Inertia Switch

[John J Phillips]

Finally have the engine and drive train installed. At start-up, the electric fuel pump would not work. I pulled the inertia switch and and connected a wire between the two main switch wires and the fuel pump worked and the engine started and ran great.
I went to the Ford dealer and bought a new inertia switch, and to my dismay, once plugged in, it also does not work. Several attempts of hitting it and resetting it did not work. On the entire build, the electrical is the most challenging for me. Does anyone have a thought? Is there a simple way to test the switch? I can't believe that both switches are bad -- but who knows. Thanks
John

[chmhasy]

The possibility is very rare the word New stands for( Never Ever Worked) I would get a multi meter and do some testing for continuity and volts

[Railroad]

Any chance you have the switch mounted upside down? Mine is, but I have not gotten to the starting the engine point. I woke up in the night and wondered if the switch includes an inverted open feature, like the car flips. Would it cut the power? I will be watching, I might have to flip mine, reset button on the top.

[chmhasy]

So if u bypass the switch motor pump works. It might have to be oriented in a up down position due to if car rolled over you want the pump to stop

[edwardb]

The switch should be mounted with the red button up. That's how they're designed to work. They're set by pushing the button down and it will stay down. When tripped, the button pops up and it's flush with the top. Pretty obvious when you look at it. It takes a bit of a shock or G-force on the sensor to trip it. Just turning it over won't necessarily trip it. At least that's my experience.

There are three terminals on the switch. It can be wired to be normally open or normally closed when set. The RF harness uses it in the normally closed mode, meaning it completes the ground circuit for the fuel pump relay. When tripped, the ground circuit is interrupted, the fuel pump relay opens and the pump stops. With a VOM, check to make sure your connector is wired to the appropriate terminals for normally closed. I recall someone posting a while back about the RF plug being wired incorrectly.

[AC Bill]

Is the red button fully depressed, and remaining so? It sits down a 1/4" or so.
You could test the switch with a multi-meter to see if you have an open circuit or not. Seems odd, but not impossible you would have two bad switches.

If you are using the stock in tank pump, relay, and ECM, you know that the pump stops running after 2-3 seconds, if you just turn the ignition to "on", and don't crank it? That has caused some confusion over the years.

[grluisi150]

Check the inertial switch connector wire. Mine was wrong, I posted a fix on the other forum #23
http://www.ffcars.com/forums/17-fact...-question.html
Gary

[edwardb]

Check the inertial switch connector wire. Mine was wrong, I posted a fix on the other forum #23
http://www.ffcars.com/forums/17-fact...-question.html
Gary

That's what I was referring to in my post #5. Thanks for the link. Makes the problem and fix very clear.

[John J Phillips]

That's what I was referring to in my post #5. Thanks for the link. Makes the problem and fix very clear.

Thanks you guys! Problem solved -- I love this forum and everyone's willingness to share knowledge.

john