Mexacali Express ('72 K10/LQ4/TH350 Retrofit)

[jpstaub]

Safety is a topic that doesn't get a lot of play in the performance world at times. I don't mind. I like to be as much of a hazard as the next guy. But I do recognize that passengers may expect not be turned into a block of carbon as a result of high pressure fuel spray after a crash.

In the Vortec Retrofit Wiring document included in a previous post you'll see a "CRASH SWITCH" in the upper right hand corner. It's wired such that power is removed from the ECU in the event of a crash. By removing power from the ECU not only do the fuel pumps stop pumping but the ECU can no longer control spark or fuel injection disabling the engine. If you talk to accident investigators one item they will mention is that when people/police first arrive on the scene of a bad head-on crash the engine of the vehicle will be screaming because the driver's foot is jammed down on the accelerator pedal. Not to be morose, but with all the idiots out there texting instead of driving it's a good idea to think ahead because they're not.

Ford did us a solid by incorporating inertial crash switches in tens if not hundreds of thousands of vehicles. If you go to Ebay and type in "inertial crash switch" you're bond to have a selection to choose from. Usually they'll come with a wire pigtail which will save you some money and time sourcing a connector. A typical setup is shown below. If you'd rather have a new switch use part no. 1S3906. Connectors are commonly available.



So now that you're a little scared for your life how/where to install the switch? An image below covers the basics. Installing the switch upright will allow the metal ball in the switch to drop in a crash breaking the circuit. I like to put the switch in the cab on the throttle pedal bracket which keeps it out of the weather, out of the way, but accessible. It also allows me to run a lead from the little used "Glove Box & Spot LT" fuse on the stock fuse panel for power. Shown below is a Ford installation but it gets the idea across.



For guys that like to know how things work the image below shows how the switch is operated. If you'd like to test it out prior to installation smack the switch against your palm to activate the inertial release. Test with multimeter; circuit should be open. Reset the switch and test again; circuit should be closed.