Compression check results.

You 'can' have that much carbon in it.....

You are the guy with the shitty wires and a miss?

I have opened up more than a few and there can be a lot in there. I did the head gasket on mine a while back and decarboned it before hand. There were still a couple loose chunks of carbon in it because I didn't road run it after the clean and these chunks were close to 1/8" thick, more than 1/16" for sure. This engine only had 40K on it.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

DougW wrote:

Your compression is good.

I would chalk any error (high reading) up to one of two things, or a combination of them. Either you pumped the cylinders up too many times, or your tester is out of calibration. Either way, you made the same error across all six cylinders and came up with numbers that arer within spec for the allowable spread.

L.W. (ßill) Hughes III did pass the time by typing:

Erm..

crap.

no. :(

That would explain why the engine didn't turn over so easily. heh.

I did remember to disconnect the ignition primary and pull the fuel pump relay though. :)

Mike Romain did pass the time by typing:

Just one shitty wire and that was on #6. Installed a new set of wires (thank you lifetime warantee) and it runs like a top. (slightly wobly, and ticks a bit, but like a top)

Wow, that is a lot of carbon buildup! Don't think it's that bad or with my extra boost I'd be getting a lot of detonation. The plugs only had a very thin flaky layer of carbon on them. Still too much though.

Probably O2 sensor again. Had this problem before with the sensor reading just a smidge off but still in spec. Wish there was an easy way to test those sensors apart from having a scope.

Opening the butterfly will allow air to enter easier. It could be the cause of low readings, but will not be the cause of high readings. Your high readings came from cranking until the needle stopped moving.

You could repeat the test and crank 3 times with the butterfly fully open, but I think you will end up with nearly identical results. I don't remember why you felt a need to do this test, but the compression looks good from here.

CRWLR did pass the time by typing:

I had a rough idle and a bad wire. So while I was in there it was easy to just pull/clean/regap the plugs and do a quick compression test. Already had the comression gauge in my toolbin.

Since the numbers are all real close with none terribly low I'm going to wait till the next sparkplug change and do it then.

L.W. (ßill) Hughes III did pass the time by typing:

It wouldn't. The blower only comes on if there is demand, otherwise it bypasses internally. That and at cranking speed there isn't enough rpm anyway.

You got a blower on there?

Ok, I have no idea what that could do to the compression on cranking. What does it rely on for 'demand'? It could be seeing high vacuum with the throttle plate closed and be spinning up.

Meanwhile if you have no ping issues, then you have no issues.

Mike

DougW wrote:

Mike Romain did pass the time by typing:

Yep. :)

Compression at idle/crank should be identical to a normally aspirated engine. (hard to type whle slightly buzzed) :D

I foobared and didn't block the throttle open. Next time.

That's what I thought. Just wanted to get a basline and find out for sure if there wasn't a big ass leak causing the rough idle.

L.W. (ßill) Hughes III did pass the time by typing:

It does turn, but compression at cranking is +0psi.

I put demand on the charger it closes off the bypass and start compressingair, till then it's more of a slight restriction than anything else. I can watch the boost/vac gauge and see perfectly normal numbers till the engine starts seeing load. Idle is about 12 in vac in drive while stopped or 18in while decelerating by letting off the skinny pedal.

I guess I'm just use to the my stock gear driven Detroits, or a friends half speed 671

that did notvary. But I did have an centrifugal that open the pulley to double thespeed: God Bless America, ßill O|||||||Omailto: snipped-for-privacy@aol.com

Good to know, thanks.

Mike

DougW wrote: