Hi Everyone,

I am brand new to this forum and Mercedes diesels in general. Recently I purchased a 1983 300D Turbodiesel in fantastic condition. It was cared for by a Mercedes mechanic (30 years of experience), and his daughter had been driving it before I purchased it. I bought a conversion kit from Greasecar to change the vehicle to veggie oil. Before I made the conversion, the car ran like a dream. The idle was right at 700 rpm and very smooth. After the conversion, I am finding that the car still runs fine when at speed, but the idle degrades over a period of about 2 or 3 minutes while at a stop. It is slightly worse when in drive as opposed to neutral. I have even had it degrade to the point that it stalls out. The idle speed not only slowly degrades, but it gets rougher and the hood starts galloping a bit as it get rougher.

So, here is the background info and some of my theories:

When cutting into the fuel lines to add the conversion solenoids, of course some air gets into the lines. The instructions say to bleed the lines by using the priming pump to manually pull the diesel into the fuel system and bleed off the air. However, I don't think that my priming pump was working correctly because I didn't get any hissing sounds or any indication that air was coming out of the loosened banjo bolt while pumping. After about 100 pumps, I gave up and tightened the priming pump back down. I then just "ran" the air out of the system by repeatedly cranking the motor and running it until it stopped running roughly and smoothed out. This took about 5 minutes. From this experience, I am wondering whether the hand priming pump could be leaking and allowing air into the system (since it seemingly doesn't work and I may have caused any existing seal to crack by pumping it vigorously 100 times). I have looked for tiny air bubble in the clear fuel lines, but do not see any. I am also wondering if I could have done any damage to the timing or something by running the air out of the system this way.

In addition to the above the only other thing that I have done is change the primary fuel filter which led to the exact same set of circumstances (unable to bleed the air out using the hand pump, and thus had to "run" it out). Everything else seems to functioning fine. There is still power when at speed, but just the idle degredation issue.

Any thoughts???

Thanks!!
Kevin

 

It may be thicker fuel and your pump has a hard time keeping fuel pressure at a idle, but when RPMs pick up it is fine. 87 300D

 

This is the Q&A section of a web site mentionedby another member on this forum that might be of some help.

http://mercedessource.com/node/3377