fuel sender troubleshoot
 

Getting started with some small repairs. Number one being the fuel gauge not working and need some advice. The truck has a tank behind the seat and a side tank that looks like it was installed by the dealer or possibly was oem. All the gauges on the cluster work fine aside from the fuel gauge. It is constantly reading empty. There is a switch on the dash that selects which tank the gauge is looking at and a valve on the floor behind the seat to control where fuel is actually coming from. Switching the switch does nothing to change the fuel gauge. My question is: can I short the fuel sender wire to ground and see the gauge go to full? I dont want to ruin anything further by doing something stupid. Just trying to eliminate the gauge as the problem. Truck is 69 N700

Thank you for any help

Probably but I prefer to use a test light, old school with a light bulb in it. Look for the gauge to read around 1/4-3/4. You can go from the sender to the switch to the gauge like that to trace the problem. Always test light to power to be sure it is working. Mark the positions on that switch very clearly. I could tell you a story why that can be very important.

The in-cab fuel sending unit float is made of two pieces of brass soldered together. Solder breaks down, gas seeps in, float settles to the bottom of the tank.

Float (C0AZ-9202-B) is available from Ford and repro parts sellers, same 1957/79 FoMoCo Passenger Cars & all trucks; 1961/79 Econolines & 1966/79 Bronco's.

floats
 

Got two on the way. Thanks!!!!

Be sure tanks are well grounded. I had corosion stop a gauge from working. Unit was fine when I pulled it out so I stuck it back in, installed the tank and it worked ever since.corrosion on the straps did not have the tank grounded properly. It had set for a few years.

grounding
 

I am thinking you may be on the right track as all of the lights on the dump bed are very dim. Seems like there is not a very good ground at all from the cab back. Also, it looks like a p.o. used a short ground jumper from the sender to the chassis on both tanks. Not sure it this is OEM or not. Will post what ends up being the problem.
Thanks!

Finally got back to this part of the puzzle putting things back together on this old truck. Started with the external side tank and removed the sender. Tested it on an ohm meter and got some very erratic results. Took it apart to find that the windings on the resistor were completely warn through and hanging all over the place, thus, non functional. I have not looked at the cab tank as of yet. The part number on the external tank sender is C4TF-9275-T. The last digit could be wrong as it is pretty rusty right there. It is possible that it is an I or an L, but it looks like a T. My question is: are there other senders that will work for this application? Or were these senders used in other cars that I can cross reference? When I tell my local parts dealer that I have a 1969 Ford N700 he (or she) looks at me like I have two heads and starts the argument that no such vehicle was ever built.

Thanks!!!!!!

D3TZ-9275-E (replaced B8T-9275-A) .. Fuel Tank Sending Unit - Includes Float & Gasket / Marked: C4TF-9275-T // Obsolete

1963/69 N500/750 // 1957/60 F500/1100 // 1957/69 C550/750 // 1961/72 F500/750 // 1970/72 C550/1000 // 1973/79 C600/900 & F500/800.

NOS PARTS LTD in Waxahachie TX has 13 = 972-937-2201.

CARPENTER NOS OBSOLETE PARTS in Concord NC has 49 = 800-476-9653.

Many thanks again for your help ND, it is very much appreciated. I ordered the new sender and found a few more needed parts on the Dennis Carpenter website. In the meantime, I used a spare sender I had from a John Deere tractor and a few pieces from the old sender. It works, but the float arm looks like an old bow tie tv antenna after my "modding" lol. Will be looking forward to the new part arriving. I have been trying to learn the pdf version of the parts catalog for my truck but I am slow and unsure. Will keep at it but in the meantime, a million thanks again! Will be diving into the brakes soon, not looking forward to that one.