Fuel Guage Pegged

[Don.V]

My '79 had all sorts of fuel gauge problems when I bought it, it has dual tanks. First, the valve did not switch but it was just a bad fuse. The gauge didn't work at all either, put in a new gauge and it was then pegged way past full. Found a rubber harness plug was undone at the firewall... connected it and the gauge worked for the passenger tank. The driver side tank still read way past full, but it turns out the sender is off a bit and the tank was full. When empty, the gauge still reads 1/4 full.

I have a 82 C10 1/2 ton that use to be a stepside. when i bought this truck i had problems due to fueling, my fuel gauge will not go lower then 1/4 tank marker or go higher than 1/2 marker. so when it reaches 1/4 mark it ran out of gas and when i go get fuel it takes forever to fuel. i can not put fuel in
without it stopping( it stops recieving gas acting like it was full, so the gas gun clicks). no lie, it takes me 15 mins. to put 5 gallons of gas in, one time i put $30 bucks of gas and it took me almost 30mins. i checked the gas hose and its not kinked. dont know what to do.

 

[bucket]

I have a 82 C10 1/2 ton that use to be a stepside. when i bought this truck i had problems due to fueling, my fuel gauge will not go lower then 1/4 tank marker or go higher than 1/2 marker. so when it reaches 1/4 mark it ran out of gas and when i go get fuel it takes forever to fuel. i can not put fuel in
without it stopping( it stops recieving gas acting like it was full, so the gas gun clicks). no lie, it takes me 15 mins. to put 5 gallons of gas in, one time i put $30 bucks of gas and it took me almost 30mins. i checked the gas hose and its not kinked. dont know what to do.

Check the vent hose that's right there next to the filler hose. It also needs to be free of kinks, and it should connect to the filler neck up near the opening. Also, it should connect on the top or sides, not the bottom. If it's at the bottom, it can cause the problem you are describing.

 

[Square80]

My '79 had all sorts of fuel gauge problems when I bought it, it has dual tanks. First, the valve did not switch but it was just a bad fuse. The gauge didn't work at all either, put in a new gauge and it was then pegged way past full. Found a rubber harness plug was undone at the firewall... connected it and the gauge worked for the passenger tank. The driver side tank still read way past full, but it turns out the sender is off a bit and the tank was full. When empty, the gauge still reads 1/4 full.

I just ran some amp wiring through my firewall and i think i might have undone this, because now im having the same problem, think that you could post some pictures or where the plug is?

 

[whiplash889]

my 74 c30 and my 77k20 does the same thing run a ground wire from the fuel tank lip to the frame just a bad gound, common on these style trucks

 

[chevyboy86]

my sending unit on my truck is unpluged and i cant figure out where to pug it in at, any help? i only have the drivers side tank

 

[smurph20]

Your only looking for a single wire that i think is pink or red

 

[Joshua8336]

got my k5 saturday, the guage read full... and stayed on full until i got home, when i pulled it in the yard it went straight to empty, any thoughts on that?

 

[Bebo]

I have a similar problem! I bought an 83 k10 not too long ago. someone engine swapped from the diesel to a 350. None of the gauges worked and the fuel gauge read a full tank. Upon investigation I noticed that someone tried to rewire the sending unit underneath the truck with all sorts of different colored wire but were snipped right before the sending unit. It is a two tank system. My question is can I hardwire the driver side tank sending unit to the gauge or the wiring harness ( bypassing the printed circuit on the back of the cluster and the tank selector switch) to make it a single tank system. I have already put in manual gauges for everything else but the fuel gauge has been a headache! I have bought a brand new sending unit and a used fuel gauge that has supposedly been tested and works (Ebay). Is there a correct way to bench test the gauge to the sending unit ? Ive tried a few different ways and the closest i get is empty when the float is down and 1/4 when the float is all the way up ! ANY help is appreciated

 

[chengny]

You know, I might be losin' it.

But, I swear I read somewhere that the tank gauges used for diesel fuel are calibrated differently than those used for gasoline and they will not read properly.

 

[Georgeb]

So here is a link on testing factory guages. Remember the sender should supply the same OHM output as the guage requires so thise values can be used for resting the senders.

http://forum.73-87chevytrucks.com/smforum/index.php?topic=25339.0

Now, for troubleshooting a guage problem you will need a correct wiring scematic for your truck. First start by checking that you have proper ground at both the tank and the guage. Next you need to start checking the sending wire from the tank to the guage at every connection along the way for proper continuity. With both ends dissconnected check the sending wire for a short to ground and also check it for high resistance end to end. There really isn't an easy way to do this without taking stuff apart. Ideally you would have access to the sender but for sure the cluster should be removed. It's time consuming but it needs to be done slowly and methodically. It's arather simple system you just need to eliminate the variables. Everything checked off the list is a step towards it being fixed.

 

[Pops]

Ok, I have the same issue with a pegged beyond full gas gauge on my 86 C 10.
This evening a friend who is much more mechanical than I am, reached back over the tank with a screw driver and said he "grounded" out the sending unit causing the gauge to go to E.
More interesting is when I bought the truck a 2 weeks ago, the gauge worked fine unless I turned the headlights on. When I did, the gauge dropped to E. Turn them off and the gauge went back to a correct reading. So I pulled the cluster and realized the main wire plug in that goes in next to the speedometer cable was 1/2 way out! When I plugged it in, everything worked except the gas gauge which, as I said is pegged at F .
So, I hate to drop the tank but don't know what I'm looking at or for at the back of the cluster. What exactly makes the most sense as my instincts tell me it's not a bad sending unit??
Thanks in advance...

 

[Georgeb]

Ok, I have the same issue with a pegged beyond full gas gauge on my 86 C 10.
This evening a friend who is much more mechanical than I am, reached back over the tank with a screw driver and said he "grounded" out the sending unit causing the gauge to go to E.
More interesting is when I bought the truck a 2 weeks ago, the gauge worked fine unless I turned the headlights on. When I did, the gauge dropped to E. Turn them off and the gauge went back to a correct reading. So I pulled the cluster and realized the main wire plug in that goes in next to the speedometer cable was 1/2 way out! When I plugged it in, everything worked except the gas gauge which, as I said is pegged at F .
So, I hate to drop the tank but don't know what I'm looking at or for at the back of the cluster. What exactly makes the most sense as my instincts tell me it's not a bad sending unit??
Thanks in advance...

Did your friend ground the sender to the tank or to the frame? If the frame then it sounds like the ground to the tank from the frame is open.

 

[Pops]

He grounded it to the tank...what does that suggest please?

 

[Boone83K10]

when the gauge is pegged at the 3 o clock position, it means there is a grounding issue. there is a wire that goes from the sending unit to the frame. you need to see if it came off of the top of the tank since it just presses on there or if it is not connected to the frame. it will be a black or blue or purple wire.