How to Check a Fuel Pump Relay

Fuel pump relay plays a vital role in the fuel injection system. Here are some tips on how to check a fuel pump relay. Have a look...
A car's engine is made up of a number of parts, each of which is extremely essential in the car's smooth functioning. These individual parts make up the whole engine. A problem in any one of the parts makes you feel something is wrong while driving, and the car runs below its efficiency. One such part of the car engine is the fuel pump relay. The car's uninterrupted proper functioning is so much dependent on the fuel pump relay and its related parts, that it is imperative for you to understand how to check a fuel pump relay.

Location and Function

A fuel pump relay is a vital cog in the car's fuel injection system. It is normally located in a plastic casing near the fuel pump and engine firewall. But for the exact location of the relay, you will have to check out your car's manual. The location may vary according to the car design. Air breathing internal combustion engines power the car's engine. The fuel pump injects the fuel during every engine cycle before the compression stroke. The engine control unit exerts control through the fuel pump relay, whose function is to power up and power down the fuel pump. This means if the fuel pump relay does not work properly, the car's ignition system won't get the fuel it needs, thus hampering the start of the car itself.

Symptoms of Bad Fuel Pump Relay

Since we have seen the significance of the relay in the start-up of the car, it is very easy to find out if there is a problem in the fuel pump relay. If your car is cranking out loud before starting, there might be a minor glitch. But if your car doesn't start at all after cranking or there is a delayed start, then the fuel is certainly not injected properly due to a bad fuel pump relay. It results in breakdown of the car engine. Also, you might feel overheating of the engine. If your ears are trained with the normal starting sounds of your car, you can notice the absence of the fuel pump working sound. If you see any of these symptoms, u should test the fuel pump relay using the following tips.

How to Check a Fuel Pump Relay

It is advisable to take your car to the nearest repair center to get your fuel pump relay checked, and if damaged, get it replaced. But if you are stranded somewhere and have no help in sight, it is better to read further and check it out yourself. Checking the relay, primarily means checking for continuity and resistance between terminals. Understand that any relay works as a miniature circuit breaker, so it is not difficult to check it. Before proceeding to test the relay, get an ohmmeter, two jumping wires and the relay diagram. The diagram may be printed on the relay itself, making it easier for you to understand the steps below.
  • Detach the relay from its plastic casing carefully, so as to get a complete view of the relay.
  • You have check four terminals - two power and two control terminals. You can find them out from the relay diagram or confirm them watching the thickness of the wires. Thick ones connect the power terminals and thin ones are for the control terminals.
  • Now, setting the ohmmeter on its lowest resistance value, connect one of the ohmmeter leads with the first power terminal and second with the other one. If the resistance is anything less than infinite, then the relay has certainly shorted and needs to be replaced.
  • Using alternate way, connect one jumper wire from positive control terminal to the positive terminal of the car battery and negative terminal of the car battery to the ground. As soon as you ground the cable, if you do not hear a clicking sound of the relay, you will need a replacement.
  • Then, finally, using the ohmmeter, if you notice that the resistance between the power and control terminals is infinite, your relay unquestionably needs to be changed.
Many a time, people simply replace the fuel pump relay with the horn relay to get a quick check done, which can be helpful as well. These tips on how to check a fuel pump relay can help you anywhere, if you have an ohmmeter and jumper wires in your car. You should carry these things, especially if your car has a history of breaking down frequently.
By Rohan Bhalerao
Last Updated: 9/22/2011
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