Full Gage Always Reading Full - Diesel Forum

**Beast** · 07-07-2009, 10:52 PM

Updated - see later post

My fuel gage has stopped working. It always reads full. Wish that was the case but I am afraid it just ain't so. My autoenginuity program has the following code:

B1203 Fuel Sender Circuit Short To Battery

Any suggestions on where to start?

Thanks

taxgod4u · 07-08-2009, 04:15 PM

drop tank and inspect sending unit potentiometer?

klhansen · 07-08-2009, 04:55 PM

It may be as simple as a broken wire to the fuel level sender.

I can't even find that code in my Service CD

Before you go to the trouble of dropping the tank, run down to radio shack and get a 15 ohm and a 160 ohm resistor. Then pull the fuel level sending uint connector at the top of the tank and stick the 15 ohm resistor across the terminals (on the truck side). With the key on, the gauge should read EMPTY. Then try the 160 ohm resistor. That should give you a FULL reading on the gauge. If those tests work correctly, then it's inside the tank. If not, you'll have to dig into the wiring. Just pulling the plug at the top of the tank makes the gauge go to FULL also, but since it's already there, it won't tell you anything.

Been doing any drag racing lately? A quick launch will slosh fuel to the back of the tank and make the float bang against the top. It may get stuck against the top, giving you a full reading all the time. The first thing to try there is crawl underneath and whale on the tank with a rubber mallet. That sometimes dislodges a stuck float. If that doesn't work, you'll have to drop the tank and pull the sending unit off.

kench · 07-20-2009, 01:23 PM

Do you only drive downhill? If so, it may be working.

**Beast** · 11-03-2009, 08:16 AM

Dropped the tank and found my problem. One of the wires going to the sending unit broke off right where it goes into the tank. This section of the wiring can be taken out of the unit but the dealer did not sell it. They wanted $400 for the whole unit that goes in to the tank. No thanks. So, I took out the pigtail, drilled through the plastic the wire goes through right down the wire that was exposed, spliced in a new section and used JB Weld to seal it up. Put it back together and all is good. Cost basically nothing except the tool to remove the fuel lines.

When I looked in the tank it was very clean. I laso found another seal sitting in the bottom. I wasn't sure if it came off when I took it apart so it kind of freaked me out. The seal on the bottom of the sending unit was still on. I saw no reason for there to be two of the large o rings and figure they dropped it in during manufacture. Hope so. Someone let me know if there was suppose to be two o rings. Also, getting that large ring that holds the sending unit in place is a pain in the butt to get to screw on right. So far no apparenet leaks and my guage now works.

short_stuff · 11-03-2009, 01:50 PM

Cool. You didn't do the harpoon mod while you were at it, did you? I've still got that on my list of things to do, when I decide I need to drop the tank for some reason. It's good to know that the tank was clean inside. I don't drive my truck nearly as much as I used to, and it worries me about what crap could be sitting/growing in the bottom of my tank.
How was dropping the tank? Did you use a floor jack to suspend it as you loosened up the brackets?

short_stff

**Beast** · 11-03-2009, 10:28 PM

The harpoon mod doesn't do much on the X. Differenet configuration for the tank as it is in the rear. Used straps and a floor jack. Not bad at all. Could probably do in one hour now.