James, thank you so much for your video. I have the Onan Marquis 5500 and it was acting exactly as you described in your video. You gave a very detailed description and mine fit exactly with the same problems. I ordered and installed a new fuel pump and new fuel filter, purchased a new fuel line and some clamps, and after the installation the generator runs perfect! Thank your for your work in producing the video. It saved me tons of money taking my RV to someone to guess about the problem!
Mine is doing the same thing except the generator is so hot you can't touch it. One person's post said he had one doing the same thing. Turned out it was the fuel pump would heat up when the temp got over 96 degrees then shut down and that was exactly like mine was doing. At night his gen set would run fine just like mine did. He replaced the fuel pump and no more problems.
Nice job. It's always good when one is able to fix an annoyance, especially one that interrupts recreation time! Going through this myself this week on our Onan 5500, I was waiting for you to bring out the IR thermometer and show us the threshold where the pump output flagged, also if it would recover while running if cooled. Modern ICE cars immerse their pumps in the gasoline for exactly this purpose (and to reduce fire potential). BTW, these pumps are solenoid devices. Back and forth with check valves vs. spinning. The pulsed output is a giveaway.
Ha-ha! I had a set of those crimp style hose clamps on new radiator hoses for a 1980 Horizon I had a good many years ago and didn't have the tool for it either. I crimped them up with a pair of dull ceramic tile trimmers which didn't close all of the way! Worked like a champ! Nice job!
I just finished replacing the fuel pump on my Onan 5500 1 hour ago.The code it gave me was 33 , however my best clue was opening the drain on the Carburetor bowl. All I got was a drip drip then it was dry. 360 hours on the meter so it’s not new but far from warn out. Whenever I primed the pump it was loud enough to hear in the Fifthwheel. It would fill the bowl on the carburetor then I would start it. Then it ran until the bowl was empty when it shut down. All the clues pointed to fuel pump fail. So for $65 bucks for 1-fuel pump & 2-fuel filters. When I primed the gas it was loud for 1 sec. then I couldn’t tell it was running. As I started it I flushed the carburetor with SeaFoam spray. I just ran it for 2 hours under load with no hiccups. Take note that every tank full of gas you run through your Generator should include SeaFoam. Yes it’s spendy but then so is the Generator you rely on. I use mine seldom because of a complete 700 Watt solar system. Both in my main battery pack for the RV & 4-8D’s in the Garage for power for most other power tools or what have you. I am not a full timer but if I need to be I want back up for the backup. Redundancy is great when you need it to be.
It was the fuel pump. Just wanted to rule out tune-up items. Replaced the fuel filters, air filter and spark plugs as they were over due for maintenance. Though it was fixed. Tested for hours in my driveway and several 2 hours trips without issue. The issue occurred again on the next long trip. Had previously read online that the fuel pump was a problem on this model and replaced it without knowing 100%. Was just going to trash the old pump, but wanted to know for sure if it was fixed before going on the next trip. So running it that way on the bucket with water, I was able to validate that the correct part was replaced.
Rick Butler if the pump was dead that would have worked. Initially the issue would only happen on the road several hours into a trip. Was not in a position to try that. Could not reproduce at home. One time after it stalled, I opened the bowl drain screw on the carb and gas came out. That set me in the wrong path for a while.
And let's just start replacing parts without proper testing, because we "think they might be the problem". That is why you are not a genset technician.
So Mr. Condon puts out this nice video with successful testing session and a great result and you're bagging on him because he didn't it right? I'm glad I watched it and discovered this is a potential problem with these generators because I have the exact same symptoms. Thanks Mr. Condon
Wow another idiot bashing someone helpful. You wont see any onan gen set technicians offering free time making videos like this. If they were they would not have any work to make money. Lol
