So i went to fill up this evening and i was below half tank and after i filled up it didnt move... now it shows between 3/4 and full and went up really really slow.... any ideas????

 

Was the truck turned off while you filled up? If you fill up with the key in the on position the gauge will seem to be slow. Turn off the engine and fill up and when you restart the engine the gauge should operate normally.

 

nope truck was off, i pounded on the bottom of tank and even waited and went back out and started truck up now and still not on the full mark..... talk about a crappy night... first this then in the holiday car wash and the dam car wash peeled my pass mirror backwards ..... then pizza hut screwed up my order... LOL i came home locked doors and shut phones off i'm gonna lock my self in closet if i need too lol

 

Just dont type a thread saying u came out of that closet. But seriously its sounds like the float. I have a 78 that used to do that. I took it out and moved the float up and the gauge went to full. But when i put it back it would only read like 1/8. I believe i finally swapped it out from a truck i had and that fixed it.

 

even if engine is off if some how you turn key on but not motor while filling gas it well not read properly even with restarting it will gradually go to full may not show till next time you drive it something weird in the computer

 

also, a low battery will cause this condition. it makes all the gauges read funny, and the fuel gauge is often the first one to do so

 

thanks i will have the battery and charging system tested this afternoon...
thanks a ton guys

 

Mine did this once before also... Drove it like that for a couple of days and filled up again. It was fine after that. It went up fast, and did everytime I turned the ignition on. Don't know what caused it, just that it worked. Let me know.

 

well this morning on the way too work it finally went up to the full mark and after driving awhile it is going down with the gas in the tank so i will know when i fill up next.. Still gonna have the battery tested etc..

 

Try pouring a bottle Chevron Techron additive into the tank. It frees up many contacts on the sending unit.
Good Luck

 

ya i was gonna ask what type of gas you are running....some of the nicer gas stations Chevron, Shell etc all have additives that help clean/keep clean the gas system....you may just have a gummed up float or something....just a thought

 

I had this happen to me this past week. I had left the keys in the ignition while I filled up. The truck was off. Anyway, the next time I removed the keys and the gauge was back to normal.

 

Ok....happened to me today....filled it up from EMPTY.....and it took 40 miles to read full....anyone figure out the cause???

 

mine does it sometimes too dont know why though

 

It's happened to both my F150 and Expy...just does that sometimes.