How to Troubleshoot Mechanical Fuel Pump Problems

Written by alibaster smith
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Mechanical fuel pumps do not use an electronic control mechanism to force fuel into the combustion chamber of internal combustion engines. Mechanical pumps are the old style pumps used on carburettor vehicles. If you're having a problem with a mechanical fuel pump, fortunately you can do a simple check to see if the pump is truly the problem. The only reason to suspect fuel pump problems with these older style pumps is if your vehicle has a rough idle, or stalls frequently.

Skill level:

Things you need

  • Socket wrench with socket set
  • Screwdriver
  • Open end wrench
  • Catch pan

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  1. 1

    Open the bonnet and remove the wing-nut holding the air filter to the carburettor. The wing-nut can be turned counterclockwise with your hand and no tools should be necessary.

  2. 2

    Pump the throttle (the accelerator) and look down into the throat of the carburettor. You should see fuel squirting into the carburettor. If you don't, your pump may have failed.

  3. 3

    Look under the vehicle. Many older vehicles have inline fuel pumps that will be located near the gas tank. You will be able to see the tank from under the vehicle. If you notice any damage or leaking from the pump itself, then your pump has failed.

  4. 4

    Disconnect the fuel line running to the carburettor. The exact connection type will vary depending on the vehicle. The location of the fuel line may also vary depending on your specific vehicle. You may need a socket wrench, open ended wrench, or you may need a screwdriver to remove the fuel line.

  5. 5

    Place the fuel line into a catch pan and crank the engine. You should get strong spurts of fuel flowing into the catch pan. If you do not, then your fuel pump may have failed.

Tips and warnings

  • For specific information about removing fuel lines as well as the exact location of your air cleaner and carburettor, consult the particular vehicle's manual (see Resources).

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