94 idit motor compression test

[paulzx]

just performed a compression test on a 94 idit that i pulled out couple of weeks ago, and i got 200 psi roughly across the board + or - 10 psi, tried it wet and got about 20 more on each cylinder. is that acceptable? the motor started withing 1/2 a turn and that was sitting all winter, smoked like it was on fire, but pop tested the injectors and they poped at 12-1500 psi and they all had a garden hose spray pattern. nice solid stream. all the injectors where stamped 1993 year. I'm not sure the history of the motor, but kinda figured it sat for a while, the truck had a busted front axle, and it was a plow truck. the truck also had about 240 km's on it.
thankyou

 

[Diesel JD]

You really should not be doing a wet compression test on a diesel. You risk hydrolock or runaway. Also you should probably be doing a test on an engine that works everyday rather than one that has set up all winter. Honestly 200 or so PSI is not that good. Book specs are 196-440 but in reality anything from 300-525 or so is normal with the highest cylinder not more than 25% higher than the lowest. You have to make sure your glow plug adapter seals tight and you need to make sure the batteries and starter are strong to give accurate results. You should crank it through about 6 compression strokes per cylinder. I'd run it hard for a few days and then check again using that procedure. I'm not easily going to believe that the true readings are 200 or so if it starts and runs well even with a lot of smoke. An engine like that would probably smoke like a freight train even when warmed up and go through a ton of oil plus be a little on the weak side power wise. Also your fuel injectors are terrible! 1200-1500 is way out of spec. They should be 1800+ with the highest within 200 psi of the lowest injector. +-50-100 psi gives better results.

 

[paulzx]

the engine is sitting on the floor, and before i did the wet test, i turned engine a few times with the starter. the intentions was to install the engine and the tranny into my truck due to factory turbo and overdrive, i don't want to spend 4 days in tear down and installation and find out the engine is on it's last legs. i've bought the truck for parts and never had a hint of intention running it on the road, but just running it in the yard, it seemed to be low on power, no snap to it and really smokey, neighbours new when it was running.
I figured that the engine never had an oil change in years (oil filter all rusty) it's been sitting for a long time.
the compressor tester: made one out of a old injector cut the top off, 1/8 pipe tap where i cut off and install a 1/8 pipe tap to #4 jic fitting on it and cut the tip off. used some soap and water to test for leaks and found none. got a check vavle off of a fire suppression system and used a CAT pressure gauge 0-500 psi.
I don't know if it's critical to use the glow plug holes, but the injector hole gotta work too. also all of the injectors where removed to doo the test.
from i'm been reading and your suggestion too is to run the snot out of it and see that frees some stuff up. i need to install first tho.

 

[OLDBULL8]

Using the injector hole will not give a true reading, the copper washer on the end of the injector is what seals, the injector threads will leak giving a false reading. Use the GP holes, a 1/8" NPT will screw in a few threads and not damage the threads in the block. The manual says 260 is low compression. Five revolutions on each cylinder @ 500 RPM.

 

[icanfixall]

I'm thinking your gauge is shot or the engine is shot. The 200 lbs is a bad engine for sure so... Sounds like time to make a dicision about tearing it down now or risk running it and having to tear it down anyway.....

 

[RLDSL]

If the things been sitting up for a long time, there's a very good possibility that the rings are stuck and you aren't getting an accurate reading

 

[paulzx]

i'll fabricate a new compression ***** out of an old glow plug and try that. it makes sense that the injector/tester is a kinda a bad idea, i'll post my results. it'll be a few days before i can get back to it.

 

[flareside_thun]

I gotta agree, since it's been sitting for awhile the rings are probly stuck or the cylinders are glazed over.....or both. Until you get that issue cleared up, you can't really go from your compression results thus far.

 

[typ4]

The injector stream pattern will cause smoke, the fact that the comp is even is good. put it in, run it, then put in some new or even reman injectors, and it will need an IP if it hasnt already, likely not given the lack of maintenance hints.

 

[OLDBULL8]

Re-reading your post, the engine has only 150,000 miles on it (240,000KM = 150,000 RIGHT?) Your compression test was all wrong the way you did it. I'd stick it in and run the **** out of it, use Diesel Kleen in the fuel for several tank full's. One thing I'd do first tho is rebuild the oil cooler O'rings.

 

[paulzx]

i'm very leary about the the compression being on the low side but on the + side of things is that they are all the same. so i'm probably going to throw it in and run some seafoam additive in the oil for bit and runner. the engine did run lowsy at that, but the injectors were vintage 93 and im sure that the IP pump is not far behind, that alone would cause the lack of power issue. i tried putting some unknown injectors in the truck before tearing down and the poor thing wouldn't even cough, did a pop test after on those injectors and they would pop at 1800 psi but the spray pattern was non existing, took a few apart and the injector pintle was seized in his 'seat'. that poor pump is kinda tired. I don't want to see a idit engine go to waste, it seems to be a high desirable item right next to a good 6.9.
I had time to fabricate a compression tester out of a glowplug, and the results were the same.

 

[TWeatherford]

I read like 150 psi on all my trucks cylinders, but people here told me it wouldn't even start if thats all it had. And it starts well, -3 F was the coldest I've seen and it was only a few revolutions and it was off. I don't believe my comp tester, but it did at least tell me they were all the same.