OBS 7.3 air in fuel lines

ramjo

ramjo

Well-Known Member
Joined
Apr 13, 2010
Location
Marion,NC
Thought I had my air in fuel lines problem fixed. Fixed the pickup foot in the tank and got lines bled out, drive it around the neighborhood for a couple days, never feels like it gets bled out. Truck sits for a couple weeks. Cranked it up and drive it around some more and it seems like its running good...nothing weird. Fast forward to today, gonna do a little longer drive on it. It had abiut half a tank in it so I Drive for about 15 miles running good, stopped to just put a few more gallons in it and no more than maybe 2-3 miles down the road I feel it losing power amd dies. Get it coasted to a parking lot, spin it over, let the air out at the regulator a couple time till I'm getting a good stream of fuel amd hit the road again. Repeat this process quite a few times to keep me going on my journey, but still not getting air out of the lines by driving. It's gonna set a few weeks till I have time to mess with it. Anybody got any ideas?

It's not the first time it has happened after putting fuel in it....maybe bad connection on top of the tank?
 
Any chance it’s a dual tank setup? When those switchover valves go bad they do funny things.
 
jeepinmatt said:
Any chance it’s a dual tank setup? When those switchover valves go bad they do funny things.
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It is dual tank. I did swap that at one point with one my buddy gave me off a truck he had. How does a fella bypass that and just run the front tank?
 
ramjo said:
It is dual tank. I did swap that at one point with one my buddy gave me off a truck he had. How does a fella bypass that and just run the front tank?
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I think you can just put a piece of pipe in the line that goes from the tank and the engine, and just bypass the valve. I had a similar issue on an old F150 I had.
jeepinmatt said:
I had a 90 F150 with the dual tanks, and it began running terribly one day, then proceeded to get worse. I checked the fuel pressure, and it was crap, so I replaced the fuel pump. No difference. So I did a little investigating, and noticed that if you crimped the return line with vise-grips, it ran great. So I traced almost all of the possible points where it could leak back to the return, and determined it must be a pinhole leak where the fuel rail was welded together. On a Ford 300i6 replacing the fuel rail is a terrible job, but I got it done. Again, no difference, still ran terrible. Then I realized the one place I didn't check was the dual tank valve. My truck only had the rear tank, and whenever the PO had removed the front tank, they just plugged the lines. But something in the valve had screwed up and was letting most of the fuel return to the rear tank. I took that valve, threw it in the trash, put some straight fittings on there, and the truck ran great.
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Thanks fellas. I just assumed when they went bad if you left it on one tank and not mess with the selector it would be ok.

@Noel sucking fuel from the other tank sounds better than suckin air....maybe I tell the guy i was looking to trade with just keep rear tank full 😆
 
ramjo said:
Thanks fellas. I just assumed when they went bad if you left it on one tank and not mess with the selector it would be ok.
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My F150 didn’t even have a front tank, so I assumed the same, which is why I wasted so much effort before checking the selector. I bought the truck for $400, so I didn’t put much effort into looking it over. Went to fill it up on the way home. Put the nozzle in the front filler and pulled the trigger and fuel shot straight to the ground! :laughing:
 
ramjo said:
Thanks fellas. I just assumed when they went bad if you left it on one tank and not mess with the selector it would be ok.
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My $0.02 is they're notorious for sticking in "a position"... be it front tank only, rear tank only, or the "funnest" stuck in the middle 🤬
And that will cause yet another issue, where the return flow gets pooched and will flow to the FULLest tank :poop:

Ran the gambit with my old '92 F-250 7.3L IDI close to 20 years ago... replaced the rotted "diesel" tanks with much cheaper "gas" tanks (just cut/filed the "clocking" notches for the diesel senders) chased the lines end to end, found the factory valve was fawked... plumbed the front tank straight thru (supply/return) and put a clicky-clak "transfer" pump rear (to front)... switch retained the gauge function on both
 
Caver Dave said:
My $0.02 is they're notorious for sticking in "a position"... be it front tank only, rear tank only, or the "funnest" stuck in the middle 🤬
And that will cause yet another issue, where the return flow gets pooched and will flow to the FULLest tank :poop:

Ran the gambit with my old '92 F-250 7.3L IDI close to 20 years ago... replaced the rotted "diesel" tanks with much cheaper "gas" tanks (just cut/filed the "clocking" notches for the diesel senders) chased the lines end to end, found the factory valve was fawked... plumbed the front tank straight thru (supply/return) and put a clicky-clak "transfer" pump rear (to front)... switch retained the gauge function on both
Click to expand...

I just have to get if fixed so I can trade with a guy. If I was gonna keep it, I would probably put the 38 gallon Bronco tank in the rear and do away the the front tank altogether.
 
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ramjo said:
I just have to get if fixed so I can trade with a guy. If I was gonna keep it for awhile, I would probably put the 38 gallon Bronco tank in the rear and do away the the front tank altogether.
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That was my ultimate fix. More fuel in one tank than both original ones
 
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