hi folks,
i had a problematic sender and let my fuel run really low. som crud must have come out of the bottom of the tank because suddenly my prefilter was dirty. i changed that and in trying to pump the fuel back in discovered that my hand pump was leaking all over the place. ordered the new pump.

it came today and installing it was trivial once i read about using vice grip pliers. however, i still see air in the topmost clear line (the "bypass return" line?). when i loosen the 17mm filter bolt and pump, nothing changes there, i just spill fuel out over the spin-on filter.

so i did some reading and then loosened the hard lines at the injectors. i haven't gotten neither fuel nor air spilling out there though. do i need to crank the starter at this point to turn the IP? am i on the right track for clearing air from this line?

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'77 240D, 504H, OM617.952, etc.

I usually fill a clean filter with diesel clean or surgically clean fresh diesel, crack all the hard lines and crank. Close off the hard lines as they show fuel and refill the filter as necessary. Oh wait 617 primer that's right, might take a lot of pumping to get fuel from the tank. I still usually cheat and fill the filter get the motor to roll over let it do the work.

i never emptied out the main filter so at least that is full of fuel.

is this all a two-man job? glow and crank engine, monitor injectors for leaking diesel, tighten, glow and crank over again?

all this with the fuel filter bolt tight, so the primer pump and air bleeding at the filter are all over?

__________________
'77 240D, 504H, OM617.952, etc.

i cranked it a few times, still have air in the same fraction of the return line, and still no fuel leaking out at the injectors. what am i missing?

__________________
'77 240D, 504H, OM617.952, etc.

The hand pump has no effect on the hard injector lines, it is only for priming the supply lines.

You must crank the engine to get fuel out of the hard injector lines.

.

__________________
ASE Master Mechanic
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Nope one person can get it. WHunter was more clear than i. Prime with bolt loose until you get fuel, tighten bolt. Loosen all the hard lines at injectors not much half turn +/-. Crank until they spit/dribble look a bit wet then tighten them after they do. Cranking pedal fully down pushes more fuel and fills the lines faster. Some lines fill faster than others for whatever reason. I crank for 15 seconds or so then check tighten any dribblers wait impatiently for the starter to cool then crank etc. After I get it running I personally like to crack each line at idle for a second or two.

thank you guys, that's helpful. i did finally get it started after lots of cranking, running the battery down... plus half a dozen cycles of cranking then recharging the battery for 5-10 minutes. i think my error was not to hit the accelerator, which i read above and then spaced until the engine was already firing on four cylinders.

it works again, so, awesome!

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'77 240D, 504H, OM617.952, etc.