i have a 78 bronco with a 400 in it.... i had fuel problems, tank was 33gal. it was rusty as well as the sending unit. swapped both out and now the gauge reads full constantly used to not read at all any ideas on what to do???? maybe flip wire connector at the sending unit around??? Or maybe someone has had this prob.:{ Any thing helps.. Thanks.

 

Check your ground.

 

The ground on the cluster or the connector ground?

 

Your fuel pump sending unit's ground (that measures yer fuel). Check it out. Make sure it ain't loose or rusted.

 

K. Will do thanks i will post if that does it or not.

 

Unplugged connector still reads past full.... still a bad ground? Back to chasing wires.

 

It SHOULD read "full" when disconnected. The sending unit alters the NEGATIVE voltage to the gauge. The more fuel in the tank the more resistance and the "fuller" the gauge reads. When the sending unit or the float fails, the sending unit sends a "false positive" if you will. What you can tell is that the gauge is working just fine. The sending unit and/or the float has failed. Time to crawl into the tank and see whats up unless you can confirm that the wiring between the sending unit and the gauge is damaged somewhere/somehow.

 

Figured it out. I checked my wiring. Found a tiny bare spot on the Orange wire grounding out on the frame.....hmm why didn't I think of that first.
Thanks for the replies.

 

So this is my first day on this site so I dont know if this is posting to everyone,here is my question. 1978 Ford F-250 side tank sending unit, mine was rotted and gone,I istalled a new one but now my level after 8 gallons down from full reads empty,I noticed there are two types one that has a 4.8 inch level arm and a 10' level arm,should I try the 10' long one.............Anyone know?

 

What gallon is yer tank

 

That's the question, I don't know how many gallons it holds. I haven't run it out of gas yet,how can I check?

 

There are 7.48 gallons per cubic foot. Measure tank and see how many cubic feet there is.

 

Or look up the tank sizes for your year. You could just drain the tank and fill it up