Fuel Gauge Issue with New pump
 

Working on a 99 Ram 1500 4x4 5.9L My fuel gauge was working fine from F to E. I installed a new fuel pump, a spectra premium that I got from autozone. After installation I noticed the gauge jumped to 3/4 when it was 1/8 or less actually in the tank. Thought maybe just filling it up would reset things, gauge read F for 100 miles until it finally started to move and truck ran out of gas with gauge saying there was almost exactly 1/2 tank left. SO I thought maybe the sending unit was bad on the new one. Brought it in and they warranty swapped it for another. I put that in the truck and the gauge still incorrectly reads the exact same as with the other pump. So obviously not a defective sending unit but perhaps an incorrect one? The installation on this pump is very straightforward so I don't think that is the issue. There is literally one electrical connector just unplug old plug in new. Line up arrow on pump with arrow on tank for orientation. Float arm snaps into pivot hole only one way and holding clamp snaps over that. I didn't notice any kind of calibration and the instructions never mentioned anything either.

This is what I figure could be wrong, since everything was reading fine before I switched pumps I would think the wiring should be ok, so perhaps autozone is wrong on the books about the fuel pump fitting my 26 gallon tank. On their site they report this particular pump works on a 26 or 34 gallon tank but maybe they are in fact two separate pumps and they just keep giving me the 34 gal pump not knowing any better? Or perhaps since I have not owned this truck from the beginning the previous owner may have modified the components somewhere along the lines and a regular pump ohm output doesn't match up anymore. I am going to try to contact the spectra guys and see if there is in fact two different pumps or if there is some calibration that needs to be done that I am not seeing. Also going to see if autozone can look into it more but they believe the pump must be able to differentiate what tank it is in because they only have one part number and no option for a 26 or 34 gal pump.

Appreciate your thoughts and input. :)

AutoZone website lists two Spectra fuel pumps for your 99 Ram
B7138M - for 26 or 34 gallon tank
B7111M - for 35 gallon tank only
Which pump did they sell you and what tank do you have ?

Buy a better quality pump.

They sold me the B7138M- for 26 or 34 and my truck has a 26 gallon tank.

What brand would you suggest? I don't have any allegiance with any fuel pump brand but I wouldn't think a company would just put a 3 year warranty on something just so I can keep swapping new ones until one works.

Delphi, or Denso. They are OEM manufacturers.

Delphi and Denso may be OEM manufactures, but what we are getting for our 20 year old (+/-) trucks
is coming from their aftermarket divisions.
Besides, they are nearly all being manufactured in China, so quality is a crap shoot, no mater what brand that you purchase.

Just my .02 cents

True, however, I have seen a LOT more failures with the likes of spectre, and air tex, than I have with the others.

Alright so I got some time to work on the truck today. I tested the old fuel pump ohm range which falls between standard of about 14-220 Ohms from F to E. Then I tested the 2nd new pump I got which also fits the range just as well as the stock original. Any idea what caused the fuel gauge to suddenly start reading wrong when I disconnected the old one and connected the new one. Both have the same resistances but now the gauge just won't read correctly. Do I have to wipe the computer somehow? Do I need to have the battery connected when I hook it up? Does the tank have to be empty?? I am at a loss.

You could try resetting the computer, as I am pretty sure even the friggin gas gauge goes thru it......

Have you tried a gauge test yet? Just hold the trip odometer reset button in, turn on the key, let go of the button, and everything on the cluster should 'test'. All the lights come on, all the gauges sweep, etc. Make sure the gas gauge does what it is supposed to.