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Discussion Starter · #1 ·
got 89 g20 van buddy was drivin down road when just died checked fuel delivery all good, tryed to do compression test and got nothin , did time chain cause wasnt sure but turns out was in time . got smoke out tail pipe when crankin,so i know i got fuel ,whats this depression valve about and is that responsible for no compression
 

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R.I.P. Sam
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:welcome:

how did you try to do compression test, if smoke out of tailpipe, its got something.

what depression valve are you talking about?
 

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Ex- 6BT Square Body Man
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depression regulator valve AKA "CDR" OR "tuna can" serves kind of the same purpose as a "pcv" on a gasser
Has no effect on the compression in the motor.
 

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R.I.P. Sam
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CDR just regulates cankcase pressure, it has no effect on compression.
I doubt compression would dissapear that fast unless crank broke. I'd be thinking more about fuel delivery or air in the fuel.
how well did it start before this happened?
 

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R.I.P. Sam
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have you checked to see if your getting good fuel flow before the filter and after?
 

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Ya unless all the rods are broken or the crank is broken at the rear main there has to be some compression.

Pull ALL the glow pugs and put your finger over the hole 1 at a time and crank. These motors build close to 400 psi so it will blow your finger away from the head if there is compression.

I would also crack each injector line loose before the cheapy comp test to see if there is fuel actually coming out of the hard lines. If there isn't it's a fuel supply or IP issue.

Keep us in the loop and we can get ya through this.
 

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Are you getting white smoke out of one bank and not the other?

Rocker arm retaining clip coming out can cause 0 compression
 

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Mad (Sean) Max
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I borrowed a compression tester from my mechanic one time and got nothing. It was basically new, he had bought it a few years earlier but had just opened the packaging and said "huh, neat" then put it in a drawer. Anyway when I brought it back to him i mentioned that I got no reading, he came out, hooked it up, we cranked it and got nothing. "huh, junk" it went back in the drawer.

I guess I'm just saying that tools don't always work right. I had lots of compression. I agree with the others that if you're getting smoke you have compression.
 
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