Gas tank only registering 1/2 full?

[HT413]

Fill up the tank and it only registers 1/2 full. The gauge then stays on 1/2 until the fuel level drops below 1/2 a tank and appears to then function normally. It's a new tank and lines (no ideaif the sender is new) and I'm thinking the sender is getting physically hung up. Make sense?

 

[67 coronet]

could be.ground the sending wire and see if the guage reads full,at least you will know the guage isnt sticking.

 

[Propwash]

He's right. Try that or ohms test it. Check it empty then fill the tank, one lead end grounded to the sending unit somewheres, the other lead on the stud for the sending wire. Range around 10-90 Ohms from one direction to the other

 

[super-bee_ski]

He's right. Try that or ohms test it. Check it empty then fill the tank, one lead end grounded to the sending unit somewheres, the other lead on the stud for the sending wire. Range around 10-90 Ohms from one direction to the other

BUT:
Dont use a PSM-6 !!
Remember the old PSM-6 multi-meter Prop?

 

[Propwash]

Ohhhh you bet Ski....Looked like a funky Geiger counter or something. Had an old crusty one sitting on the shelf at squadron supply. Thing was more of a conversation piece than anything else. Thank god we had Fluke 87's to use, but I did enjoy the 14 minute long video from 1968 in tech school on the old PSM-6's...Cutting edge stuff...lol

 

[5.7 hemi]

Well at least you'll always have gas, lol!!

 

[Dennis H]

I gave up on mine. New everything. Goes just past half when full. New tank. New sender. Good ground. Bent and adjusted the sender etc. No avail.

 

[Big Jim]

Have you checked the voltage limiter on the back of the dash?

 

[HT413]

a little update -

as you guys suggested, I grounded the sending wire and the gauge went to Full, so it's not the gauge. I decided to get under the car and see if the sending unit was installed correctly - well the damn thing wasn't put in properly and the spanner bolt just fell off in my hand. because I had the *** end of the car on stands, a couple gallons of fuel came out. i caught it in an oil pan but man that was a little stressful.

so this weekend i'll siphon the rest of the fuel out, drop the tank and get the thing in the right way. I noticed someone coated the spanner bolt in some sealant, so I'm assuming it was leaking the whole time. I try to look at the positive, so who knows, it may well have been leaking the whole time and been a hell of a fire hazard.

This weekend I'll check the resistance across the full sweep to see if it goes from 10 - 90 ohms.

 

[67 coronet]

if it ohms out ok,hook it back up to the car while out and move it by hand to make sure everything is ok.just ground the sender body to the car and move by hand.i always double test mine just to be sure of contacts and such.

 

[HT413]

Ok, like almost a year later here's the update. Didnt fix the problem, but I *think* i have an idea that might work. When the gauge sees 10 ohms it reads full, 90 ohms it reads empty. After solving my overcharging issue by cleaning up bad and corroded contacts, i'm thinking doing the same here will help. There must be resistance in the circuit that is tricking the gauge into thinking the tank is emptier (higher resistance) than it really is.

All other gauges work great (except the bypassed ammeter) so i think the gauge vr is fine.

 

[red 69 runner]

Have the same exact problem,when the gage says E i fill it up,usally takes about 9 gallons,This was a brand new sender that I got with my tank from Vans Auto.old sender went to 3/4 full.Havent had time to remove all the gas and drop the tank again,so I just fill up when it hits E

 

[wannadrag]

Have the same exact problem,when the gage says E i fill it up,usally takes about 9 gallons,This was a brand new sender that I got with my tank from Vans Auto.old sender went to 3/4 full.Havent had time to remove all the gas and drop the tank again,so I just fill up when it hits E

I have a vans sender and it reads 3/4s when full.Tried one of those Spectra premium ones that are supposed to be the better one of the 2.That one didn't read anything till the tank was 1/2 full so I dropped the tank a 3rd time and put the vans one back in.