Gas/Fuel Gauge wacky

[Ralph50]

2000 Le sabre, 132,000 miles.
So I had trouble with the gauge working from full to about 5/8 of a tank and then would stop moving. The pump is accessed from an access cover in the trunk, awesome decision by lead engineers at GM. Pulled the pump out and found that the little electrical contacts at the fuel sensor, (can see them when looking at outside of fuel sensor gauge which is on the side of the plastic reservoir. Can look up pictures on Rock auto. I bent the tabs so that it was contacting the rheostat contacts. Well put it all back together and what a waste of time. Did not fix the problem. Now I have ordered a new pump asm from Rock auto for 127 dollars, good price for a Delphi. I wish I would have done the job right the first time. I found I can rent the tool to remove the steel retainer ring on top of the fuel pump from Auto Zone. That retainer would not come off by pounding on it. Had to get the tool.
This weekend I will replace the pump again. I will also check that there is no baffle broke in the fuel tank and this is preventing the float from dropping to the bottom of the tank.
This time, i will only use a flash light around that open fuel tank. Was not thinking clear the first time and used a 110 v trouble light, but it was 90 degrees the last time and just didn't think it through, what would have happened had I broke the light near that open fuel tank.

[Levithan9]

Ralph50....

More than likely the cause of the malfunction of the gauge is that the contacts on the fuel sending unit are no longer making contact. Even though you said you bent the tabs to force contact, what has happened is the segmented resistors have failed. If you look closely when you remove the fuel pump unit again, you can see several segments on the fuel sending unit. The FSU uses a 5v reference and as the float arm drops down from gas being used, the resistance either gets higher or lower, depending on the way the system was designed, which in turn makes your gas gauge drop down to "E".

Take an ohm meter, and probe the 2 leads coming out of the FSU, and ever so slowly move the float arm up and down, and watch your readings. I can almost bet you'll see the ohm meter either drop out, or go excessively high.

Hope this helps.

[Ralph50]

I already purchased a new Delphi pump asm.
Just waiting for good day to install.
I must check for any tank baffles in the way of float.
thx

[Tech II]

All you needed was the fuel sender, not a pump assembly.....

[Ralph50]

I checked on the sender asm it was eighty dollars. would rather replace the entire asm for 127 dollars

[Tech II]

If you are only paying 127 for the whole fuel module(including the level sender), I would be a little leery of it....there are fuel pumps and there are fuel pumps.....

[Ralph50]

Fuel pump is a Delphi discontinued from rock auto,

[Tech II]

That's real cheap......surprised.....figured around $300 for a Delphi or AcDelco

[rkvons]

Originally Posted by Ralph50

I already purchased a new Delphi pump asm.
Just waiting for good day to install.
I must check for any tank baffles in the way of float.
thx

It's a good idea to take a look in there to make sure nothing is in the way, but also you can disconnect the fuel pump relay so the pump does not run and then lay the new pump assembly in your trunk, turn your key to on and move the float arm around to see if the gauge responds correctly. There will be a delay when you move the arm to when you see a response, but it should go end-to-end without any problems.

[Ralph50]

I checked the old pump and the problem was the bushing that the float arm pivots on. The bushing was so worn that it caused the metal contacts to move away from the card that makes the gauge work.