02 trailblazer pump ground

gee · August 24, 2014

Hope someone can help. I have a 2002 trailblazer LT 6cyl. when i turn the ignition on no fuel pump heard

already did these things

1. tested fuse good

2. switched out relay good

3. dropped tank have positive for 3 seconds

4. no ground for fuel pump detected...i used a test light for thiese tests

any help is appriciated.

Doug_Scott · August 25, 2014

You may find that dropping the tank broke the ground circuit. Not sure, but maybe the tank itself is the ground when mounted in the frame. If tank is plastic, then there must be a ground wire somewhere. If the ground is in the plug that connects to the tank, and it is not connected or is broken somewhere down the line, then you should be able to see the same power level at both power in, and ground wire out. If the ground is good, you will not see any power on the ground line.

This can be an odd thing to understand, but think of it this way, on a simple circuit, with a light bulb, you connect the power to one side of the bulb, and ground the other side of the bulb. Bulb will light up, and if you check voltage at the power in side, you should se battery voltage. Now, disconnect the ground wire, and turn bulb on again. Bulb will not light up due to no ground. If you check the ground side of the bulb you will also see battery voltage. If you think of the power coming into the bulb, going across the filament, then out the ground side, with ground connected, circuit is complete, and the voltage is used up going across the filament. Unplug the ground wire, and the power cannot flow, so it essentially goes to where the break is, and stops. The flow will continue until the wire is "full", so when you check voltage, it will be the same as the power side. This is not the exact scientific way to describe it, but I have never gone wrong thinking of DC circuits that way.

Has the fuel pump been changed? If not, unplug the connector from it, and using schematics check all the pins from proper readings. To check the ground wire you will need to a continuity sensor(similar to an ohm meter, except you can't use an ohm meter on a live circuit more than once).

gee · August 31, 2014

sorry didnt get back sooner..works been real busy. turns out the ground wire as it comes out of the loom was broke. why gm didnt give it a bit more slack is beyond me but i digress. thanks for your help...the replies and diagrams Really helped. I changed the gas pump just cause of the milage on the car. Thanks guys.