Online Auto Repair | Diy Car Repairs | Automobile Information

A defective sending unit or a gauge that is not calibrated right may be giving a false reading. Probing the tank with a flexible wire or dowel rod down the fuel filler tube will let you know if there is actually liquid gas in the tank.

If there is lots of good quality fuel in the vehicle the next step would be to listen for the fuel pump operation noise. When the key is turned on the pump should buzz like a hornet for a couple of seconds to build up system pressure of about 60 PSI.

The pump is usually energized through a relay and the oil pressure switch. Protecting against internal engine damage is the reason for this. For obvious reasons the car makers have decided to not let the engine run with no oil pressure present.

This is also a safety feature. If the automobile has been damaged in a collision the engine stalls, the oil pressure goes to 0 and the gas pump stops running automatically.

On most modern vehicles the computer will energize a fuel pump relay when it receives a cranking signal from the crankshaft position sensor.

An oil pressure switch as mentioned above might still be included in the circuitry for safety purposes. Check your auto service manuals for the specific circuit layout on your vehicle.

Failure of the pump relay or computer signal to that relay can cause long cranking times because the fuel pump does not come on until the engine cranks long enough to build up sufficient engine oil pressure to close the contacts on the oil pressure switch.

This allows the vehicle to start even with a bad relay. If a buzzing sound is not heard when the key is on or while the engine is being cranked check for the presence of voltage at the pumps Electrical connector.

The fuel pump might actually be good, but if it does not receive voltage and have a good ground it will not run at all.

If all testing shows good on the electrical circuit side of the pump motor and the thing still does not run then you are most likely looking at a burned up pump motor.

If the fuel pressure pump does not run and there is no electrical voltage at the terminal connectors on the vehicle side then there are a few different components that can cause this problem.

Consulting an electrical repair diagram is the fastest way to diagnose the electrical side, but always check your fuses first.

Check the circuit fuse to see if it is blown. Replacing the fuse might bring power back to the fuel pump, but for how long? Until you have discovered what caused the fuse to blow, this problem will happen again.

A blown fuel pump fuse can be caused by shorted internal windings in the pump itself. A short in the wiring that runs to the gas tank can also cause it. In most cases this wiring is well protected, but it does run along the frame rails that are capable of rubbing through the wires installation.

The use of original equipment parts is highly recommended if you have found that replacement of the pump motor is needed. If you plan to replace the pump motor check to verify that the replacement car part meets the required flow and pressure specs for the vehicle.

In my own personal experience at replacing fuel pumps I have found that the cheaper aftermarket units do not last as long. And often infant mortality were the parts fails right away.

removing the fuel tank and installing the replacement parts is a task I would only like to perform one time. My own experience with using original equipment replacement parts is that they provide longer lasting auto repairs and satisfied drivers.