How to test a fuel pump on an Onan 4000 generator

navegator wrote:
What amount of fuel is in the vehicles fuel tank, if it is 1/4 or less the generator will not run, fuel line to generator is at the the 1/4 level, easy to forget, check the amount of fuel...

That's what I was thinking.

In our rig, it's 1/3 tank, not 1/4, so anything below 1/2 tank, I'd fill up to make sure that is not your problem.

And I also agree with the others. Stand outside with the generator cover off and listen while your mate is holding in the prime button. No sound means something has gone wrong. On my generator, there is a duplicate primer button right on the generator so if you have one, you can test and listen outside by yourself.

What amount of fuel is in the vehicles fuel tank, if it is 1/4 or less the generator will not run, fuel line to generator is at the the 1/4 level, easy to forget, check the amount of fuel, then check the fuel filter, and then check the grounds chassis to generator, they do corrode with time.

navegator

Nice Plane, Harvard! Is that the ones the Yanks call a TEXAN?

These in line fuel pumps work by cocking a 12 VDC spring loaded solenoid that has a check vave. The spring provides the fuel pressure and the 12VDC power is a pulsed source that does the cocking.

Pump should run when you hold the Start/Stop switch to OFF. If you disconnected from the Carb, it should pump gas into a can.

When it quit, acting like it was out of gas, the On/Off Switch should have winked out a Trouble Code. I want to say "36" which would show as "--- ------" is a non-specific "Dunno what Happened" code commonly associated with Out of Gas.

As CD said, if you've got it connected to a battery or charger, polarity's right, it should pump.

In a green ONAN box, that part is around $100. There are un-branded replacements on Amazon for around half that. My guess is they're made by the same bunch on the same bench in China.

You CAN substitute a low-pressure auto supply pump (3-5-psi) but ONAN would say they aren't legit unless they serve as fuel shut-off when not running. You "should" have a dedicated genset fuel pickup on your main chassis tank. I don't think your non-running genny would siphon your main tank through its pump, filter and carburetor. The Needle/Seat valve would have to leak also. So that could be your quick fix if your proper part doesn't come through. MrGasket, Purolator, NAPA, etc. Just get Low Pressure.

2014 sounds like the part might be under warranty. Getting to the right place in time to actually exercise it probably suggests fixing it yourself.

From all you say, unless the pump isn't getting power from the control board or isn't grounded, it's bad. If you applied battery to the hot terminal and grounded the pump, it's bad.

Still, if a crack or pinhole developed in the lines or the strainer on the suction side of the pump and it's sucking air, will probably run out of gas...

The fuel pump on our Onan 4000 makes a buzzing sound when it runs. From the three steps you performed, it sure sounds like the pump is toast.

Probably an obvious statement, but since there is only one wire (12V positive) on the pump, the metal frame of the pump must be connected to the negative terminal on the battery for the pump to run.