Hello All,

I have a 2000 Blazer LS with 100,000 miles. Lately the fuel guage needle jumps back & forth when lower than 1/2 tank. Is this a problem with the sending unit? If so, is it an easy or expensive fix? Thanks..

 

yea ifeel your pain, I have had to deal with it aince i got my blazer. If i remember correctly, it has to do with the sender in the tank. You have to drop the tank to do replace it. My dealership quoted me $400 dollars or something like that so I've just dealt withit for a while. Sometime I might just do it myself soem weekend.
My guage only reads correctly when its completely full.
hope this helps

 

Yup, you have to drop the tank to replace the sender. Thankfully now you can purchase just the sender. You used to only be able to get the sender with the entire fuel pump assembly.

 

Thanks for the info guy's. I think I'll put up with the jumping until I get some cash together for the sender.

 

well i have the same problem but it only jumps around if im in park, its wierd and if im in park and i rev my engine up to about 4000 rpm's my mph gauge will start to increase. not sure if its all related or not.

 

oo man i have the same problem but ill live with it too if its that much work!

we had the fuel pump replaced when we bought it, would that have something to do with it?

 

I readthe following article about the problem:

The buffer is placed between the fuel tank sending unit and the dash gauge to smooth out the signal from the sending unit to the gauge. This keeps the gauge needle from moving up and down too rapidly in response to fuel sloshing around in the tank as the vehicle passes over pavement irregularities.
The buffer trims the highs and lows off the sending unit signal and passes an averaged value to the dash gauge. The dash gauge needle still moves up and down in response to actual changes in the fuel tank level, but its movement is more gradual and deliberate than it might be otherwise.
The buffer system is disabled when the transmission is in Park or Neutral, which makes sense because fuel shouldn't be sloshing around in the tank when the vehicle is standing still. You can test this buffer on/off function by bringing the vehicle to an abrupt stop, then shifting to Neutral as quickly as possible. The sudden stop will keep the fuel sloshing around in the tank for a while (especially if the tank is less than half full), and this will be reflected in the gauge needle movement while in Neutral.
As the processed sender signal from the buffer module reaches the dash gauge, the gauge needle may vibrate as you describe. The software guys have an expression for this sort of situation. They say "It's not a fault, it's a feature." In other words, it may look like something's wrong, but it could take an instrument panel cluster replacement to completely eliminate the needle vibration. As long as the gauge is reading accurately, without huge fluctuations, you may want to tell your customer to save himself a few hundred bucks, keep his eyes on the road and stop squinting at the gauge needle.