87 Ranger inertia switch...

rusty ol ranger · Feb 24, 2018

87 2.9 2wd.

Troubleshooting why its not getting fuel, relays are clicking. Ive never dealt with an inertia switch, but mine has a white plastic, um, popper on it and it feels like a tripped circuit breaker, i pull it up, it falls down. Can someone tell me how the hell these are supposed to look/feel? The pics online show a actual button.

Input?

RonD · Feb 24, 2018

Button pops up when it trips, you push it back down to reset, but once tripped in an accident it should be replaced.
It you can lift "button" up and it falls back in place then inertia switch is not "tripped".

Just use a test light or volt meter on one connector and a Ground, cycle key off and on, you should see 12 volts for 2 seconds.
Repeat for the other connector on the inertia switch, if both have 12volt then switch is OK.

Inertia switch is a 12v in/12v out cutoff switch, it has a heavy metal weight inside, in an accident(sudden stop) the weight keeps moving a breaks the internal connection to cut 12v going to fuel pump(s).
Button will pop up when weight moves.

rusty ol ranger · Feb 25, 2018

RonD said:
Button pops up when it trips, you push it back down to reset, but once tripped in an accident it should be replaced.
It you can lift "button" up and it falls back in place then inertia switch is not "tripped".

Just use a test light or volt meter on one connector and a Ground, cycle key off and on, you should see 12 volts for 2 seconds.
Repeat for the other connector on the inertia switch, if both have 12volt then switch is OK.

Inertia switch is a 12v in/12v out cutoff switch, it has a heavy metal weight inside, in an accident(sudden stop) the weight keeps moving a breaks the internal connection to cut 12v going to fuel pump(s).
Button will pop up when weight moves.

Ok i will do that.

I just think its odd that neither pump is running. But the relay is clicking, but i guesz the relay could be bad even if its clicking

ericbphoto · Feb 25, 2018

If the relay is clicking and the fuse is good, I believe you will see the 12v for 2 seconds, as mentioned above, on at least one terminal of the inertia switch and that means the relay is good. The relay sends power to the inertia switch. This test is to see if the inertia switch is open or closed.

This diagram here should be close enough to your trucks wiring.

RonD · Feb 25, 2018

In 1987 Fuel Pump Relay passes 12v to fuel pump from a Fusible Link connected to Starter Relay's Battery terminal/post

The Starter Relay, often called starter solenoid, on the inner fender is the Power distribution point for the vehicle.
Positive battery cable is connected to one of the Starter relays larger posts.
Then all the fusible links and fuses are connected on that same post.

One of the fusible links will run to the Fuel Pump relay, it can also be a 30amp fuse.
This is the 12v power that runs the pump(s) it is not what powers the relay to "click" open or closed.
So relay clicking doesn't mean this fusible link/fuse is good

On the dual fuel pump systems there is a splice on the 12v wire by the high pressure pump(frame rail), this is where Ford tapped the 12v wire from inertia switch to power the high pressure pump.
A failure at this splice can disable both pumps

12volt pathway
Battery"+"-------Starter Relay post------fusible link-----fuel pump relay---------inertia switch---------splice--------fuel pumps

87 Ranger inertia switch...

rusty ol ranger

Im a Jeep guy now.

RonD

Official TRS AI

rusty ol ranger

Im a Jeep guy now.

ericbphoto

Overlander in development

RonD

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