Gen fuel pump replacement-T32

6

660griz

Active Member
Having strange issues with my Onan 5.5k generator. It will run for around 30 to 45 minutes, depending on outside temps, and then shutdown with a code 36. Generator is almost too hot to touch. Dealer verified issue but, doesn't work on generators. Called Cummings service and they said they would have to run it, see it shutdown, use and external fuel source and see if it would run longer, etc. Costing $100s of dollars just to find a possible fix.

After much research, I suspect the fuel pump is getting hot and 'vapor locking'. Generator starts fine after a cool down.

Ordered a replacement but, I just can't seem to get the old one out. Got the fuel pump loose and the fuel line to carb disconnected but, there just doesn't seem to be a way to get it out without lifting generator up. Anyone have this problem?
Am I missing something? Tips?
 
Last edited by a moderator:
BLR

BLR

Well-known member
How old is the gas??

If the gen sits more than a month without being run you could have issues..
We had problems and we ended up saving it by doing a main line of seafoam.

May not be a fuel pump issue

Hopefully someone that has removed fuel pump will chime in

Sent from BLR Logistics
 
carl.swoyer

carl.swoyer

Well-known member
BLR said:
How old is the gas??

If the gen sits more than a month without being run you could have issues..
We had problems and we ended up saving it by doing a main line of seafoam.

May not be a fuel pump issue

Hopefully someone that has removed fuel pump will chime in

Sent from BLR Logistics
Click to expand...
Do an lp conversion. My Onan Marquis lp 5500 is 11 years old. Fires up Everytime. No worries about stale fuel. I'm running everything on my Landmark Rushmore. If you stay with gas start using Marine grade fuel. The ethonol causes the fuel to go bad as it attracts moisture. I leave one lp tank in the off position, this gives me time to get a refill. I get 8 +- hours on a full tank

Sent from my XT1254 using Tapatalk
 
6

660griz

Active Member
The first time I noticed the issue was after a fresh fill up. Got to hunt camp and it was hot for November. Turned on both A/Cs to cool the camper down. Generator shut down after 45 minutes. Too hot to touch. Fired right back up after cool down.
When the outside temps are low the generator will run for hours with relative light loads. Coffee maker, lights, etc.

Are you saying bad gas can cause an overheating situation?

I have had bad gas in ATVs and motorcycles. For the most part, they wouldn't fire up.
And if they did, they ran very poorly.

Generator fires right up and runs fine...until it dies. :)

Removal instructions are probably going to be specific to the T32. Removing from an Onan 5.5k Generator is pretty straight forward but, I got moved here so...hopefully some T32 owners/or the manufacturer, that have done this will see this post.

If not, I will loosen the gen and forklift it up just enough to get the fuel pump out.

BLR said:
How old is the gas??

If the gen sits more than a month without being run you could have issues..
We had problems and we ended up saving it by doing a main line of seafoam.

May not be a fuel pump issue

Hopefully someone that has removed fuel pump will chime in

Sent from BLR Logistics
Click to expand...
 
6

660griz

Active Member
Replaced fuel pump and filter. Had to jack up the gen to get the pump out.
Primed and the generator started right up. Ran for about 20 minutes and shut down. Code 36.
Pulled fuel lines from on top of the gen to outside. Gen started up and ran the A/C for about 30 minutes and shutdown. Code 36.
I am going to take it to a Cummings service center. I give up. The generator is too new to be acting this old. Apparently, my issue is unique.
My last thing to try is to loosen the gas cap and run it. Maybe it is not venting and creating a vacuum the fuel pump can't overcome. Other than that, I got nothing.
 
LBR

LBR

Well-known member
660griz said:
Replaced fuel pump and filter. Had to jack up the gen to get the pump out.
Primed and the generator started right up. Ran for about 20 minutes and shut down. Code 36.
Pulled fuel lines from on top of the gen to outside. Gen started up and ran the A/C for about 30 minutes and shutdown. Code 36.
I am going to take it to a Cummings service center. I give up. The generator is too new to be acting this old. Apparently, my issue is unique.
My last thing to try is to loosen the gas cap and run it. Maybe it is not venting and creating a vacuum the fuel pump can't overcome. Other than that, I got nothing.
Click to expand...
My thoughts exactly on the gas cap.

I happened to stumble across a tidbit about our generator & fuel gas caps...after filling tanks up and I tighten the caps all the way CW (clickclickclick), both fuel tank caps will seal completely to atmosphere. Then when I turn them 3/4 turn CCW (to where they will start to come off), they will vent slightly.

I had totally topped off both tanks and we then boon-docked in the 90°+ desert....we went offroading the next day and came back in hot mid-afternoon. The DW goes in the back door and heard a heck of a HISSING sound. I listened, thenI looked underneath the CY and our 30 gallon tank looked pregnant with a gas smell also. Turned the fuel caps CCW 3/4 turn and it hissed like an angry snake for 30 seconds...problem solved.

Try loosing the cap to see if it clears ...maybe/maybe not...easy to try tho.
 
smp2000

smp2000

Member
I have a couple week old T322 and had the same thing happen to me last week... Both a/c's running and about 100` outside it cutoff within about an hour. Once it cooled down it fired right back up. I only have maybe 4 hours on it. Ran it today with only 1 a/c and it ran perfect. I will check the gas cap later today...
 
avvidclif

avvidclif

Well-known member
The gas tank has a valve to let outside air in but not let gas or vapors out. If it doesn't work correctly after a bit the generator dies for lack of gas as the tank now has a vacuum that the fuel pump can't overcome.
 
6

660griz

Active Member
Well, leaving the gas cap loose didn't work.
I think, for my next trick, I am going to see how long it will run from a fuel hose in a gas can.
 
6

660griz

Active Member
Guess I am off to the repair shop.
Tried fuel pump and filter, loose gas cap, running straight from gas can, and taking a little oil out. No help. Still shutsdown with a code 36. Repair shop says it may be control board. $500. Yee haw!
 
6

660griz

Active Member
Re: Gen fuel pump replacement-T32-Solved...Maybe

Took the camper to a Cummings/Onan service center. They called yesterday and said the fuel pump was bad,(that I just replaced).
I told them to go ahead and replace it, turn on both A/C units and if it runs for an hour, call me and I will come pick it up.

No call.

Today they call back and say that the new pump failed because the hot air is being recirculated. This was what I thought originally but, dealer said the gen was installed fine.

Service center is going to come up with something to keep the hot air from reentering. We'll see.
 
esscobra

esscobra

Well-known member
anything will work to keep the hot exhaust from being sucked into intake- especially when wind is blowing that way- onan used to sell one- but I had metal shop build me 2- 1 for exhaust and 1 for intake - I will try and get/find pics - has not been issue except for 1 time wit strong winds perfectly blowing ehaust into intake direction - I researched happens when gen is not high enough off ground- I noticed that units with gen prep have a spacer to raise gen up -
 
G

G-Man

Member
You are looking for the same mount pedestal I am for my Torque 345.

It's ONAN part # 026-00279, "Towable Tray" listed in the ONAN accessories catalog. It elevates the generator 6" in the bay and has a divider between the cold air intake and exhaust ports.

You also need to close off the half moon alternate exhaust pipe exhaust holes that aren't used to kep hot air from entering your generator bay from the air blowing passed the muffler housing. ONAN service manual says to use a small rectangle of sheet metal with sheet metal screws to secure it to the aluminum metal base to block the unused openings for the muffler pipe to exist.

The mount base also lifts the generator 6" in the bay making it much easier to remove/install the generator (clears the campe door lip that is 4" high) for service work if required.
 
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