I got MAD soot. No good.

topshelf · Post by **topshelf** » Mon Aug 31, 2009 12:42 pm

I have had 17 VW diesels. I have had engines all apart have been in Injection pumps have and injectors, i adjust my own valves etc. I am not saying this to look like a hero just to equate you with my mechanical aptitude. This problem stumps me. I have 2 vw diesels both NA. One is an 85 mechanical lifter and the other is a 91. I have had the 91 about 4 years and after owning it for about 18 months I noticed that I started getting a significant soot buildup on the trunk. The car burned ZERO oil. I had put a rabbit style fuel filter on it but have done that on many of my diesels with no issues. I loved the big bumper body so I decided to trensplant the great running m85 mech motor into my 91 body. The 85 motor didn't burn oil, had great acceleration and no soot. So i made the transplant and now the 85 motor produces soot and the 91 motor in the 85 body does not. The 91 body has always needed about 2 seconds of cranking to start unless it is the first start with glowplugs. I was frustrated as heck at Christmas so I ripped off the water separator under the car and plumbed the lines together. I am lost as heck. Swapping motors in 90 degree weather was not a bunch of fun and i still have the problem. Thanx for any help.

MPalm · Post by **MPalm** » Mon Aug 31, 2009 1:43 pm

I think the -91 has some restriction on the intake side, how's the air filter?

topshelf · Post by **topshelf** » Mon Aug 31, 2009 2:03 pm

Air filter has been changed multiple times over the years. Currently the car has the 85 intake. I swapped everything in desparation. Still have soot.

Quantum-man · Post by **Quantum-man** » Mon Aug 31, 2009 9:06 pm

The '85 had soot in the old body, only it didn't show up?

Or the '91 weighs more so it's like continuously loading the engine. More loading means more carbon soot from the greater fuelling...

topshelf · Post by **topshelf** » Mon Aug 31, 2009 9:10 pm

I am not sure if you are posting a theory or a question, I take it as a question. No, there was no soot associated with either motor in the 85 body. What could an air leak into the line between the filter and the tank show up as?

Quantum-man · Post by **Quantum-man** » Mon Aug 31, 2009 9:41 pm

topshelf wrote:I am not sure if you are posting a theory or a question, I take it as a question. No, there was no soot associated with either motor in the 85 body. What could an air leak into the line between the filter and the tank show up as?

I was referring to the shape of the body as a possible factor, but then moved on to the likelihood of both engines smoking in the later body simply as a natural function of being heavier and loading the engine more, so calling for more fuel to maintain the same performance.
Maybe protrusion of exhaust?

How do economies compare between bodies and engines?

topshelf · Post by **topshelf** » Mon Aug 31, 2009 9:44 pm

The odometer is broken in the 85 but I would say that the economy is better without soot. That is why I wonder if it is an air problem.

Post by **Fatmobile** » Tue Sep 01, 2009 12:21 am

Soot means not enough air for the fuel, maybe turn the max fuel screw down.
Does the tailpipe have a turndown tip on the '85?
That got rid of the soot on the back of my '91 Golf.

topshelf · Post by **topshelf** » Tue Sep 01, 2009 12:30 am

I had thought about turning down the fuel screw but then i realized that the soot was there with the 91 motor and pump and then went away when i put it in the 85 body and was not there with the 85 motor in the 85 body but is there now in the 91. It has got me so stumped.

Quantum-man · Post by **Quantum-man** » Tue Sep 01, 2009 4:06 am

If it's not a weight issue, and if it's not a change in fuelling and if it's not merely different exhaust termination, then its either a restriction of air flow at air filter, which I believe you have discounted, or it's a more restricted exhaust in the '91
I for one know that later exhausts in the Quantum TD became more restricted [pipe downsized]in vw replacements. I moved over to GL5 /syncro stuff to maintain tube sizes, maybe 25% different....

What could an air leak into the line between the filter and the tank show up as?

Poor idling, occasional cut-out I don't think soot, unless advance mechanism affected by air build-ups.
How do you know there has been a change in the '91 from no soot to soot buildups? Maybe exhaust replacement, or change of airfilter brand...

Post by **Fatmobile** » Tue Sep 01, 2009 8:42 pm

I think air in the fuel usually shows up as white smoke,
I could be wrong, it's been awhile.

topshelf · Post by **topshelf** » Fri Sep 04, 2009 11:08 am

I am gettin a small bit of rough idle at start up with the cold start lever in. If I pull it out I get less white smoke and smooth idle. Is that normal? Then if I rev the non moving car to about 200 rpms the blcak smoke starts rolling out. Thanx for all the replies.

Post by **Fatmobile** » Fri Sep 04, 2009 10:43 pm

I am gettin a small bit of rough idle at start up with the cold start lever in. If I pull it out I get less white smoke and smooth idle. Is that normal?

That is normal.