Trouble with my onan generator

[MrRichard]

I've got an Onan 4.0bf3cr16000b in my 1978 Sportscoach. The generator only runs when I'm holding the start switch. I replaced the fuel pump thinking that was the issue, but it's still doing the same thing. I'm starting to think it might be the R1 resistor or the oil pressure sensor. Anyone know what causes the pumps to act up like that? and does anyone know exactly where that oil pressure sensor is on this model?

I'm also looking for a parts catalog or cross-reference to find reliable Onan generator parts, so if anyone has recommendations or links, I'd really appreciate it.

 

[LevelUpLifter]

@MrRichard Usually, those classic Onan "start switch hold" issues are caused by a safety circuit (like a low oil pressure sensor or generator AC output sense) not getting its signal. The start bypasses these.

for the oil pressure sensor, look on the engine block, often near the oil filter, with one wire.

For parts/cross-references, hit up Flight Systems or Cummins QuickServe Online (with your full spec number!). You're on the right track with R1 and the oil pressure sensor!

 

[GeneratorREX]

Could the control board be failing to keep the run circuit energized after start maybe the R1 resistor or oil pressure sensor isn't completing the feedback loop? Have you checked for voltage drop?

 

[MrRichard]

@MrRichard Usually, those classic Onan "start switch hold" issues are caused by a safety circuit (like a low oil pressure sensor or generator AC output sense) not getting its signal. The start bypasses these.

for the oil pressure sensor, look on the engine block, often near the oil filter, with one wire.

For parts/cross-references, hit up Flight Systems or Cummins QuickServe Online (with your full spec number!). You're on the right track with R1 and the oil pressure sensor!

That helps a ton, thanks! I'll check near the oil filter for the sensor and test the circuit, I didn't know about Flight Systems, I'll try QuickServe with the full spec too

 

[MrRichard]

Could the control board be failing to keep the run circuit energized after start maybe the R1 resistor or oil pressure sensor isn't completing the feedback loop? Have you checked for voltage drop?

]I haven't checked for voltage drop yet, but I will now, I'll test R1 and the sensor while I'm at it.