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Compr test results- what do you think?

davo727

davo727

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Location
Cleveland, Texas
Hello, My first diesel, been a chevy truck guy forever.


#1- 330 psi #2- 390 psi
3- 360 4- 370
5- 350 6 -350
7- 360 8 -270



Engine was warm, idled for a few min. Bought the truck not running , had been sitting for months. New lift pump and fuel filter and oil change and bled inj lines and got it running. Put 5 gal of fresh fuel in it but dont know what was in tank before. It idles good but in neutral giving it throttle it smokes a lot- blue and sounds rough. Cant drive it clutch was installed wrong which is the reason they parked it. I will pull trans and clutch this weekend.

Does that 270 on #8 mean its hosed ? Is it even firing with the compression at 270? This is not gonna be a daily driver, I got it to pull a gooseneck trailer for when I start clearing and doing construction on my property 25 mi from here. Thanks for you guys thoughts on this, Dave
 
Any of you guys have an opinion on whether a 270 lb compr reading on #8 is a terrible thing , or dont worry about it and just run it?
 
Here are the numbers from my compression check.

1 = 380 - 2 = 340
3 = 380 - 4 = 320
5 = 400 - 6 = 320
7 = 280 - 8 = 360

I pulled the engine because it was a rebuild and only had 10,000 miles on it and I wanted the rebuilder to replace the engine. Also the anti freeze had got into the oil (blown gasket or head cracked) and had corroded away the rod bearings.

Even with the few low cylinders it ran like a champ - tons of power.

Vibration was bad but that could have also been caused by the rotted engine mounts and balancer.

If it were me and everything else were fine I would keep on running.


K2500 Suburban
 
Thanks for the response and your reccomendation . This thing had sat for months due to the clutch issue. I think I have it running on all 8 now- bled inj lines. Im going to drain and clean the fuel tank, CDR cannister was missing need to add that.

And Im not sure whats up with the wastegate- its a 92 and it just has a spring loaded can with a rod to the wastegate, no vac lines or anything else going to that can. Which way on the rod travel is closed and which is open for the wastegate? Fwd or aft? Hope to get the trans back in it this week so I can test drive it. Right now I wonder if the turbo is doing anything.

This truck has no vacuum pump- is it supposed to?

Coolant looks good and no bubbles or foaming going on and didnt see any coolant in the oil.
 
I was thinking about this on the way to work today.

I would recommend pulling the coolant crossover pipe and checking for bubbling coolant.
It takes less than an hour and will help with the decision process.

Mine was very active on the drivers side and sure enough the valves were rusty and pitted and also the bore had worn heavily in #7 (I have some pictures and shall try and find them). The rebuilder assured me that the head was fine and was just the gasket. I asked him to put this head back on the drivers side just in case the head is bad and I can replace it easily.
 
i believe that you should have around 400 psi per cylinder. the 270 is quite low. i'd say run the test on that cylinder again just to make sure you get the same results before doing anything like pulling the engine out for a rebuild.
 
davo727 said:
Thanks for the response and your reccomendation . This thing had sat for months due to the clutch issue. I think I have it running on all 8 now- bled inj lines. Im going to drain and clean the fuel tank, CDR cannister was missing need to add that.

And Im not sure whats up with the wastegate- its a 92 and it just has a spring loaded can with a rod to the wastegate, no vac lines or anything else going to that can. Which way on the rod travel is closed and which is open for the wastegate? Fwd or aft? Hope to get the trans back in it this week so I can test drive it. Right now I wonder if the turbo is doing anything.

This truck has no vacuum pump- is it supposed to?

Coolant looks good and no bubbles or foaming going on and didnt see any coolant in the oil.
Click to expand...

IIRC, from what I read, 92 don't have vacuum system. It is using mechanical wastegate. You are lucky. IP is mechanical too. The expert or people who own 92 can probably verify that.
 
I also think 92 is mechanical wastegate(better).Throw a squirt of motor oil in the low cylinder and repeat test see if you get a substantial diffrence. if you do the rings are toast, if you don't the head gasket or valves could be the culprit.
 
chrisk1500 said:
Hope like hell that the oil in the cylinders doesn't ignite...
Click to expand...

Forgot we're talkin diesel. My bad.
If you used a squirt of maybe like 60 w and all the other glows are pulled for the test think it would still lite off ? I'm assuming fuel is disabled during a test ?
Is there anything else you could use to test it ?
I had a dead cylinder once and put shop air into it to see where I heard it more through intake, exhaust or crankcase. Unfortunatly it was crankcase. was a cracked piston. Lands between the rings broken and one of the compression rings gone. ONe thing for sure 100lbs low is not a good sign.
 
Last edited:
Some Gee whiz info: Truck has an April 1996 141 casting block in it.

Guess that would explain the GM Goodwrench stickers on the valve covers.
 
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