Fuel pouring out rear tank cap

[warhog]

I'm at work and went to leave for lunch, fuel is steady pouring out the rear tank filler neck cap. If I loosen the cap it comes out faster than a pump. I assume it'll stop eventually but what the heck is going on?

Side note both fuel gauges randomly pegged themselves on empty two days ago an haven't worked at all.

 

[towcat]

your fuel switching valve has died.
you are pumping out of your front tank and returning to the rear.

 

[warhog]

Thanks! Can you tell me where the valve is located? (Crosses fingers I can fix it in a parking lot)

 

[warhog]

Oh and I'm seeing two different valves on the part store list, how would I know which number of valves I have?

 

[warhog]

Okay so at well over $300 for the valve, an not in stock around me...is it generally safe to attempt to drive it home?

 

[gandalf]

As Towcat said, your fuel selector valve is stuck. It's on the frame rail, driver's side, about even with the front end of the front tank. Try giving it a couple gentle taps, maybe break the stuck valve loose. It's probably safe to drive the truck home, though you may be dumping fuel the whole way. If you do drive home, be sure to switch to the rear tank so that you're at least making a bit more room for that returning fuel.

 

[warhog]

Thanks guys. I don't think it's the valve actually. I'm reading dead empty on both tanks (they were both full) and blowing fuses for the switch. Sounds to me like a wire somewhere...power not making it to the dash switch? Would that make sense? And the valve is just getting screwed up because of that? I can't switch tanks or anything. Maybe I'm way off base. I'm getting towed home now since it dumped a full tank on the ground and I couldn't switch

 

[LCAM-01XA]

The only way to push fuel out is to return more than is sucked out. Laws of physics say this can't happen. So fuel has to come from somewhere. The only thing tying the two tanks together is the selector assembly. It is stuck internally and draws from one tank but returns in the other. Both supply and return switchover valves inside it of are mechanically operated by the same motor. The electrical switch that switches between senders is also connected to the same motor. IIRC the senders make gauge read full on low resistance and empty on high resistance. No connection between contacts in electric switch inside valve assembly is an extreme form of high resistance, so gauges will peg empty just cause of that, regardless of actual fuel levels.

Does the motor require constant power supply applied to it to stay in one or the other position? Will it default to some middle "tank crossover" position if power is removed? I know for a fact that the engine will run w/o power to the tank selector valve, but I never ran it long enough to see if the fuel will transfer from one tank into the other in the process...

Crawl under there and get to measuring voltages, w/ connector unplugged from valve assembly (and fuse replaced under dash) you should see 12V on one of the wires and 5V on another, other 3 wires will show zero voltage. If no 12V nowhere you have a power supply issue, and the fuse blowing again w/ connector unplugged you have electrical issue again. If fuse don't blow and you do see 12V on one wire, then your valves have jammed or motor has died - this will cause too high current in the circuit and blow the fuse.

For replacement valve installation read this mess here: http://www.ford-trucks.com/forums/9...riven-fuel-selector-valve-no-fuel-gauges.html

 

[warhog]

Thanks, i appreciate the help! i was towed home, and able to bang on it enough to run to get me to the store and bank (not without $60 more dollars in fuel though). Unfortunetly the only one thy had in stock didn't come with a pigtail, and they swore it was a direct plug in. Even though i tried to explain it was universal...SO i got home and was just going to make some jumpers for now, but i can't get my fuel line disconnect tool in there enough to pop off the lines. i'm too afraid to break them, so here's to another costly shop bill....

 

[79jasper]

The disconnect part is replaceable, IIRC.
You can bypass it for now until you can get the right valve, I'm pretty sure someone here found a source for new OEM valves.

 

[LCAM-01XA]

.SO i got home and was just going to make some jumpers for now, but i can't get my fuel line disconnect tool in there enough to pop off the lines. i'm too afraid to break them, so here's to another costly shop bill....

The only disconnect tools you need are gonna be a small flat-blade screwdriver and a curved pick. And pick is actually optional. Have you done those kind of quick-connect fittings before? Basically all you gotta do is slide the screwdriver between the white plastic retaining clip and the black plastic fitting, then slide/wiggle/pry/yank the clip out off to the side of the fitting, once white clip is out the fitting will just pull off the valve port. The clip has a little "tooth" on one of its prongs that prevents it from falling off on its own, this tooth can bear to push in if you plan on reusing the clips, but if you get new clips you can just force the clip and tooth will break or fold and clip will come out, there will be no damage to black fitting either, just the tooth on the clip will get deformed. In a pinch when reassembling the thing you can just use zip-ties instead of them clips, remember our systems are under vacuum there all the time so as long as you have something that prevents the fitting from sliding off the tank port due to vibrations you'll be all set. I actually ran a ziptie for years (lost the retaining clip into the grassy jungle and was in a hurry), not a single problem w/ it, lol

 

[gandalf]

Pulling those clips is easy, other than the fact that you're flat on your back (in my case), space is tight, and the whole thing is awkward. If you're very lucky you might be able to re-use the clip, but don't count on it. I bought a pack to have on hand when I pulled the lines on my truck, just because I already know about my luck. My favorite local parts store ordered them in in just one day.

Pictures help. Here's one which will show the two size clips, and the Dorman part number. Not the best picture, but I haven't even finished my first coffee of the morning.

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