Onan 5000 won't start

I have an Onan Marquis genset. The Emerald is the previous model. Sorry for the bad info . . . .

But an oil pressure sensor might be under that cover near the oil filter?

Best,
- bob

Took a minute and checked for a oil pressure sensor near the fill plug as suggested. Nothing like that near the fill plug. Here's a picture of the genset.

Looks like I will need to drag the whole unit out. To do that, the exhaust pipe and muffler must come off first!

ksg5000 wrote:

To my knowledge Generators are installed with fuel lines positioned so they can't drain the main RV tank dry - no sensors involved.

Well DUH. :?

Sometimes it takes me a while to catch on.

No doubt you are right.

"In addition to that, somewhere there is a "sensor" that tells it the main tank is getting too low. It is possible that has malfunctioned also."

To my knowledge Generators are installed with fuel lines positioned so they can't drain the main RV tank dry - no sensors involved.

427435 wrote:

My tank is full-----how would the genset know the the level of the MH tank? I figured it would just stop running when the genset's gas pickup stops supplying fuel.

While that is possible, I think it is HIGHLY unlikely.

My "cheap" little C even has a safety so that the genset won't run the engine out of fuel......thus leaving you completely dead in the water.

On mine, there is a fuel sensor somewhere (or tied into the main gauge somehow) that stops the genset when it reaches a pre-determined level of gas in the tank. I don't know where the sensor is or exactly how it works but I know that it DOES work on mine.

Vulcan Rider wrote:

JumboJet wrote:
My generator ran fine last October. When I went to start it in March, it would not run. I disconnected the Oil Pressure safety switch and it fired right up. I replaced the switch and it has run fine since then. May be your issue also.

In addition to that, somewhere there is a "sensor" that tells it the main tank is getting too low. It is possible that has malfunctioned also.

My tank is full-----how would the genset know the the level of the MH tank? I figured it would just stop running when the genset's gas pickup stops supplying fuel.

JumboJet wrote:
My generator ran fine last October. When I went to start it in March, it would not run. I disconnected the Oil Pressure safety switch and it fired right up. I replaced the switch and it has run fine since then. May be your issue also.

In addition to that, somewhere there is a "sensor" that tells it the main tank is getting too low. It is possible that has malfunctioned also.

darsben wrote:

427435 wrote:
Thanks for the replies and for the link to the manual. I hope it's the oil pressure sensor. In any event, I will post back with the resolution when I get time to work on it. Right now garden and yard work are taking precedence.

If you changed the oil that could be the problem. Onan had a problem with some 5000 generators that foaming when the engine was filled to the correct level caused the low oil level switch to open. Their cure was a different dipstick (small) that had markings at a lower level.Mine is one of them

Oil hasn't been recently changed. Same oil that was in it 2 months ago when it was last started.

Just thinking about the oil pressure switch------------why wouldn't it's lack of pressure signal be ignored while cranking? There wouldn't be any pressure until the engine is running (or cranked for a long time).

427435 wrote:
Thanks for the replies and for the link to the manual. I hope it's the oil pressure sensor. In any event, I will post back with the resolution when I get time to work on it. Right now garden and yard work are taking precedence.

If you changed the oil that could be the problem. Onan had a problem with some 5000 generators that foaming when the engine was filled to the correct level caused the low oil level switch to open. Their cure was a different dipstick (small) that had markings at a lower level.Mine is one of them