Volkswagen Hesitation, Poor Acceleration

This problem can occur in most 80s and early 90s BMWs and VWs (and Volvos, but we won't go there). If you experience hesitation and/or poor acceleration (most often after the car has been driven for some time) and at the same time the fuel pump starts making loud noises-check the pre-pump. On those cars with a failed pre-pump, the car will start and run fine, but after it's warmed up, the next time you accelerate, the car falls on its face. And then after you let off the gas pedal, it runs fine again.

The main fuel pumps in those cars cannot suck fuel, they are designed to pressurize and the pre-pump feeds them the fuel. Also on these cars the fuel feed iscoming out of the top of the fuel tank, not the bottom like the early ones.

But when it fails (which almost all original one's do), you experience the above problems.

How to tell if your car is equipped with a pre-pump? Go to the online catalog and search for the fuel pump, if your car is so equipped there will be two choices-main and pre-fuel pumps. If the car has the original pre-pump in it with higher mileage, it's most likely no good.

How can you tell if it is original? The pre-pump is mounted to the fuel level sensor, you can find an access panel to this either under the back seat or in the trunk floor. This fuel level sensor plate will have two fuel lines on it, if the fuel lines have the original crimp-style clamps (the ones you have to cut off to remove), the pre-pump is original.

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