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Motorcycle Fuel Pump: Construction, Working and Troubleshooting

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Motorcycle Fuel Pump: Construction, Working and Troubleshooting

Post by admin » Fri Aug 25, 2017 11:34 am

Let Us Now Get To What A Fuel Pump Is:
Fuel pump used in our motorcycles are also known as in-tank fuel pumps. The fuel pump assembly also houses the float assembly which aids in indicating the fuel level on the speedometer console. Poor working/weak , failed fuel pump leads to insufficient supply of fuel and hampers the vehicles performance. Fuel pump delivery plays an important role in vehicles fuel injection system as the fuel for combustion is delivered from the pump.Let us now understand the working and construction of a fuel pump…


A fuel pump is made up of five key elements, Housing, Armature, spring loaded one way valve, inlet-outlet passage and the impeller . The housing houses 2 permanent magnet of opposite poles placed vertically along the inner wall surface of the sleeve and the armature is housed in between the magnets in such a way that the armature is surrounded by the two magnets. The construction is similar to that of a DC motor. An internally grooved plate is fixed on one end of the sleeve and an impeller is mounted on to the shaft of the armature just above the plate( at the bottom end of the sleeve). The impeller is placed exactly below the fixed grooved plate in such a way that the grooved section of the plate and the impeller vanes are parallel to each other. The bottom end of the sleeve has a cover plate which seals the housing completely.The bottom end cover plate is provided with an inlet for the fuel to enter into the pump. The other end, i.e the upper end of the pump houses the input terminals for the motor to function and the fuel entering the input at bottom end of the pump is pumped out via the output which is at the upper end of the pump.

When DC current is applied across the + and – terminals the commutator supplies current to the armature and the armature-permanent magnet set up works similar to that of a DC motor. As the armature rotates, the impeller at one end of the armature rotates against the fixed grooved plate creating suction within the housing and fuel gets drawn inside through the inlet provided at the bottom end of the housing. The fuel gets filtered through the filter padding(strainer) provided at the inlet nozzle. As the impeller rotates more fuel is drawn in due to the suction and the fuel moves out through the space between the magnet and the armature and ultimately to the outlet provided on the upper end of the housing.
To avoid back pressure and fuel returning back to the pump via output due to suction created , a small spring loaded valve is provided which blocks the output in such cases hence avoiding the above scenario of back flow.

Clogged strainer leads to low fuel pressure as the fuel suction is reduced at the strainer end due to clogging. Adulterated/poor quality fuel also leads to pump failure. The sediments in the fuel tank can accumulate on the armature causing pump failure. Insufficient /excess voltage at the pump’s DC input leads to poor functioning of the pump.
Fuel filter if clogged, results in reduced fuel delivery.


1) Cleaning of fuel tank at right intervals.

2) Replacement of fuel filter as a part of periodic maintenance.

3) Use of good quality fuel.

4) Alongside fuel tank cleaning fuel filter strainer also has to be carried out.

5) Locate and inspect the fuel pump relay as a faulty relay will lead to insufficient input voltage to the pump.
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