I have my car for sale (75 xj12 carburated) because its not running but got a tip to check the inertia switch by the passenger door, I looked and it was removed, with a wire bypassing it which has burnt housing. I've been tracing it back to under the dash as far as I can reach but can't figure out where they originate to change the wiring, looks like could be the harness through the firewall? just dissapears behind the heater fan. Does anyone know anything about these? Does the inertia switch simply kill power to the pump so it wouldn't click? Or is it a seperate solenoid or something?

I'm hoping the burnt wiring was why my car was running on/off. I have til the Monday to get it running or it has to go **cough cough old lady cough cough**

It was running in the fall then stalled on me one day, after that it would start, then die right away and I'd have to wait a few hours before it would catch again.

I hear the cap and rotor could need cleaning cause it was in storage and that could do it, do I need to remove my a/c? I just picked up a dozen spark plugs I'll be changing out too.

Also which hose to pull off to check fuel under the hood? Pumps are clicking, I'm just used to working on chevettes.

I'm sorry for so many questions third post, I'm just out in the snow trying to get it up so I can keep it. Pls help :s

 

My understanding is that the inertia switch is in teh power circuit to the fuel pump relay.

The track of the wiring, NO idea, but into the main cabin loom, for exit into the engine bay (where the relay is located) makes sense to me.

On our RHD cars the bulkhead connector is down alongside the accelerator pedal, under the trim panel, and a pain to get at. Not sure if the LHD swapped all that around????.

 

Under the trim is the heater fan. So as I'm understanding it if the inertia switch was the issue my fuel pumps wouldn't turn on at all? On leaving the fuel pump and filters there are no obstacles for the fuel before the carb? Do you know which line to pull off under the hood to check fuel pressure or a trick to check spark?

Sounds like I'm back to square 1 lol

 

Diagnosis and analysis are eith synonyms or close kin. One must go to the theory. An IC engine needs compression, air, fuel and spark in the correct amounts and at the right time. So the protocol is to test for the presence and adequacey of each. I 've learned to beging with spark as the loss of it in an adequate amount seems most likely. If that works, thence on to fuel. A short cut is to jump 12v battery to coil post +. This assures an available supply for the distributor and coil to do their magic with. it also islolates a bad igntion switch or wiring. Lack of fuel pressure at the rail is indicative of a few things to check out. Simplist, is an adequate amount of fuel in the tank!!!

An inertia switch is a fail safe for electric fuel pumps. Think, a collision and a burst line and the fuel pump trying to meet and endless demand. Add a spark from any source and it's BBQ time. So, the impact jars the switch and the pump is disabled. They make decent antitheft devices as well.

it happened to me on my Tbird when i was rear ended on the freeway. it occurred to me and a look at the manual with a CHP and we found the switch, tripped it snd the bird screamed and I was on my way. The CHP remarked that he just learned somethong tht was applicable to his Mustang of similar vintage as both cars were buyilt on the Fox platform.