Compression test

[arrowstrap]

I had posted this in another tread but got no input so i assume it was due to my stray from the original content.

i checked my compression and i have 360 to 370 PSI. i did not have the GP adapter so i built one however i due to the angle i can only get about 2 - 3 threads in. i could be getting an inaccurate reading, but if i was would all the cylinders be so close within PSI range? i have heard if a diesel drops below 350 it will not start. i am concerned with the life of my motor if this is the case. any input on compression numbers?

i have ordered the proper fitting but i must wait a week for it's arrival.

1-370
2-366
3-360
4-364
5-360
6-360
7-360
8-360

 

[DaveBen]

Looks good to me. If your compression is low it will not start or run, but you would have plenty of notice, like it would run, but very badly and hard starting. I doubt you have a worn out motor.

Dave

 

[arrowstrap]

this truck starts right up and purrs like a kitten. just trying to figure based on 208k miles and compression if the motor is worth dropping stage 1's into.

 

[DaveBen]

208K miles is nothing to worry about. These engines should over 300,000 miles.

Dave

 

[hheynow]

208K miles is nothing to worry about. These engines should over 300,000 miles.

My '97 has 310K with the original injectors and drives like a bat outta Hades.
Compression looks fine. Have you had any UOAs (used oil analysis)?
A good UOA is another barometer of a healthy engine.

 

[arrowstrap]

hmm.. no UOA.. i'd have to look into where i can get it done.

what exactly would that discover?

 

[trackspeeder]

hmm.. no UOA.. i'd have to look into where i can get it done.

what exactly would that discover?

It will tell you if the engine is tired. Worn rings,bearings ect. The compression number you posted would be a tired engine. In reality I think your adaptor was not working correctly. Your numbers should be 100 higher.

Go for the new injectors. Make your engine happy.

 

[DaveBen]

Most of us use Blackstone Labs for oil analysis. It will show if your oil is breaking down, if it is getting diluted with fuel, whether your bearings are wearing, and other stuff like this. Go here:
Blackstone Laboratories - Diesel Engines

Dave

 

[95_stroker]

I had posted this in another tread but got no input so i assume it was due to my stray from the original content.

i checked my compression and i have 360 to 370 PSI. i did not have the GP adapter so i built one however i due to the angle i can only get about 2 - 3 threads in. i could be getting an inaccurate reading, but if i was would all the cylinders be so close within PSI range? i have heard if a diesel drops below 350 it will not start. i am concerned with the life of my motor if this is the case. any input on compression numbers?

i have ordered the proper fitting but i must wait a week for it's arrival.

1-370
2-366
3-360
4-364
5-360
6-360
7-360
8-360

Somebody will chime in with the correct "new engine" numbers but I think it was 425-450 range so you numbers look real good for an engine with +200K on it. They are very uniform which is what you want to see. Just to appease your curiosity pull the oil fill cap while the engine is running on the valve cover after you have gotten the engine to operating temp and see if you get a steady blow of vapors out the hole, it would indicate a little blow by which I would expect out of an engine with those miles and compression reading.


Drop in the Stg I's and get a chip and enjoy it.

 

[arrowstrap]

I have the US General diesel compression tester kit from harbor freight. the box says its for my motor but it does not have the GP fittings that fit! i ordered a GP adapter and the fitting did not fit my gauge so i clamped a section of hose to each fitting and retested my compression on one cylinder. the gauge read 420# before the hose exploded. even though i do not know the true max PSI, i am much happier with this reading.

word of warning DO NOT BUY HF DIESEL COMPRESSION TESTER FOR 95-97 7.3L!