Generator only runs for 4 hours.

Havana Shamrock

Well-Known Member
SILVER Sponsor
Sep 9, 2008
5,422
Sarasota Fla.
Boat Info
2019. 250 SDX OB
Engines
300 Verado V8
since last season my gen will run 4 hours then shut down, (Onan 13.5kw) I open the racor and have to fill with fuel. I have checked fittings, hoses etc i disconnected the supply and return from the Racor and pressure tested both sides and they held pressure. I had to close the selector valve to keep air from just going into the tanks so no leaks up to the valve. It doesn’t matter which tank it runs off either. I thought it was the bowl on the Racor as the threads where stripped installed new Racor today and same symptoms.
Anyone else have luck with this problem?
 
So the generator is shutting down due to a lack of fuel as indicated by a less than full Racor? Am I understanding correctly?

My custom is to switch the selector valve when I fuel up. One time, I wasn't wearing my glasses, and I moved the switch all the way over to the other side. At the time I didn't realize that was "OFF". When I started the generator, it ran for about 5 minutes before shutting down. If yours is running for 4 hours, the vacuum leak must be quite small. How long did you hold your pressure test for? When you replaced the Racor filters, did you change the o-ring on the T handle? I'm spit-balling here.....

One additional thought...is it possible for something to hold pressure, but not a vacuum? In my mind, the Racor shouldn't be under a positive pressure. If that's not true, then I'm wrong about this whole thing.

Jaybeaux
 
Joe

I had a similar issue on my 52 which I could not resolve for weeks. I had Cummins on the boat and they found the fuel feed line had collapsed internally and was weak enough that it would get sucked closed under load. Could be your problem, might not. Good luck.
 
Gages on both sides of the racor filter will give you more data to diagnose....it sounds like you are under heavy vacuum on the engine side, and it is slightly leaking air past the orings on the racor housing. I like Brians collapsed hose theory .
 
Not knowing the history of your boat or the fuel treatment it has received, here is one more possibility........there is some debris on the intake screen at the bottom of the intake tube going to the generator. Put some mild pressure on the tank to Racor fitting and see if you hear a delay then air rushing into the tank. If that clears the problem, then PM me and we'll talk about how to treat the existing fuel to break up and remove the sludge.
 
Havana - It doesn't take much of a vacuum/air leak to mess with the fuel delivery. Our generation of boats have a history of issues with hoses including the liners inside of the hoses as bmac alludes. However, even if the liner collapsed and blocking the fuel delivery it should not have dried up the Racor; so there is definitely an air leak between the Racor outlet and fuel tank outlet. Also, as you state that the issue occurs regardless which tank the generator is drawing from, therefore the hoses, fittings, and isolation valves on the fuel tanks can be eliminated. So, it deduces to the selector valve or hoses to the Racor filter or the Racor filter assembly it's self. Simple test is to disconnect the generator's fuel supply line at the Racor and the supply fuel lines at the tank selector valve; Install caps on the selector valve and with a Mityvac tester pull a vacuum on the system from the Racor outlet fitting where the generator's fuel supply was disconnected. Do a vacuum retention test; you should easily hold 20 inches of vacuum for 24 hours if the system is not leaking air. If the system does not hold the vacuum then it's a process of elimination; Racor/fittings, Racor supply hose, or fuel tank selector valve / fittings.
If you wanted to an overall system test then simply disconnect the fuel supply line at the generator, close the fuel tank valves and with the Mityvac tester pull a vacuum on the entire system from the disconnected line at the generator. Then test to one tank, switch the selector valve and test to the other tank.
 
Air can get into a spot where diesel fuel won't leak out.......this is from 35 years of running farm and construction equipnemt, diesel cars trucks and their in-laws. With the system of hoses, fittings and filteration Sea Ray uses, a fuel leak between the tank and the Racor is rare.........if your problem isn't a blocked pick up then my vote is the gaskets or threaded fittings on the Racor itself.
 
Thanks for the help guys.
I isolated the fuel supply and ran th Genny on a seperate portable tank (no bubbles)
I have concluded as Brian pointed out It May be the supply hose.
When I open the cap air rushes in so there’s a vacuum being created.
The only thing the Racor has in common is the supply hose.
It’s not the valve as I have pressure tested both sides and they both hold pressure.
I’m having a new hose made in the am so I’ll see if that’s it.
Thanks again
 
Air can get into a spot where diesel fuel won't leak out.......this is from 35 years of running farm and construction equipnemt, diesel cars trucks and their in-laws. With the system of hoses, fittings and filteration Sea Ray uses, a fuel leak between the tank and the Racor is rare.........if your problem isn't a blocked pick up then my vote is the gaskets or threaded fittings on the Racor itself.
"and their in-laws" - classic.....
 
Hey Joe.... I'm curious to see what you find. I'm not following the logic here but maybe I'm missing something....... If the portable tank is not vented, I would think it makes sense that pulling fuel from it would create a vacuum. I would also think that if the supply hose is collapsing, that would actually reduce or eventually reduce the vacuum effect in the tank but I guess there could still be negative pressure with a partially collapsed hose.
It's still possible it could be the supply hose as Brian mentioned. That would make sense that the genny is pulling fuel faster than a collapsed hose can supply, eventually emptying the rancor bowl........
Keep us posted......It may save some of us a lot of time trying to diagnose the same problem.....and you're retired so.... you have plenty of time to diagnose the issue! Lol....... Good luck
 
Hey Steve,
Sorry for the confusion the portable tank was vented and running a seperate supply line directly to the Racor.
I replaced the original supply hose on Friday thinking it has to be the problem but right on time(4 hours) the Genny quit
So I have a new Racor and supply hose from the valve to the Racor and still emptying the Racor
It’s driving me crazy as there’s not much more to the system.
I’m going to try and run directly off 1 tank disconnected from the valve and see if I can determine if the valve is ok.
I don’t see any bubbles being formed in the Racor but I have to add fuel when she quits.
 
Hey Joe,
Hope you guys had a great trip. Did you ever solve your generator issue? This sounds to be the same as what you are/were experiencing.

IMG_0846.PNG
 
Just an update.
The Racor is new,supply line from selector valve is new,and the lift pump is new I disconnected the selector valve and ran directly on 1 tank at a time and still the Racor runs low on fuel.
Still hunting.
 

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