3B compression...whats a good number? (1 Viewer)

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

Joined
Dec 15, 2004
Threads
132
Messages
1,132
Location
Folsom, CA
Guys,

I tried a search on this but the datbase is down. Whats a good DRY compression test reading on a 3B with 200kms on the clock?
 
Hmmm....how's 340? I didn't want to say anything first so's not to taint my sample audience
 
340 cross the board or one cyl 340?

still that's low for the 3B. I think min in the FSM is something like 400...
 
nope..not 1 cylindar...all 4 accross. No wonder I make s*** power at 9lbs boost. Anyone else out there who has actually done a compression test? I'm getting worried here...help me feel better
 
mine was
405
400
425
400
like 2-3 years ago

but I haven't done it since I rebuilt the head on this. I'm very curious as to what my #'s are today. I just can't spend 100+ on a guage and I dunno anyone with a diesel compression tester..

You have to be burning some oil.. no?
 
Is the glow plug hole are the place to make the compression test ?
 
wesintl said:
340 cross the board or one cyl 340?

still that's low for the 3B. I think min in the FSM is something like 400...
rebuild is 280...
 
Make certain you disconnect the EDIC linkage when compression testing so the injectors do not load fuel into the cylinders..
 
Aslo make sure your compression tester is OK. I just had mine re-calibrated. It was 20lbs off.

The cheaper testers tend to fail often and they all get contaminated easily..

My 3B is

415
420
420
415
 
ya...somethings rotten in denmark here. This thing has been babied it's whole life, there has to be something wrong with 340. I just looked in the FSM and waynes pretty much bang on...427 is spec and 284 is min
 
David*BJ70 said:
Is the glow plug hole are the place to make the compression test ?

I think on direct inj you can use the injector plug hole,Im not 100% though
 
that is excellent numbers, seems like you might have a bit of carbon built up on a couple cylinders...
accordign to the manual "425 or more", i tested a 3B a few years back that had 480, 425, 425, 425... i tested it mor ethan once to make sure it wasn't the gauge... not sure why but the customer was happy...
 
Is this a cold engine or a hot one? The numbers are different. The real numbers are on a hot engine. I was told that they can be tough to start and run when the pressure is low as well because of insufficient pressure for ignition.

I think my compression gauge fits the injector holes. I haven't done a compression test for a few years.
 
Just tested my BJ42 and am NOT happy.... 420, 390, 375, 375 Thats dry and at operating temp. Will try a wet test in the next week or so.

Colby
 
colby1979 said:
Just tested my BJ42 and am NOT happy.... 420, 390, 375, 375 Thats dry and at operating temp. Will try a wet test in the next week or so.
Colby

Did you do a valve adjustment 1st?

gb
 

Users who are viewing this thread

Back
Top Bottom