Gas Tank Question
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Senior User
Joined: Apr 2010
Posts: 368
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From: Loganville, Ga
Gas Tank Question
Ok, I've been fighting a guage problem and just thought of something. Does the gas tank itself need to be insulated from the frame? I put a new gas tank in while I was rebuilding the truck. I remember there being something like roofing felt between the old tank and the straps and frame. On my new tank I sprayed a little undercoating on the top of the tank so it wouldn't rub the frame rails.
So do I need to insulatethe tank with something?
Thanks!
1986 Flareside, Edelbrock 500cfm, Offenhauser DP, EFI exhaust, DUI distributor, the mighty 300, 4spd OD.
So do I need to insulatethe tank with something?
Thanks!
1986 Flareside, Edelbrock 500cfm, Offenhauser DP, EFI exhaust, DUI distributor, the mighty 300, 4spd OD.
Thread Starter
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Senior User
Joined: Apr 2010
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From: Loganville, Ga
That was my first thought. But when you're dealing with a metal tank full of gas it's best to ask those who know better than I. I'll see what I have in the garage I can use for a safe ground strap.
Thanks!
Thanks!
Senior User
Joined: Feb 2012
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From: Grants Pass, OR
I replaced my rear tank and it had rubber pads on the straps and rubber pads between the skid plate and tank. I think they are for mechanical insulation not really electrical insulation.
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Joined: Nov 2007
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From: Denver Metro Area, CO
Well, in principle, what Gary said is correct - at least the tank sender needs to be grounded.
But, you're right, klricks, there's a ground wire in the harness for that.
My tank straps were "insulated" with some sort of stuff resembling rubber. It was dry rotted and falling apart so I replaced it with, um, I seem to recall bicycle inner tube and duct tape.
This insulation is to avoid metal-to-metal abrasion as the truck bounces around and holes wearing through the tanks over time.
I had a power steering high-pressure tube fail on my DD because of metal-to-metal abrasion.
It took over 20 years but it eventually wore through and I suddenly didn't have power steering.
But, you're right, klricks, there's a ground wire in the harness for that.
My tank straps were "insulated" with some sort of stuff resembling rubber. It was dry rotted and falling apart so I replaced it with, um, I seem to recall bicycle inner tube and duct tape.
This insulation is to avoid metal-to-metal abrasion as the truck bounces around and holes wearing through the tanks over time.
I had a power steering high-pressure tube fail on my DD because of metal-to-metal abrasion.
It took over 20 years but it eventually wore through and I suddenly didn't have power steering.
FTE Legend
Joined: Jul 2010
Posts: 32,875
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From: Northeast, OK
I don't think that is true. There are ground return wires in the connector which are grounded to the sender frame. 2 ground wires if you have dual tanks. So the tank does not need to be grounded for the sender to work.
I replaced my rear tank and it had rubber pads on the straps and rubber pads between the skid plate and tank. I think they are for mechanical insulation not really electrical insulation.
I replaced my rear tank and it had rubber pads on the straps and rubber pads between the skid plate and tank. I think they are for mechanical insulation not really electrical insulation.
I did my usual trick of projecting my truck onto this situation. Mine has only one wire to the sending unit and no ground wire. That's true of both of my 81's and was true of both of the 82's I've owned. But, Nolan's is apparently an 86, and they have in-tank pumps so have different wiring to the tank. So, it is very possible a ground was run with those wires.Nolan - Check to see if there is a wire that grounds to the sender frame. And, if you have a DVM, check the tank to see if it is grounded. I'll bet it is. And, please accept my apologies.
Postmaster
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From: Broken Arrow , OK
I seem to recall bicycle inner tube and duct tape.
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Senior User
Joined: Apr 2010
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From: Loganville, Ga
Sorry Gary, no in tank pump. In 86 it seems the EFI was an option. You could still get a carb in base models like mine. At least that's what I have seen.
Also there is a rubber O-ring that goes in around the sending unit. It's required because without it the sending unit is loose.
And my sending unit does have 2 wires to it.
Also there is a rubber O-ring that goes in around the sending unit. It's required because without it the sending unit is loose.
And my sending unit does have 2 wires to it.
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FTE Legend
Joined: Jul 2010
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From: Northeast, OK
Sorry Gary, no in tank pump. In 86 it seems the EFI was an option. You could still get a carb in base models like mine. At least that's what I have seen.
Also there is a rubber O-ring that goes in around the sending unit. It's required because without it the sending unit is loose.
And my sending unit does have 2 wires to it.
Also there is a rubber O-ring that goes in around the sending unit. It's required because without it the sending unit is loose.
And my sending unit does have 2 wires to it.
Old School Hot Rodder
Joined: Feb 2006
Posts: 6,472
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From: Exmore, VA
I would still ground the tank, I don't know on the mechanical fuel pump applications, but on the 351 and 460 with the hot fuel handling package there are 4 wires due to the in-tank low pressure pumps. I have run into a number of replacement pump units where the gauge sender ground was a dummy. Ford used the same style pin on all four terminals, just the sender ground had a metal ring on the inside. The Chinese built replacements, and even a NAPA one have insulating rings on all four, and no ground for the sender as a result.
If you ground the sender wire(s) the gauge should go all the way to full on an 86. If it doesn't, the you have a gauge problem. On these trucks, open circuit will read empty.
If you ground the sender wire(s) the gauge should go all the way to full on an 86. If it doesn't, the you have a gauge problem. On these trucks, open circuit will read empty.
Hotshot
Joined: Feb 2004
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From: Marengo, Iowa
On the carbed/diesels, there is 2 wires, and both are for the sender. On the gas fuel injected, there are 4 wires, 2 for the sender, 2 for the pump. The sender will work and read hanging in the air. I have tested them that way, take them out of the tank, plug them in and mover the float around to see how the resistor responds.
Posting Guru
Joined: Jan 2012
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From: Dallas, GA
On the carbed/diesels, there is 2 wires, and both are for the sender. On the gas fuel injected, there are 4 wires, 2 for the sender, 2 for the pump. The sender will work and read hanging in the air. I have tested them that way, take them out of the tank, plug them in and mover the float around to see how the resistor responds.
Yes...I've done that too and do as a practice just to make sure what you're putting in works. Not fun to find out it don't after it's installed. You're moving a variable resistor in the circuit...so it don't know, or care, how it's moved.
2 part test....remove the sensor lead and put it to ground. Gage should peg high. Now you know our gage is working.
EVTM even walks you though a "Bench" test of the gage/regulator.
Postmaster
Joined: Nov 2009
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From: Broken Arrow , OK
I posted a link somewhere on how to take the sending units apart and clean the circuit boards when they arent working right. Sometimes if you dont have a bare wire somewhere making the gauge go nuts it can be a dirty rusty circuit board. Also I have run across floats that have holes in them which will let fuel fill the float and cause it not to work right.