New fuel pump = empty tank reads 1/4

[AZ Tahoe]

So a few weeks and 200 miles ago I replaced the fuel pump. It was the complete pump and upgraded the contection while I was there. Everything has been great since then. No more falling on its face or hard starts just a happy camper. Then yesterday I ran out of gas with a 1/4 tank. Funny thing is I was thinking to myself I feel like this has been at 1/4 for a while but blew it off. Filled the tank and ended up putting 3 gallons more in than I have ever and now it reads 100% full. So now that I know the float or something isnt working and at some point I have to drop the stupid tank at some point has anyone had this issue? What did I do wrong here?

Thanks

99 2dr 5.7

 

[SunlitComet]

what pump part name and number you get?

 

[AZ Tahoe]

NEW REDLINE BY HERKO FUEL PUMP MODULE E3963M FOR CHEVROLET TAHOE 1998-1999


http://www.ebay.com/itm/380876497822?_trksid=p2059210.m2749.l2649&ssPageName=STRK:MEBIDX:IT

 

[Nak]

The 98-99 rigs use the new fuel senders. 40 - 240 ohms as opposed to the older rigs using 0 - 90 ohms. The good is that they can be more accurate. The bad is that if the replacement sender isn't precisely the same as the oem sender you can get pretty bad inaccuracy. You could replace the sender with a GM unit which will likely--but not certainly--be the same calibration as your original. Or, you could have a tuner re-calibrate your VCM. Your gauge is not analog. The VCM reads the sender resistance and sends a data signal to the instrument cluster. This can be calibrated with EFI Live or similar. A dealer should be able to re calibrate this as well.

 

[SunlitComet]

first az, i honestly would smash that pump with a sledge hammer. i don't care if it says it was assembled in the us. based on price alone it sounds like a piece of junk. stick with delphi or delco only.

and nak, you are wrong about a few things in your post. the senders actually have a range of 40-250Ω. also the fuel gauge is analog in operation and readability. the system actually takes an analog signal from sender and processes it digitally in the pcm for its own use and sends a pulse width modulation signal to the gauge itself. pwm generates an analog signal(to fuel gauge) using a digital source(circuits in the pcm). the gauge has coils in it and is incapable of interpreting a digital signal.

 

[Nak]

Yep, 40 - 250 not 40 to 240. Just remembered the range of the top of my head... My point was there was a big change in how fuel senders worked in 1998. Also correct about the gauge--data driven gauges came later. However, the main point that the sender and gauge can be calibrated via tuning is correct. The odds that a Delco or Delphi unit would be much closer to accurate are extremely high, but not certain. Ideally, any fuel sender change in a '98 or later rig should be accompanied by a calibration. However, if you're using a quality sender the accuracy would probably be close enough for most people.

I agree with Sunlit's comment about the quality of that module... A calibration would fix the accuracy, but how long will the pump last? Also, a quality module will cost less than a calibration. (Bear in mind, a calibration might possibly be required even with a Delco or Delphi unit.)

 

[97Tahoe2d4x]

Sorry to hear your problem. Personally, never heard of HERKO brand.
After my hard learned lesson putting in a cheap pump in my rig, I wouldn't trust anything but Delco or Delphi pump, especially when dropping the tank is such a PITA.

I see the seller offers 60day money back if you decide to drop the tank......

 

[SunlitComet]

have never need to redo any on the pumps i replaced on them. in fact i would like to know exactly what calibration you are changing. i hope it it not tank size. the reason for the wide 40-250Ω scale so was that the system can get an accurate read for evap testing purposes. the resulting gauge result you may see was just an added result of it. you should not and try not to recalibrate anything in the pcm for changing a fuel pump. ever!

 

[ccapehartusarmyINF.(ret)]

okay ive got the same problem ive replaced my fuel pump in the last year or so and ive ran out of gas with the fuel guage reading 1/4 tank and the annoying thing was is i didnt run out of gas anywhere close to a gastation

 

[livingez_123]

$48 for a fuel pump assy....you really did what you paid for.