In Tank Fuel Pump Guide

Fuel pump close-up of part

When you are looking to buy a fuel pump to replace your old one it is important to match up the part numbers to be sure it’s the correct one for your car. Get it right the first time – You do not want to purchase the wrong one and then go though the process of finding the correct one all over again.

At Your Car Spares Ltd  – What we test and look for!!!!

If a car has a faulty fuel pump you might have problems trying to start it and you may get a loss of power , therefore our first test is to see if the car does start. If the fuel pump doesn’t provide sufficient fuel pressure and volume to the engine it can cause problems such as misfiring , hard starting , stalling and rough idling. It’s not easy to diagnose a faulty fuel pump because there are various parts that can cause similar problems but you can use a multi-meter to check the voltage of the fuel pump. You will need to be aware of what voltage your fuel pump needs and that you know which wires are for the fuel pump and which ones are for the fuel level sensor. We also check that the fuse for the fuel pump is in good working order.  Once the fuel pump has been removed we will check the condition of it. If there are any cracks or substantial damage we wont keep it.

Where to find the Part Number

The part number is usually found on the top of the fuel pump where the inlet and outlet pipes are. This means you don’t need to remove the fuel pump from the fuel tank to find the part number. Below we will show you an example of where to find the part number.

fuel pump

Fuel pump serial number location

Pump serial number

Pump serial number

How does a fuel pump work?

There are two different types of fuel pumps used in cars and they are mechanical fuel pumps or electrical fuel pumps. A mechanical fuel pump can be found in older cars that uses a carburettor on the engine , whereas modern vehicles use an electrical fuel pump to send fuel through the injection system. In modern vehicles the fuel injection system performs better at high fuel pressures and a mechanical fuel pump can’t generate the power an electrical fuel pump can.

Mechanical Fuel Pump

Mechanical fuel pumps suck fuel from the engine into the carburettor. The fuel pump receives power when the camshaft turns. When it turns a cam will pass beneath a pivoted lever to force one end up. This causes the other side of the pivoted lever to go down , pulling the diaphragm down with it. This causes a forceful suction that brings fuel through the fuel pipe. As the cam turns more and it has released the pressure on the lever a return spring will force the lever back into its original position causing the diaphragm to retract with it.

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Electrical Fuel Pump

The electrical fuel pump has an almost identical set up as the mechanical fuel pump but it uses an electromagnetic switch / solenoid to pull the diaphragm. The diaphragm is pulled by the solenoid switch through an iron rod and this brings petrol into the chamber. Once the fuel is sufficient , a pair of contacts are prized apart causing the current to the solenoid to break which in turn releases the diaphragm. There is a return spring that lifts the diaphragm to retract the iron rod so the contacts can close and then iron rod and the diaphragm gets pulled down by the solenoid switch.

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