Gas Tank Question

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Apr 17, 2012 | 12:22 PM

#16

batchman

Mountain Pass

Joined: Oct 2000

Posts: 180

Likes: 0

From: Backwoods Massachusetts

Quote:

Originally Posted by 85lebaront2

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.

I would not recommend grounding the tank. If something hot inside were to touch a grounded tank it could draw a spark. If the tank is not full that would mean vapors are present.

If the tank is not grounded then it would not complete a circuit.

JMHO,
- Jeff

Apr 17, 2012 | 12:37 PM

#17

85lebaront2

Old School Hot Rodder

Joined: Feb 2006

Posts: 6,472

Likes: 11

From: Exmore, VA

Jeff, the original fuel pump modules were grounded by the black wire to the chassis grounds, if you have replaced these with aftermarket ones you have to ground the tank or the gauge will not work, up through 88 they read empty with no ground, 89 up they read full with no ground.

Apr 17, 2012 | 01:47 PM

#18

fellro86

Hotshot

Joined: Feb 2004

Posts: 11,697

Likes: 3

From: Marengo, Iowa

Gas tanks have been grounded for a very long time. If you don't, you risk static charge buildup. Also, by the philosophy of a short being the risk, the pumps in the tank have their own ground, so the risk is still there. The sender itself does not run full 12v, and is low amperage.

Apr 17, 2012 | 02:20 PM

#19

nolan62

Thread Starter

Senior User

Joined: Apr 2010

Posts: 368

Likes: 3

From: Loganville, Ga

Are you sure the sender does NOT run at 12v? I noticed that there wasn't 12v on that connector. Do you know what the correct voltage is?

Apr 17, 2012 | 02:31 PM

#20

82f100460

Posting Guru

Joined: Jan 2012

Posts: 1,410

Likes: 1

From: Dallas, GA

Quote:

Originally Posted by nolan62

Are you sure the sender does NOT run at 12v? I noticed that there wasn't 12v on that connector. Do you know what the correct voltage is?

All of your instruments (fuel, coolant and oil) run off the intrument voltage regualtor that provides 5V to the senders....optimum. may be little off from there but should be by much.

Apr 17, 2012 | 02:39 PM

#21

klricks

Senior User

Joined: Feb 2012

Posts: 177

Likes: 0

From: Grants Pass, OR

Quote:

Originally Posted by nolan62

Are you sure the sender does NOT run at 12v? I noticed that there wasn't 12v on that connector. Do you know what the correct voltage is?

The voltage is 5V which pulses on and off at a rate of about half a second.
A digital volt meter will show erratic reading. If your meter has a bar display then that works or use an analog meter. A test light would work as well but be somewhat dim.