Another gen problem

I had a similar issue with our Onan Marquis 7000 - it would start and run for 15-20 mins and then quit. Tried everything until finally replacing both the fuel filter and fuel pump. Now it runs for days with no issues.

Could be a cracked fuel line coming from the tank causing it to suck air. Had the same issue on my 5500 and chased what I thought was overheating, vapor lock issue with no success. Replaced the fuel line all the way from the tank to the generator fuel pump and have not had any more issues.

Quick check....run a line from your genny fuel pump into a gas can on the on ground outside the compartment and see if it keeps running longer than does now.

Mine would run in 100 degree weather for a couple of hours from the can and quit after about 20 minutes when hooking the main line back up.

Worth a look...cheap fix.

I had similar problem with a 4K onan. After taking it in and out twice and to a shop twice I fixed it myself. Took the cover off, found a square plug with multiple wires coming and going. Sorry I don't know what it would be called, about 2" square. Unplugged by gently prying open with screw driver, multiple tiny pin style connectors, very tiny so be careful. Sprayed with electrical contact cleaner, both male and female sides, plugged and unplugged multiple times to clean corrosion. Plugged back in, fired up and problem solved. Not saying this is your problem but solved mine. Generators live with corrosion due to road spray like anything else. Good luck, Don

another issue some ONAN's had was the fuel pump getting to hot. This caused vaporization leading to no fuel flow. The cure seemed to be moving the fuel pump off the genny to a spot on the compartment wall.

lc0338 wrote:

10forty2 wrote:
If it runs for 20-30 minutes and then stops, but after cooling it restarts and runs again, then it's not likely a fuel delivery problem. Sounds more like the control board is getting too hot and causing shutdown due to overheating. May be a bad component/sensor, may be something as simple as not enough ventilation in the genset compartment. It may also be a small crack in the circuit board that opens up a connection when it gets hot due to expansion but closes back after it cools some.

Try running the genset with the compartment door open. If it keeps running after the normal shutdown time, then it's probably a heating problem.

Yeah right, lets forget the simple things. This must be a real complicated issue. lol

Wasn't trying to dis your suggestion....just adding another one. Sorry if it offended you...

10forty2 wrote:
If it runs for 20-30 minutes and then stops, but after cooling it restarts and runs again, then it's not likely a fuel delivery problem. Sounds more like the control board is getting too hot and causing shutdown due to overheating. May be a bad component/sensor, may be something as simple as not enough ventilation in the genset compartment. It may also be a small crack in the circuit board that opens up a connection when it gets hot due to expansion but closes back after it cools some.

Try running the genset with the compartment door open. If it keeps running after the normal shutdown time, then it's probably a heating problem.

Yeah right, lets forget the simple things. This must be a real complicated issue. lol

If it runs for 20-30 minutes and then stops, but after cooling it restarts and runs again, then it's not likely a fuel delivery problem. Sounds more like the control board is getting too hot and causing shutdown due to overheating. May be a bad component/sensor, may be something as simple as not enough ventilation in the genset compartment. It may also be a small crack in the circuit board that opens up a connection when it gets hot due to expansion but closes back after it cools some.

Try running the genset with the compartment door open. If it keeps running after the normal shutdown time, then it's probably a heating problem.

lc0338 wrote:
have you replaced the fuel filter. may be partially clogged and not letting enough fuel through fast enough.

X2. I had a surging problem with my Onan 5500. A new fuel filter corrected the problem.

have you replaced the fuel filter. may be partially clogged and not letting enough fuel through fast enough.