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Replace Fuel Pump

Posted by Mike Bumbeck On May - 29 - 2009

fuel_pump_leadAs most all of us have discovered when the tank ran dry, an engine requires fuel to run. As this fuel is flammable and generally explosive, it is kept in a tank away from the combustive action going on inside the engine. This setup presents the problem of how to get the fuel from the tank to the carburetor or fuel injectors that feed the engine fuel. Enter the fuel pump. The fuel pump draws fuel from the fuel tank and delivers enough to the engine to keep things moving.

When cars used carburetors, the fuel pump was usually a mechanical deal bolted up to the side of the engine. Carburetors are now about as common as console black and white console televisions with built in hi-fi phonograph and stereophonic sound. Fuel injection is the fuel delivery standard. A modern fuel pump is capable of maintaining the pressure and flow required by the electronic fuel injection system, itself powered by electricity created by the alternator. If the fuel pump quits? Game over.

Step-by-Step Gallery with E-Z Captions

Electric Motor

The fuel pump more or less an electric motor. The motor turns rollers or turbine vanes inside the fuel pump. The pump takes fuel from the tank, pressurizes it, and delivers it down the fuel lines into the engine. Fuel  pressure to the engine is controlled by a fuel pressure regulator. The fuel pump keeps spinning regardless of what the engine demand is up to. Divorcing the fuel pump from the engine has spawned all manner of fuel delivery arrangements. There are inline single fuel pumps, single in tank pumps, and even a combination of in tank and inline. Consulting the service manual is the first step before attempting to service a fuel pump.

Symptoms of a tired or waning fuel pump include excessive whining, hard engine starting, or bucking and loss of power under full throttle conditions. Before replacing pump, first be sure that filters, fuel pickups, fuel pump relays, and electrical connectors are in good working order. A clogged fuel filter can restrict fuel flow and cause some of the same symptoms as a dead or dying fuel pump. Finally, exercise the utmost in caution if working with gasoline. Do not work near gas wall heaters or water heaters. Pilot lights can ignite fumes! Use safety glasses, gloves, fuel-approved containers. And yes – have a fire extinguisher nearby.

4 Responses

  1. Brian DR1665 Said,

    Fortunately, the Galant VR4s provide *just* enough room to snake the fuel pump up and out without having to drop the tank. That would be a royal PITA.

    The whining is a good way to put it. If your Mitsubishi is whining, then you’ve got some problems. Usually, they just lose their temper and give you the silent treatment, which is frustrating to no end. I recently resurrected a Galant VR4 which had fuel delivery issues (among others). There was a Wally in the tank, but it had seized up and I had to replace it. The car sat up north for a couple years with a quarter of a tank of fuel in it, so you can imagine the venom just stagnating in the bottom of the tank. Even with a total tank drain, flush, and refill with fresh gas, I had to replace the pre-filter on the new Wally after about 50 miles, because it was starting to whine.

    Old Mitsubishis are a good time, aren’t they?

    Posted on May 30th, 2009 at 9:44 am

  2. casadelshawn Said,

    Don’t forget, fuel is used as a lubricant in most fuel injection pumps. If you run the tank (and the pump) dry, you’ll have a much higher chance of toasting the pump. And most of them aren’t cheap. Grrrr…

    Posted on May 31st, 2009 at 3:44 pm

  3. Turbobrick Said,

    And if you’re really lucky you’ll run into a system that uses internal and external pumps = double the potential points of failure. If one starts whining it’s usually the other one that’s actually having problems. Leaking pickup hoses inside the tank can also fake the symptoms of a dying pump.

    Posted on May 31st, 2009 at 7:08 pm

  4. DREW84 Said,

    Try not to disturb anything you don’t want to replace as parts for Starquests are getting harder and harder to come by from the factory. I’ve had a lot of customers looking for parts that are discontinued.

    Posted on June 5th, 2009 at 5:51 am

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