Injector pump gurus

MSM

Well-known Member
I have a stanadyne DB pump on a cummins engine in an Onan generator. It has been sitting for several years but only has 36 hours run time on it. Engine will start and run for 3-5 seconds and shut off.It will immediately restart and die. I have temporarily eliminated the shut down system by running 12 volts directly to the fuel shut off solenoid. Fuel is clean, new fuel filter, excellent fuel flow to the injection pump.I have temporarily installed an electric fuel pump to eliminate any problem with the mechanical transfer pump. Fuel return fitting is clean and open,but no return fuel to the tank.
Acts as if it is not properly charging the injector pump with an adequate amount of fuel.
Any suggestions before I take the pump to a pump shop. Thanks
 
Still sounds like a blocked return line. If you can remove the two bolt side cover so fuel can leak out to see if it will keep running. If cover is on the back side with no easy access try running with the return fitting completely out of the cover, with a catch tray as this will be a messy test. There should be a little fuel out the top, but how much depends on what vent wire is in the head. It will shut down if the return is blocked anywhere in the system even with a known good cover return valve.
 
I agree with Dieseltech. No fuel return means a plugged return system. If you can't get to the door. You can also remove the fuel fitting from the top of the pump. If you find what looks like black sand. Seals in pump are coming apart. Time for an overhaul. Be sure and time the pump before you remove it.
 
Be sure that you hooked the throttle up, before trying to start it. I didn,t hook it back up, on my 580E back hoe, and had a man out to help take the pump off, and repair it. that was the first thing he noticed. YES I was embarresed!
 
Lack of fuel coming out the return does NOT have to mean something is plugged. It's possible the fuel-charging pump in the back many not be working. If not, no fuel from an outside source is going to work its way through.

I'd first pull the top cover off the pump and see if any fuel is coming of there.

If not (no fuel) - I'd pull the timing window off the side and make 100% sure the pump is actually turning and does not have a snapped driveshaft.

If that is all OK - I'd pull the low pressure fuel-pressure regulator and screen out of the inlet of the pump. Make sure the screen is clean and the piston and spring are working as they should.

If that looks OK, I'd pull the back cover off the low-pressure inlet/charge pump and see if the two pump vanes are not broken or stuck or worn out. Old ones are fiber and newer ones are steel.

Also note that the fuel shut-off solenoid has NO direct mechanical connection to the internal parts of the pump. Even if it has power and you hear it "click" . . the fuel still may be shut off. All the solenoid does is move out of the way of spring-loaded linkage and it's that linkage that turns the pump on. If it's stuck, it won't run regardless if the solenoid is working or not.
 

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