Gas Gauge only going to 3/4 full

[chuckbrandt]

Hey Folks,
I have a head scratcher for you. The gas gauge in my son's '67 F-100 has always read 3/4 full when full. Seems to work otherwise and so do the other gauges. Thinking it was the sender I replaced it and it reads the same. When I connect the orange wire to ground the gauge goes to Full. When I hook my digital voltmeter to the ground / orange wire I see the pulse but because it is digital I can't tell what the voltage is. I assume it is the IPVR? Should I replace it even though it obviously sort of works? I assume the gauge is not adjustable.

Chuck

[basketcase0302]

I would first pull the sending unit back out and check the float. If it has a pin hole, (common) in it-it will be giving that similar reading due to being too heavy. Then I'd go to the IPVR on the back of the instrument panel. Here's the fuel gauge tutorial:
http://www.fordification.com/tech/fuel- ... -units.htm

[Texasswamp]

I'm having the exact same problem. I replaced voltage reg. and sending unit(both from Dennis carpenter). Full tank reads 3/4 full. Maybe I'll check the float. Don't think it's the ipvr in your case because it also controls current to the temp gauge and you say the temp gauge is working correctly .

[Texasswamp]

Also I don't get a pulse on mine. Seems weird?

[basketcase0302]

Texasswamp on Wed Mar 07, 2012 2:37 pm
Also I don't get a pulse on mine. Seems weird?

Very hard to see on a digital meter. My Fluke will just go up and back down through the range very quickly, (can't actually see a 5VDC reading). You can also run the sending unit arm up through the range while you have it pulled out, (making sure it's grounded) and watch the gage for movement. Also possible to have a bent arm / float with fuel in it, (I've seen them with only a slight amount of fuel-no full of fuel).

[70_F100]

Replace the gauge.

They wear out, too...