hey i got a 01 zr2 blazer the gas gauge reads but it works very weird when i press the brake it will work or when i park level it will work. im thinking its a ground issue i just don't know where to start if someone has done or knows what to do can you help me out. Thanks

 

Could also br the sending unit on thexpump. Mine did similar stuff also had no speedo. Put in axnew pump and everything worked again. Anyway could be the the ground on the pump wires ontop of the tank

 

Fuel level sender runs from the module connector to a ground splice pack behind the rear bumper. From there it runs up to the front of the vehicle and grounds to the back of the cylinder head. Can't remember if it's left or right though Easiest to check resistance from the module connector to body ground. There are 2 black wires in the module connector: The second black wire is the fuel pump ground which grounds on the top left rear corner of the frame. Both wires must be less than 5 ohms resistance to ground.

 

Anyone wanna post a pic of exactly where this ground is? Mine's acted funny since I bought the truck, and I've looked for it twice.......never found it. :-[

 

You need to check resistance first. If it's excessive, you can either trace the wire, find the problem and repair it, or connect both grounds together at the module connector and run it to a new clean body ground. Post #3 explains where the level sender ground circuit goes.

 

The ground in the back is on top of the rear cross member in front (towards the engine) of the spare tire if yours is under your truck.

 

The ground on the top left rear corner of the frame is for the fuel pump. The level sender grounds on the back of the cylinder head.

 

Did you say there were two wires that should be in the back? and is it only 96-97 that are grounded on that cross member or is that what you mean by the back left corner of the frame?

 

This applies to 1996 & newer. In the fuel pump module connector there are 4 wires: Grey is voltage feed for the pump and it comes from the fuel pump relay. Purple is the fuel level signal that eventually goes to the fuel gauge in the instrument cluster. The other 2 wires are black: One of them is the ground for the fuel pump. On a 2 door it's on the top of the left rear corner of the frame. On a 4 door it's on the frame crossmember near the rear of the tank. The other black wire is the ground for the level sender. For some odd reason, GM routed this wire to the rear of the (right???) cylinder head. When the tank is down, for whatever reason, I take both black wires and splice them together where they exit the connector. Then splice a single 14 gauge, (or larger) wire to them, and connect it to a nearby clean body ground. This eliminates 10+ feet of wire, and connections, where the fuel level sender ground wire could fail.

 

Im an idiot, didn't pay attention to the ZR2 part. My bad, but that makes sense, I have been having the same problem. So im going to look for that one on the engine