Because a mechanical fuel pump uses the motion of the engine’s camshaft to operate it, the pump must be mounted on the side of the engine. A lever or push rod from the fuel pump passes through a hole in the side of the cylinder block and connects with a lobe on the camshaft. Since two metal surfaces leave miniscule gaps between them, a fuel pump gasket is needed to prevent the engine oil from leaking out.
On or around an automobile engine, a gasket is intended to fill up the spaces between two metal surfaces in order to prevent leakage. In order to do this, a gasket therefore must be flexible enough to fill all the spaces and still compress when needed, but also strong enough to withstand the high temperatures of an engine and its components. Gaskets are often made of cork, and some cork gaskets have a rubberized coating to help them seal better and last longer. Some heavy-duty gaskets, such as head gaskets, are made of metal with a rubber-like coating, which enables them to withstand the extreme heat and pressure created by the engine cylinders.
Whenever a new fuel pump gasket is installed, a type of glue called gasket sealer may be used. Gasket sealer is designed to reinforce the seal by affixing the gasket to the metal surface. However, some mechanics maintain that gasket sealer is not necessary. The adhesive is only made to prevent the gasket from slipping while the part is being installed, and is not strong enough to plug a leak. Furthermore, using too much gasket sealer is actually dangerous, as it can clog oil passages and cause other damage to the engine.
Because of its flexible construction, there is a likelihood that the fuel pump gasket will need to be replaced any time the fuel pump is removed from the side of the engine. This is especially true if gasket sealer has been used on both sides of the gasket, as the gasket is more likely to tear in this case. The old gasket and sealer will therefore need to be scraped off, and the metal surfaces cleaned and dried, to minimize the chance of leaks and give the new gasket and sealer something to adhere to.