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Curtis B.
Curtis B., service manager
Category: Heavy Equipment
Satisfied Customers: 17558
Experience:  30 years exp. with diesel engines, heavy equipment and forklifts, including lp forklifts
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Bobcat 731 w/ 2cylinder Deutz 511 diesel. I rebuilt the top

Customer Question

Bobcat 731 w/ 2cylinder Deutz 511 diesel. I rebuilt the top end without a problem, but it sat for several months and now i'm having fuel issues. new hoses, new filter, rebuilt the fuel pump (it was almost solid inside with junk). It starts as long as I have the button depressed next to the injection pump (must be a bypass button for cold starts or something), but soon dies out. About the only thing I have left to do is have the injection pump rebuilt. Its a Bosch PFR2K75A448/2 with ID number XXXXXXXXXX Any ideas? Where would you recommend I send the injection pump. Or should I just take out the pump and try to flush/clean it out myself? Sincerely, John
Submitted: 3 years ago.
Category: Heavy Equipment
Expert:  Curtis B. replied 3 years ago.

curtis b :

Check the fuel return to be sure it is open. If it is stopped up, the engine will only run till pressure builds in the return and then quit. It return is ok, I would run a test line from the fuel pump suction line back into the fuel tank and try it . You could have a fuel suction issue. If both of those things check ok, I would try cleaning the injection pump. Just don't break anything, at this point , you don't have anything to lose. Let me know. Thank you.

Customer :

Curtis - I have since learned that the button activated by an external solenoid next to the injection pump is an excess fuel solenoid. Hard to find diagrams that explain most of those things. Sometimes I feel a bit like Sherlock Holmes. I will check the fuel return. Makes sense. On this machine, it appears to be a vapor return...banjo fitting connected by a banjo bolt to the front injector...connects to a line that returns to the tank. I misplaced the banjo bolt while I was rebuilding and had to order a new one. I guess the best way to try may be to just disconnect that bolt and try to get it to run. I'll also blow out the line. That's the one line I didn't replace. I may have junk in things only because I chose to used compressed air to force fuel back into the system after I put it back together. On the test line part, I assume the following: On 731 fuel goes from tank to engine mounted mechanical fuel pump, then to filter, then to mechanical injection pump. I will run line from suction side of fuel pump to tank, prime and check. Same might work for injection pump. I'll try. I'll get back with you. Have to go to funeral today, will try to wedge in spare time. Sincerely, John

curtis b :

Let me know how it works out.

Customer :

What a sage you are. The vapor return worked fine. I hooked up the fuel supply directly to the injection pump and it worked fine. I then moved hoses around and isolated the filter and then the mechanical fuel pump. The mechanical fuel pump is the restriction. I rebuilt it last week, but that's just gaskets and strainer, etc. I suspect the pump rod or something has failed. I never really was able to get a good squirt out of it. But that's sure a lot cheaper than buying an injection pump. I should have thought to isolate individual components and remember always to check the simplest thing first. I really appreciate your help.

Curtis B., service manager
Category: Heavy Equipment
Satisfied Customers: 17558
Experience: 30 years exp. with diesel engines, heavy equipment and forklifts, including lp forklifts
Curtis B. and other Heavy Equipment Specialists are ready to help you
Expert:  Curtis B. replied 3 years ago.
Thank you for the feedback and bonus!!!!
Customer: replied 3 years ago.
Curtis - For your future data bank, I checked my fuel pump once more. I had put an extra copper crush washer on the bolt that went through the banjo fitting on the suction side. It was just enough spacing to restrict flow through the orifices in the bolt. I fixed and everything seems to work fine. Sincerely, John
Expert:  Curtis B. replied 3 years ago.
Thanks for the extra detail. Have a good day.

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