Weird Fuel Gauge Problem
 

Hey Guys,

I just replaced my fuel filter a few weeks ago (2001 SS), and now I'm having a kinda weird problem with my fuel gauge. I average about 300 miles out of a tank, so I'm basing all of my observations off of this. The gauge used to read perfectly, and would be at the halfway point after around 150 miles of driving. After the filter replacement, the gauge reads "F" for about the first 100 miles, drops to around 7/8ths of a tank after 150-200 miles, and then for the last 100 miles of driving the gauge will drop from there to "E". While the gauge still works well enough for me to know when I need to fill up, it's obviously a little annoying because it's usually WAY OFF. My Monte is sitting at around 220k miles (on the original pump/sending unit), and I know that weird stuff starts to happen at this age, but it's strange that this happened immediately after swapping the fuel filter.


Is it possible that during that process I messed something up with the pump? I just relieved the pressure by pulling the fuse for the pump, and let the engine come to a stop. I know this isn't the best way to relieve pressure, but I don't own a pressure relief tool and I've done it that way before with no issues. Is there some kind of bleeding procedure that needs to be done after changing the filter, or anything else that I might have missed? I don't really have any ideas at this point other than taking the pump out and taking a look at the sending unit. I'm also pretty confident that there isn't a problem with the physical gauge because the servo can move it through the whole range of motion when I first start the car, just like all the other gauges. I don't really want to replace the whole sending unit, especially if it's still pumping fuel and telling me when to fill up, but any troubleshooting advice is appreciated.

Thanks!

Crazy stuff?? anyway here is a youtube link that I found that may help.

I am unaware of any way changing the fuel filter would cause that issue with the fuel gauge. When changing the filter, I do not believe you are around any of the wiring for the pump or sending unit (so odds of accidentally damaging that wiring should be slim to none). I wonder if the stepper motor is failing. You may need someone with a GM Tech II (or high end diagnostic scan tool) who could do a gauge test and/or read what the PCM believes the fuel level is currently at and compare with the gauge.


As for how you relieve the pressure, I would concur that letting the car idle to a stop is a pretty harsh way to do that.

In the past, what I have done is simply turn the car off, remove the gas cap. If I want to go one extra step, go to the fuel rail, find the schrader valve and using a screw driver and a towel around every thing, push the valve to open it and release any held pressure.
After that, put a tray/pan under the filter to catch any run off and change the filter. No biggie.

Here is what the shop book actually says to do to relieve the pressure:
1. - Disconnect the negative battery terminal.
2. - Install the J 34730-262 adaptor to the fuel pressure connection.
3. - Connect the J 34730-1A to the fuel pressure connection. Wrap a shop towel around the fuel pressure connection while connecting the fuel pressure gauge in order to avoid spillage.
4. - Install the bleed hose into an approved container and open the valve to bleed the system pressure. The fuel connections are now safe for servicing.
5. - Drain any fuel remaining in the fuel pressure gauge into an approved container.
6. - Remove the J 34730-1A and install the fuel pressure port cap.