1990 Geo Prizm Fuel Pump gauge

My first post! My 1990 Geo Prizm--new to me so I don't have a history--will crank and I have spark, but no fuel. The pump is not pumping--I took off the back seat and it does not even make any noise. Also the fuel gauge does not register even though we have put 8 gallons of gas in the tank. I have checked all the fuses, and have replaced the fuel relay--at least I think it's the fuel relay, next to the headlight relay in a box on the drivers side front wheel cover under the hood. What I really need is a wiring diagram for the fuel electrical system. Does anyone have one they can scan for me? And/or has anyone had similar problems or does anyone have any ideas to help me troubleshoot this problem. Sincerely, Shane Morris. You can email me at geckopest@yahoo.com or respond here. Is the gauge stuck on empty or full?

I can tell you what the two fuel pump wires should have what at the connector that plugs into the top of the sender.


At the sender connector on top of the tank:

fuel pump feed and ground:
You should see battery voltage on the light blue/black wire when you crank the engine.
You should have 0 ohms on the White/ Black wire

With the connector unplugged, the fuel gauge should be at full with the ignition on. If it is showing empty with the connector unplugged and the ignition on, you either have a short to ground in the circuit coming from the gauge or the gauge is faulty.

If you have a yellow/blue wire, that comes from the fuel warning lamp. If you ground that wire with the ignition on, the warning lamp should come on.

I don't know what color the gauge sender wire is, but it should be the only other one left. If you ground the gauge wire with the ignition on the gauge should go to empty.

It probably wouldn't be a bad idea to check the condition of the ground for the fuel pump and gauge/lamp since they ground at the same point and your having problems with both. The lug is located on the LH C pillar.
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