how to test fuel sending units?

Angie · May 14, 2016

I have an 83 with 2 tanks and I am needing to test the 2 sending units in the tanks to the Hastings gauge I built in the dash. i know it is supposed 73-10 OHMS to move the needle. i can hit the float with a magnet to raise and lower it. whats the proper way to test the whole circuit before i place the cab and box back onto the frame?

thanks

adsm08 · May 14, 2016

You have two options.

1) You can resistance test the whole circuit, or at least as much as you can put together without the body on there, and move the floats.

2) You can resistance test the sending cards now, put everything back together and ground the signal wire to the gauge, see if it pegs out.

RonD · May 15, 2016

Ford used a Yellow wire for sending units for many years, not sure in '83
The wiring for sender is:

5volt pulsed power regulator------Gauge-----(yellow)-------sender----(black or orange)-----Ground

There should be 2 wires at each gas tank, 1983 shouldn't have in-tank electric pump, they used mechanical pump on the engine.

Remove connector at the tank and use OHM meter.
Set OHM meter for 200ohms or 1,000(1k) ohms
Connect OHM meter to each connection at the tank
Should read between 73-10ohms, 73ohms empty, 10ohms full
Move float and watch OHMs change

To test wire to gauge you need to Ground the "yellow" wire.
Turn key on
Select tank you will be testing on the cab switch
Gauge should show below empty with wire unplugged, OHMs are above 73
Now ground the "yellow" wire to frame
Gauge should go to above Full, ground will be 0 OHMs

Test other tank, remember to change the cab switch

Angie · May 15, 2016

Thanks ADSM, The cluster isn't bolted into the dash yet so it is easy to place it beside the main wiring system to test the gauges. wanting to hold an ohm meter at the wiring system before hooking the gauges up to test resistances. then trying the gauge for both tanks.

I am reading that the gauge needs to be proper resistances for the sending units to work proper and being 73 - 10. I have no idea what the gauges are set at that I placed into the cluster. It is a NOS Hastings fuel gauge that I picked up still boxed at a car swap meet.

The back tank is the original, with the 83 sending unit. the front was a nightmare to get, LCM truck tank for the 83, however, the sending unit isn't available anymore for these tanks and I placed in a sending unit from 83-84 bronco 2 as this fit the tank after a bit of tweaking to the float to make it sit properly.

Hope this sheds a bit more light on the "how do I do this"

cheers
(could post a pic if that helps)

Angie · May 15, 2016

Thanks Ron...

we missed each other. and that is the explanation i was needing.

how do I wire in the 5 volt separator? I was able to get a couple to wire in from "ebay" do I place it just before the gauge at the cluster?

RonD · May 15, 2016

5 volt separator?

Selector switch?

There are 2 kinds, one just does the Fuel gauge, it will usually just have 3 connections.
Wire to fuel gauge goes to the center, then wire from each tank goes either side, so it just selects which tank level gauge displays.
Then you would have a manual tank selector lever next to drivers seat to change fuel flow from tanks.

Second type does the gauge selection and also has connections for 12volt electric flow switch.
12volt OFF is one tank
12volt ON is the other tank
This needs to be wired to a Key on circuit for the 12volts
12v into switch when key is on, then 1 wire from switch to flow valve
Flow valve needs to be grounded to frame or with a ground wire.

Then you need to match gauge selection with flow selection.
So 12v OFF = Front tank on valve and front tank sender
12v ON = rear tank on valve and rear tank sender

This is a universal electric valve: http://www.ebay.com/itm/New-FUEL-TANK-SELECTOR-SWITCHING-VALVE-3-PORT-Main-Aux-gas-FV1T-Duel-DUAL-Switch-/171249453850
You just need one with 3 ports
One to fuel pump on engine
One to each gas tank

Or use manual switch: http://www.amazon.com/Moeller-Fuel-Three-Way-Valve-Brass/dp/B000MTB7QA

Angie · May 15, 2016

5volt drop down. (separator) splitter)

The tank switch is factory and is a slider built in the dash, slide it and that is it. Should still be working fine (as it did when taken apart).

thanks

RonD · May 15, 2016

Like this one: http://www.ebay.com/itm/NOS-1983-1984-1985-FORD-RANGER-BORNCO-II-DUAL-GAS-TANK-SWITCH-E3TZ-9A050-B-NEW-/360870940654

If it is already installed and electric valve is there then as you say, it should still be working.

5v pulse power supply seen here: http://www.fordification.com/tech/fuel-sending-units.htm
It will be behind the dash

The 5v pulse voltage at the sender should show voltage going up and down, a pulsed voltage.
Key on of course and tank selector in correct position

Angie · May 15, 2016

The drop down 5volt is like this....

http://www.ebay.com/itm/DC-buck-converter-Car-power-supply-Voltage-Regulator-volt-Adapter-8-20-12V-to-5V-/131785547018?hash=item1eaf07dd0a:g:ZawAAOSwyQtVzjN7

and yes the slider in the dash is exactly the same as the one you linked to.

I may have the wrong one for it might not be a pulse style. not sure if that makes a difference or not.

thanks

RonD · May 15, 2016

Not quite following you on this one.

That wouldn't be for the fuel gauge.

Does the fuel flow switch use that?
I wouldn't think so on a stock Ford system.

Picture of dash board power supply here: http://www.fordification.com/tech/fuel-sending-units.htm

Angie · May 16, 2016

Ok, now I see where I am getting mixed up. I have rebuilt the whole gauge system with after market sets and bypassed that pulse thing, (not knowing what it is). I was told i needed 5Volts to feed the sending unit/fuel gauge and picked up that converter.

here is a link to the picture. Post #21
http://www.therangerstation.com/forums/showthread.php?t=156327&page=3

Now i need to rewire in that part.

thanks

RonD · May 16, 2016

Yes, me too, was thinking Ford system, stock.

how to test fuel sending units?

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