Fuel gauge replacement and effect on generator

[Neptune03dog]

I have a HR Neptune 03 Cummins diesel 300hp, Onan 55oo genset diesel. My fuel gauge reads full all the time and needs to be repaired. Is this something I could do at home or does it require dealer attention. Also, if my fuel gauge is not functioning will it effect the generator as in it will quit running as, code reads 45, which means below 1/4 full and can not run. Also my oil pressure gauge is erratic at times. Any thoughts or suggestions would be appreciated. Thanks in advance for your responses.

[Rudyp]

You talking about the control monitor circuit board on the wall (remote start)? I too have the same problem, will start up and then stop a few seconds later,
received codes 36 and then 45. I replaced oil, oil filter, air filter, and fuel filter to no avail. Fuel in tank shows more then 1/4 full of diesel. I put over a 1/2 of diesel 1st before I did all the above, I a beginning to think it maybe the diesel fuel gauge. Any suggestions? Thanks.

[Neptune03dog]

Yes circuit board in 5500 Onan diesel generator.

[MrWizard]

circuit board, in the Onan controls ?

[Neptune03dog]

Wanted to let everyone know the problem was the pc board. Had it replaced at a cost of $790 at Cummins/Onan in Jax Fl. Thanks to those who gave input.

[wa8yxm]

Fuel gauge not functioning will not affect generator save that you won't know when the tank is down too far....

Is it something you can fix at home.. Fuel gauges reading FULL, suggests to me one of two problems.

Most likely is a SHORT on the sensor lead.. MOST of that lead you can indeed reach and fix.. Some of it is atop the fuel tank and dropping an RV fuel tank is not for the faint of heart and requries a transmission jack (yes a transmission jack).

The lesser option is an open (usually if the wire is open it reads empty) in which case the same statment as above applies with a greater chance it's atop the tank.

The third option is a bad gauge (User replacable) and a bad sender unit (INside the tank and reauires dropping same).


NOW: in SOME cases, you can access the top of the fuel sender via a panel INSIDE the RV... But alas, only a few are built that way.. Mine is not.

[dougrainer]

IF your HR has the Roadmaster chassis. The pick up tube system is separate from the Fuel gauge sending unit. The fuel gauge sending unit on a Roadmaster can be calibrated. But the odds are it is defective given its age. Depending on the model Roadmaster, you can have 2 adjustment pots. One for the main fuel gauge and one for the APU level for the dash indication on the gauge. NO APU (genset) has any type control that will KNOW when the fuel level is low and not run or pull fuel. It will run the fuel pump regardless of the fuel level or any indication. The Fuel sender unit on a Roadmaster is very easy to replace and the tank does not have to be dropped to do like on a Frtliner chassis. You just have to calibrate it once it is replaced. Monaco will be where you get the sending unit. Doug

[MrWizard]

the generator has its own fuel pickup
the genny will quit running when the fuel is too low, regardless of what the gauge says
NOT because of what the gauge says

[Neptune03dog]

Thanks Fishinghat, I will find or make new ground. My fuel tank is full but generator will not run. I cranked it up to let it run for an hour or two as I do every two weeks when not using and it ran about 5 minutes and then quit. The starter works but it will not crank. I replaced the fuel filter but still does not work. Had fuel hose replaced about 200hrs ago as it had cracks and was sucking air. Ran fine until now. Not sure I want to tackle dropping tank and replacing sensors or tubes. Once again thanks for your response

[Fishinghat]

Since both the fuel gauge and the oil pressure gauge are erratic, a bad ground comes to mind as the cause. Clean the grounding point and reattach the wires.

As for your generator, it is designed not to run when your fuel tank is below 1/4 to keep you from being stranded in the middle of no-where, as you indicated. However, I'm under the impression that this feature has to do with the placement of the fuel pickup from the tank, not the fuel gauge, but that could just be the way my coach was set up.