Topic: Gas tank mounting

[68 S Code]

Another issue I am having is that the fuel gauge is not registering in the dash cluster. i spoke with the local mustang shop and they mentioned if the tank was grounded. I said it had been installed with the seal between the tank and the pan so grounding would have to be with the 11 screws holding it down. They said that the small screws aren't enough and asked if I had installed the bolt on the drivers side rear corner of the tank. I would have to check it out. Last night while dealing with the brakes I popped the trunk and saw the hole they were refering to. Problem is that the hole is in the tank but not in the trunk drop. Checked the FAM and they only refer to the 11 screws. No mention of this bolt. Should I drill and install it? I do have brackets for rear bumper guards so I would figure that these could provide a ground. I hate to think that I need to drill this hole if Ford thought they didn't need it.

[TLea]

Only holes I know of are tank mounting screws and bumper guard brackets. Hard to believe out of 11 screws one isn't making a ground  Try a jumper wire between sender and frame and see if it works. I think you'll find it is something other than grounding

[68 S Code]

Yes the jumper wire is still a test I have to run. Odd that gas tank is punched with a hole but car is not.

[Bob Gaines]

Another issue I am having is that the fuel gauge is not registering in the dash cluster. i spoke with the local mustang shop and they mentioned if the tank was grounded. I said it had been installed with the seal between the tank and the pan so grounding would have to be with the 11 screws holding it down. They said that the small screws aren't enough and asked if I had installed the bolt on the drivers side rear corner of the tank. I would have to check it out. Last night while dealing with the brakes I popped the trunk and saw the hole they were referring to. Problem is that the hole is in the tank but not in the trunk drop. Checked the FAM and they only refer to the 11 screws. No mention of this bolt. Should I drill and install it? I do have brackets for rear bumper guards so I would figure that these could provide a ground. I hate to think that I need to drill this hole if Ford thought they didn't need it.

It would be prudent to determine if the problem is in the Sender or ground (unlikely) or if in the gauge or the wiring to the gauge. Disconnect the sender wire and ground sender wire with a jumper. The gauge should be full tilt if the gauge and wiring is in order. If it doesn't move you have a problem with the gauge or the wiring. If that end is in order pull the sender from the tank and hook it to the sender wire ,ground the sender with a jumper while moving the sender float arm into the full tank position. The gauge should read full. If not the sender is bad. If it registers on the gauge as full then you can think about the possibility of a bad ground between the tank and the surrounding sheet metal. It dosn't take much of a ground to make a circuit for the sneder. I think your Mustang shop source is misinformed if they don't think that at least one of the 11 sheet metal screws that makes contact with the metal tank flange and screws through the metal lip of the trunk floor sides doesn't have the potential to be a good ground . Seriously? MILLIONS of 65 -70 Mustangs built suggest otherwise.  . Bob   

[J_Speegle]

......... Odd that gas tank is punched with a hole but car is not.

Yes that is typical. Possibly a locator hole to align both halves during assemble

[68 S Code]

Good point. I bench tested thr gauge and found it to be working. Next step is to test the wiring. If I use a small screwdriver test light should there be enough current to light up the bulb? I can see if it lights at the under dash harness and then again at the gas tank plug. So far grounding the plug has yielded nothing.