1987 fuel pump/gas gauge wiring

[atsrmf]

I have a 1987 El Capitan with the Ford 460 carburetor engine. Whoever replaced the fuel pump that is in the tank got the gas gauge wires revered, so when I fill up the gauge reads below empty. When empty is read 7/8 full. Needless to say, I ran out of gas to learn this lesson the hard way! Does anyone know the colors for the wiring? I have searched on google to no avail.

[77rollalong]

atsrmf wrote:
Rollalong I agree, move the float manually and see what happens. If the gauge is no good I'll install a new one under the dash. Knowing the E-F resistance I can order a matching gauge easily online. Running out of gas in a Class A sucks, you're not pushing it anywhere!

Yes for like of better words its like trying to push a Brick **** house. with the price of gas now here, iam not sure what its going to cost to fill up ours, and the 460ci is not easy on fuel at all, i think thats one reason it has twin tanks under it .

[atsrmf]

Rollalong I agree, move the float manually and see what happens. If the gauge is no good I'll install a new one under the dash. Knowing the E-F resistance I can order a matching gauge easily online. Running out of gas in a Class A sucks, you're not pushing it anywhere!

[77rollalong]

personally , I hate dropping gas tanks... don't like working with gasoline. when you get the sending unit out, you may want to hook it back up and play with the float outside the gas tank and watch the readings..

[atsrmf]

Thanks for all the replies. I think Matt from Michigan got it right this time. I know the guy who put the new assembly in the tank, and he either installed it wrong or put the wrong part in. It's good to know the resistance required as 77rollalong stated, that would be needed for further troubleshooting. I think I will end up lowering the tank, something I wanted to avoid.

[77rollalong]

I just did a little more reading on your problem, in my Mitchels on demand . From what iam reading there is two different type of sending units used, i-metal and Magnetic, the resistance test for the bi-metal type is full tank 10 ohms; empty tank 70 ohms. the resistance test for the magnetic type is full tank 160 ohms; empty tank15 ohms.

Calbration Test :

1 required test equipment is a 10 Ohm resistor and a 70 ohm resistor.

2 Disconnect wiring at sending unit. connect one of the resistors between the lead wire terminal and ground. turn ignition switch to "RUN" or "ACC" position. With 10 ohm resistor, guage should show a full scale reading. with 70 ohm resistor on Aerostar and 73 ohm resistor on all other models, guage should read at "E" mark
3 With no resistor (open circuit) guage reading should be the same as with ignition in "OFF" position. if reading is okay, replace wire connection to sender.

4 If guage does not move and stays below "E", check for an open circuit in the wiring Assembly, guage windings, or Instrument cluster printed circuit, if guage pointer moves with no resistor connected, check for a short circuit in the sending unit lead wire. If guage reads out of calibration, replace IVR (if equipped) and retest. If calibration is still incorrect , replace guage.

To me it sounds like who ever replaced the sending unit last has put in the wrong one though...

[77rollalong]

On the carb version there is no fuel pump in the gas tank, it only a single wire (orange) single tank, orange rear tank, Green/red for front tank, EFI is the same colour wires, one side of the fuel sender should be grounded, other goes either directly to the fuel guage, or goes through the fuel tank selector switch... and back to the fuel guage... according to the wire diagram i have here

[Matt_Colie]

We are stretching old memories here, but as I recall, that is a single wire resistance gauge. What really happened is that the person put in the wrong sender/pump package.

Matt

[atsrmf]

I thought of doing it at the gauge, but access to the back of it is a nightmare. It would be easiest to swap the wires just outside of the tank. There are 4 wires I believe, 2 go to the pump and 2 to the gauge. I can check the wire color at the pump relay to figure the 12v feed to the pump. I just don't want to cut the wrong wires, but I have a VOM to assist.

[olfarmer]

If you can get to the back of the fuel gauge you could try reversing the wires.