does anyone know what is up with my fuel gauge? the needle starts at just below full and when I turn the key on it goes way above full. I only put 10 gallons of gas in the new tank along with new electric fuel pump and sending unit from Holley.

 

Either you have a open in the signal wire, or no ground.

Ground the signal wire to the sending unit, turn on the ignition. The gauge should read empty. Remove the ground, the gauge should read beyond full.

if that check out, make sure the ground for the sending unit is clean and tight. If so, the sending unit is defective.

 

So this is NOT a factory sending unit? Do you know what the resistance rating is on that sender? Does the sender match the gauge? If you are using a stock gas gauge, it requires a 0-90 ohm sender (0 ohms EMPTY, 90 ohms FULL). Most aftermarket senders are 240 ohms empty and 33 ohms full.

 

I called Holley up and they said my sending unit should be 0 to 90 ohms! I have my ground wire connected to the frame, or should I connect the ground wire to the body where is was from factory?

 

The frame SHOULD be grounded, but who knows. A wire to the body wouldn't hurt and is easy to test.

 

It is grounded, I did a continuity test with my meter! thanks for reply

 

I did all the checks and my gauges stays the same! I have 10 gal. of gas in tank and the ohms on sending unit read 15.4 ohms and there is 6.4 volts on the wire coming to the sending unit from gauge. the gauge reads just below full and goes up from there when key is turned on!

 

do you know what kind of voltage should be on the wire to sending unit? mine reads 6.1 volts! and 15 ohms on the sending with 10 gallons of gas in tank.

 

The voltage is supposed to vary depending on the level in the tank. That's how the gauge operates. The variable resistor in the sending unit varies the voltage on the wire to the gauge. That's how all your sending units for factory gauges (oil and temp) work.

 

I did not know that. I also wanted to say that I just got done hooking up my original sending unit ( out side the tank) with ground wire to original position on body and to the wire going to dash and I still have the same issue!!

 

Therefor it could be the ground wire to the original position on the body (try grounding it to a new clean spot).

Or it could be the wiring to the dash, you can temporarily run a new wire if the ground checks out OK.

Another thing you can do is use the new sending unit and connect it directly to the gauge and ground it inside the car. If it works there, then it's definitely in the wiring or the ground at the rear.

 

well I did hook the ground wire to a clean spot on the frame (checked continuity to body) and still have same issue. I guess my next check will be the wire going to the gauge, I will run a new wire from SU to gauge and see what happens! thanks for info!

 

Try doing it by the dash if you still have the sending unit out. It will confirm that it is definitely the factory wire from the dash to the SU.

 

Got it!

 

ain't I suppose to have 12v between the top two screws with metal tabs? if so, I do not!