Just bought a 1988 kw w900

SCHMITTY

SCHMITTY

Not enough time
Seller had the head gasket replaced and said it probably needs injectors.

It has the ntc 444 and i think the stc is not working correctly. Anybody have tips for checking the stc system ? I’ve been reading through old forum posts online.
 

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Nice find.

If the step timing control isn't working it'll smoke at idle. There a a handful of causes for the malfunction. What's up with it symptom wise ?
 
White smoke at idle and smells of diesel fuel, occasional mis, smoke seams less noticeable maintaining speed on the highway , under full throttle there’s black and grey smoke. I have felt the miss at highway speed. It has been sitting for a few years. I’ll get a t made up for testing the oil pressure before and after the stc valve , probably run the overhead next doing obc method, check the cam lift while I’m in there with my dial indicator and magnetic base. Im not opposed to buying a new stc valve and injectors but I have thrown money away without trying to diagnose in the past and that always ends badly for me.

Ill take a cold start vid and a operating temp vid in a hour or so
 
SCHMITTY said:
Seller had the head gasket replaced and said it probably needs injectors.

It has the ntc 444 and i think the stc is not working correctly. Anybody have tips for checking the stc system ? I’ve been reading through old forum posts online.
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Sweet truck; I’ve always liked W900’s. Personally I would spend as little as possible on that 444 and save for a 3406 Cat 425. Look for a 4MG serial prefix. You can’t beat the legendary “four and a quarter”. I was raised on Cummins, the first engine I ever built was a small cam 855. I’ll always love Cummins but Cat really is the best.
 
A lot of time the STC system is okay, and oil pressure is the culprit. The system is supposed to fill a void under the injector link with oil to advance timing at idle to eliminate the raw fuel smoke. If you touch the fuel pedal enough to bring oil pressure up 5-10 PSI see if the smoke goes away some. Could be a cracked piston cooling nozzle, or a leak in the internal oil manifold plumbing.
 
mhuggler said:
Sweet truck; I’ve always liked W900’s. Personally I would spend as little as possible on that 444 and save for a 3406 Cat 425. Look for a 4MG serial prefix. You can’t beat the legendary “four and a quarter”. I was raised on Cummins, the first engine I ever built was a small cam 855. I’ll always love Cummins but Cat really is the best.
Click to expand...

I still have fond memories of the 3116 I had in a Kodiak, Not.
Was an over heating pos they never could fix under warranty, they just patched and rhode me out until it was over.
 
Snedge said:
A lot of time the STC system is okay, and oil pressure is the culprit. The system is supposed to fill a void under the injector link with oil to advance timing at idle to eliminate the raw fuel smoke. If you touch the fuel pedal enough to bring oil pressure up 5-10 PSI see if the smoke goes away some. Could be a cracked piston cooling nozzle, or a leak in the internal oil manifold plumbing.
Click to expand...

It clears up under higher rpm. The smoke dies down a little but 75% of the time it is pretty bad. The worst seems to be when I come to a stop and it’s at operating temperature. The oil pressure is 80-100 on a cold start , drops to 25 when warm, 40-50 cruising. YouTube won’t let me sign in. I took some videos when I had it out today.
 
mhuggler said:
Sweet truck; I’ve always liked W900’s. Personally I would spend as little as possible on that 444 and save for a 3406 Cat 425. Look for a 4MG serial prefix. You can’t beat the legendary “four and a quarter”. I was raised on Cummins, the first engine I ever built was a small cam 855. I’ll always love Cummins but Cat really is the best.
Click to expand...

He had a 93’ t800 with a flat top sleeper and a 3406. He wanted 2.5x as much for that one and it was kind of beat up. Idled smooth though
 
Well, I can't smell the smoke on YT but it sure looks like fuel. Oil pressure sounds right.
You'll want to pull the valve covers, and look for oil leaks on the internal manifold. STC issues will not cause a miss though.
 
jasonc said:
I still have fond memories of the 3116 I had in a Kodiak, Not.
Was an over heating pos they never could fix under warranty, they just patched and rhode me out until it was over.
Click to expand...

That actually had nothing to do with the engine. Chevy was too cheap to put a real fan/fan clutch in those trucks, a well known problem. The biggest issue with the 3116 is people keep trying to fix and/or maintain them themselves. There's not a whole lot you can do on those without the Cat special tooling. If you kept the rack in synch., and top end adjusted they had a nice purr.
 
mhuggler said:
That actually had nothing to do with the engine. Chevy was too cheap to put a real fan/fan clutch in those trucks, a well known problem. The biggest issue with the 3116 is people keep trying to fix and/or maintain them themselves. There's not a whole lot you can do on those without the Cat special tooling. If you kept the rack in synch., and top end adjusted they had a nice purr.
Click to expand...

:hehe:
Please stop bringing that Cat mouth into a vintage Cummins thread. :doh:

Next thing you'll pull Faulkner will be in here with his Cat spewing face. LOL
 
Any recommendations for a place to send in my injectors or buy from ?
The compressor seems to be running non stop also.

The egt probe is installed after the turbo. Should I move it to the manifold ?
 
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4x4dually said:
I wonder if Jeff Mumau could do them....
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Nope. I could replace them. If you want to send them for repair, Diesel Controls in Ohio is the way to go.

The air compressor may be running all the time means you probably have a hole in the main line from the compressor to the air dryer. You'll never hear it leaking, so either spray soapy water on it while it's running, or remove the line at the compressor and put shop air into it. It'll show up then.
 
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