95' duel tank fuel gauge not working.... HELP!!!
 

I just bought this truck last friday and have been fixing all the little things the previous owners overlooked. My problem is that the fuel gauge doesn't work . The guy that sold me the truck only had it for about a month and said he never ran the back tank cause he didn't know how much was in it . He only ran the front tank and filled up every 150 miles just to be safe. When I switch to the back tank it keeps running but just kinda smells like bad gas so my guess is the pump is good (I let it run for a few minutes). When the ignition is off the gauge goes up to just above E and when I turn the key on it goes all the way down. The fuel selector switch doen't budge it , but if I unplug the switch it goes all the way to full and the truck won't run (I know it runs the pumps). I am thinking the gauge is good or it wouldn't move at all , and the switch is good cause the truck runs on either tank.

So is it possible that both tanks have a good pump but a bad sending unit? I find that highly unlikely. I work at a parts store and have seen some weird stuff before. Also I have been working on all my own cars and other peoples cars for the past 15 years now including my 91' mustang that is getting a 351w soon.

Just so you guys know , one of the other owners pryed up the part on the light switch for the interior lights so he could put some aftermarket blue led lights that plug into the cig lighter and drooped the wires all over. I bent back the tab and now I have dash lights. Also , he left one bolt out of the radiator , that was found by my son in the door pocket along with the rest of the nuts to tighten up the light bezels. Also , there is no fan shroud . Oh yeah the seat was stuck in the short person position and I'm 6'4". It is an Eddie Bauer so it has electric seats and the motor is burned up. I tried to jump it but only one motor out of the 3 motor pack worked , so I had to unhook the motor and twist the seat up manually. I fixed the drooping drivers door with new door bushings and pins yesterday. There is more , but the fuel gauge is what bugs me.

I come to you guys as a fellow Ford lover and new (to me) ford truck owner. Please , all thoughts are welcome , cause with the things I have seen on this truck , anything could be possible. I think this truck looks pretty good , it just had an idiot as an owner and the guy before me , said " I wanted to learn how to fix vehicles with this truck , but it is just too much for me to handle." It's not too much for me , I just don't want to spend money on unneeded parts. Sorry this is so long but I wanted to try to give you as much of the details that I could. I have to go to work today and I am bringing a u-joint and the hanger in to get new ones. Gotta go take those off now. Thanks for the help in advance.



P.S. I did a search and found nothing before I posted this.

First of all, dump the gas in the back tank, and change the sending unit. Check all wiring connections. Replace the filter. Work on one thing at a time. Relax. All answers will come to you soon. There's alot of helpfull people here.

My guess is a bad selector switch, just because the pumps work does not mean the gauge side is OK. Images of a bad switch below.

Could also be wiring or a bad ground at the radiator, you did say something about a radiator bolt and that is where the gauge is grounded at.

Also make sure you have a good body (not frame) ground.

Here is a wiring diagram of your fuel and gauge system:
http://i54.photobucket.com/albums/g9...el-sel1995.jpg

Photos of the bad switch:
http://i54.photobucket.com/albums/g9...torSwitchN.jpg

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OK since the switch is only 12.44 I am going to start there. Plus I talked to one of the managers today about the switch. We usually don't take back electrical parts but I told him what was going on in my truck and he said if I put the new switch in and nothing changes that he wouldn't have a problem taking it back.

The ground from battery to body looks good just checked that yesterday when I took off both terminals to clean and re-tighten. As for the ground on the radiator , I didn't see any loose wires anywhere near it. I did get a haynes manual while at work today so I will do some studying tonight.

Thanks for the help so far, keep the ideas coming . I'm not gonna stop until I can tell how much fuel I have in both tanks from the gauge on the dash.:-jammin

G100 is your fuel pump and gauge ground, but if the pumps run the ground should be good.

Image of the ground location:
http://i54.photobucket.com/albums/g9...e/1994G100.gif

PS 1994 and 1995 are the same.
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OK, Got the selector switch in today . Went out and tried it and no difference. So, that tells me it is not the switch. Is it likely for both sending units to be out or is there something else I can check before taking off the bed? I was told the best way to get to the pumps/sending units on that truck, was to take off 6 nuts and pick up the bed and move it back (after unhooking wires and filler necks of course). Anything else? A sending unit is $130.00.

Unplug the tank plug at the frame rail and ground the fuel sender wire and then rmove the ground. The needle should swing peg to peg.

Its not as easy as checking grounds, but it might be worth it to drop one of the tanks, and check to make sure the float on the sending unit actually floats. Its not uncommon for a hole to rust in the float itself, and just sit at the bottom. Same thing happened to me, turned out to be as simple as a sunk float.

That same thing happened to me in my old 78' Ramcharger. I was on the way to work the other day and stopped to get gas . After filling the front tank I decided to put a few gallons in the rear tank just as a reserve. I already knew the back tank worked cause I had driven around the neighborhood on the back tank. After getting back in the truck I flipped the switch just from curiosity. The needle on the gas gauge slowly went up to just over empty. But the key point is it moved. After work I decided to stop back at the gas station for a fill of the rear tank. End of story, the back sending unit works, it's just the front one that is out.:-drink:-jammin

Sorry to reply to such an old thread, but I have the exact same problem with the 95 F-150 XLT 4x4 I bought last year, which had the front fuel pump recently replaced. Except for rare occasions, the gauge reads empty whenever the front tank is selected, but the rear gauge works fine. Did you ever find out what was causing this on your truck?

Same thing with my truck. Since this happens on rare occasion as you said, I would think you have a loose or an about to break wire causing a short like I did. Follow your wiring to the tank and check it over carefully. Good luck Sandy

That makes sense
 

I certainly will. Thanks a ton.

Has anyone ever had one tank read full (even though it is not) and the other tank read empty (even though it is not)? That is my problem… anyone have ideas?

Yes that scenario happens quite often. Best bet is to start your own thread instead of tagging onto a zombie thread like this. It would also help to know the year, model and engine truck you are working on.