Fuel pump/sending unit

[87gn199]

My car has an issue with the sending unit. The gas gauge works fine until the fuel level goes down to about half. Then rapidly it just goes to the empty side. I dropped the tank, there were several gallons still in there, thinking about changing the fuel pump while I am at it, any suggestions on which one?

Any ideas what the problem could be? Dont know what type of sensor they use but if its resistance based I figured it could be a problem with the current/voltage in the wire. Dont exactly know how to approach this, is the problem coming from the tank or the dash or somewhere else?

edit: here is a picture of fuel pump, says walbro on it

 

[TurboBuRick]

Do you have a volt meter? Ohm the sender.

RL

 

[williamsGN]

http://home.comcast.net/~84gngary/sendingunit2.html

DW pump from GNS Performance

 

[GNRick]

Your hanger looks really rusty. I would just get a new one from NOS4GN or Racetronix, in stainless steel. Glen also sells the hoses precut. Then you don't have to try and fix the old one.

 

[standupjskiguy]

The wire windings on the side, where the wiper rides up and down gets dirty. If you look closely at it you might see some gunk on the windings.
I just had this same problem with the wife's 85.
Get some 600 grit paper and slide a piece between the windings and the wiper.
Slide it back and forth just a few times to clean the wire. Flip it over and clean the wiper.
Don't take the winding's off. It is calibrated by the screws that hold it on. If you move those,
it will throw off your gauge, I.E. it won't read fully full or completely empty.
BTW, check those fuel lines that are between the tank and main run hoses. I.E. 3- 30 inch pieces, that are held in a rubber block above the tank. Mine started leaking as I removed
it. Rust in the area of the rubber block, had worked it's way through the high pressure line and would have been spewing fuel at 40 psi very soon.

 

[GNRick]

The wire windings on the side, where the wiper rides up and down gets dirty. If you look closely at it you might see some gunk on the windings.
I just had this same problem with the wife's 85.
Get some 600 grit paper and slide a piece between the windings and the wiper.
Slide it back and forth just a few times to clean the wire. Flip it over and clean the wiper.
Don't take the winding's off. It is calibrated by the screws that hold it on. If you move those,
it will throw off your gauge, I.E. it won't read fully full or completely empty.
BTW, check those fuel lines that are between the tank and main run hoses. I.E. 3- 30 inch pieces, that are held in a rubber block above the tank. Mine started leaking as I removed
it. Rust in the area of the rubber block, had worked it's way through the high pressure line and would have been spewing fuel at 40 psi very soon.

Those were the pre cut hoses I referred to. They are different inside diameters so you want to get the right ones. You should also check the metal fuel lines that run up to the motor as they could be real rusty too. And also the 24" metal lines that the hoses attach to that plug onto the hanger. NOS4GN carries all of them. Oh I guess it is Highway Stars now.

 

[GWHIZZER]

Those were the pre cut hoses I referred to. They are different inside diameters so you want to get the right ones. You should also check the metal fuel lines that run up to the motor as they could be real rusty too. And also the 24" metal lines that the hoses attach to that plug onto the hanger. NOS4GN carries all of them. Oh I guess it is Highway Stars now.

I had a similar problem, except my gas gauge read half when it was full. I bought a NOS sender and installed it, only
to have the same problem. I tried another gas gauge from an old instrument cluster and that was the problem!
Good luck with yours.

 

[GNRick]

You could attach the wire harness to the new sending unit before you actually install it in the gas tank. Then just lift up the float with your fingers and have someone in the car watch the gauge.

 

[87gn199]

Thanks for the advice guys, Checked the resistance, its was between 99 and 9 ohms, Cleaned it up, got it between 92 and 2 ohms. Going to check the brake lines and put it back and see if that helped in anyway.