fuel gauge difficulties

[Dirtautoguy]

A few years ago on my 1996 chevy k1500, my dad and I replaced the fuel pump in my truck. It certainly was a learning experience for both of us. we chose to just drop the tank down and do it that way. after we got it all put back together it all worked and it was good to go, however then the gas gage didnt work from half a tank up but it did work from half a tank down. So I figured hey I know when its out of gas right? and it worked that way for several years. untill recently when I put some gas in the tank and now the gas gauge is really freaking out. it bounces from straight down and fighting with the oil pressure gage which probably isnt good. to full to half. but soon as it gets below half a tank it stops freaking out but still doesnt seem accurate.

 

my first thought is fuel sending unit. but i have done a lot of reading about it and heard anything from the instrument cluster to a ground or a bad sending unit or loose sending unit. I do remember when we pulld the tank we didnt know about the little ground wire that went from the tank to up on top of the frame and it seemse to me like we might have stressed it pretty bad what ground does that go to exactly?

 

I plan on checking the grounds, wires first and i want to have the new part on hand if i have to drop the tank again so i dont have to do it twice.

 

Is there anything else i should watch for or check?? thanks

[00Silverado4x4]

I'd also make sure all your connections on the pump are good. You may have a loose or even corroded connection.

[thx1138v2]

I replaced my fuel pump and sending unit in the tank earlier this year. When I looked at the sending units alone (no fuel pump) I noticed on the part numbers there were "HV" and non-HV models. I asked a round but didn't find a definitive answer of what the difference was. I think, though, that the "HV" in the part number needs to match the type of gas gauge in the dash. So a non-"HV" model sending unit with a HV model gauge or vice versa would cause the bad readings on the gauge.

 

I had the pump and sending unit replaced by someone else about 10 years ago and after that the gauge went way past full and dropped quickly from 1/2 tank down to empty. When it said 1/2 tank it was about 1/3 or 1/4 tank. I think they were mismatched.

 

I checked the non-HV unit I got before I put it in this time and it read correctly so I installed it and it is accurate. I had the bed off so it was easy to connect the wires and just move the float by hand to check it.

 

I'm thinking the "HV" stands for high voltage or something similar but don't know for sure. It would affect the resistance in the sending unit.

 

I'm wondering if you have a mismatch on the sending unit/gauge and it has damaged the gauge.

[Dirtautoguy]

well thats really good to know. but i havent ever replaced the sending unit and it worked fine untill we replaced the pump. i havent had time to look at it yet but im trying to get to it. ill post anything i find

[Dirtautoguy]

I was told on another forum to try and ground the purple wire on top of the tank. if the gauge went to full they said that the gauge is working and that the sending unit is bad. So I tried it and it went to E not F so maybe thats what he meant to say. Im looking at new units. I would like to put an acdelco one in it but my wallet wont really allow that right now. so im looking at either a spectra or dorman brand. what are your thoughts?

[Dirtautoguy]

today I finally got the fuel sending unit replaced today. we lifted up the bed and used blocks of wood to hold it up. it took about 2 hours (including the time we took to go get a swived joint for the rear bolts by the hitch) and my gas gauge now works good again

[2018GMC]

A few years ago on my 1996 chevy k1500, my dad and I replaced the fuel pump in my truck. It certainly was a learning experience for both of us. we chose to just drop the tank down and do it that way. after we got it all put back together it all worked and it was good to go, however then the gas gage didnt work from half a tank up but it did work from half a tank down. So I figured hey I know when its out of gas right? and it worked that way for several years. untill recently when I put some gas in the tank and now the gas gauge is really freaking out. it bounces from straight down and fighting with the oil pressure gage which probably isnt good. to full to half. but soon as it gets below half a tank it stops freaking out but still doesnt seem accurate.

 

my first thought is fuel sending unit. but i have done a lot of reading about it and heard anything from the instrument cluster to a ground or a bad sending unit or loose sending unit. I do remember when we pulld the tank we didnt know about the little ground wire that went from the tank to up on top of the frame and it seemse to me like we might have stressed it pretty bad what ground does that go to exactly?

 

I plan on checking the grounds, wires first and i want to have the new part on hand if i have to drop the tank again so i dont have to do it twice.

 

Is there anything else i should watch for or check?? thanks

if your truck has a trailer plug, 4 pin or 6. It could be a broken wire or ground back there. That's what was wrong with my volt gauge. Replaced tow plug and now all is well.

[robert salinas.robert]

Back up lights and warning lights were not working.White wire from tow plug grounded to frame.White wire removed from frame, the back up lights and warning lights now work.Bad ground from trailer hitch must be the problem.Somebody didn't know what they were doing