BAC Forum
General Boards => Technical Support => Topic started by: Anand Shah on June 18, 2021, 12:36:05 AM
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Hi All - need some help with an Onan 12.5kw Generator - trying to leave for a trip in 3 days but can't keep it running and kind of need it.
First: Rig is 2007 Beaver Marquis
Second: Generator is a Kubota powered Onan 12.5 QD
Third: Code the Genset is spitting is 36
Fourth: Fuel is well past 1/2 tank. Added more anyways.
Fifth: Changed air, fuel filters and oil already
Here is the issue, if cold, it will start and run for an hour or so and dies. Won't start again - try priming - no go. Went in for a tune up to see if it was a filter problem. Fuel Filter, Oil, Air Filter Changing Started, ran for an hour or so and died.
Went back to the truck repair place and we hunted down the issue to fuel pump on the genset losing power after an hour or so. We gave the fuel pump hot 12v directly and the generator started right up. Checked the AGS controls and hit the test button and it also attempted to start the genset to no success, everything looked ok at the AGS unit.
Their best guess is a (1) bad fuel pump relay (heating up), but don't know where it is (not on the front/rear run boxes, assuming in the genset somewhere), (2) a bad control board (but can't figure out where it is either - help?) Assuming same as the relay? it is under the black panel on the top front side of the generator but not clear? Or (3) potentially a bad fuel pump that is drawing more current than it should.
I'm hoping that one of you wonderful folks on this forum knows these things better we do - we looked through the Onan Manual and the Beaver schematics and no real solution to a fuel pump relay or circuits (there is a diagram in the Onan book, but it doesn't tell me where the board would be or if there is a removable relay, etc).
Would love any advice on how to get closer to a solution here and what parts I might need to order or hunt down given that I have little time left before we get moving.
Thanks big time in advance. I read this forum literally several times a day. I owe many of you a cold one for the help I've already gotten and hope I can add useful input as I learn more about my own rig.
Anand
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Anand, our 10 k gen had the same universal fault code and after replacing the fuel pump found that our control board was bad. However in the irv2 forum their are several post stating that you can unplug the control harness and spray with contact cleaner and solve the problem. I also saw info on the location of the control board on the forum which Cummings could also help you with. Give it a try .
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This quote from a mechanic site has another thing to look at - it could be sucking air through a bad fuel line...
"Fault #36 happens when the engine stops running due to a reason unseen by the controller /inverter unit.
"The most common cause of this is running out of fuel , so you may want to replace the fuel filter as a first step.
"The next thing I would do would be to run the genset with a shortest possible length of fuel hose drawing clean fuel from a fuel can. We need to try to isolate the problem from the coach. The fuel lines on the coach could be sucking air , or there could be a broken pickup tube inside the coach fuel tank.
"The electric fuel pump could also be the problem. If the genset still quits running with the fuel container setup , I would suspect the electric fuel pump.
"A defect in the controller/inverter could also cause this , but they are expensive to replace , and not the most likely."
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Anand,
Look at the 10KW Parts Catalog under Generators in Coach Assist. It shows location of control PCB and relays. Diagrams are toward end of document.
Steve
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As always, very helpful. Thanks. I've found the relays in this doc, going to try that + cleaning connectors and see if that keeps the voltage to the pump constant. If not, I'm going to aim for the control board (hopefully not). The fact that it runs with 12v on the pump suggests it is getting fuel just fine, but will also double check the fuel lines. Will report back tomorrow evening once I try these.
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SOLVED!
Thank you for all of the responses - it may still be a overheating control board issue, but cleaned all of the pins on the connector to controller board and the 10 pin remote connector. Also replaced the fuel pump relay which was hot to the touch after 10 minutes of running. Not sure which of these worked but it ran like a champ after that.
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Good to hear. Sounds like possibly a resistive contact in the relay.
Steve
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I LIED.
Turns out this did not fully solve my problem. It ran for 4 hours yesterday before I turned it off; Today it died after an hour or so, wouldn't start for a few minutes, but then started up and ran for another hour or so.
The different this time seems to be that I can get it to start and run again, for the most part, and for longer than before.
I'm guessing control board and/or fuel pump next. Since the pump works ok most of the time, maybe a wiring issue. Will check the relay again to see if there is still resistance there. I ordered an "aftermarket" control board that will arrive in time for 1/2 the price of the Onan one. Let's see if it is anywhere close to as good - not to create new problems :)
Thanks,
Anand
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Sounds like an electrical overheat issue. Would expect a fuel problem to result is some sputtering or missing, not just die and then re-start.
Steve
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Just to close this thread - replaced the control board with one from Flight Systems. Took 20 minutes and it seems to have solved my problems. Let’s see, hasn’t shut off on me yet.
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My Onan 10K quiet diesel would run for about 2 1/2 hours then shut down. Steve Huber asked me how many hours on the Gen. I told him it had 1340 hours. He advised that the blower belt was worn and could be the issue. So I crawled in and let the adventure begin. 2 hours later there it was or I should say what was left of the blower belt. Put a new belt on and the velocity was 10 times stronger out the discharge area underneath. I am not sure if your 12.5 has a blower driven belt.
Hope this helps, Fred
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I will check. Could very well be! I have 3700 hrs.