Friday, July 8, 2011

Fuel Pump Shut-Off Switch (Inertia Switch)

No fuel to your engine? A good number of us are probably familiar with Ford’s fuel pump issues and have had to go through the replacement process.

Well, it seems there is another item that could mimic a non-working fuel pump. It’s called an inertia switch or fuel pump shut-off switch, and is designed to cut off the flow of fuel in the event of an accident to prevent fire.
The switch has a magnet inside that holds a steel ball up, if there is sufficient impact to knock the steel ball loose the fuel pump is shut off. If this switch should somehow get triggered or in some way malfunction, you would find yourself with no fuel getting to the engine.

A dishonest mechanic or service writer could exploit the inertia switch to sell a new pump install, or worse still, charge you for a pump install that doesn't really take place. This scenario is tougher for the shop when you ask for them to give you back the replaced parts. They may or may not have a spare old fuel pump to give you, in that case. 

So, you ask, where is this switch located? 

It can be located in two different locations, behind the passenger foot well kick panel, or in a bracket above the brake pedal.  The passenger footwell location seems to be the more common. It is located in the passenger side footwell, under the plastic trim piece. The trim is held on with spring clips and pops off. The switch doesn't look like much, similar to a plastic plug.  On top of the switch there is a hole in which the red reset button resides. When in the 'on' position, the button is recessed and not visible. When tripped, the button pops out. Pushing the button inward, resets the switch. On some vehicles it may not be necessary to pop off the trim piece – there may be a little hole or notch in the trim through you can put your finger to push the red button in to reset the switch. The red rubber reset button, about the size of a quarter,  is located about 90 degrees from the face of the panel and slightly below the cutout. You should be able to feel around and locate it.

If resetting the switch does not solve the problem, check the fuse: Power starts at fuel pump fuse #17 in engine fuse panel out as yellow wire to fuel pump relay, out of relay as dark green wire to inertia switch, out of inertia switch as pink wire to fuel pump.

Contributors: Larry Wade, Kevin Lindsay, RonB, WxToad, Delta Mike

Updated: 28 Sep 15