Compression test

[westcoasttowing]

I want to test my compression on my '95. I was told to remove all glow plugs. Before I do it, should I disconnect the wiring harness to the injector pump so fuel dosent' spray out everywhere?

[DmaxMaverick]

You only need to disconnect the ESS (Engine Stop Solenoid) connector at the IP, the wire to the cylinder-shaped solenoid on top of the pump. This will prevent fuel being sent to the cylinders. This may set a DTC for the solenoid, but if you disconnect the IP harness, it will set a bunch of them, and some are difficult to clear immediately, and it may trigger limp mode for a few starts after.

For the compression test, the engine needs to be up to operating temp, all glow plugs out, and each cylinder test at 6 "puffs". Move along quickly, to test all cylinders at the same temp.

[westcoasttowing]

just did my compression test. I had to modify one of my adaptors in my kit. So when I tightened it in the glow plug threads there is still a tiny wiggle. So I don't know if the actual #'s are right but they are consistent at 200 lbs on each cylinder. My truck idles fine but there is a misfire when revving. prior to getting to this point I got an 094 code which was misfire cyl. 4 I went ahead and put all new marine injectors hoping that was the problem but apparently not. So that's why i did a compression test. Only 2 things that cause misfire and that's either low compression or a fuel issue, right?

[DennisG01]

Someone else can probably give you more specific numbers, but I believe you should see somewhere in the 350+ PSI range. However... since all of your numbers are consistent, it 'could' be a tester gauge problem - but that's a lot to be off.

[westcoasttowing]

Yeah I think this used block I bought is junk. I had a mechanic inspect it before I bought it and he said it looked good. he uncapped the main bearings, said no excessive wear, he said all of the cylinders still had crosscut marks so he assumed rings were good. It has brand new heads/ injectors but i used the old pushrods. ... my question is would an used motor lose compression like that in all 8 cylinders? if so the thing must have 600K miles on the sumbitch

[DennisG01]

my question is would an used motor lose compression like that in all 8 cylinders?

That's the part that struck me as odd, too. They're just too balanced. While I don't have an immensely strong background in this type of thing, to me it seems like too much of a coincidence that they would be that even. Which is why I was wondering about your gauge. Unless, of course, I'm off base on the PSI spec.

[DmaxMaverick]

If you did the compression test on a cold engine, the values are essentially useless. They will not indicate the wear of the engine, but if they were all consistently the same, I'd suspect an injector, valve, valve train issue, or head gasket.

[westcoasttowing]

latest symptom is lots of blow by after it warms up. its coming from the dipstick tube and oil filler tube and out of the crankcase breather filter into the turbo. No exhaust smoke though. only at start up. and it has an intermittent squeal. Ready to pour gas on it and burn it down. :(
:mad:

[westcoasttowing]

will a carburated 454 work with my manual 5 speed? Tired of this pile of **** engine

[AKMark]

Yes

Chevy blessed us with not changing the transmission bellhousing pattern.