White cloud after cold restart

[JHZR2]

1991 350SD. 42F outside.

Did a cold start and ran the car for about five minutes, driving around the block. Went out to the car maybe 10 minutes later and did another start, and the car put out a giant white cloud of smoke. It was pretty dark outside, so the exact tint of the color wasn’t something I could see, but it did sort of smell like burning fuel.

The car starts and idles perfectly, although recently, it sat for about a month of time, while I was doing some suspension work. When I started it up, the engine felt like it was pulsing a little bit, not vibrating, not missing, just pulsing for lack of better terms (still smooth) until the fuel system caught up and then it idled perfectly smooth. I thought nothing of it because after that it started and ran absolutely great. It has no problem with power or anything else.

I have never seen this white puff smoke from this car before. However, another thing that I noticed in recent time when trying to pull the car up ramps is that it dumped a pretty significant clump of damp (not fuel, not coolant) black soot on the ground at the point where the exhausted faced the ground, when I gave it enough throttle to climb up the ramps.





I’m wondering what this might all point to? I don’t think it’s a glow plug issue, because the lights don’t stay on to alert me that one is out, and it starts just fine. I have to wonder if it may be a leaking injector?

Any thoughts on this? Why would I get a big puff only at a cold restart?


And I’ve been around MB diesels for over 20 years. I get it that some white smoke during cold conditions at initial cold start is normal as long as it doesn’t happen all the time. This doesn’t happen all the time. But the smoke today is unlike anything I’ve ever seen, like the Seafoam videos. That’s not normal…

Thanks

[Sugar Bear]

Is it losing any coolant? Any odor to the smoke?

Use a glass jar to sample the fuel for water.

[vstech]

350SD...

HOW IS THE OIL CONSUMPTION?

[JHZR2]

Originally Posted by Sugar Bear

Is it losing any coolant? Any odor to the smoke?

Use a glass jar to sample the fuel for water.

Smells like partially burned diesel.

Fuel appears clean and clear. Car has been parked in a garage.

Checked coolant system. No remnant pressure, no losses.

Oil level is perfect.

[JHZR2]

Originally Posted by vstech

350SD...

HOW IS THE OIL CONSUMPTION?

It will consume some (an quart) over thousands of miles of highway use.

Oil leaks all fixed at the IP. That was my main issue.

No noticable consumption with lower intensity use.

[JHZR2]

I tried the same thing again today. Did a cold start, started perfectly and smooth. Idled for about 10 mins so the needle started to register and I could feel that the head wasn’t super cold (40F) metal.

The. Let it sit for about 10 mins. Restarted. Nowhere near the smoke cloud I had last night, but more white smoke than the first full cold start.

I think maybe the relay is being tricked to think the engine is warmer than it is, either limiting or turning off any glow. Yet the engine is cold and the air coming in is colder.


So then… unburned fuel.

Has anyone else experienced this? I noted when checking GP resistance at the harness that the relay was made in India.

[vstech]

That would imply the gp relay has some intelligence to it.
Afaik, the relay LIGHT is all that is affected by temps.
The relay will engage the gp's until you release the ignition key...

Is it different on the 91?

[Sugar Bear]

How was it parked/stored? Do you think water could have gotten into the exhaust system and is getting burned off?

I've encountered a lot of exhaust smoke on non-MBZ vehicles i.e., coolant in the exhaust from a bad head gasket which needs to be burned off after the head gasket was replaced.

[JHZR2]

Originally Posted by vstech

That would imply the gp relay has some intelligence to it.
Afaik, the relay LIGHT is all that is affected by temps.
The relay will engage the gp's until you release the ignition key...

Is it different on the 91?

I thought the 603.97 had some more smarts. Maybe the 602 and 603.96 too (?).

Not a huge afterglow but a longer runtime of the GPs. Is t one of the temperature sensors in the head part of that?

Time for me to search…

[JHZR2]

Originally Posted by vstech

That would imply the gp relay has some intelligence to it.
Afaik, the relay LIGHT is all that is affected by temps.
The relay will engage the gp's until you release the ignition key...

Is it different on the 91?

Yes, my memory was right. The 603.97 had afterglow with a head temperature sensor.

So did US bound 602 engines and maybe some others.

[BiodieselMB]

Catalytic converters clog up and ruin fuel efficiency and get worse over time.

[JHZR2]

My car doesn’t have a catalytic converter.