailing plugs out when I test it or just the side I am testing?

 

With a charged battery, no intake manifold, and a teaspoon of oil, it did 100/95. That sounds closer to correct!

Thanks.

 

oh wow i gave good useful advice finally. hadnt had one of those in a while.