Okay, Just found another problem. Just purchased a 97 Blazer LT a couple of days ago. When purchased, the fuel gauge read just under a full tank. Now it reads FULL. Needless to say, I haven't put any fuel in it!! I just noticed that before starting the car, it reads full. As soon as you start the car, the gauge drops to half a tank, the quickly raises back to full. Any suggestions?? Sure hope I don't have to drop the tank!! I also don't wanna run out of gas on a long work trip I'm taking next week!! Thanks for any and all suggestions or advice!!!

 

My advice in the short term would be to fill up ASAP and reset the trip meter. Then fill up every 200-250 miles and keep track of the amount of fuel you pump in. This will give you some time to figure out what is happening with your fuel gauge, whether it is the sending unit (highly likely) or a problem with the ground, 5V reference wire, or the sensor return wire to the PCM.

 

So, if the sending unit, which I think is pretty likely as well, that entails dropping the fuel tank as well doesn't it? If that's the case, while I have the fuel tank out, what else is there that I should replace?

 

If your replacing your sending unit in order to fix your gage, you have to drop your tank. If your doing that, I'd say clean your tank, and give it a really good inspection. You might as well if you have to replace your sending unit to fix it, I had the same problem, I had to replace my fuel pump, so I replaced the sending unit as well, fixing everything.

 

I thought I'd read that there's another sensor in the tank that I figured I could also replace while having the tank dropped. Wouldn't wanna go through all that work to have the second sensor go back a month later...lol.

 

There are two possible problems you can face actually 3. Bad Gage, Wire From Sending Unit, or Sending unit. The first two are not as likely. The culprit is usually the Sending Unit.

 

...or you could live with it until your fuel pump goes bad. There are many of us in this forum whose sending units are bad, but are using our trip meters until the fuel pump needs replacing. Mine has been bad for over 3 years now, but I won't spend the money for all that labor until I have to. In my truck, filling up the tank at 250 miles gives me about a 50 mile cushion before the tank is empty.

 

I just replaced my fuel pump two weeks ago. Mine gave signs of a gradual death before finally going kaput. However, I've read other stories from people here whose pumps died suddenly and without warning. Since yours is a '97, I'd first try to find out if any previous owners already replaced it. If not, I'd probably bite the bullet and just replace it anyway.

One thing to look out for is the evap valve located at the front-top-left of the tank. It's connected to an itty-bitty hose that comes from just above the fuel rail. If you drop the tank without disconnecting it, you'll probably break it, as I did. The evap valve cost $26 at the stealership, though it probably cost less than $5 to make. The hoses are hard to find, so fortunately I didn't break that. There are also multiple posts on the Forum that tell you all the steps required in replacing the pump. Just run a search to find them. Good luck.

 

Well, it seems this is getting more complicated. I just spoke with all 3 Chevy dealerships in my area. They're all telling me that the Pressure Sensor is part of the Pump assembly and the entire assembly has to be changed. The Assembly costs $550-600. They're all saying that the problem sounds more like the Fuel Level Sensor, which is a $150.00 part.

Here's where things get a little confusing....
I called Car Quest to price things. They're telling me that the Fuel Pump, Pressure Sending Unit AND Fuel Level Sensor are all part of the Pump Assembly and they sell the entire assembly for $331.00.

Dealerships weren't able to tell me if the Fuel Level Sensor OR the Pressure Sending Unit controlled the gauge. They also said that neither can be diagnosed so there wouldn't be any way to tell which is bad, without taking them both out...Grrr.

I do know that the gauge isn't stuck. When you turn the key on, the gauge does move. When you start the vehicle, the gauge raises to Full.

If at all possible, I'd much rather spend the $150.00....lol. Of course, the dealerships all tell me that to be safe, I should replace everything. I do understand the risk of changing the Level Sensor and then having the pump go bad and having to drop the tank again, but I also understand the dealerships wanting to make more money...lol. Any suggestions??

Obviously, until I get this figured out, I'll rely on the odometer and fill up at about every 200-250 miles.

 

The sending unit is the sole source of reference for the fuel gauge in the dash.

The pressure sensor is used for evaporative emissions system monitoring only.

The sending unit is not that expensive. Be informed and have them quote the price again. You can get it through RockAuto.com or GMPartsDirect for around $75 last I checked. Run a search and you should find a few posts by me with the PN for 4dr & 2dr sending units.