Hi, new member so I’m sorry if this is in the wrong spot.

I have a 2000 Blazer 4 Door with the 3 button 4x4.

When the ignition is off, key is out, the fuel gauge reads empty.

When I turn the ignition to the run position the instrument cluster comes to life like it should and the fuel gauge goes to full and then back down to where the fuel level is actually at.

When I turn the key to crank the engine, as soon as the engine starts the fuel gauge jumps past full and stays there. It’ll stay past full for as long as the engine is running. Once you turn the engine off the gauge goes back to where the actual fuel level is.

Any ideas as to what the problem is or what I could check. Thanks.

 

What is the battery voltage when the truck is running?


George

 

When running the battery voltage is just above 14 volts.

 

George,

Where is the best place to measure this voltage? The voltage gauge on my truck was never right.

 

That's a good charging voltage. That said, if you have a charger handy hook it up with the truck on but not running and tell me if the gauge goes wonky.

Most of the gauge cluster gets its instructions via the class 2 serial data bus. Can you connect a basic scanner at key on and will it stay connected after you start the engine? Any codes?

George

 

That depends on what you want you are trying to analyze. The health of the battery and how much its being loaded or the charging voltage of the alternator/regulator then at the battery terminals. The ignition/computer voltage then at the UHFB near one of the big high current fuses like ECM1. Easy peazy for a quick check, the cig lighter socket.

George

 

With the battery charger connected and key on the fuel gauge still reads like it should. Doesn’t act wonky.

I don’t loose any communication with my scan tool.

I did find however, a bunch of terrible crimp connectors that are very corroded which come from the fuel pump. It seems the previous owner had a new fuel pump installed and who ever did put it in, did a not so good job. One of the wires broke when gently pulling on the harness.

I did check to see if the gauge responds by grounding the purple wire from the connector and it does read empty when doing so.

Is it safe to say fixing these connections and possibly a new fuel pump assembly would fix my problem?

 

Sure, maybe this behavior is vibration related but it should be fixed no matter what.

George