Prolonged driving problem

[stuart750]

When I drive my '80 240D for a prolonged period of time, it gets in a bad mood. I usually have to drive it for at least an hour. before the problem starts to happen (sometimes it does, sometimes not), but when it does, the car feels like it's taking less fuel (without me changing the pressure on the throttle), and slows down for a short period of time, before going back to normal.

I don't know if the fuel lines are dirty, or what it is, because it normally runs great.

It stalled last night after driving it for about 90 mins with a short break in between. It first just started to slow down, in which I gave it more juice, this didn't do a whole lot, and the car continued to slow down. I took it out of gear, pulled over, and before I stopped, the car stalled, as it wasn't getting enough diesel to keep it idling. I thought it had overheated (the thermostat doesnt work), but it wasn't that. After waiting about 45 mins (and trying intermittantly in between), I finally got it running, having to floor it to get enough gas, (and putting some kerosene in the air intake manifold), and the car idled ok.

After about 1 minute of idling while I floored it, the engine was back to normal, idling without having to give it any encouragement. It drove home normally, no funny sounds or anything. Good thing I had a new battery for all that cranking I did.

What could the problem be?

[toomany MBZ]

Fuel filters or tank screen comes to mind.

[Carpenterman]

After changing the fuel filters and it happens again, loosen the fuel cap and see if there is a vacuum in the tank. You may have a clogged pressure relief line.

[Biodiesel300TD]

Originally Posted by Carpenterman

After changing the fuel filters and it happens again, loosen the fuel cap and see if there is a vacuum in the tank. You may have a clogged pressure relief line.

Thats what I'd put my money on.

[Skippy]

This:

Originally Posted by Carpenterman

After changing the fuel filters and it happens again, loosen the fuel cap and see if there is a vacuum in the tank. You may have a clogged pressure relief line.

Search "tank vent" for a wealth of information on this subject.

[vstech]

if it is a tank screen, it's not too bad a repair job. you could have stuff settling on it, and it clogs after a long drive, but shutting down, lets the debris wash off...
if it's the tank vent, you could implode your tank. I've seen them with only 5 or 6 gallons of capacity after a long drive... check the vent!

[layback40]

X3 on tank vent. If after doing a filter change & strainer clean, it still does it, you could try back blowing the fuel line. Make sure the tank is low or empty & the fuel cap is off. Compressed air applied to the supply line before the primary filter & blow back towards the tank. I have removed all sorts of c##p that way.

[Diesel911]

I had a small air leak that only showed up after it got good and hot under the hood. I had hard Fuel Inlet lines that though the clamps were tight the Hose had no elasticity to seal.
Replacing the Fuel Inlet Hoses cured it.

To see if it is a Fuel Tank Screen problem (if you still have 1/2 tank of fuel or more) swap the positions of the Fuel Inlet Hose and the Fuel Outlet Hose (Cigar Hose) and it will by pass the Fuel Tank Screen and draw Fuel From a higher position in the Fuel Tank (this will also cause you to run out of Fuel early so only do it for testing).

[stuart750]

Found the problem, a leak in the primer pump was letting air in and diesel out.