Hey guys. I am looking for a onan generator mechanic in the NJ NY area.

RJ Control in Dover NJ. Rich & Matt are Onan experts, racers & awesome guys to deal with...

Thanks Bill....

Yea I work on them practically everyday...

Matt is busy in the office everyday and business is good. He sold everything racing related about 3 years ago. He had a very successful run in the sport...


973-328-6880 ask for Rich.....

Rich, question...
I have a 7000 Onan 7HGJAB-900A 2003 Sat for a long time in the trailer. Varnished. I cleaned the tank, replaced fuel lines and filters, removed carb and cleaned varnish out. The control solenoid on the bowl was stuck too. New gaskets and Its free now and works. New plugs, oil, filters etc. Runs great but has a slight surge loaded or unloaded. I can pull the choke back a little and smooths right out. The altitude control does not seem to have an affect on it. Its at 0 here. Figured I would ask the Guru.

Pry the black plastic cap(altitude adj.)straight off very carefully. A slightly bent screwdriver works best. The cap limits movement on the mixture screw it sits on. It’s knurled and so is the screw. It’s a brass needle and breaks if you bend it trying to get the cap off. Once off, run the machine to full warm and try backing the screw out half a turn or more. If it cures it, pop the cap back on. You may have not cleaned the carb fully. Doesn’t take much to lean out slightly and run unstable. A real common problem and the mixture screw is the first and easiest thing to adjust.

quote:

Originally posted by SCDIV1:
Pry the black plastic cap(altitude adj.)straight off very carefully. A slightly bent screwdriver works best. The cap limits movement on the mixture screw it sits on. It’s knurled and so is the screw. It’s a brass needle and breaks if you bend it trying to get the cap off. Once off, run the machine to full warm and try backing the screw out half a turn or more. If it cures it, pop the cap back on. You may have not cleaned the carb fully. Doesn’t take much to lean out slightly and run unstable. A real common problem and the mixture screw is the first and easiest thing to adjust.

I really took my time cleaning it but could have missed some doo doo.
Than you Rich. Hope all is well there.

Thinking fuel is not great.. smells. but it did get better with adjust. I'll drain the carb and the tank again. fresh fuel then try it. Think maybe new gas cleaned tank up ??

quote:

Originally posted by SCDIV1:
Thanks Bill....

Yea I work on them practically everyday...

Matt is busy in the office everyday and business is good. He sold everything racing related about 3 years ago. He had a very successful run in the sport...


973-328-6880 ask for Rich.....

i may need to talk to you when I get my new coach back, it shut itself off after about 8 hours of run time, 12.5k diesel. Didn't get a chance to see what the code was, I think I accidentally cleared the code while trying to read it.

Will the last fault code shutdown is stored in memory. Press stop 3 times and it should start a blink sequence. 1 blink is overheat 2 blinks low oil pressure 3 blinks, press stop once and see what the blink sequence is then.

quote:

Originally posted by stk 758 BP!:
Thinking fuel is not great.. smells. but it did get better with adjust. I'll drain the carb and the tank again. fresh fuel then try it. Think maybe new gas cleaned tank up ??

If you removed the float bowl and various pieces at the bottom and cleaned it all and it still runs lean warmed up you need to pull the carb off and remove the jet and emulsion tube. Emulsion tube has numerous small holes to help fuel atomize. Has to be clear and the passage up from that tube area as well. Carbs are very pricey but I change them. No parts available separately and the floats go bad. Taking the carb off you gotta be careful not to lose the little blue plastic bushing in the governor arm. Linkage has to be right and spring can be moved around to but speed has to be checked. Output frequency (hz) 62 no load. Without a meter that reads Hz you can’t verify engine speed....

quote:

Originally posted by SCDIV1:

quote:

Originally posted by stk 758 BP!:
Thinking fuel is not great.. smells. but it did get better with adjust. I'll drain the carb and the tank again. fresh fuel then try it. Think maybe new gas cleaned tank up ??

If you removed the float bowl and various pieces at the bottom and cleaned it all and it still runs lean warmed up you need to pull the carb off and remove the jet and emulsion tube. Emulsion tube has numerous small holes to help fuel atomize. Has to be clear and the passage up from that tube area as well. Carbs are very pricey but I change them. No parts available separately and the floats go bad. Taking the carb off you gotta be careful not to lose the little blue plastic bushing in the governor arm. Linkage has to be right and spring can be moved around to but speed has to be checked. Output frequency (hz) 62 no load. Without a meter that reads Hz you can’t verify engine speed....

Thanks. I did find plugged emulsion holes the first time I cleaned it. I’ll pull it again and make sure it’s clean. I really appreciate the help!

Happy Easter!

Hold the tube up to a light......holes are very small...

You can use stripped out pieces of copper wire from small stranded wire sometimes to help clean out a small carb passage. Modern carb cleaner is poor compared to the old stuff..

Those machines can really give me fits when they run erratic....

I keep a new carb on the shelf and swap it right out after maybe 2 trys with the old one....

Another thing I forgot to mention is the intake manifold and gaskets can develop an air leak. The gaskets fail.....regularly...


Spray some carb cleaner at the base of the intake at the heads and along the manifold joints with it running .....Intake is 2 piece stuck together with silicone....One good backfire and the intake can pop a leak. I engine speed changes when you spray around you have an air leak and a carb will never fix it....

quote:

Originally posted by SCDIV1:
Will the last fault code shutdown is stored in memory. Press stop 3 times and it should start a blink sequence. 1 blink is overheat 2 blinks low oil pressure 3 blinks, press stop once and see what the blink sequence is then.

I checked It out, it has code 36. Possible fuel issue, the truck had a faulty fuel sender for the guage so I though maybe that was it, so I replaced that sender. Fired up the generator, it ran about 2 hours then just shut off. This is the second time now that I noticed a slight raise in rpm just before it shuts off. Any ideas?

Hey Will, I bought a set of ceramic bearings from you a few years back and am looking for another set for dragster fronts. Do you still sale them and if not could you recommend someone? I tried sending you a PM but never heard back from you. PM me if you don't mind.
Thanks,
David

Back to Onan generator Q&A.

quote:

Originally posted by Will Harrison:

quote:

Originally posted by SCDIV1:
Will the last fault code shutdown is stored in memory. Press stop 3 times and it should start a blink sequence. 1 blink is overheat 2 blinks low oil pressure 3 blinks, press stop once and see what the blink sequence is then.

I checked It out, it has code 36. Possible fuel issue, the truck had a faulty fuel sender for the guage so I though maybe that was it, so I replaced that sender. Fired up the generator, it ran about 2 hours then just shut off. This is the second time now that I noticed a slight raise in rpm just before it shuts off. Any ideas?

Check to see if it stored a fault code on the last shutdown......Press stop 3 times and it should recall the last shutdown fault code......if it's 3 blinks press stop once.....read code...



Fault code #36 means shutdown with NO command from the controller......replace fuel filter first, check your fuel lines and fittings for any looseness.....might be the fuel pump....

Pumps don't suck fuel well....especially from a long run. A loose clamp can allow air to be drawn into system......probably not your issue but you have to verify everything....

Random mysterious shutdowns are difficult to diagnose and fix......Sometimes the control board itself is the issue.....The circuit that powers the fuel pump opens and it shuts off and may or may not light a code. Usually 36......I have run machine for hours and hours trying to induce a failure....Control Boards and its connector and pins are always suspect...The Control board usually gets replaced.....

It's a common fault on all Onan's......fuel pump circuit opens with some run time....and heat....There is no relay...the pump and other items are powered directly from that control board.....A Printed and foil type circuit on a sealed, potted PC Board...…….. Cost over $700 for a 12K diesel... Comes in a Cummins-Onan box and is made in...…..take a guess.....!!!!

This message has been edited. Last edited by: SCDIV1,

Ok so, i got a chance to mess with it and I think I stumbled on a very telling symptom. I started it and it ran for anmbout 35 minutes then died. I checked cides, same code 36. Figured out the prime button for the fuel pump is hold the shut off switch down for extended time. I can hear the pump running. Started it again and it ran for just a few minutes bobbled rpm like running out of fuel. Tried starting it and it started and ran just a few seconds. Like the fuel pump wasn't running.


Immediately tried "priming it again just on a hunch and nothing. No fuel pump. Tried a couple times, nothing. Waited a just a short time, maybe 2-3 minutes and tried priming again, boom fuel pump is running. Started the gen and runs fine, for at least a few minutes. Shut it off on purpose as I think I've found the symtom that will tell what the issue is.

The times when it shuts off, I believe the fuel pump isn't running, therefore runs out of fuel. Now the question would be, why does the fuel pump shut off? It sounds to me like the board isn't sending signal to the pump to keep running. What are your thoughts?

I have a 12.5k does the same thing, same loss of voltage to the pump, it's the control board. $650 for a new one. I put a toggle switch on my pump to turn it on. now it runs great!

Joe

edit current price $843

This message has been edited. Last edited by: sr4440,

be sure to change the fuel filter will fungus in dieseltanks is very common

The control board does power the fuel pump directly and there is no relay.

It is a common failure on Onan’s in general. Gas or diesel units.

Fuel pump output randomly quits and they shut off on a code 36 pointing you to other items. I’ve had machines that ran for hours before they did it. Others a very short time. Heat makes it worse usually.

The PC Board is the problem. The circuit foil fails and is not really repairable. Board is sealed, mounted in a tray-holder.

I’ve changed many for this exact issue

I do know of some racers who did externally power the pump off a separate switch to avoid paying for a control board. The boards are very expensive and made in China !

I’ve had to deal with this issue for years and it’s shameful to me but it is what it is as the saying goes.

There is an aftermarket made control board for some machines but not the big diesels.

I’ve used the aftermarket made units and they are better and cheaper.

Nothing but Cummins-Onan for the diesel units.

The brown wire on the fuel pump is B+ 12 volts positive. Black wire B- Negative

Pump runs continuously when generator runs.

Does anyone have a part number for the board, looking up the big diesel parts seems to be difficult.

I'm thinking bypassing it sounds good, but wonder if that would be possibly a potential bad issue if the gen had some other issue and couldn't shut the fuel off. I'm thinking I may bypass it for purposes of testing further. If the bypass works then its absolutely the board.