Deuce keeps getting air in fuel system

[ivbeenrokd]

I'm having running trouble with the deuce and wanted to see if anyone has any advice. This has gone on for several years being manageable in the past but has gotten progressively worse to where it's no longer manageable. It seems like it's getting air in the fuel system which causes it to cut out and even die at low RPM. It was horrible during the Knoxville Veteran's Day parade, died 6 times and has a hard time starting back until I bleed the air out again. It's had a fuel leak on the IP for a while so I thought that was the issue. Found the fuel leak to be the #2 line on the IP, fixed that Friday. After running it yesterday and today I've found that I still need to bleed air out before I start it (using the nut on top of the 2 secondary fuel filters) and it still dies. This seems to be worse in cold weather. I can bleed the air out, run it for an hour, and there's air in it again. I can run it, let it sit for a day, and there's air in it again. I haven't found any other leaks in addition to the one I fixed Friday. Any ideas?

Thanks,
John

 

[Justgaudot]

Hi John, I'm not a duece guy, YET. Just a lowly boat mechanic faced with the same problem, I think the first thing I would do is pressurize the fuel system and look for leaks those on some seals they only leak under vacuum so if that didn't reveal any thing the next step is to vacuum test the system empty and use toilette bowl wax around possible leak sites until it holds vacume.
Another thought, check the fuel pickup tube real carefully. I once had a pickup on a boat leaking just a little air right at the base of the pickup tube. I would check the pick up first.

 

[Jeepsinker]

Probably the soft line on the lift pump inside the tank. I've only seen one or two that WEREN'T rotten.

Whatever it is, it is going to be between the lift pump and the booster pump on the injector pump.

You can plug the fuel return line where it comes off the secondary fuel filters and turn the lift pump on to find your leak, if it turns out that the rubber hose in the tank isn't rotten.

 

[rustystud]

Probably the soft line on the lift pump inside the tank. I've only seen one or two that WEREN'T rotten.

Whatever it is, it is going to be between the lift pump and the booster pump on the injector pump.

You can plug the fuel return line where it comes off the secondary fuel filters and turn the lift pump on to find your leak, if it turns out that the rubber hose in the tank isn't rotten.

I totally agree with Jeepsinker "replace those fuel pump lines" ! Mine where in bad shape and my truck was a 1988 Air-force deuce ! Just be sure the hose is rated for "full submersion" . There is a difference ! That is what I think has happened with most of our trucks. The military mechanic just used standard fuel hose when they needed to replace the fuel pumps.

 

[Jeepsinker]

Right, because immersion rated hose isn't readily available. I sure can't find any around here.

 

[rustystud]

Right, because immersion rated hose isn't readily available. I sure can't find any around here.

I had to special order mine too.

 

[ivbeenrokd]

Thanks for all the advice guys.

Some pertinent info relative to where this conversation is going now:
*I replaced the factory lift pump several years ago with an aftermarket 24v external lift pump that sits on top of the tank because the internal when out. When I did this I really can't remember at all what I did internally with the hose so I'll either have to dig up some old pictures/notes or pull the top off the tank to check it.
*Since my truck is a 4 door now if I need to pull the top off the tank that will be a pain because I'll have to either completely dismount the tank and slide it out or I'll have to unbolt the bed and slide it back. I've got around 35 gallons of fuel in the tank right now so I might side for sliding the bed back if need be.
*This problem existing before we did the 4 door, but was much worse last winter (which was the first winter after completing the 4 door) When we did the 4 door I did new lines from the tank outlet for probably about 6 feet of line so there's a connection where those come together that I better check. It could be the original problem before the 4 door was the #2 line on the IP and now the main problem is one of those other areas.

Question:
If I plug the return line do you think there's a concern of putting too much stress on the pump if I leave it that way too long while I'm looking?

Thanks,
John

 

[daytonatrbo]

Right, because immersion rated hose isn't readily available. I sure can't find any around here.

Not sure about the 3/4" or so hose on the lift pump, but I recently got some 3/8" immersion rated, high pressure fuel injection hose at NAPA.

The only issue is that they sold it in pre-packaged 1' sections, and that was over $30.

 

[daytonatrbo]

Thanks for all the advice guys.

Some pertinent info relative to where this conversation is going now:
*I replaced the factory lift pump several years ago with an aftermarket 24v external lift pump that sits on top of the tank because the internal when out. When I did this I really can't remember at all what I did internally with the hose so I'll either have to dig up some old pictures/notes or pull the top off the tank to check it.
*Since my truck is a 4 door now if I need to pull the top off the tank that will be a pain because I'll have to either completely dismount the tank and slide it out or I'll have to unbolt the bed and slide it back. I've got around 35 gallons of fuel in the tank right now so I might side for sliding the bed back if need be.
*This problem existing before we did the 4 door, but was much worse last winter (which was the first winter after completing the 4 door) When we did the 4 door I did new lines from the tank outlet for probably about 6 feet of line so there's a connection where those come together that I better check. It could be the original problem before the 4 door was the #2 line on the IP and now the main problem is one of those other areas.

Question:
If I plug the return line do you think there's a concern of putting too much stress on the pump if I leave it that way too long while I'm looking?

Thanks,
John

With my 109 box, I have to slide the tank out to get at the fuel pump. I undid the strap bolts at the top, rested the straps on some jackstands and slid the tank out. Granted, there's only about 10 gallons of fuel in my tank right now.

 

[ivbeenrokd]

With my 109 box, I have to slide the tank out to get at the fuel pump. I undid the strap bolts at the top, rested the straps on some jackstands and slid the tank out. Granted, there's only about 10 gallons of fuel in my tank right now.

That's a good thought. I could probably add some wood to your system and make a safe way to do that.

 

[Justgaudot]

Does anybody know if US Coast Guard approved hose would be OK for submersion. I've seen plenty of boats sink and we never had to worry about replacing fuel line after it went under salt or fresh water. That would be very readily available. A little more expensive but very available.

 

[daytonatrbo]

Does anybody know if US Coast Guard approved hose would be OK for submersion. I've seen plenty of boats sink and we never had to worry about replacing fuel line after it went under salt or fresh water. That would be very readily available. A little more expensive but very available.

We are talking about immersion in fuel, not water.

The inside of typical fuel hose is lined with a different rubber that stands up to fuel. The outside does not. Immersion rated fuel is the higher quality rubber throughout.

 

[Justgaudot]

I see, thank you.

 

[loosescrews]

My truck does this as well if I turn on master power and start it straight away. I generally flip on master power, do my walk around, drain my filters, then start. I don't have a problem with it anymore.

 

[Jeepsinker]

If you plug the return, don't leave it running for 20 minutes. I don't think it would like that. I would do short 5 minute spurts, since you are dead heading such a small electric pump.

Or keep an eye on it to see when it starts to get hot. It may do ok for quite a while that way.

And absolutely DO NOT start the truck with the return line plugged.

 

[ivbeenrokd]

I'm swinging by Advance Auto to get some supplies to plug the return. I did go ahead and look over the feed line and return line paths and find no leaks anywhere. There is minor seeping in different areas of the IP, but it's extremely minor.

 

[Jeepsinker]

Being as it is getting air in the system while running, that tells me the leak is on the suction side. That's why I said it has to be between the fuel pickup and the booster pump.

 

[rustystud]

If you plug the return, don't leave it running for 20 minutes. I don't think it would like that. I would do short 5 minute spurts, since you are dead heading such a small electric pump.

Or keep an eye on it to see when it starts to get hot. It may do ok for quite a while that way.

And absolutely DO NOT start the truck with the return line plugged.

Boy you got that right Garrett ! Don't ever run the truck without that return free ! Not unless you want to see what happens to a fuel filter canister that is over pressurized !

 

[Jeepsinker]

Well, that, or a crankcase full of fuel.

 

[ivbeenrokd]

Being as it is getting air in the system while running, that tells me the leak is on the suction side. That's why I said it has to be between the fuel pickup and the booster pump.

That makes sense, but then if I bleed it, don't run it, and let it sit then it still has air in it. If it was all good from the lift pump on then the pump should hold it's prime and keep that from happening, right?