cylinder compression test

[marblecrusher]

Alright I was about to install some new injectors then decided while i was doin that i might as well pressure test each of the cylinders and see how there doin Im goin on 450k just curious lol. So whats normal psi on compression test wet and dry test?

Thanks

-Jordan-

 

[marblecrusher]

350-400 psi, does that sound right? Thats the only answer ive found digging around and it didnt seem very reassuring

 

[icanfixall]

Do not do a wet test. Anything you squirt into the cylinders will make fuel.... Oil is fuel for these motors. Just warm up the motor till its at operating temp. Then let it cool enough so you can safely work on it. Thats all you really need... Remember that oil is being squirted up under the pistons anytime the motor is turning so that will do for a wet test... Hope that makes you feel better about doing a wet test. These aren't gasser motors and I think some of us on these forums forget that....

 

[marblecrusher]

yea that makes sense, this is the first time for a compression test on a diesel so im used doin a wet and a dry test, thanks though, do those psi numbers sound right?

 

[RLDSL]

yea that makes sense, this is the first time for a compression test on a diesel so im used doin a wet and a dry test, thanks though, do those psi numbers sound right?

Right in that neighborhood would be decent

 

[marblecrusher]

sounds good, thanks

 

[icanfixall]

Marble... This is a fair warning about doing a "wet test"... Oil is fuel for thses motors. These are not gasser motors with huge combustion chambers in the heads. Our heads are flat and the pistons raise up out of the cylinders as much as 31 thousands. That leaves around 40 thousands clearance and not much room for liquids... The only thing that keeps the pistons from hitting the heads is the thickness of the head gasket. You thinking squirting some oil into the precups is going to tell you something important about lbs of compression is flawed. How much oil are you thinking is going to tell you anything. Then the amount of oil you plan on using is going to be close to hydrolocking the motor. Anything close to 15 CC will lock up the motor. The precups will CC out to around 20 CC so use this as information for what you are planning on doing. The oil added to the cylinders will probably not tell you anything about the condition of your motr and the chance of bending a rod is high. These motors are not like a gasser than will benifit from oil used during a compression test. Oil in a cylinder during a compression test for a diesel is fuel to a diesel but... Please post what your numbers are..... Both ways...

 

[marblecrusher]

No im just going to do a dry test, i agree with what your saying about the wet test like i say im used to gasser motors

 

[marblecrusher]

the only access i have to use one for free will be a week before i can get ahold of it and his adapter kit runs for checking through the glow plugs, so im gonna go ahead and do the injectors and get it running then worry about the compression test on down the road, thanks for the advice so far guys

-Jordan-

 

[hesutton]

Sounds like a plan Jordan. When you do your test. Go ahead and remove all the glow plug before you start testing. That way, there is only one cylinder with compression (the one you're testing) and your starter and batteries will thank you.

Heath

 

[marblecrusher]

Ha ha yea that makes sense, the last one I did one on was a little 1.8L acura so i didnt really have that problem lol

 

[Clydesdale]

where does one find said tester to go to 400 psi?

 

[87crewdually]

Around 400 but most importantly all cylinders should be around 10% of each other. 380-420 would be a high/low range.
On a warm engine pull all the glow plugs and unplug the fuel shutoff solinoid wire on the left (driver) side of the Injection pump before testing.

 

[icanfixall]

Look on Ebay under COMPRESSION TESTER. You will find plenty of them there but... A $25.00 tester will be a $25.00 tester. Try to find a snopon used tester and figure on spending around $100.00 gor a good tester. Harbor Freight units wont do a complete 8 cylinder motor before breaking. Several members have bought them and really complained. They are plain junk and a waste of money. Northern Autoparts sells a nice diesel tester. The gauge goes up to 1000 lbs....

 

[Clydesdale]

good to know.. he is a snap on guy.. but was wincing at the $200 for the snap on gauge. Was planning on the HF, we may buy two...