When I installed my Walbro pump for the first time, I noticed that the gas gauge wasn't working properly. I pulled down the tank again but to my surprise everything was perfectly fine. Then I remembered how I waited a long time with the pump assembly outside of the tank. Two mechanics told me that the gasoline on the sensor dried up and left tiny crystals on the sensor (part that contains the float). They said that there is nothing that can be done except to replace the whole sensor. I'm not sure if this is general knowledge, but just in case I wanted to warn all of you to be careful.
-Neil

Also, I'm thinking about ordering a magnaflow free-flow catalytic convertor. I'll let you know how it turns out.

 

Man, that does not sound right. I know that a great many of these pumps have been upgraded and you are the very first one to have a problem with the fuel gauge afterward. I am just not buying that gas dried up thing. One my first one that tank unit was out of my truck for several hours. I had to stop and do something for the wife...

Is there any chance you bent the rod that holds the float?

I don't know what year yours is, but on the later trucks they have some kind of ECU that controls a bunch of stuff including the fuel gauge. There is a reset proceedure that may apply to your truck.

Gadget

www.GadgetOnline.com

 

Yeah, doesn't sound right to me- gas evaporates pretty cleanly, and certainly wouldn not "crystalize."

 

Do you ever see crystals on fuel pump nozzles? NO! If fuel crystalizes as it dries don't you think you'd see them on nozzles? That's BS. The float thing floats and on the non floating end it measures the angle of the rod. Don't let some shop con you into a replacement.

Then again, maybe somone put sugar in your tank. I think Gadget is on the right track, as usual.

 

Yeah, I guess it didn't make much sense to me. I thought there was a problem with the ECU before, but I already tried taking out the fuse and disconnecting both terminals of the battery. I don't think the arm is bent because the gauge isn't giving the wrong reading; it gives no reading at all. Actually, when I start it up, the gauge shows a completely full tank. Then in about 20 seconds the gauge falls to completely empty and stays there until I restart the truck.
The second time I pulled down the tank I checked everything and it seemed fine to me. The lever was moving smoothly also, so that's why the "crystals" didn't make much sense to me.
By the way, it's a 2000 Limited

 

I replaced the fuel pump on my 2000 a few weeks ago and had the sensor out of gas for 4-6 hours. I am certain it was bone dry before it went back into the tank (parts run, etc). The gauge is working exactly as before.

I was very careful when I had it out of the tank when cutting the fuel line, etc. I can send pictures of the completed work if you want to compare the angle of the bend in the float, etc. (just PM me if you want the photo's).

 

This point intrigued me...

I've had this exact symptom before, but for me, it happened after I installed my electric fans (FLX-210's). When they kicked in, the gauge would drop, but then it would come back up (slowly) once the fans turned off. I figured that I had too much current drain, and it was messing with the current to the fuel sensor.

This "got fixed" (along with other symptoms) when I recently replaced the alternator with a higher current model.

So, have you done anything to the electrical system lately that would create more current draw? Or, is it possible that a gasket or some other insulator has cracked and is causing a short in the sensor wiring?

If you pull the sensor out, flip the truck to ACC, can you move the sensor lever by hand and affect the gauge reading?

 

I had mine out over night the first time I replaced the fuel pump.

Chris