Onan Generator 4.0

Izzyblueye · 03-04-2010, 07:12 AM

I don't know if this is the best place for this question, but here it is. Does any one know where the fuel filter on an Onan 4.0 is? I have checked the manual and there is little to nothing in it on fuel filters. Can this be changed DYI or is it a dealer specific issue?

My generator will start just fine, run for 20 min full load, no pulsing. Then it starts to sputter, lose RPM and finally stop. It will not restart unless left set idle for an hour or so, then it will start and do the same thing. Gasoline in main tank is full up. Oil is right on the full mark. I have not been able to locate a fuel filter.

whem2fish · 03-04-2010, 07:18 AM

not sure about yours but mine is in the bottom of the fuel pump
look at the pump does the bottom unscrew if so the filter is a screen
ill check back
dave

Clay L · 03-04-2010, 10:08 AM

Follow the fuel line into the back of the generator. The hose is clamped to the filter. As I recall the filter screws to the fuel pump.

Izzyblueye · 03-04-2010, 06:28 PM

Thanks guys, I will check your information out. Sure hope I can find it.

Clay L · 03-05-2010, 08:04 AM

I think that you will find it okay. To remove it I think I used a deep socket inserted from outside the generator. reinstalling it was harder. I couldn't see the filter where it screwed into the fuel pump so my wife held the front of the filter in place while I screwed in it.

lonestarace · 03-07-2010, 06:50 AM

My 4.0 had a little inline filter between the fuel pump and the gas tank.

I had the same problem and it turned out to be the electric fuel pump(Facet brand). I had replaced it 6 mths prior. The way I finally figured it out was to put a transparent fuel line in between the carb and the electric pump. When it quit, the fuel line was empty.

I bought a different, much cheaper unit at AutoZone, wrapped it in pipe insulation so the heat didn't get to it, and never had a problem again.

whem2fish · 03-07-2010, 07:34 AM

same on fuel pump replaced mine yesterday got it on ebay $31
dave

lonestarace · 03-07-2010, 09:56 PM

I could also be the oil pressure safety switch. When the oil gets warm (and thin) the pressure drops and the safety switch kills the ignition. It located near the oil filter. Take the oil filter off, and thye switch it next to the filter gasket pad.