fuel gauge

[dilerin]

Replaced dead fuel pump on '98 K2500 at 196K miles. Since I knew the job would be difficult for me (I'm 82) and so wanting to do it only once, I bit the bullet and bought the pump from Chevy according to VIN, but for a gut-wrenching price (GM 19369943 module kit). Installed and tested system with tank still on ground and truck starts and runs as normal. However, when I turn on the key the fuel gauge slams hard enough upscale to make me wince, and then immediately back down to near empty which would be about right for the amount of fuel in the tank (now ~3 inches in 32 gal tank). Don't know yet if it will track as I add fuel. Any idea why this is happening? It wouldn't be a grounding issue, I wouldn't think, as the pump itself runs normally. Whatever it is I ain't doin' the job again, but I would sure like to know what's going on. I liked things much better when fuel pumps were mounted on the block - where they belong!
FYI, I decided to drop the tank, which was full, rather than raise the bed and I'm glad I did. Even with the tank out and in the backyard it was nearly impossible to push the pump unit down against the O-ring uniformly enough to get the retainer in place (a snap ring rather than a tabbed ring). Differences between old and new is that the pump/fuel gauge connector is of a different design such that the old connector has to be cut off and replaced (new one supplied with pump assy. kit), and the bottom external fuel strainer/sock has been eliminated, thus making them more money per unit while affording you less protection.
Finally, I did have some luck. The old pump died quietly at home and not out on the road. I am hoping for the same.

 

[Schurkey]

Those are "balanced-coil" gauges, not "stepper-motor" gauges...right?

The GM "Balanced-coil" gauges are set up on a 0--90 ohm sending unit. An empty tank sending unit has nearly no resistance (high current flow) while a full tank has 90 ohms resistance (low current flow.)

A broken wire between gauge and sending unit, or between sending unit and ground is infinite resistance; the gauge needle goes past full. My '88 K1500 had a broken fuel gauge wire under the driver's feet area of the frame. Gauge was past full. Good thing I stopped at the gas station anyway on the drive home, the tank was nearly empty.

The gauges "can" be wired to swing the needles during start-up. I'm thinking that as long as the gauge settles down to an accurate reading...leave it alone.

If you've got stepper-motor gauges, they're controlled by the computer. The computer may swing the needle to full-scale as a gauge-test before settling down to the "correct" reading

I have a '97; but it gets driven so seldom (and so long ago) that I don't remember how the gauges act at start-up.

The older fuel pump hangers had two grounds...one for the pump, one for the sending unit. So the sending unit ground could be funky and not affect the fuel pump.

 

[mattillac]

A few short videos co-starring "the fuel gauge".

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Pretty sure that hard bounce to the right past full is normal.

Probably want to ignore those videos otherwise, maybe even mute them while viewing.

Just used them to show the fuel gauge in action.

Best of luck.

 

[dilerin]

Those are "balanced-coil" gauges, not "stepper-motor" gauges...right?

The GM "Balanced-coil" gauges are set up on a 0--90 ohm sending unit. An empty tank sending unit has nearly no resistance (high current flow) while a full tank has 90 ohms resistance (low current flow.)

A broken wire between gauge and sending unit, or between sending unit and ground is infinite resistance; the gauge needle goes past full. My '88 K1500 had a broken fuel gauge wire under the driver's feet area of the frame. Gauge was past full. Good thing I stopped at the gas station anyway on the drive home, the tank was nearly empty.

The gauges "can" be wired to swing the needles during start-up. I'm thinking that as long as the gauge settles down to an accurate reading...leave it alone.

If you've got stepper-motor gauges, they're controlled by the computer. The computer may swing the needle to full-scale as a gauge-test before settling down to the "correct" reading

I have a '97; but it gets driven so seldom (and so long ago) that I don't remember how the gauges act at start-up.

The older fuel pump hangers had two grounds...one for the pump, one for the sending unit. So the sending unit ground could be funky and not affect the fuel pump.

Thanks very much for the input. I, too, don't drive the truck much anymore so also do not remember the initial reaction when the key was first turned on. But now the upscale speed of the needle is remarkable to the extent that I'm surprised it's not ripped off when it hits the upper stop. Tomorrow I'm refilling the tank, and for those who might be interested will report whether or not the gauge at least tracks and indicates correctly after the initial mayhem is over. If it does, I'll leave it alone as suggested.

If I learn anything useful I will post it. Again, thanks for the input, all of it informative.

 

[dilerin]

A few short videos co-starring "the fuel gauge".

xc_hide_links_from_guests_guests_error_hide_media

xc_hide_links_from_guests_guests_error_hide_media

xc_hide_links_from_guests_guests_error_hide_media

Pretty sure that hard bounce to the right past full is normal.

Probably want to ignore those videos otherwise, maybe even mute them while viewing.

Just used them to show the fuel gauge in action.

Best of luck.

Yes, the videos show exactly the action I am seeing, and it's a relief to see it. I did not notice that in 196K miles of driving. Very strange that what the eye sees is apparently not always reported to the brain; at least to mine. Thanks very much for taking the time to gather and post this information.