M1031 6.2 Engine Questions

[Road Warrior 88]

I have a 1986 M1031 shop maintenance truck. The timing is set perfect with brand new OEM injectors and it seems to be running OK but its running rich and smoking. Has anyone else encountered this similar problem and found the remedy? I'd appreciate any good advice from some experienced and knowledgeable fellow members out there on this one.

 

[Kaiser67M715]

Non turbo right? Verify IP numbers, drivers side, hard to see, but possible.

Ran fine before injectors? Other maintence? Smoke doesn't clear when warm?

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[ken]

What color is the smoke? Is it coming from both exhaust pipes? Or just one? Air cleaner dirty? what elevation are you at?

 

[Road Warrior 88]

Black smoke coming out of both l/r exhaust pipes. Perfectly clean air filter. Elevation 3300 above sea level.

 

[Road Warrior 88]

Yes, non turbo charged. Original injection pump pulled and sent to Oregon Fuel Injection Service then reinstalled so no mistaking it for the wrong IP. I replaced the injectors because I had 200+ new in the wrapper OEM Delphi injectors from a good buy. I sold these same injectors here on Steel Soldiers 3 years back and had not one complaint. But to answer your question it ran fine before I replaced them. Even when it warms up to operating temperature it still smokes black.

I own 2 of these M1031 units and the other one smokes just a little on start up then clears up after a minute or two. The other one was fed the identical injectors too. I noticed what looks like a vacuum type distributor at the back of the engine which may have something to do with the problem. Let me know if you can think of any other variables that might come into play.

Much appreciated. John

 

[cucvrus]

The vacuum type distributor in the rear of the engine is the vacuum pump for the automatic transmission. It does nothing else and is not timed in any way shape or form. It has an eccentric that activates a rubber diaphragm to create vacuum since a diesel has no vacuum. Have a great day. If it wasn't broke don't fix it comes to mind. Put the old nozzles back in and see if the problem goes away. New is NOT always better. The balance between the 2 injection pump and delivery nozzles must be a matched balance. The nozzles must pop at the precise time and pressure. To much or not enough is not good either.

 

[Kaiser67M715]

Loosen the injector hard lines one at a time, see if there is any significant change in smoke, or sound. Any time I buy new injectors I get them pop tested, last set had 4 bad injectors(leaked and very poor spray, low pop pressure)

You should also verify the CDR/PVC valve did not fail, by disconnecting it from the intake. It seems very rare and I've only heard one count of the CDR failing and the intake sucking oil mist straight from the crankcase. That would cause an overfuel situation.

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[ken]

If the IP was rebuilt and the engine runs ok, I would bet the fuel rate is set higher. There is a 3/32 head allen screw behind the cover on the drivers side of the IP. It looks like home plate on a base ball field. This screw would need to be rotated counter clock wise 1/4 turn. The engine will need to be rotated by hand until this screw come into view. There is another way to do this but it involves removing the top of the IP. I know Oregon puts paint globs on every fastener on the IP's they rebuild. So if you open it up and adjust the fuel rate you will void their warranty. I would contact them and get their ok. Or send it back to them. If you run it with too high a fuel rate you will need to open up the air flow and exhaust flow to compensate. Or risk melting pistons and exhaust valves.

 

[Chaski]

You indicated that the timing is “set perfect”. How do you know that?

How does it start when cold?

 

[doghead]

Too much fuel in a non turboed motor will not create damaging heat.

Just wastes fuel.

 

[Keith_J]

RPM at idle requires very little fuel. If it smokes at idle and the smoke is black, chances are timing is off. The tiny fire is extinguished by expansive cooling before the carbon can burn .

Some 1031s had incorrect governor wiring from the factory. They hooked the high idle to the governor kill which meant the engine was always high idle.

 

[eme411]

pull the injectors and test them , my money is on them being bad and needing to be adjusted, were the caps on both ends? or were they without?

 

[Road Warrior 88]

I found a mechanic familiar with the old 6.2 GM diesels. He stopped by and found the problem in under 30 seconds. It was a cracked vacuum and cracked plastic fitting right by the injection pump. No it runs as it should, perfect. I want to thank everyone who had replied with advice.

 

[Barrman]

Something doesn't add up here. The vacuum lines by the IP and the plastic fitting that looks like an F are for the transmission shifting. They have nothing to do with how the engine runs. You could remove them and the engine shouldn't change.

Glad you got it fixed, but something just doesn't read correct.