Onan LP generator not starting

Spikedog · 07-11-2013, 10:27 AM

Onan KY 3.6kW Microlite generator running on propane - 2005 model L. It will crank but not start.

It ran well over the July 4th holiday, but wouldn't start last night. I was troubleshooting an A/C issue (fixed now) and I tried to start the generator while still on shore power. It cranked but didn't start. I unhooked shore power and tried again - no fire. I took off the air filter and sprayed some starter fluid in - hey, it ran for a short time, must be a fuel delivery issue.

I've checked the fuel solenoid shutoff valve - it clicks when I go to 'prime.'
The stove top works, I've got plenty of propane in the tank, traced the hose to the generator (no extra valves or damaged tubing). There is a vent hose coming out of the side of the genset next to the fuel inlet. I read about clogged vent hose issues, and didn't see any other vent hose candidates coming out under the generator, so I ran a short screwdriver up the hose (no resistance). The oil level is OK, although my driveway is tilted. It has run before in the driveway with no issues.

I printed out the service manual this morning. If it was a 5 amp fuse, it shouldn't crank?!? If it was the low oil cutoff, it should crank but not stay running after releasing the start button?!?

Am I missing something here? If it was the spark plug, why would it kick on while I hit it with starter fluid?

**Herk7769** · 07-11-2013, 10:40 AM

Check your oil level.
Even slightly low can cause no ignition.

Spikedog · 07-11-2013, 10:45 AM

The oil level was at 1/2 when I checked it, but as mentioned my driveway tilts a bit. Not knowing which side the sensor is at (the manual says the right side, which would actually help), I'll add some oil anyway.

I shouldn't have gotten an ignition on the starter fluid though, right?

Spikedog · 07-12-2013, 08:43 AM

I added a bit of oil last night, bringing the level to full. Cranks, but doesn't start. It'll still fire with some ether, but won't run. Gotta be a fuel delivery issue.

**Herk7769** · 07-12-2013, 09:43 AM

What is the fuel level of the truck?
While I don't own a MH, I believe the generator requires a minimum fuel level in the truck to avoid running you out of gas.

When was the fuel filter last changed?

There is a "bleed" hole in the carburetor that meters fuel to the generator engine that can be blocked with dried fuel additives. Removing the bowl and cleaning the jets with Carb Cleaner might avoid a carb rebuild.

TURBS · 07-12-2013, 09:46 AM

Quote:

Originally Posted by herk7769

What is the fuel level of the truck?
While I don't own a MH, I believe the generator requires a minimum fuel level in the truck to avoid running you out of gas.

When was the fuel filter last changed?

There is a "bleed" hole in the carburetor that meters fuel to the generator engine that can be blocked with dried fuel additives. Removing the bowl and cleaning the jets with Carb Cleaner might avoid a carb rebuild.

Propane fuel filter ?

Propane fed gennie

Mulligan no. 2 ?

TURBS · 07-12-2013, 09:49 AM

I'd venture to guess with my limited propane experience that there's an issue with the Propane regulater.

Turbs

**Herk7769** · 07-12-2013, 10:24 AM

Quote:

Originally Posted by f1100turbo

Propane fuel filter ?

Propane fed gennie

Mulligan no. 2 ?

Tough Crowd....

Off to see the Lone Ranger.

Spikedog · 07-12-2013, 10:56 AM

Yeah, Herk, I'da been more gentle. Maybe....

Turbo, do you mean the regulator on the propane tank or a regulator on the generator itself? I see there is a generator demand regulator in the manuals, but have not laid eyes on it. It must be on the back of the generator, and it's pretty tight quarters in there. Although I'm learning more as I go, I don't know much about this unit. No fuel filter in there, just safety shutoff solenoid, then demand regulator, then the carb. That's the fuel delivery system in a nutshell.

TURBS · 07-12-2013, 10:59 AM

Quote:

Originally Posted by Spikedog

Yeah, Herk, I'da been more gentle. Maybe....

Turbo, do you mean the regulator on the propane tank or a regulator on the generator itself? I see there is a generator demand regulator in the manuals, but have not laid eyes on it. It must be on the back of the generator, and it's pretty tight quarters in there. Although I'm learning more as I go, I don't know much about this unit. No fuel filter in there, just safety shutoff solenoid, then demand regulator, then the carb. That's the fuel delivery system in a nutshell.

Regulater on the engine.

**Herk7769** · 07-12-2013, 05:25 PM

Lone Ranger was a hoot. Highly Recommended.

I have a Tri-Fuel generator and the propane plenum needs to be purged for several minutes before it will run on propane. The purge button is in the center of that silver disc on the other side. Maybe there is a similar button on yours.

TURBS · 07-12-2013, 05:38 PM

Quote:

Originally Posted by herk7769

Lone Ranger was a hoot. Highly Recommended.

I have a Tri-Fuel generator and the propane plenum needs to be purged for several minutes before it will run on propane. The purge button is in the center of that silver disc on the other side. Maybe there is a similar button on yours.

Our forklifts have the same purge button.

Dang long movie I might add !

Spikedog · 07-15-2013, 08:32 AM

Mine's got a 'prime' button, basically hold the stop toggle down for 30 seconds. I mentioned that in my 1st post.

I changed the oil and spark plug over the weekend. That pretty much exhausts my troubleshooting skills, and I'm dropping it off tonight at an Onan/Cummins shop. Taking a shot at a new shop - I usually let either the RV repair place or the small engine shop work on my RV generator.

Spikedog · 07-18-2013, 08:48 AM

So far not too impressed with the Onan/Cummins repair shop. They've got the generator out of the rig, and I stopped by last night since I couldn't get any decent info over the phone. They confirm the lack of fuel is the problem (duh), but don't seem to be making progress. I helped the tech, and we blew out a restriction in the vent from the demand regulator. Apparently this is common, and is called the dreaded mud dauber problem on other forums.

After pulling the demand regulator apart and not seeing any issues, we put the regulator back on. The tech turned the gas back on (he's got it set up with remote power and a bottle of propane), and didn't feel any gas coming out of the outlet of the regulator. Thinking this was wrong, he ordered a new regulator (~$200). After I got home, I got to thinking, the gas shouldn't come out unless there was some vacuum? After all, it's called a "demand regulator", right? He never tried to start it while I was there.

Spikedog · 07-22-2013, 02:45 PM

After I called the manager the next morning, they just put everything back together and it ran fine. It was the clogged vent tube not letting the demand regulator work properly. Charged me $750 for 9 hours of shop labor, and I'm the one who told them how to fix it in the first place. That shop has seen the last of me.

Spikedog · 08-05-2013, 09:57 AM

Since the problem is related to debris or insects getting up the vent tube, I figured having a grating, shield or something porous on the tube end would be useful.

What I came up with is from the world of fish aquariums - an airstone. They have a large surface area, very small pores, a hose nib, and are about a dollar apiece. I put one on my vent tube and did about 5 days of boon docking. I can run a heavy load like the A/C or something light like the coffee maker - no problem! You can get them virtually at any pet store too.

Spikedog · 07-23-2015, 11:53 AM

This airstone fix is still working great. I had one campout where the airstone got covered in mud and the genny wouldn't kick over. Cleaned the airstone and viola! If the airstone is really wet it can be a problem too. Seems to be a good permanent fix.

You may also like: