The title says it all. My gas gauge isnt working. i put about 5 gallons in and it says its empty. When I turn the key its below the empty line and moves up to the line. Any ideas whats wrong and how to fix it?

Also when I put gas in it seems to sit in the filler neck and slowly drain into the tank. Any idea whats going on there?

Thanks in advance

 

I had the same problem with my truck so I took out the sending unit and cleaned a bunch of crap off of it. Then I had to fix a hole in the fuel float because it was full of gas. Now it works when it wants but I think the old ones get James and army accurate. Just my opinion tho good luck!

 

Sorry I mean get jamed and are not very accurate

 

Il try that when I have access to a lift at school
Thanks for the help

 

X2 on the sending unit.

 

Someone told me it could be a bad ground. Where would the ground be at?

 

Most common problems are:

1) Bad sending unit
2) Float filled with gas
3) Bad ground

The sending unit grounds to the nearby frame cross member unless you have an in-cab tank. The frame is grounded by a ground strap attached to the firewall, which itself is grounded to the engine block through another ground strap. The frame does not ground directly to the block through the motor mounts, which is a common misconception.

 

How do I know if the ground is bad?

 

Turn the key to accessory, then crawl underneath the truck and unplug the sending unit. Firmly connect the sending unit lead to the nut that grounds the sending unit pigtail on the crossmember by means of a jumper wire or alligator clips. If all the wiring is good (including the ground), the gauge will peg to FULL.

If that doesn't work, try grounding it to bed sheetmetal instead. If that works, then the problem is at least the ground. The sending unit can then be troubleshot with a multimeter.

 

The sending unit float is made from two pieces of copper soldered together. Solder breaks down, gas seeps in, float settles to the bottom of the tank.

COAZ-9202-B .. Sending Unit Float / Available from Ford ~ MSRP: $15.94 ~ FTE Ford Dealer Parts Dept sponsor tousleyfordparts.com price: $10.52 / Tousley Ford: White Bear Lake MN

Applications: ALL 1957/79 FoMoCo vehicles.
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If the vent hose has collapsed, these notoriously slow-fill fuel filler tubes become even slower. As original, the vent hose was taped (black electrical tape) to the filler hose in three places.

 

Dennis Carpenter carries a solid float made by Stewart Warner






The Vent hose needs to be secured to the fill hose, but higher than the fill hose.

 

X2 on checking the float in this case.

The sending unit is working, or passing current to ground. This is why the gauge raises to the "E" line when the ignition switch is turned on.

If it was a ground issue, the gauge would not come up to the "E" line. It would remain below empty, like when the ignition switch is in the off position.


Now off on a tangent...

The engine to firewall ground is pretty straight forward.

Where is the ground located, between firewall and frame? I've yet to see that one, and it's not listed in the factory wiring diagrams I have. Not saying there isn't one, because, read below...

I have seen some strange ways Ford grounded things. Through the steering column to the gear box to the frame. With the rag joint having a small ground strap connecting the seperate pieces. Without that ground the horn doesn't work among other things etc...

Another on the 300-6's is to run the Negative battery cable down to the frame where a metal tang, pinched on the cable, grounds the frame, halfway along the cable. The cable continues to one of the starters mounting bolts.

And yes I've seen them grounded through the motor mounts as well. With a grounding strap running through it in a similar way of the rag joint etc...

With swapping out original parts with aftermarket, those grounds above tend to be eliminated. I can't tell you how many times people have had questions on why electrics suddenly went wacky, only to find that one of those ground were eliminated by swapping a part.

It depends on year, engine, and model where the grounds are located and how. There is more than one way, etc...

 

On mine (1979 F100) it is on the driver side of the cab at the bottom attached to a spot where the cab sheetmetal "lips" around. I will try to get a picture this evening.

 

Can I take the sending unit out of the tank while its still on the truck? or does it need to be taken off

 

If this is an aft tank, no, the sending unit is on top. The tank has to drop, or the bed come off.