unburned fuel smell; runs hard w/ load

[ramcatdoc]

Hey, y'all!

My '85 M1009 has been running very smoothly for a good while. Recently, I've noticed an unburned diesel smell around the truck when it's parked, and in the cabin when i'm driving it. It's actually bad enough to burn my eyes. I also notice the truck tends to run harder than usual when accelerating on a hill in a lower gear. Runs very smoothly when cruising, though.

No black smoke. No diesel smell around the fuel fill cap. No puddles or drips under where she parks in the driveway.

Any ideas?

 

[Goose2448]

Only thing I could figure is injectors, or a cracked fuel line. Other than that I don't know. But I would not be driving it until its figured out.

 

[Keith_J]

How has this change impacted the fuel mileage? I'm thinking late injection timing from an internal malfunction in the cam ring positioning system.

There is a cold start advance solenoid, failure here would be manifested as hard starting. The fuel pressure timing advance works respective to engine speed so if you are smelling the unburnt diesel at 40+ MPH, this is probably the issue.

 

[ramcatdoc]

No problems starting the CUCV. It has always started easily, even when cold. It just runs heavy when I am accelerating from a stop on a mild incline, putting some load on first gear. Sounds a little louder than usual in this situation, too. Once I reach a cruising speed, it downshifts and runs fine. But I still smell unburnt diesel in the cabin. Do you think I'm running too rich? (I'm a real novice with fixing motors; I prefer fixing people!)

As far as mileage is concerned, my speedometer is far from accurate. We call it CUCVs-per-hour instead of MPH. 40 is really 35; 55 is really 50; 75-80 is really 65. So i've never been able to even estimate mileage. I don't think I've been refilling the tank more often than usual, though.

 

[Matt65]

Interesting. You smell Diesel, but see no leaks on the ground, and no black smoke.

When you say runs hard with load, do you think it's dropping to 7 or less cylinders?

 

[Keith_J]

Unless you can see smoke, you are NOT running rich. Forget all you know about gasoline engines, diesel engines always run with excess air, LEAN BURN is the norm. Power is modulated by injected quantity, there is no throttle plate and there is no manifold vacuum.

Do you have leaking seals on the injection pump? The valley between cylinder banks has a drain which will drip diesel on the left rear of the engine, by the engine-transmission junction.

Late timing will give a different smell, some smoke and a very quiet engine. Plus reduced mileage and power.

 

[68impalass]

Check out the injector by-pass hoses. One could be dripping on the exhaust manifold. That could be why you smell the fumes but not see a leak.

 

[southdave]

If really concern about it do a compression test.. valves may not be seating well and your getting some blow back on the intake side or vise versea dumping in the exhaust system ie kinda of valve float situation to some degree in my opinion also check your cdr valve