Fuel delivery issue-please help!

[Tree Frog]

Okay, I've got a 1982 240D. I recently started running about a gallon of biodiesel in 3/4 tank of dino diesel (I've run two tanks of this mix so far).

I was coming into work last week and the car began to lose speed. I pulled over and checked the primary fuel filter...sure enough it was clogged (I'd just changed it a month earlier). Slapped another filter in, primed the system and got to work.

This morning on my commute, she started to slow down again-just like a clogged fuel filter. Pulled into a parking lot and checked. The fuel filter has caught some gunk, but it's not clogged. However, there was a bubble of air at the neck where the filter goes into the priming pump. I primed the system, got it started and made it into work. Well, I just made it into work. By the time I turned into the parking lot, it had started chugging again, and it shut off just as I reached my parking space.

Any ideas what this could be? The only thing I can come up with w/o researching is that the screen in the tank is plugged, thus causing fuel starvation. However, I thought I'd ask the experts.

Gee...I hope I can get home. Any tips on a quick temporary fix would be most appreciated.

[tangofox007]

Have you replaced the secondary filter? If the primary was clogged, the secondary can't be in very good shape.

[Tree Frog]

Originally Posted by tangofox007

Have you replaced the secondary filter? If the primary was clogged, the secondary can't be in very good shape.

You're right...I changed the primary but not the secondary. I'll slap one in tonight before I go home...

[Biodiesel300TD]

Definitely change both filters. I tried the same thing on my 240, just changing pre-filter. It helped for a little while, but the issue came back. If the car still has the issue after changing the spin on filter I would suspect the tank screen. But I'd bet the spin on filter will solve the problem.

[Tree Frog]

Originally Posted by Biodiesel300TD

Definitely change both filters. I tried the same thing on my 240, just changing pre-filter. It helped for a little while, but the issue came back. If the car still has the issue after changing the spin on filter I would suspect the tank screen. But I'd bet the spin on filter will solve the problem.

Sweet. I hope it does the trick.

I'm tempted to drop the tank and flush out all the accumulated crud...but not that tempted!

[GRIESL]

Originally Posted by Tree Frog

I'm tempted to drop the tank and flush out all the accumulated crud...but not that tempted!

When I bought my car it had never seen a drop of bio. Then I began to introduce it 10, 20, 30, 40, 50 percent at a time. Now I'm 100%. But along the way, I lost count of primaries changed. I got to a point where I put an extra one in front of the one there. I changed at least 5 or 6 secondaries, and had the tank screen replaced (it was covered in lots of goo). I've said before, if I had it to do all over again, I may consider dropping the tank and having it cleaned.

I would also keep an eye on fuel lines--the stock stuff doesn't hold up to bio--especially the injector return lines.

Good luck.

[GeneE]

When I started putting B10 in my 1983 300d, I would have fuel delivery problems every time the tank neared empty. Replacing the in-line filter was a fix that worked, but only temporarily. Draining the tank revealed a very clogged tank screen. Cleaning the tank screen fixed it for another few hundred miles, until the tank screen got clogged again. I finally bit the bullet, and had the tank removed and washed out. Now I've been trouble free for about 10K. I've read that biodiesel is more solvent than petro-diesel, so it apparently loosens up crud on the inside of these old tanks. Getting all this crud out one pre-filter or one tank screen at a time is frustrating, so I'd say if you keep having trouble, go for the tank cleaning. A local shop did it for me for about $200.00 and it was worth every penny.

Good luck!

Gene

1983 300d (133k)
1983 300sd (118k)

[tangofox007]

Originally Posted by Tree Frog

I changed the primary but not the secondary. I'll slap one in tonight before I go home...

When you get finished "slapping" the new filter on, it might be entertaining (and enlightening) to "whack" open the old one.

[Tree Frog]

Okay...just changed the secondary (screw on filter) and reprimed the system. It'd run until the fuel in the primary filter was gone...it seems that the fuel's not getting from the tank to the filters.

The primary filter refills very slowly.

Could this be the tank screen? Could it be the fuel pump?

Any help would be greatly appreciated.

[rrgrassi]

Could be air, but could also be a clogged secondary filter again. I also run Bio-D and at first I had the secondary filter plugging in a matter of 30 miles. That is not happeneing anymore...

[Tree Frog]

Originally Posted by rrgrassi

Could be air, but could also be a clogged secondary filter again. I also run Bio-D and at first I had the secondary filter plugging in a matter of 30 miles. That is not happeneing anymore...

I checked the primary while I was in it. It's clean (so far...)

[Bajaman]

Time to check the tank screen.

[tangofox007]

You might try blowing some compressed air backwards through the supply line. (Remove the tank cap.) That might get you some temporary improvement as well a confirm the diagnosis.

[Biodiesel300TD]

I can take a lot of pumping on the primer pump to get the system reprimed, espicially if you didn't fill the spin on filter with fuel. I would pump a whole lot more before you tear into anything else. I replaced me lift pump gasket a week or so ago and it took me about an hour of pumping and sucking with my mity vac to get the system fully reprimed again. So keep pumping.

[zeke]

When you go under the back of the car, check the fuel hoses that connect the fuel tank with the hard fuel lines. Usually these have never been changed, and apparently the 20+ YO braided lines get all weepy when you push BioD through them. Could be air getting in the lines.