Onan 4K - Code 36 - Low Fuel or What?

[Baja_Man]

Hello--

A concern with my Onan 4000 Microquiet series. It is on my 2009 Tahoe Toyhauler.

Background....

Purchase this TH last year. Genny ran fine when purchased. 145 hours on the clock. Brought it home and drained all gas out as owner said it was several months old. Serviced genny with new plug, new fuel filter, new air filter, and changed oil. All OEM Onan parts. Put in 5 gallons of fresh fuel. Genny ran but was running up/down in the rpms. I exercised it for one hour with AC running. I believe the RPM fluctuation was a dirty carb.

Now, 6 months later, I decided to run genny but went ahead and drained fuel as it was 6 months old. Put in 5 gallons of fresh fuel and added 2-3 ounces per gallon of Seafoam to clean carb and stabilize fuel.

Genny will not start. Primed for about 15 seconds and it wants to start but will not start. Removed fuel line at carb and pressed start to see if fuel was pumping and it was pumping fine.

Attempted to start again and this time primed for one minute and it started and ran for about 5 mins then stopped. The trouble code lights indicated 3 and 6 which is 36. In my Onan manual this code states low on fuel.

I went ahead an added 5 more gallons of fuel with more Seafoam (2-3 ounces per gallon). Primed a few more times and got it to start and ran for about 10 mins. RPM were running up and down, then settled, then went back to up/down. Went to turn on AC and genny died.

Questions:

1. Do TH gennys have the protective shut off of fuel when tank reaches 1/4 full... as do motorhomes? How would I know where/if this shut off valve exists on my TH?

2. Is it possible that 10 gallons (1/3 tank) is not enough fuel to run correctly?

3. What else can it be?

Thanks!

[SMarquez]

If there was any fuel left in the carb it is probably shot.

[Baja_Man]

nayther wrote:
if you didn't put anything in the gas, then let it sit for 6 months, the pilot jet is plugged. Guarantee it and it cannot be fixed. Replace the carb, they're cheap. Do a search and you'll see many have tried to clean them (my son is one) but there are too many tiny passages.

I see you're in CA so you're getting ethanol in your fuel if you use regular, it is hydroscopic (attracts moisture) so if you don't run it then the fuel evaporates and leaves the moisture behind. did you pull the float bowl (easy to do)? If there's white residue then that's your answer. You experienced part of that when you started it last, "runs up and down". At that point it might have cleaned itself out if fuel system cleaner was used, but it sat and got worse.

Fuel that sat for 6 months was drained. Fresh fuel has been used.

[nayther]

if you didn't put anything in the gas, then let it sit for 6 months, the pilot jet is plugged. Guarantee it and it cannot be fixed. Replace the carb, they're cheap. Do a search and you'll see many have tried to clean them (my son is one) but there are too many tiny passages.

I see you're in CA so you're getting ethanol in your fuel if you use regular, it is hydroscopic (attracts moisture) so if you don't run it then the fuel evaporates and leaves the moisture behind. did you pull the float bowl (easy to do)? If there's white residue then that's your answer. You experienced part of that when you started it last, "runs up and down". At that point it might have cleaned itself out if fuel system cleaner was used, but it sat and got worse.

[SAR_Tracker]

Baja Man wrote:
Hello--
....Do TH gennys have the protective shut off of fuel when tank reaches 1/4 full... as do motorhomes? How would I know where/if this shut off valve exists on my TH?
....

All that is, is the bottom of the generator fuel pickup is physically higher in the tank than the MH engine fuel pickup. I agree with either the fuel filter (there's one on the carb of my generator, and another inline by the wheels...)

OR

the rubber fuel line may have cracks in it, allowing air to enter the system.

Take a small (1 gallon) can of fuel, and run a short fuel line from it to the carb (after disconnecting the existing line). Try and start the generator. If it runs, you've ruled out problems with the carb. Now it's a matter of isolating the problem(s).

[dedmiston]

Does your unit have a fuel filter? It might be part of the problem.

I had a fuel filter go bad on my last 5500 and replaced it. I've also seen people delete the filter and run without it.