So, the new, reconditioned Onan is not doing it's job reliably. My son picked up the motorhome to take it on a trip to Colorado Springs last evening and drove it about 7 miles to Costco to get gas. He shut down the generator while pumping gas and it would not restart until some time after he got home to his house, another 5 miles.

I had set the timing and adjusted the carburetor and run the generator, under load, for at least a half hour with no issues. I suggested that Mark re-adjust the carburetor, which he did and said it was running better. It quit again on him later and he decided to replace the fuel pump that came with it, a 7-9 psi solenoid type, with a new Mr Gasket #425 (2-4 psi). He did that quick this morning before they left and said it was running well.

After a stop at Walmart on the way out of town, they left it running, but it had quit while they were shopping. In Deming NM, it restarted, but apparently only ran for about 45 minutes before it quit again. I looked up the spark plug number and suggested he check to make sure it has the right plugs in it, Grasping at straws here.

Any suggestions?

So, the new, reconditioned Onan is not doing it's job reliably. My son picked up the motorhome to take it on a trip to Colorado Springs last evening and drove it about 7 miles to Costco to get gas. He shut down the generator while pumping gas and it would not restart until some time after he got home to his house, another 5 miles.

I had set the timing and adjusted the carburetor and run the generator, under load, for at least a half hour with no issues. I suggested that Mark re-adjust the carburetor, which he did and said it was running better. It quit again on him later and he decided to replace the fuel pump that came with it, a 7-9 psi solenoid type, with a new Mr Gasket #425 (2-4 psi). He did that quick this morning before they left and said it was running well.

After a stop at Walmart on the way out of town, they left it running, but it had quit while they were shopping. In Deming NM, it restarted, but apparently only ran for about 45 minutes before it quit again. I looked up the spark plug number and suggested he check to make sure it has the right plugs in it, Grasping at straws here.

Any suggestions?

On Jun 15, 2017, at 7:52 PM, Carl Stouffer wrote:

> I had set the timing and adjusted the carburetor and run the generator, under load, for at least a half hour with no issues. I suggested that Mark
> re-adjust the carburetor, which he did and said it was running better. It quit again on him later and he decided to replace the fuel pump that came
> with it, a 7-9 psi solenoid type, with a new Mr Gasket #42S (2-4 psi). He did that quick this morning before they left and said it was running well.

It is highly unlikely that this is either a carb adjustment or a spark plug type issue; neither would result in a successful 45 minute run followed by a failure.

Have you ruled out the control system by jumpering battery+ to coil+ and then attempting a start/run?

He hasn't tried that, but I did tell him to jumper pins 9 & 5 to bypass the low oil shut down switch. We'll see how that works today.

Have you ruled out fuel delivery by removing the fuel hose from the carb and then jumpering battery+ to coil+ to see if fuel comes out the hose with good flow and pressure?

Yes, fuel delivery is good

Do you have known good fuel hose between the tank and the Onan's pump?

All fuel lines were replaced in 2010 and inspected during the generator swap. All looked good.

Does it have breaker point ignition? Have the points been cleaned or had the condenser replaced?

It has Onan solid state ignition, timing is set to 21 degrees BTC.

I agree with others that 7-9 psi of fuel pump pressure is far too much.

That pump has been replaced with a new Mr Gasket 42S - 2 - 3.5 PSI

Jim Miller
1977 Eleganza
1977 Royale
Hamilton, OH




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On Jun 17, 2017, at 1:57 PM, Carl Stouffer wrote:

> After further checking and testing, the symptoms do point toward the coil as the problem. I took the known good coil off the old generator, boxed it up, and sent it up to my son this morning. At least that will allow us to confirm or eliminate the coil as the culprit.

Regarding coils...

I have used the 166-0820 coil for dozens of hours in my Onan as a replacement for the original coil. The -0820 is about 20 years newer than the one that came with our Onans.

In addition I am experimenting with the 166-0761 coil which has worked in initial tests but I've not had the opportunity to test it with prolonged runtime so at this time I cannot declare that it is a viable replacement. This part is even newer than the -0820.

These coils have worked for me in their original Inductive (Kettering) ignition mode as well as with the MSD CDI box that JimK sells.

--Jim

Jim Miller
1977 Eleganza
1977 Royale
Hamilton, OH




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Back to this: After swapping out the coil for a known good one, the Onan still would only run for a very short time and then quit. While I had my son on the phone, I had him pull a spark plug and ground it to the engine while cranking. He said there was a nice fat spark (this unit has the Onan solid state ignition). He then loosened the carburetor float bowl and found it to be dry. He put the old (too high pressure) fuel pump on and it fired up. All this in the RV park where he really couldn't mess with it too much.

Back on the road on Friday AM. it would run for a while, quit, and not re-start. He found a split in the fuel line near the pump, fixed that, and thought that was the problem. The too high pressure pump then overpowered the needle valve and flooded out the carb, so he put the Mr Gasket pump back on (with a Wix filter). It still would run for a while, maybe 20 - 40 minutes, and shut down.

After driving through the night to beat the heat, they arrived home at about 2:30 AM. Mark got up and exchanged the possibly defective Mr Gasket pump for a new one which I will install. This is sounding more and more like a vapor lock condition and I will install the new fuel pump back on the frame away from the heat of the generator per Ken B's suggestion. I will try to insulate the line as well. Maybe that will do the trick.

Any other suggestions?

On Jun 25, 2017, at 8:52 PM, Carl Stouffer wrote:

> Oh, forgot to mention that the behavior was unchanged by jumpering from 5 to 9 or even from bat + to the coil.

That's good info. Your message above crossed the ether with my previous one which suggested that very same test. At this point you've ruled out the control system - so now try running the Onan from a fuel can sitting on the ground beside the coach and see how long it will run.

--Jim

Jim Miller
1977 Eleganza
1977 Royale
Hamilton, OH




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