Fuel Guage upgrade- help

[Blown4.6]

just purchased a Auto Meter fuel gauge fromSummit. I figured it would be easy...but something just isn't working correctly. The new gauge reads 1/4 tank lower than it really is (e.g., when I fill it to the top, the gauge reads 3/4...etc).

Anyway, the guage has "S", "G" and "Ign" post on the rear. Obviously, send, ground and ignition. However, the stock gauge has just two connections ( a black wire/boot and an orange wire/boot). I assumed that the black was a ground and the orange was the sender.......but that didn't seem to work out.

Way I've got it now: orange to "ign" and black to "send".....I've just run a good ground to the "G" terminal. Why would it seem to work but just be off by 1/4 tank??

Stock Gauge-
red wire from stock gauge is:_______________

black wire from stock gauge is:______________

On the new gauge:

connect_______________to "ign"

connect_______________to "g"

connect ______________to "S"



Thanks for the help in advance.

 

[jae902]

It probably reads 1/4 off because the resistance is off. The new guage should tell you how many ohms for empty, and how many ohms for full. You might need a new sending unit, or measure your existing sending unit and exchange the guage for one that is compatible. Open the sending unit, push the float all the way down, get an ohm meter, black to ground and red to the sending unit. Read what it says at empty and full. Call up summit, and tell them u need a guage with these readings.

 

[Edbert]

I'd start by checking your sending unit too. Has it ever been changed? I cannot imagine a 35-40 year old float and variable resistor is still accurate. I made that opinion when I replaced my old fuel tank and saw how much nasty crap was in it. If you can get a multimeter reading off the sending unit you can see if it is in or out of spec.

If your sending unit checks out, you should knnow that there are different gauges too. When I ordered my Autometer I had to choose which type of sending unit I had, maybe you got the wrong one?

 

[Blown4.6]

I'll call Summit. I have a new tank that is going in; so, maybe I just buy a new sending unit that is compatible with this gauge.

Thanks!