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How much time should it take to fill fuel lines from rear tank holding scradier valve open cranking engine with mech. pump? If don't get fuel from valve what to check besides fuel line obstructions and tank selector valve. truck runs fine on front tank switch to rear and truck dies after about 20seconds (out of fuel ). I have just changed rear tank and added 5 gallons of fuel. Any suggestions. Thanks in advance.
Cargo Master
Joined: Mar 2006
Posts: 2,789
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From: Sand GAp, KY
You started it on the front tank then switched to the rear and it died? This is after changeing the tank or you haven't tried it yet? If it is after then the selector vale switch is probably the culprit.
Postmaster
Joined: Apr 2008
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Both times I changed a tank in my truck (first the front tank, then a few months later the rear) all I did was fire up on the other tank and warm up the engine, then just hit the switch and the empty fuel line between the tank pickup and the TSV filled so quick there was not even a hickup from the engine. Since you have these issues with only 1/4 tank worth of fuel in there, are you sure your shower-head hasn't fallen off the pickup tube? Add another 5 gallons of fuel in the tank and try again, if she stays running you'll have to drop that tank again and fix your fuel pickup...
Post Fiend
Joined: Nov 2003
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From: Nutter Fort, WV
Another possibility is the O ring in the fuel line connection split when you put it on the new tank.
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Postmaster
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Indeed, the sending unit is a separate part from the fuel pickup shower head, even tho they drop in the tank as one assembly. You can separate the shower head from the pickup the sending unit from the pickup and return tubes bracket, the float arm from the sending unit, and also the float from the arm. When you're always on "E" even with a full tank it's usually cause the float has developed a pinhole and has filled with fuel and sunk to the bottom of the tank, not so often cause the sending unit itself has failed. And when you air-lock the engine at 1/4 tank or below it's usually cause your shower head has disintegrated which is a very very common issue with these trucks.
Never seen that, but I think it's entirely possible, especially if the lines were somewhat rusty in that area, and they usually are - I've pulled those connectors apart cause of that, so who's to say the o-ring can't be damaged the same way.
Never seen that, but I think it's entirely possible, especially if the lines were somewhat rusty in that area, and they usually are - I've pulled those connectors apart cause of that, so who's to say the o-ring can't be damaged the same way.
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Post Fiend
Joined: Nov 2003
Posts: 21,285
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From: Nutter Fort, WV
Another place that a nice clean surface with a dose of motor oil on it before installation can make the difference between success and failure.
It don't take long for those connections to get enough surface rust on them while unplugged to damage the O ring when you hook it back up.
Or at least that is the way it is here with all of our humidity.
It don't take long for those connections to get enough surface rust on them while unplugged to damage the O ring when you hook it back up.
Or at least that is the way it is here with all of our humidity.
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Ok changed tanks because knew that tank i put on worked, and sending unit works now so fss must work, it was completely intact. Have had to splice in a piece of rubber line from supply on sending unit to fuel line going to ftsv as ford oviously changed supply and return connections between '87 and '91 on sending units. Had the same problem getting truck to run when changed front tank, but only took about 5 mins to get it running then, have spent 20 mins now on back and still won't run. Truck did run on rear tank before changing them. What else to check other then vent?
Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 15
From: Nutter Fort, WV
So you might have pulled a tank where the fuel pickup tube was good but the gauge sending unit was bad.
You may have installed a tank where the gauge sending unit is good, but the fuel pickup tube is bad.
If the fuel pick up tube is bad, 5 gallons of fuel will not be enough for it to pick up the fuel.
Look at the pictures in the first post in this thread.
You will see exactly what we are talking about with the fuel pickup tube.
Very common problem, and the truck will run out of fuel somewhere between 1/4 and 1/2 tank on the gauge.
https://www.ford-trucks.com/forums/8...rear-tank.html
You may have installed a tank where the gauge sending unit is good, but the fuel pickup tube is bad.
If the fuel pick up tube is bad, 5 gallons of fuel will not be enough for it to pick up the fuel.
Look at the pictures in the first post in this thread.
You will see exactly what we are talking about with the fuel pickup tube.
Very common problem, and the truck will run out of fuel somewhere between 1/4 and 1/2 tank on the gauge.
https://www.ford-trucks.com/forums/8...rear-tank.html