I’m about at wits end with a 1990 Cummins that I’m working on. About a year ago, while out cutting a Christmas tree at 7,000 feet, I started her up at the end of the day, and a plume of white smoke started flowing out of the exhaust. This was the first time in 4 years of ownership that this happened. It has continued to this day, the colder it is, the worse the smoke, the higher in elevation, the worse the smoke. It abates a little after warm up, but is present under power. The exhaust has an acrid smell to it, like partially burned diesel, and the wall in my garage is stained from the smoke it produces during warmup. The truck has 160,000 on the odometer, it’s equipped with a Banks PowerPack, and a Pre-Luber. To date I have checked or replaced the following items and systems:

1. Head gasket replaced, head machined, valve seats checked for cracks, head magnafluxed. No problems seen.

2. Injection pump replaced and timed. The pump was going bad anyway, the truck was dying at stoplights.

3. Intercooler checked for leaks. Negative.

4. Compression test. 470 pounds across all 6 cylinders.

5. Injectors replaced.

6. Fittings on high pressure fuel lines checked. Negative.

7. All low pressure fuel lines checked for air bubbles. Negative.

8. TDC timing check. I suspected that the Cam/Injection pump timing gears had broken their keys and slipped, but a dial indicator on the #1 piston showed perfect TDC on the injection pump.

Does anyone have any idea what the hell else could be wrong? I replaced the primary (low pressure) fuel pump 2 years ago due to leakage. It doesn’t show any leakage now.

The fuel mileage is excellent, but the truck does seem down on power a little.

Any and all hints appreciated.

ANDY

Have you checked the turbo? White smoke w/ the smell you are describing is unburned fuel.
I haven't done anything w/ Cummins in a long time, but are you sure the inj pump is supposed to be at TDC and not a couple of degrees BTDC?

I should have said that the injection pump timing pin in the injection pump gear is exactly at TDC. The pump itself is BTDC by a few degrees. I have played with the timing in both directions to no avail.

Would an oil leak in the turbo produce this kind of smoke? It seems more fuel-ish in odor, but years of breathing diesel fumes may have me fooled...

Andy

A couple of things to check are:
1. air cleaner- if it is restricted(dirty)you will not be getting enough air to burn all the fuel
2.turbocharger- could be leaking oil into the intake stream
3.thermostat- if the engine is running too cool it will not burn all the fuel
4.Restricted exhaust-would cause excess exhaust backpressure and not allow the cylinder to empty completely therefore the cylinder would get an inadequate fresh air charge and therefore incomplete combustion.
5. broken piston ring-allowing oil into combution chamber

Thanks Russ....I'll check those items.

Andy

If the engine is burning oil, the smoke would have a blue haze to it.
Pull the intake tube off the turbo and check if it is free. If it's binding, your not getting enough air. Also check the edges of the fins. They should be real close to the housing, with no knicks, notches, or bends.

This may sound crazy, but my '99 24 valve has the same problem every time I fill up with diesel in the Tahoe/Reno area. As soon as I get back to Central California and fill up with standard issue truck stop fuel, everything returns to normal.

-Jeff

Capt. Throttle,

The truck gets filled in Reno most of the time, but it was filled in Redding all summer and still had the same problem. It's interesting that your new 24 valve does the same thing...have you tried diagnosing it?

I figure it is not oil burning, because the smoke is definately white and has a fuelly smell to it, but I'm willing to check anything at this point.

The air filter is a K&N, freshly cleaned. I figure the turbo should have nothing to do with the smoke at idle because no boost is being used or produced. For that matter, even a massive intercooler leak would not be noticeable at idle.

I'm confounded. Someone suggested that the primary fuel pump might no be giving enough volume to the injection pump, causing it to cavitate and mess up the injector pressure. Does this sound plausible to anyone?

Thanks again,

ANDY

Since the problem only happens when I fill up on the I80 side of the Reno/Tahoe area, I don't worry about it and try not to buy diesel there. Come to think of it, I specifically remember it being Union 76 diesel that caused the problem. I have been to the Redding area several times and never had a problem there. I try to fill up at truck stops only, because the diesel fuel doesn't stay in the tanks long there, but that wasn't an option when I filled up at the 76 station. Sorry I couldn't be of more help.

Your at the wrong web site to get help with the Cummins. Go to turbo diesel registry (http://www.turbodieselregister.com/) and get the help you need. You won't be able to post unless you become a member. But the search function should help give you some answers. Believe me, if the problem can be solved, someone will know about it there. Good luck.

Originally posted by Bigguy:
<STRONG>Your at the wrong web site to get help with the Cummins. Go to turbo diesel registry (http://www.turbodieselregister.com/) and get the help you need. You won't be able to post unless you become a member. But the search function should help give you some answers. Believe me, if the problem can be solved, someone will know about it there. Good luck.</STRONG>


You cant search without being a member either. but its worth the $35 for the magazine alone really

Oh and heres a TSB on excessive white smoke
http://www.dodgeram.org/tech/tsb/1994/18-10-94/18-10-94a.htm

Donno if it'll apply though. Good luck!

[ 10-10-2001: Message edited by: mike ]

Sometimes ter is not a lot of individual knowledge on POR, but combined knowledge is pretty high. After all, put 7,000 tech heads together, and someone is bound to know something....

Andy