Onan 5500- -Won't Stay Running- -Help?

[MrMud]

I have a 2003 Onan Marquee Gold 5.5 HGJAB-901B gas unit with 194 hours. I run the unit monthly and keep the fuel tank full as not to have problems with condensation. The oil & filter was changed recently and has about 10 hours at present. The fuel filter has not been changed and that is my first step in trouble shooting. If it does not start, my next step is to check the fuel pump along with the fuel lines to be sure that it is not a fuel problem. This is the first of any problem I had with the unit.

My Onan was running for approximately 20 minutes for the monthly exercise and she just quit. I was running 2 AC’s, the hot water heater and the frig to give it a good workout (+/- 36-42 amps) planning for the hurricane season. I have an EMS system that manages the electrical system with sharing different components as not to over load the unit. So, this problem should not be the cause.

When I heard it shut down, I turned everything off and tried to start it. It will run as long as I hold down the start button, but when I release it, it stops. The trouble shooting code indicating on the switch is 32. That indicates low cranking speed or low battery power. I check the battery connections and put a charger on the batteries which is not the problem. I tested the house batteries with a battery tester and it is in the green area. The oil is full and still clean/clear. I flipped the 30 & 20 amp breakers on the unit itself with no avail.

What are my alternatives for the next step? Inquires will be appreciated. Thanks to all.

 

[pegasuspinto]

These aren't real complex-don't get too frustrated. If it runs OK with the switch held down, quit looking at the engine and battery-they are OK.

They won't keep running if the output quits. But the computer will bypass that if you start it again after it stalls-I forget the exact proceedure, but after a couple of tries it will bypass. You will see the light flashing rapidly letting you know it's in diagnostic mode and the output is dead.

Last one I saw did that, the output wire had worn through, which killed the excitation faster then the breaker would pop. Flip the circuit breaker inside the unit off and see if it starts and runs OK without the light flashing. If so, there is a short downstream of the breaker. If you pull the positve battery cable off (disconnect the battery and/or insulate the bare battery cable end) you have a 10mm bolt under the switch holding the plastic cover down, you can then pull that up and off to get to the back of the circuit breaker. Turn off the breaker, turn off all the loads, and use a multimeter on the load side of the breaker to check that each leg to each other and to ground is infinate resistance. A common short point is right where the leads exit the liquidtite conduit fitting on the bottom of the set, if people didnt use the liquidtite conduit. the fitting has sharp corners that cut the wire without conduit in place. Both the negitive and ground bolt with a 10mm bolt about 3 inches back from the cover bolt (there are two sets of grounds under the cover), and the output leads go from the breaker right out the condiut fitting as well-except there is a loop with a zip tie between the engine plate and the bottom mount plate that makes just pulling new wires pretty hard. If you can get the cover off easy you can route new wires without much trouble after removing the computer cover (the black cover behind and mates with the switch cover)-if you can't get the cover off, you can cheat and run the new wires out the grommet on the cover and abandon the broken wires in place. Of course, you will have to check for shorts in any of the rest of the system as well....

Check the armature is turning-you can look over the top of the switch and see the generator and should be able to see the armature is turning inside. It's belt driven, I would be shocked to see your low hours unit snap a belt, but anything can happen. There is a brush block you can access as well, and you can check the brushes, and can visually check to see the slip rings didn't migrate up the shaft (seen it happen on one of those).

To go much further, the cover has to come off. (which in some cases means you have to remove the set) Common failure points are the wiring harness or the computer (which houses the regulator as well). Someone will soon post a link to the manuals, I bet, and it would be wise to go through the troubleshooting, but keep the common trouble spots in mind.

Robert

 

[Kevin K]

I think this is the correct service manual.

http://www.cumminsonan.com/www/pdf/manuals/983-0501D.pdf

This is a large file, 7.7 Mb, please allow time for it to download.

 

[K D Redd]

A eight year old belt, if stored in a hot environment, would NOT surprise ME to see it broken no matter how many hours are on it.

Kent

 

[MrMud]

UPDATE 9-2-11

After all the trouble shooting, the problem was a broken belt. When the belt broke some of the threads of the belt got between the shaft and ruin the seal. The parts to fix it were $132.00 and labor was $906.00 along with the tax for a total of $ 1126. For a belt to break, that was a expensive repair. They said around 8-10 years the belt needs to be changed. To repair it, they had to remove the whole genset and tear half apart to get to the belt and pulley. To change the seal the bottom part of the engine had to be opened up.