I have a 1980 300td wagon that sat half the winter. It now starts, but then dies, suddenly, after about 3 or 4 seconds. The same thing happens when I leave it at a low idle or rev it up. Fuel is flowing from tank, through freshly changed filters to hp pump and all injectors have been bled. Is could the vacuum modulating valve on the top of the injector pump hp pump get stuck and behave like the ignition is switched off? Could my return line be blocked (I've had it off and blown on it, and it had some resistance)? My next attempt will be a heavy dose of injector cleaner in the filter and see if that frees anything up, but I'm at a bit of a loss. Again, the shut-down is instant, not like it is bogging down, starved for fuel, and then quitting. It is more like the key is turned off.

Any help or suggestions are greatly appreciated.

 

remove the return line and run it into a container by passing the line to the tank. that should tell you if the return line is clogged.

 

Thanks Andy. I had that thought of that too, but I wasn't sure whether this would introduce air into the system. Is the fuel line on the block side of the injector pump an intake line, allowing the injector pump to use fuel from the return line, or is it an excess fuel line from the injector pump which adds fuel to the return line? If the first, I thought injector pump would then suck air if return line is disconnected from pipe leading to tank.