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fuel sys meltdown under dash

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Old Sep 9, 2004 | 05:48 PM
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fuel sys meltdown under dash

I could use some help. 88 F250 gas/dual tanks. When I bought the truck the rear tank didn't work, but gauge appeared to.

Recently installed a new in-tank fuel pump in the rear tank. Had to put a new connector on the wires as the old one crumbled when it came off. I'm pretty sure I got them back where they should be.

Dumped in 10 gal gas and went for a ride. Engine ran fine on the rear tank. Gauge didn't seem to come up where it should have - stayed near empty.

After 5 miles I smelled hot electrical and then saw the smoke under the dash around the tank selector switch. Shut things down immediately and tore the dash panels off - no fire but did melt things.

Selector switch wires brown/white and red/yellow melted and switch bubbled around the 2 and 3 pins. Only melted as far as the connector.

Inertia switch melted down - both wires and the switch.

Didn't blow the fuse.

Did I screw something up when I connected the in-tank pump? Or is the cause likely something else? Any ideas appreciated. Thanks!
Tim
 
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Old Sep 9, 2004 | 09:01 PM
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Dealford
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Just a real quick guess, the selector switch hadn't been used for quite some time & the ground got corroded?
What are the colours of the wires to the rear tank fuel pump?
These should be 2 separate circuits?
AL.
 
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Old Sep 9, 2004 | 09:16 PM
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Here's a diagram that has a little bit of info on your wiring.

http://www.autozone.com/images/cds/g...3d800a3a44.gif

I would venture to say there is something wrong with the wire going from the switch to the rear fuel pump/tank.
 
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Old Sep 10, 2004 | 10:42 AM
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Thanks for the info and links. I'll check it out and let you know what I find. Is it possible for the pump to work and still have a bad ground or bad wire? That's what's throwing me off.

I 'spose it could carry some of the load, enough to run the pump, but the defective wiring draws too much current and heats things up slowly. It took about 10 minutes of driving for this to get crispy.

Again, thanks. You guys are terrific!
 
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Old Sep 10, 2004 | 02:14 PM
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Originally Posted by mtflat
Is it possible for the pump to work and still have a bad ground or bad wire? That's what's throwing me off.

I 'spose it could carry some of the load, enough to run the pump, but the defective wiring draws too much current and heats things up slowly. It took about 10 minutes of driving for this to get crispy.
That's a good point, but I would first look to see if the fuel pump wire may be loose under there, possibly hitting the frame somewhere randomly. Or possibly to near an exhaust pipe or something. Going over a bump may be all it takes.
 
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