Onan 5500 fuel pump not priming

The most common problem with a 10 year or older Motorhome, is, the rubber fuel line from the Fuel tank pick up tube to the Genset has dry rotted. The small cracks cause air thru the rubber and that disables the fuel pump from getting its prime to pull fuel. A quick way to determine this is to connect a gallon gas can and remove the existing fuel line from the genset and connecting a good new rubber line and see if the Fuel pump then primes. Usually it will. Doug

PS, If you hear a click, that may be the fuel cut off solenoid opening. BUT, you should also hear the Fuel Pump rattling trying to pump. This would mean your above fuel line is good. Also, I believe the fuel pump has a pressure cut off. When the fuel pump cannot pump, its internal pressure switch shuts off. When testing the fuel prime you need to disconnect the metal line at the Carb input. Onan and other Genset makers require a LOW pressure fuel pump which is what Onan makes and supplies. The aftermarket Automotive similar looking pumps are 2 to 3 times the PSI of a genset pump.

Thanks Doug...so the prime seems to be intermittent. It was just running for about 5
Minutes then stops. After it stops all I hear when I go to prime is a click...no fuel
Moving. If I wait about 10 minutes it’ll prime and start again, run for about 5 min then shut off. My fuel tank is between 1/4 and 1/2.

Rsnawder wrote:
Thanks Doug...so the prime seems to be intermittent. It was just running for about 5
Minutes then stops. After it stops all I hear when I go to prime is a click...no fuel
Moving. If I wait about 10 minutes it’ll prime and start again, run for about 5 min then shut off. My fuel tank is between 1/4 and 1/2.

Get the fuel tank above 1/2 tank and retest. Your 1/4 tank pick up may not be accurate. Doug

Will do..then I’ll report back. Thank you

Filled to 3/4 tank, same results. I’m going to try 2 things:
1). Charge all batteries to fill then try again
2). Leave the gas cap off.

It’s a stretch...any other suggestions?

Thanks!

Gas Gensets use about .7 gallons per hour. Connect a 1 gallon Gas can to the Gas input of the Genset and run the Genset. If it fails, then you need a new fuel pump. IF it stays running then think about a rotted supply line from the fuel tank. Doug

Rsnawder,

I know you may not think it is old, but 15 years (yours is supposed to be 14) is about the life of a fuel line these days. Make sure it is replaced with something alcohol compatible.

Matt

YOu say it primes and runs. then it stops and won't prime. then it primes and runs, then it stops and won't prime.

The fuel pickup in the tank has a strainer (pre-strainer) just like the water pump has. If you've left old gas in the tank (Gasser) or algae has grown (Diesel) that pre-strainer may be clogged.

Then there is the fuel filter it too can clog

And a pinched fuel line not letting fuel through.

all of those will act exactly as you have described Error code will show "No fuel".

I had a similar problem with my '84. Fuel pump would prime, generator would run for a while, fuel pump would start to clatter (as it ran out of fuel). Run times varied - it was frustrating.

Turns out it was a loose hose clamp at the fuel pickup at the tank. A dry rotted line would behave the same way.

Disconnect the fuel line and run it right from a gas can. If it runs without any trouble, there's your answer.

Awesome! Thank you everyone. I will start with the fuel line to a gas can and roll from there. I’ll update. Thanks again!