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Dirty, Rotten, Lying, Blazer Gas Gauge

I hope my Discussion Title isn’t too over the top but that just about sums up my feelings over this matter. I recently purchased a 2001 Chevy Blazer LT and it is a pretty spotless vehicle considering it’s age. I have owned Blazers in the past and generally speaking, I really do like them. Not long after I bought my latest Blazer I noticed my gas gauge was giving me some erratic readings. If I put the Blazer in park or neutral and if the gas in the tank hasn’t had time to stop sloshing around, I notice that the gauge will jump all around and seem to react almost instantaneously to the sloshing ocurring in the tank. In other words there seems to be no dampening of the gauge needle to smooth out the reading. If I were to put the Blazer into any gear (this includes reverse), the needle stops right where it was at the time I put it into gear. From there, the gauge seems to reestablish itself and I believe the gauge thinks it is reading correctly and continues to drop as I use fuel. The problem is that if the gauge reestablishes itself incorrectly at a higher than actual reading, I run the real risk of driving my nice, clean, undented, shiny, lying Blazer right out of gas. In fact, I did do just that. I brought the vehicle back to where I purchased it and I paid to have a fuel sending unit replaced. They also replaced the fuel pump. Both were AC Delco parts because I was told not to buy aftermarket replacement parts for this particular repair. The repair was done a couple of months ago. Needless to say, there was no change to my problem and the dealer, being a small Mom and Pop type was a bit perplexed and it cost me $530.00 of my hard earned cash. The dealer then called a local GM dealership and was told that they needed to reflash the computer on the Blazer. I brought the Blazer back to my dealer who then dropped it off at the local GM dealership and supposedly reflashed the computer. I’m guessing they were actually were reflashing the program in the non-volatile memory section of the computer assembly. I picked up the vehicle and I still had the problem. So now I’m reaching out to the millions upon millions of people who tune in on a fairly regular basis to the Car Talk brothers. Can anyone tell me what the problem is and what the fix is? I’ll owe you and Click and Clack big time.


Lou Lou

( Lou Carta)

There are some problems in this universe for which there are simply no answers. (Maud Dib, Children of Dune). Lets hope yours is not one of those problems.

Try disconnecting the ground wire from engine to body and cleaning the connector. It may be high up near the upper corner of the engine compartment, driver side, near the air inlet for the cabin.

When that fails to help, you will know that I don’t know.

There isn’t a funny farm big enough to hold all the people who have been driven over the edge by car problems. That’s why we need the internet. We can all meet here and tell each other great big stories.

The fuel gauge on my 2000 Blazer quit working 3 or 4 years ago at 80k miles. Evidently the contacts in the GM sending units would be corroded by high sulfur fuel. I’m not sure what your problem is since the sending unit and fuel pump were replaced.

I never bothered to fix the gauge. I keep a log of each fill-up so it was fairly easy to determine seasonal mpg. I fill up the tank each time and refuel when there is roughly 3 gallons left in the tank (240 - winter, 255 - summer). The truck is at the age where things wear out or get brittle and break, I’ve learned to live with its quirks.

Ed B.

The problem is in your sending unit, the part(s) that measure the level of the gas and send it to your gauge. It can be replaced if you’d like without undue teardown. I believe in the Blazer it can be accessed under the rear seat bottom.

Ed’s correct about the high sulphur fuel problem. There was a class action lawsuit as a result of this problem, but I don;t recall the details. At 11 years old, I’d guess that your failure is just a normal wear & tear issue. I doubt if it would be covered by any warranties or lawsuits.

Mountainbike: the OP said they had the sending unit replaced, so that’s apparently not the problem. The next suspect up would be the wiring harness for the fuel pump, mostly because it’s easy to check. The main harness bulkhead at the framerail that plugs into the harness that goes to the sending unit has a tendency to corrode, so you may try unplugging it and cleaning the contacts. If that doesn’t work, the issue may be with the instrument cluster. Do any of the other gauges display erratic behavior? From what I have observed, lots of GM vehicles from this era tend to develop jumpy and erratic gauges as they get older, trucks more so than cars. I don’t know the exact cause, but I would suspect iffy solder joints in the cluster, sort of like the problem Chrysler vehicles tend to have. If this problem bothers you tremendously, you will probably end up replacing the instrument cluster to fix it, bu if it were my vehicle, I would live with it. No fuel gauge is intended to tell you EXACTLY how much fuel you have, it’s more of a rough estimate. I never saw one I trust for precision, so I always reset my trip odometer when I fill up so I know how far I have driven and never, ever run out of gas.