My 300SD engine stalled yesterday and will not start

Still sounds like air in the system (between injectioin pump and injectors). Crack those injector lines again and crank for 30 seconds - let starter cool - crank another 30 seconds with throttle all the way to the floor. If nothing check lift pump. I am seeing more lift pump failures as these engines age. (bolted on side of injection pump - easy replace). To test disconnect banjo fitting at top of filter from the plastic line coming from the lift pump. Put line in cup. Crank with starter motor. You should get a steady (not high pressure) flow of fuel. If not there is a restriction from the tank to the lift pump or lift pump is bad. To be sure connect a small bottom of fuel to the inlet of the lift pump and test again. Make sure your hand primer pump is not leaking (could be sucking air)

I tried everything you suggested. Cranked the engine with the lines cracked open at the injectors, but there is absolutely no fuel coming out of the injector lines at the injectors. At high pressure the IP can produce, there would be fuel squirting all over the injectors. I removed the banjo fuel line fitting from the lift pump to the main filer housing and cranked the engine. There is good steady flow of fuel. Which means that the lift pump is working. The hand primer pump is working too. As I kept working it, I loosened the top bolt on the main fuel filer housing and fuel came gushing out from the filter gasket under pressure. I also disconnected the banjo fitting from the filer housing to the IP pump. When hand primed, fuel flows out of the main fuel filter to IP line port. I removed the fuel line from the main filter housing to IP pump, made sure it is unobstructed, and reinstalled it. Primed the system again, tried to start, without any success. Not even a hint of engine trying to start. No fuel coming out of the injector lines at all. It really seems like the IP is not pumping at all, like the drive gear sheared off the shaft or something. Is there a Woodruff key or something on the shaft holding the gear that could have sheared? What IP failure modes are there?

Is the next step to remove the injector lines at the pump and crank the engine to see if there is any fuel welling up in the pump delivery valve housing?

Prior to this failure I noticed that the engine seemed to be running a bit lean - did not sound right at higher RPMs and the IP mounted transmission control valve was making strange buzzing noise all the time with the engine running. I did not notice that before. Looked kinda odd to me.

From my experience the injection pump is the last thing you want to go after. From the sounds of what you have done it may be the culprit. Here is a way to know for sure.

Connect an indepent fuel source with a fuel hose directly to the banjo fitting on the drivers side of the IP through a plastic pre-filter. Use a hand bulb primer pump with internal check vavle (in line) in the hose to build pressure in the pump. Remove injector number one and reconnect outside engine to metal hard injector line. Put a cup or other container under the fuel injector. Crack the nut at the injector and crank the engine over until you get some evidence of fuel coming out of the nut (air bleed procedure). tighten the nut back up and crank with the starter motor again. If you can not get a high pressure spray out of the injector then you have some type of internal failure in the pump. Remove and have tested at a Bosch facility. I also have some good used 617 turbo pumps if you want to go that way. Good luck. Kent Bergsma

Thanks for the additional advice, Kent. I have some extra fuel injectors so I can use one of those for the test. I may have one of those rubber bulb fuel transfer lines from harborfreight which will probably work. I need a fitting to screw into the IP fuel inlet port, right?

BTW, I did disconnect the fuel hose at the fuel tank screen fitting and fuel came out in a strong steady stream as if there was no screen there at all. So I do not see any issue there.

To remove the injection pump, one must remove the timing chain first, or just loosening the tensioner on the timing chain will suffice to slip the pump drive gear off the timing chain? If I remove the valve cover, can I see if there is anything funny with the IP pump drive gear? I would like to check that.

Well, today I decided to give it one last try before doing anything with the IP. I cracked loose the fuel line banjo bolt fitting from the main filter to the IP, and then used the hand primer pump to pump up the pressure until I saw fuel squirting out. Then I tightened the fitting and cranked the engine for about 10 seconds. I finally started seeing fuel coming out of the injector lines. Tightened those, and cranked engine again for about 10 seconds and this time it started! So evidently I did run out of fuel and I never thought it would be this difficult to start the car again. Thanks for all the help!. I am glad I did not have to replace the injection pump.

Way to stick with it and work through the problem. Now you know why I said the LAST thing you want to consider is your fuel injector pump. I hope this thread will help others diagnose their fuel delivery problems.

1985 300D 300K
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1997 Camry 119K
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super good thread guys. I had a similar problem a few months back and in the end it was nothing but air. Diesels must NEVER run out of fuel.NEVER!