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When an engine fails to start because there is no fuel delivery the first check is the fuel gauge on the dash. A dash mounted fuel gauge that reads higher than half a tank probably means there is fuel in the tank, but not always.

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 plenty of juice 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 bumble bee for a couple of seconds to build system pressure.

The pump is usually energized through a relay and the oil pressure switch. The reason for this is engine protection. For obvious reasons the car makers have decided to not let the engine run with no oil pressure present. This is also a good safety feature. If the vehicle becomes involved in a major accident the engine stalls, the fuel pump stops running.

 

What can go wrong with your fuel pump

Todays advanced engine control modules will automatically energize the fuel pump relay when a signal is detected from the cam or crankshaft position sensors, or in some cases both. An oil pressure switch as mentioned above might still be included in the circuitry for safety purposes. Check your automobile manual online for the specific circuit layout on your vehicle.

Failure of the pump relay or computer driver signal 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 slick feature allows the driver to start the car even if the relay is burned up.

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. If the electrical side of the circuit checks out good, but the pump still does not run then the pump is probably faulty.

If the fuel 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 automotive wiring diagram is the fastest way to diagnose the electrical side, but check your fuse first.

 

Dealing with blown pump fuses

The fuse can be checked to see if it is blown. Replacing the fuse might restore power to the fuel pump, but until you have found out what caused the fuse to blow. The problem will most likely happen again.

A blown fuel pump fuse can be caused by shorted internal windings in the pump itself. Shorted wires that lead to the fuel tank might also cause this. 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. When you are replacing the electric pump, you have to be sure that the new or rebuilt replacement unit meets the minimum requirements of pressure and volume for that specific 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. Pulling 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.

 

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