Community Forums

CamJam1 · 10-19-2020, 02:48 PM

My generator fuel line needs replacing, and rather than drop the tank I'm looking at running a new fuel pickup for the generator. Going back a few years I see where a forum member with the handle DieselClacker pushed a rigid 1/4" nylon fuel line into the 1/2" vent line like a catheter. He meant it as a temporary fix, but it worked so well he just sealed it up with Goop and kept it permanently.

I climbed under the coach today to plan my assault and take some photos. Fortunately, Workhorse pointed my filler and vent line hose clamps down so that I can get to them!

I also noticed that I do have the second set of unused filler/vents on the other side of the tank with what looks like rubber caps over them. Using that vent access seems to be an even better solution. Are these truly just rubber caps on these ports, or is there some sort of metal plug underneath? Seems like I could poke a hole into the rubber vent port cap and use the same catheter trick, or perhaps come up with a more professional way to insert a pick-up tube into that 1/2" vent port.

Just wondering if there's anyone else who has tried this before me? No sense reinventing the wheel.

vettenuts · 10-19-2020, 03:24 PM

I think it would work, only issue I can see off the cuff is the line you feed in interfering with the movement of the float. Not even sure how close the fill is to the pump though so it may not be an issue.

LETMGROW · 10-19-2020, 03:42 PM

It might work. Depending on the angle the pipe enters the tank you might want to insert a length of steel tubing into the end of fuel hose to weight it down. Otherwise the hose could float if there was air in the line.
You could do this hookup with a plastic 'Tee'.
BTW, DieselClacker is still active on this forum. Maybe you could PM him.

CamJam1 · 10-19-2020, 04:57 PM

Good thought on contacting DieselClacker.

If I go with the extra vent port it should be easy enough to fashion a new pick-up tube out of copper tubing.

vettenuts · 10-20-2020, 05:22 AM

I actually wonder if you can feed in a smoothly bent metal line.

CamJam1 · 10-20-2020, 10:51 AM

My reason for a new generator fuel line is that my generator periodically shuts down, though it seems to be only at temperatures above 90F. After reading how chronically common this is with these Onan generators I've had a change of heart overnight (again) and am back to thinking that this is vapor lock, or more specifically, fuel pump cavitation.

My coach came from Lake Havasu, AZ, one of the hottest places in the country. The previous owner obviously had this problem and had tried to correct it, including installing a separate gas tank to feed the generator. That seemed to have worked, but I didn't like the basement locker space it took up and it always smelled like gasoline in the lockers, so I removed it and went back to using the original fuel pickup. PO had also relocated the fuel pump away from the heat of the generator, but I now realize that this was a mistake in that he placed the fuel pump ABOVE the generator.

Vapor lock usually occurs on the low pressure side of the fuel pump. Remember in science class how you could boil water at room temperature in a vacuum? To minimize this:

1) The fuel pump should be close to the fuel tank. That's why modern cars have the fuel pump INSIDE the tank (plus the fuel helps keep the pump cool).

2) The fuel pump should be placed BELOW the fuel level in the tank. I believe Onan originally placed the pump underneath the generator for that reason.

3) Keep the fuel line as short as possible with minimal fittings and/or bends. They create additional resistance and make cavitation more likely.

4) Insulate the fuel line. This one is obvious.

It occurred to me (in the middle of the night, of course) that my current setup is wrong on nearly all counts. I see no evidence that the current fuel line is leaking on top of the tank, so I've decided to try to improve the current setup before running a new fuel pickup. I think simply lowering the fuel pump and moving it closer to the tank will be enough, but I'm going to replace most of the rubber fuel line with insulated steel tubing while I'm at it.

Isn't retirement fun?

Guzzimark · 10-20-2020, 02:47 PM

I had to drop the tank out of my P32 to change the fuel pump. It took me a while to figure out that I needed to "just do it". After I committed, it really wasn't too bad and was clearly easier than just giving enough room to get the pump to clear the floor. It did, however, stretch the generator fuel line pretty tight because I didn't really need to disconnect it. And the generator still worked fine afterwards.

CamJam1 · 10-21-2020, 08:19 PM

Today I moved the generator fuel pump back to near the gas tank, keeping the existing rubber fuel line. I mounted the pump to the bracket that holds the rear sway bar-- behind it actually so that it will be protected from stones thrown up by the rear wheels. It now sits just below the level of gas tank too.

Our 90-degree days are probably over for the year, so it might be next year before I know if my vapor lock problems are solved. Immediately though I noticed that the fuel pump is not getting hot like it was, so I take that as a good sign.

If problems continue next summer I'll replace the fuel line too.

LETMGROW · 10-22-2020, 07:15 AM

If I may offer a suggestion. While you are working on your pump you could splice in a wire and a toggle switch to the ground wire. I put my switch in my wet bay as it's next to my generator.
I use this switch to turn the fuel pump off while the generator is running with no load on it. The carburetor runs dry of fuel and the generator shuts down. This is useful in two ways. When you are driving without your generator running these carbs oftentimes will spill over fuel from the float bowl and tend to flood the engine making it hard to start and contaminating the engine oil with fuel. Running the bowl dry will greatly reduce this.
Secondly, when the RV is going to sit for any length of time you can start the generator, shut the pump off and let the carb bowl run dry which will greatly reduce the chance of fuel gumming up the carb.
After the carb runs dry with the pump off and the engine quits running simply switch the pump back on and it will start and run normally.
Lynn

04georgieboy · 10-22-2020, 07:25 AM

Look up Kevin Caudill on YouTube. He does an installation using the spare capped off tubes on the fuel tank to install an engine fuel pump as a spare pump.

dieselclacker · 10-22-2020, 09:16 AM

Quote:

Originally Posted by 04georgieboy

Look up Kevin Caudill on YouTube. He does an installation using the spare capped off tubes on the fuel tank to install an engine fuel pump as a spare pump.

I did this several years ago,without Kevin’s video, and it worked out really well. I used an old Mercedes fuel pump that I happened to have,that was used on their CIS injected engines. Installed as an emergency “get me home” backup system, not intended for permanent fuel pump solution.

CamJam is trying to correct a hot stall problem with his genset.

CamJam1 · 10-22-2020, 05:31 PM

Good idea on the switch. I actually have a spot for it in the wet bay already that is intended for a water pump switch, but for some reason the factory didn't install the switch on my rig.

I'm done with the pump for now but will keep Kevin Caudill's video in mind if I find I still need it once hot weather is upon us again.

LETMGROW · 10-23-2020, 10:43 AM

I believe you are on the right track with your changes. Hopefully you have solved your problem.
If you do continue to have a problem you could try wrapping the fuel line from as far back as possible to as close to the engine as possible including the fuel pump with insulation made for wrapping water pipes. The insulation with the foil covering on it which will reflect heat.
Lynn