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Fuel pump inertia cutoff switch

steveg

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I bought two of these on Amazon - looks identical to the one Moss sells. Neither works.
Has anyone used one of these successfully? Or is there a different switch that works?

screenshot.1820.jpg
 
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steveg

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Update:
Here is the problem: with the wiring supplied the switch is normally off. When you jar it with your hand, it turns on. When you reset the button, it turns off. This is the opposite of what's needed.

The wiring needs to be like the drawing with the middle socket empty:

screenshot.1821.jpg
 
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Perhaps it is intended to power a relay that in turn shuts off the fuel? If so, an unnecessary complication.
 

gonzo

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Thinking it was also a good idea, I just purchased the same, if not similar inertia cut-off switch from Amazon with plans for installation somewhere under the dash of my BJ 7. Does the switch work now that you've switched the wiring on the unit as described? As you stated, the unit should "on" until it's jarred "off" (@> 10Gs), re-set "on" by pushing the button. GONZO.
 
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Deleted member 8987

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So....the plug and harness appears to have two wires offset to one side.
Of course there is no photo of the socket portion on the switch proper.

One side of the switch NO, the other NC? As in move one of the wires?

Have you checked the pins on the switch proper to see if one is NC?

But, why?
 
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steveg

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The switch functions correctly with "C" and "NC" wired. The included harness connects "NO" and "NC", so I won't be using that wiring. I've ordered a Delphi GT280 pick and am hoping I can switch the female connectors within the supplied plug; if not I'll make my own wires with metri-pack females.

Gonzo - I like the idea of mounting it underneath the wiper motor on the cabin sidewall and splicing into the connection between the fusebox and the line back to the pump. Heater plenum adjacent to fresh air inlet would be good, too.

screenshot.1822.jpg
 

Gliderman8

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Are you able to add the COM wire to the plug that comes with the switch?
 
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steveg

steveg

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Are you able to add the COM wire to the plug that comes with the switch?

I don't have any GT280 female connectors with which to make a new wire - so I need the special pick in order to move the 'NO' wire to the 'C' position. Will follow up when I find out if I can undo the internal latch with it.

I do have Delphi Metri-Pack female connectors so in the meantime I may make up a couple of wires using those with shrink tube around them. Metri-packs will slide onto the pins shown in the picture above.
 

Gliderman8

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Thanks Steve. Let know how it goes.
 

RAC68

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Hi All,

Steve, by its original described operation, I wonder if your inertia switch was meant to establish an emergency lighting response i.e. trigger the flashers?

I scavenged 2 inertia switched from the the boot side compartments of 2 junk-yard resident late '70s (I think) Ford sedans at least 15-years ago and installed one in my Healey and the other in my Triumph TR7. I mounted each on the frame rear bumper support inside the boot of the car (left side on the Healey) and wired them to disable the pumps in case of an accident (substantial jarring). Since the units are hidden, simply hitting the units directly will also disconnect the pumps and act as an incognito anti-theft device.

Although wiring your units under the dash may result in the disabling of the pump in the case of an accident, I would make sure the mounting is not shock resisting and the unit receives sufficient shock to cause it to respond in an accident.

Ray(64BJ8P1)
 
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roscoe

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Ok, I'm all in favor of safety improvments but if you've been hit hard enough to break a fuel line forward of the pump and cannot turn off the ignition, this item might save you from a nasty fire. But, to my mind it is more likley you'd be in a minor accident where no fire is going to happen and you want to limp out of the way of someone else hitting you and oops....your engine cuts out 'cause the switch got tripped. Does the switch info say how many G's it takes to trigger? I would be happy with a real rollover switch ( not that most of us would survive any rollover, fire or not) or making sure the G trigger point is high enough to avoid nusiance triggering. Kind of like if your air bag goes off in a 5 mph impact. Waste of an airbag. In a rear end collision we're all probably going to smell gas just before a big whoomp sound, g switch or not.
 

Gliderman8

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I just ordered an inertia switch; should have it next week.
I was thinking of adding a small LED indicator light wired in with the power for the pump. If the light is off then I know the switch is tripped.
Any thoughts if this is a good plan or not?
 
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steveg

steveg

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I just ordered an inertia switch; should have it next week.
I was thinking of adding a small LED indicator light wired in with the power for the pump. If the light is off then I know the switch is tripped.
Any thoughts if this is a good plan or not?

A warning light is for when the condition is present, i.e. your fuel pump is off. With the switch I used, which seems to be very common (and the same as Moss sells), you can use the "NO" pin to run a warning light if the switch is tripped.
 

RAC68

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Hi All,

I was thinking of adding a small LED indicator light wired in with the power for the pump. If the light is off then I know the switch is tripped.
Any thoughts if this is a good plan or not?

Although your idea would present a good state indicator of the inertia-switches, after at least 15-years of installation, I can't remember any time when that was a needed or desirable. Even the few times I used the tripped switch as an incognito security advantage, I knew the state as I had overtly tripped it. Normally, it provides a function without consideration and even when it actives, you will be aware.

In short, if you want it, do it but, personally, I see no need,
Ray(64BJ8P1)
 
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