Chevrolet Repair: FUEL PUMP, oil pressure switch, fuel pump relay

Question
Gentlemen

I have Chevrolet Tahoe 4X4 97 models. I have faced so many problems with fuel system. Since January 2005, the fuel pump was replaced with new one 4 times. I visited Chevrolet dealer including many wok shops and no one could resolve the proplem.My car problem start with up normal noise from the fuel pump itself with high temperature on the pump relay. The sound start after one hour from starting the car. The pump start to fail since the sound is generated after one week of operating the car. Untill now,I have spent around 3500$ just on this issue trying to resolve this problem

Your assistance is highly appreciated.

Mr.AL-YAHYA, FAISAL
00966554297197


Answer
OK, Here is how the fuel pump circuit works:

As soon as you turn ON the ignition switch to start the engine a 2 second battery voltage signal is sent from the computer to the fuel pump relay and from the relay back to the fuel pump in the fuel tank.

Once the engine starts, The computer BYPASSES the fuel pump relay and now sends a constant contionous battery voltage from the computer to the oil pressure switch of which is now CLOSED because the oil pressure is UP because the engine is running. Therefore the battery voltage flows thru the oil pressure switch back to the fuel pump to run the fuel pump constantly until you turn OFF the engine.

What I would suspect is that you have a corroded or damaged connection either at the:

1. computer wire connectors or an internal computer fault.

2. A faulty or corroded wire at the oil pressure switch.

3. A faulty or corroded wire connection from the oil pressure switch back to the fuel pump electrical connections in the electrical harness.

4. A faulty or corroded GROUND wire from the fuel tank electrical connector to the frame. There should be a single BLACK wire that is attached to the frame coming from the electrical connector at the fuel tank.

If their is any damaged wire or corrosion of these wires or electrical connections this will cause HEAT to build up within the wire and caue a voltage DECREASE to the fuel pump, oil pressure switch or the fuel pump relay.

This is WHY you are experiencing HIGH TEMPERATURES at the wires and components.

You need to put an ANALOG volt meter on these electrical circuits and watch to see if you see a voltage drop after the vehicle has been run for a few hours.

Whenever any circuit gets HOT, This is usually a sign of a partially SHORTED electrical circuit and or a damaged or corroded circuit.

There is a possibility that the VOLTAGE REGULATOR within the computer is starting to fail and causing your decreased voltage signal to your fuel circuit.

This problem is a very EASY fix IF you know what and how to test the system.



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