Fuel Guage Adjustment - 68 Mustang

Marcus

Marcus

Well-known member
Gentlemen: Just installed a new gas tank, sending unit, etc. in my 1968 Mustang Convertible. Pretty straightforward installation; however, now with a full tank, the fuel guage reads 1/2 full. I can't locate any instructions with sending unit giving instructions if an inaccurate reading occurs: Any suggestions from this group of elite experts?
 
Hi Marcus. I should not get into this because I don't know dooky about '68 Mustangs. But I DO know that if the original was a King Seely unit and your replacement is a resistance unit I wish you luck in getting it to read accurately through the range. Most, including me, try to set it (through trial and error) to where it shows empty just before you run out of gas and "fagetabout" accuracy above that. Some of the replacement units have adjustable resistance units so you can adjust up and down according to the tank depth. Some measuring, float arm bending, and luck will get you close. Someone will know if/when Ford stopped using King Seely, but I know they used them through the '50s. Let us know how you make out.
 
Marcus, I do not believe you have the old King Seeley set up. A couple years back the fuel gauge on my 72 Mustang stayed on empty. In this case the sender was bad. From everything I read it works on resistance so should be same for 68
Frist thing is to determine that V. regulator on back of instrument cluster is sending 5V to sender. You probably need an analog v. meter if original mechanical regulator is still in there. If it has been replaced with a solid state one a regular DVM should work.
The float resistance for my 72 is 8-10 ohms full and 60-86 ohms empty. Seems like a pretty big range but that is what I read. I did write down that I was getting 2.4 volts back from sender and gauge was reading around 5/8-3/4 full. Hope this helps.
 
40 Cpe is correct: King Seeley gauges and contemporary senders have incompatible operating designs. I fiddled with series resistors until I was able to correlate a tank low fuel level with the 'E' on the gauge. For the newer sender on my '41 I think it was about 50 ohms.
 
Huge help, guys: Thanks! 40cpe (Gene!); Bob and Alan - I have an analog and digital volt meter, so I have a good starting point. Project now on hold; going to San Antonio for Oldest Grandson's graduation from USAF Basic Training - so proud of him (and totally his choice - no influence from USA retired Grandfather!)
Let you know what I find and solution (if there is one) when I get time for more fun with the toys......
 
We're proud of our grandchildren, and rightfully so. Have a safe and enjoyable trip!
 
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