Fuel pump trouble shooting

old sparky · May 15, 2020

I have a B7100 that I cant get running after running out of fuel. I cant get a solid fuel, air bubles are always there. So to prove my fuel pump is good or bad. Can I bypass my pump with a electric pump? To see if my pump is bad?

thanks,

Peter 315 · May 15, 2020

Yes you can but are you sure all the fuel filter gaskets are on correct?

old sparky · May 15, 2020

no, My fuel assembly was leaking and I couldnt get the filter out. So I bought a new assembly and just bolted it on. bleeding of corse. I have tried getting it running and think I just about got it then it slows rpms. Then I try bleeding while running and usually make it worse, then it dies. I think I have a electric fuel pump in the garrage and thought I may put it on to try?

rScotty · May 15, 2020

old sparky said:
I have a B7100 that I cant get running after running out of fuel. I cant get a solid fuel, air bubles are always there. So to prove my fuel pump is good or bad. Can I bypass my pump with a electric pump? To see if my pump is bad?

thanks,

No you can't use an outside pump. Diesel fuel pumps are special. They take in a constant flow of fuel from the fuel filter assembly and as the motor turns the diesel fuel pump sends fuel to the injectors in a timed pulse at several thousand PSI. That pulse of fuel opens the injector and sprays a little fuel into the combustion chamber at just the right time to meet the piston coming up on the compression stroke.

So a diesel fuel pump - called an "injector pump" has almost nothing in common with a low pressure constant flow electric pump.

What you are seeing is very probably a poor connection in the fuel line between the fuel filter assembly and the diesel fuel pump that is allowing air to be sucked into the fuel line. Maybe so/maybe no...but that is a common problem and gives the exact symptoms you are seeing. Running a diesel out of fuel can be a hassle that has you believing all sorts of crazy stuff, but it is almost always a bad connection in either the fuel lines or the fuel filter bowl that is putting an air bubble into the fuel line.
good luck,
rScotty

Agvg · May 16, 2020

If it starts you have an issue with fuel delivery, remove and inspect al pipes and fittings from the tank to the pump, and check if there are a strain in the tank it self.

old sparky · May 16, 2020

FYI. The problem is the fuel pump. The low pressure pump that supplies the injector pump is bad. After getting to it. I saw it was leaking, so it was sucking air also. I bypassed it with the electric pump, bleed the lines and it runs and accelerates as it should. I will get a pump ordered. Would there be a problem running an electric pump permanently? I ordered a replacement but wonder?

thanks

PILOON · May 16, 2020

Permeant electric, no I don't think so. Often a cure for many similar situations.
BTW, that is a 'lift pump'.

Peter 315 · May 16, 2020

old sparky said:
FYI. The problem is the fuel pump. The low pressure pump that supplies the injector pump is bad. After getting to it. I saw it was leaking, so it was sucking air also. I bypassed it with the electric pump, bleed the lines and it runs and accelerates as it should. I will get a pump ordered. Would there be a problem running an electric pump permanently? I ordered a replacement but wonder?

thanks

The newer tractor have a electric transfer pump ,lift pump , what ever you want to call it......