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You need to check the the sending unit changes resistance when you go through the sweep. I’ve seen a couple GM’s that were misleading because when I was testing the resistance, I was holding the float arm up, making the contact good. When the float hung on it’s on weight, it broke the connection. I just happened to notice the contacts weren’t contacting while the float hung there. I hope this makes sense.
Since that sending unit is easy enough to get to you might consider taking it out of the tank unplugging the fuel pump at the pump and turning the key on while you move the wiper throughout it’s travel, note that it will not register immediately and will take some time to register a change on the dash but if you then have good readings it could be that the arm is getting hung up on something, I would check to see if the baffles in the tank are secure as I’ve seen these break loose in the past and cause issues similar to yours. You shouldn’t have a spark when you turn the key on but you could also unplug the main relay under the dash just to be sure you don’t’ have a spark during your testing.
The problem has gotten a little worse now. I’m now getting a check engine light and the code is P0453. This relates to the fuel tank pressure sensor. Can pressure in the tank actaully cause the fuel sending unit to raise and lower? Any suggestions or directions on this would be greatly appreciated.
You will need scan tool data to aid in diagnosing that code.
Those sensors work similar to MAP sensors.
check to see if your gas cap is on tight. reset the cel and see if it comes back. check the connector and sensor itself.
plug and unplug a couple times to clean the connector. I don’t know if there are vacuum lines to it or not. if there
are check for cracks or broken lines.C8-)I discovered the problem. I was taking the approach of the fuel sending unit being bad but what was actually bad is the fuel tank itself. I found a large dent in the bottom side of the tank. This was causing the sending unit to measure the level incorrectly even though it tested correctly outside the tank. The fuel sensor was my fault, when I was working in the area of the sending unit I forgot to reconnect the fuel pressure sensor. I guess I will have to live with a fuel gage that is all over the place. Thanks for the comments and suggestions.
If you can get to it, you could try using a piece of wood (not metal) and banging the tank back out with a deadblow plastic hammer, so there are no sparks. This is only if you can get the wood on the inside part of the dent thru the fuel pump access hole. At least that’s what I would try.
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