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EFV-8 Club Forum / General Ford Discussion / 1936 Fuel gauge at dashboard

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Posted By Discussion Topic: 1936 Fuel gauge at dashboard     Dustbowl 05-24-2019 @ 3:31 PM reply profile send p.m. Member Posts: 74 Joined: Feb 2011 I had trouble with fuel gauge system so I replaced the sender with an aftermarket unit. Now the dash gauge reads half full whether tank is empty or full. I recognize problem is still likely to be the sender unit but I want to be sure the dash unit is working correctly before going to trouble to take out the sender unit (I have a Cabriolet so have to take out rumble seat door and seat before I can get to the sender) A few years ago, TomO posted the following suggestion on how to test the dash unit. "The dash unit and wiring can be checked by grounding the sending unit wire at the sending unit and then turning on the ignition. The gauge needle should move toward full. If it doesn't, check for 6 volts at the gauge. If you have 6 volts, the gauge is bad. " Is this still the best method or is there a better way (no implied criticism of TomO)/ kubes40 05-24-2019 @ 5:11 PM reply profile send p.m. Senior Posts: 3366 Joined: Oct 2009 TomO knows his stuff and his advice was as perfect then as it is now. From what you describe, my money is on a poor quality sending unit. The repop gas tank sending units are poop. That's putting it kindly. I'd suggest you search for a NOS unit. They do become available on eBay quite frequently. Expect to be within the $150 - $200 range... a bargain for a quality part in my opinion. Mike "Kube" Kubarth MG 05-24-2019 @ 7:23 PM reply profile send p.m. Senior Posts: 1247 Joined: Nov 2009 Do you still have the original sending unit? Were you able to determine that it indeed was the cause of your " fuel gauge system' trouble? Did the original sending unit have a cork float on it? There is a good discussion thread on this subject on the FordBarn at this link > https://fordbarn.com/forum/showthread.php?t=190106&highlight=cork+float fenbach 05-24-2019 @ 7:40 PM reply profile send p.m. Member Posts: 227 Joined: Dec 2009 you can remove the sending unit, ground it somewhere and move the arm by hand to see if the needle moves. also, check the wire from the sender to the guage. check the resistance of the sender. I have an aftermarket sender. the resistance varies from 37 to 254 ohms. if yours is anywhere close to that, take a look inside the gauge. it has a couple very fine wires. mine had broken. proceed with caution. the mechanism is rather delicate. 4 MAINS V8 05-25-2019 @ 2:03 AM reply profile send p.m. Member Posts: 6 Joined: Oct 2016 One of the most overlooked faults is the actual fuel tank not earthed correctly. Years of corrosion on the mounting points can cause high resistance and low or no gauge reading. Best to run a new wire from a sender mounting screw to good earthing point. TomO 05-25-2019 @ 7:37 AM reply profile send p.m. Senior Posts: 7243 Joined: Oct 2009 Did your repro sending unit ever read full or empty? Because you have the rumble seat and the difficulty of getting to the sending unit, the next best way to test the dash unit is to ground the sending unit wire at the dash unit (the yellow wire at the bottom of the dash gauge). This will not test the integrity of the wire to the sending unit. I agree with Kubes40 about the quality of the reproduction sending units, but you should be able to adjust the unit to give you a better indication of the fuel level by bending the arm. It will never be as good an indicator of fuel level as an original unit. If your unit is not rusted away, it can be repaired. The sending unit arm may be binding on the side of the tank or a tank baffle. The Chassis parts catalog shows the float goes to the left (driver's) side of the car. When you remove the sending unit, you can check for clearance to that side. You could also rent an inspection camera, feed it into the filler pipe and see if there is interference between the tank and the sending unit. You could also use it to determine if the float is moving to the bottom and top of the tank by driving the car to use fuel and then by adding 1-2 gallons of fuel, while watchin the float. To determine how to bend the arm, measure the internal depth of the tank and bend the arm so that it will be near the bottom of the tank nd the total swing will be less than the total depth of the tank. Tom Dustbowl 05-28-2019 @ 11:13 AM reply profile send p.m. Member Posts: 74 Joined: Feb 2011 Tom, Many thanks for you additional suggestion " the next best way to test the dash unit is to ground the sending unit wire at the dash unit (the yellow wire at the bottom of the dash gauge). This will not test the integrity of the wire to the sending unit." What should I expect when I ground the yellow wire? Will the dash gauge then read full, or empty, or will I learn something else? TomO 05-29-2019 @ 7:54 AM reply profile send p.m. Senior Posts: 7243 Joined: Oct 2009 A working fuel gauge will move toward the full mark when the sending unit wire is grounded and the ignition switch is turned on. Do NOT leave the ignition switch turned on after the gauge reads full as damage to the dash unit can occur. If you still have your original sending unit, you can check it out by connecting a jumper wire from the dash unit sender terminal after removing the current wire from the gauge, and another jumper from the sending unit flange to ground. Turn on the ignition switch and move the sender arm from bottom to top slowly while observing the gauge. The gauge needle should move from empty with the arm at the bottom of its travel to full at the top of its travel. Tom

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