I have an 82 300sd that I converted to run on waste vegetable oil. I am in hawaii so it is a single tank system. I have removed the stock filter and added two stanadyne fm 100 filters, a 30 mic and a 5 mic. The fuel lines have been replaced with biodiesel compatable, and they go through a flat plate heat exchanger and electric boost pump before going into the injector pump. There are no (more) leaks.

The problem is the car will somehow get a bunch of air in the fuel system. I will bleed it and bleed it for a really long time and it will finally start running again. It will run for about a week or so then just die out again. It's really frusterating because it makes me think I fixed it and then it happens again. I have checked all my connections and made sure they are tight, non are leaking.
If I take off the fuel line that goes to the tank and put it in a jar of biodiesel or veggie oil it will bleed very quickly and start and run fine. I have replaced the primer pump and injector return lines reccently. The car will have the same problem regardless of the fuel. I don't know what to try next? Can anyone help? ALoha

The air must be coming in through an as yet undiscovered leak.

Good luck.

Tom W

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Sounds like you've narrowed it down to the line between the fuel tank and the primary filter- check all connections in that section.

__________________
'83 300D Turrrbo 295K miles

I have been having the same problem with my 83 300sd, but much more frequently now. Mine dies out every 15-25 miles now depending on how hard I am running it. I agree, it is very frustrating. Let me know if you figure it out, and I will be sure to try that fix as well. I have replaced my lines and am getting ready to replace the primer pump whenever the weather decides to cooperate.

I have checked the short rubber line from the tank to the metal lines and it looks fine, no signs of leaking whatsoever. What about the tank vent? Maybe if it were clogged it would be hard to pull the fuel up and make a leak at any tiny little connection? Is the tank supposed to be under vacuum when I take the cap off? How do I check the vent?

So I've been fiddling around with it. I notice there is a pssss....pssss....pssss...pssss coming from near the primer pump area when the engines running, now it seems to just be a constant pssssssss, very faint hard to hear sometimes. I have been checking all the connections over and over running my hand over them and I feel no suction or air, all vacuum lines seem intact as well. Is this noise just the injectors firing or something??
I pulled off the line coming from the tank and put it in a jar of diesel then pumped until fuel was coming out of the filter bleed. I put the hose back on and it started up fine. I will open the bleeded from time to time and it will either spray out all over or do nothing. I have been idling it for over 20 minutes now with the fuel tank cap off and it seemed to be running fine. I put the cap back on and ran it for another 10 minutes and when I open the cap it goes whoosh. I took apart the tank vent and cleaned it, now the cap no longer goes whoosh when I open the tank.

I took it for a drive and it ran fine, I think it was just the tank vent being clogged that was causing all the trouble. I still am afraid it will run fine for a week then leave me stranded again like it did before.

Is there an easy way too see if any of my connections are letting air in? I have an electric pump that comes on with the key, when I turn the key on and let the pump run the fuel system definetly builds up pressure, would it not with an air leak?

No anxiety required it was just the fuel tank under vaccum. Very common.
In fact one problem that is probably missed is when the vent is not totally obstructed but still just open enough to affect general performance.

Another possible problem could be a clogged tank screen. It's a miserable job to check it though, so I would save it for a last resort. You might first blow compressed air from the front and have someone listen to hear if it bubbles up in the tank. I suppose that might rule out an obstruction in the supply line. You could do the same with the return line for that matter.

__________________
1987 Mercedes 300D ~200K (Greasecar & Biodiesel)
1993 Ford F-250 7.3 IDI diesel 165K (Biodiesel)
1996 Thomas/International Bus with DT466 engine