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The load side contains a small spring-loaded armature that’s attracted to the magnet. When the ECM powers the control side of the relay, it sends voltage through a small coil which causes a magnetic field. (Engine compartment fuse box usually)Ī relay contains two separate circuits, a control side which is controlled by the ECM, and a load side which powers the pump. If your fuel pump has an external relay, and most have, its location is generally detailed in the drive’s manual, just like the fuses. They are either external and are fitted in the fuse box or are ECM integrated. What Does A Relay Do?įuel pump circuits employ a relay to control a high amp circuit with a low amp circuit. Inertia switches do go bad and are another possible reason a fuel pump won’t run. It activates on impact and kills power to the pump. Your car may also have an inertia switch fitted.

Most car engines will shut off after an accident, but the ignition may remain on.

Wiring the pump not to the ignition but instead to the crankshaft so that it only runs when the engine is actually turning is a safety feature. This number represents the fuse location number you checked in the driver’s manual. Looking closely, you may find the fuse location number printed on the fuse box floor at the foot of each fuse. Removing the fuse box cover reveals the fuses, which, apart from color, all look identical. Either side of the trunk wall behind the carpet.Under kick panel, drivers and passenger front.In most cases, the fuse box under the hood will contain both the fuel pump fuse and relay. It will likely show all this information in an easy-to-follow diagram form.

A good driver’s manual will show the location of the fuse box and the fuel pump fuse number, rating, and color. It’s better to do a little research in the driver’s manual before removing covers in search of possibly the wrong fuse box. Most are well hidden from view and may require panels like glove boxes, trunk carpeting, or kick panel removal to access. As a result, it’s not unusual for a car to have three, four, or more fuse boxes. Modern cars use a ton of electrics and computer modules to manage the various systems.