Updated: Compression Test Results

[marshallnoise]

I charged up the battery and left the battery charger on while testing and did NOT have the throttle open and got the following numbers:

Original Test Results: (1) 135, (2) 92, (3) 92, (4) 103, (5) 105, (6) 135
*Edit per richard.bratton, I rearranged the order of the compression test results to match the correct naming convention.*

Am I in need of a freshen up with new rings and a hone?

Thought just occurred to me: I should probably get the valves adjusted prior to running the compression test, right? I would assume that would be a factor. True?

Update:
I did the valve adjustments, nearly all of them were tight with a few a tad bit loose. I didn't snap a picture but the head, lobes and all the top end (didn't check bearings) looked SUPER clean. Was very happy to see that. No varnish at all. Pulled the plugs (all of them) and was able to retest number 1 and number 2 with the throttle wide open before having to pack it in for the evening: (1) 180, (2) 110. I will complete the test another day and also do a wet compression run to see where my problem spots are.

Pretty clear to me even with an incomplete test that I will have to pull some of the pistons, rehone and rering. No biggie.

This thread can die now.

[richard.bratton]

Open the the throttle, pull the fuel pump relay and try again. I hope you get better numbers because those are scary low and your engine is likely in need of a rebuild. FYI, cylinder #1 is closest to the radiator. Your next step is a leak down test. How many miles on the engine?

[marshallnoise]

Open the the throttle, pull the fuel pump relay and try again. I hope you get better numbers because those are scary low and your engine is likely in need of a rebuild. FYI, cylinder #1 is closest to the radiator. Your next step is a leak down test. How many miles on the engine?

I will do a valve adjustment first, then do the test as you prescribed. I did pull the fuel pump fuse prior to testing.

Should I also pull all the plugs? I would think it would make it easier to spin the motor. I just tested each cylinder with all the other plugs in (not connected to the boot).

EDIT: And it was a 90 735iL with 177K.

[nick526]

If you pull the plugs (I would) you can also run a wet compression test. Put a capfull of oil in the spark plug hole for any cylinder that shows low compression. If the compression then improves significantly, most likey your rings are worn out.

[navytapaul]

I'd do it anyways, won't hurt anything and at least you'll feel better knowing your bottom end is nice and clean.

[marshallnoise]

I'd do it anyways, won't hurt anything and at least you'll feel better knowing your bottom end is nice and clean.

Yeah, I may go ahead and do it anyway. I hear the parts aren't too expensive on this engine anyway.

I will do a proper compression test with the valves adjusted, throttle wide open and the battery fully charged first, then do it again with capfuls of oil. It doesn't take that much effort and if the motor is strong...then see what gives.

All I know is that this whole project is moving WAY fast for a methodical accountant planner type guy. Haha!!! :shock:

[navytapaul]

they are pretty cheap, only reason i didn't do mine was because it was recently rebuilt or I would have. m10's and m30's use the same rings and bearings so it will save money there.

[marshallnoise]

they are pretty cheap, only reason i didn't do mine was because it was recently rebuilt or I would have. m10's and m30's use the same rings and bearings so it will save money there.

Sweet. That's even better news. I will take a stab at cracking open the valve cover and seeing what I have under there. If its decently clean, then I will march forward.