Inertia switch or not ?
- Thread starter Bob from Cleveland
- Start date
Ken Roberts
Supporter
I installed one. Keep it next to the drivers seat for a quick reset if needed. I bought the version that was used by various manufactures such as Porsche and GM. It will be moved to the side of the handbrake cover and not the front as shown in the picture. This style is just a ball sitting in a cup. When the ball gets displaced the current flowing from one half of the cup to the other half is interrupted. I installed it on the low current "ground side" of the fuel pump relay.
Last edited:
Bob,
They are needed. If you have a shunt and the fuel line become ruptured you have 10-40 gallons a minute flowing who knows where. Ineria means moving and in this case, a hit by another or thing, you want the pumps to stop.
They work in rollovers as well. Here is the one I use like the one above in Ken's post.
https://www.pegasusautoracing.com/p...nnVO8YQAMgHhoO8uAWbzZiH4rgGe7DQBupBoCdDvw_wcB
Do a search on the web and you will find some simple ones that can be reset if tripped inadvertently. I have mine placed near the drivers seat so I can check it every time I start the engine. I also have a safety switch that works off the oil pressure. When the pressure drops to say 20 psi from an oil surge in a high speed curve to a possible engine malfunction, my Accusump will pump 3 qts of oil into the engine. If that isn't enough and it drops further the safety switch will cut the power to the pumps and hopefully save most of my engine. Mine is currently wired to the fuel pumps but I have noticed that on shut down the pumps continue to run for a few(up to 15 seconds) seconds. I plan this winter to switch that from the pumps to the ignition. Thus shutting the pumps down faster, as well as all electrical activity negating sparks(at least most of them).
Since it works on low pressure there is a bypass switch(on most) that will allow for cranking without having to wait til the oil pressure climbs enough to allow the pumps to run. In changing the cutoff to the ignition, hitting the start button will give no results and require me to use the bypass button. Since my fuel pumps are wired separately from the ignition I can turn the engine over without cranking. Allowing me to pre oil the engine if it has setup all winter. Most switches require an inertia event of around 10 or so Gs to activate. They will trip under lower effects, but they are quick events and may spike to that pressure for a second or two. If solidly mounted it is easily reached by the vibration of the event(curbing etc.) or even by your hand accidentally.
Hope that is clear enough for you.
Bill
They are needed. If you have a shunt and the fuel line become ruptured you have 10-40 gallons a minute flowing who knows where. Ineria means moving and in this case, a hit by another or thing, you want the pumps to stop.
They work in rollovers as well. Here is the one I use like the one above in Ken's post.
https://www.pegasusautoracing.com/p...nnVO8YQAMgHhoO8uAWbzZiH4rgGe7DQBupBoCdDvw_wcB
Do a search on the web and you will find some simple ones that can be reset if tripped inadvertently. I have mine placed near the drivers seat so I can check it every time I start the engine. I also have a safety switch that works off the oil pressure. When the pressure drops to say 20 psi from an oil surge in a high speed curve to a possible engine malfunction, my Accusump will pump 3 qts of oil into the engine. If that isn't enough and it drops further the safety switch will cut the power to the pumps and hopefully save most of my engine. Mine is currently wired to the fuel pumps but I have noticed that on shut down the pumps continue to run for a few(up to 15 seconds) seconds. I plan this winter to switch that from the pumps to the ignition. Thus shutting the pumps down faster, as well as all electrical activity negating sparks(at least most of them).
Since it works on low pressure there is a bypass switch(on most) that will allow for cranking without having to wait til the oil pressure climbs enough to allow the pumps to run. In changing the cutoff to the ignition, hitting the start button will give no results and require me to use the bypass button. Since my fuel pumps are wired separately from the ignition I can turn the engine over without cranking. Allowing me to pre oil the engine if it has setup all winter. Most switches require an inertia event of around 10 or so Gs to activate. They will trip under lower effects, but they are quick events and may spike to that pressure for a second or two. If solidly mounted it is easily reached by the vibration of the event(curbing etc.) or even by your hand accidentally.
Hope that is clear enough for you.
Bill
Last edited:
My 04 F150 has nearly an identical switch. I replaced the fuel filter years ago and used the fuel cutoff switch to disable the fuel flow. The switch is located in the passenger foot well. I was told to hit it with a mallet or hammer and that would trip it. Well, I took it too literally and hit the cutoff switch directly several times and broke it. I ran for quite some time with it jumped out until I finally replaced the switch. I plan on putting one in my slc.
A.J.
A.J.
Scott
Lifetime Supporter
The wiki does a pretty good job covering this topic and as others have indicated you want one.
https://slctech-slcbuilderswiki.pbworks.com/w/page/76531277/Fuel System
Make sure that it switches both pumps. I also updated the page with Bill's recommend link.
https://slctech-slcbuilderswiki.pbworks.com/w/page/76531277/Fuel System
Make sure that it switches both pumps. I also updated the page with Bill's recommend link.
I used one in my cobra. I hated that SOB. Kept tripping for no reason so I tore it out and havn't used one since.
I just control the fuel pump with a simple off/on switch under the dash.
I'm of the mindset that if something happens in one of my cars where I'm at the point that i'm unconscious (i.e., unable to use my switch) and the fuel pumps have to be turned off I'll probably be better off dead than surviving. (positive thinking, i have it)
I just control the fuel pump with a simple off/on switch under the dash.
I'm of the mindset that if something happens in one of my cars where I'm at the point that i'm unconscious (i.e., unable to use my switch) and the fuel pumps have to be turned off I'll probably be better off dead than surviving. (positive thinking, i have it)
Scott
Lifetime Supporter
I don’t agree with Alex’s advice. My guess is that he pissed it off and it was looking for some payback;-) A comparison to a cobra isn’t highly relevant. I also have a cobra and it doesn’t have an inertia switch, but my SLC sure as hell will. <?xml:namespace prefix = "o" ns = "urn:schemas-microsoft-com
fficeffice" /><o></o>
When I built my cobra in ’89 there weren't forums like this and I didn’t even know what an inertia switch was. That said, I don’t feel compelled to put one in at this point because I have an old-school Webber setup and the cockpit is totally open.<o></o>
The SLC is a very different story, EFI with high-circulation pumps and you’re enveloped in the car. In addition, many people are installing door actuators which may impede their ability to quickly exit the car. If I had an issue with the false positives I’d replace it with alternatives (several times) before dropping it. Worst case it takes a couple of minutes to wire it out and you’ve spent $100.
fficeffice" /><o></o>When I built my cobra in ’89 there weren't forums like this and I didn’t even know what an inertia switch was. That said, I don’t feel compelled to put one in at this point because I have an old-school Webber setup and the cockpit is totally open.<o
></o>The SLC is a very different story, EFI with high-circulation pumps and you’re enveloped in the car. In addition, many people are installing door actuators which may impede their ability to quickly exit the car. If I had an issue with the false positives I’d replace it with alternatives (several times) before dropping it. Worst case it takes a couple of minutes to wire it out and you’ve spent $100.
I absolutely use these in all cars with electric fuel pumps and will likely never change that practice.
Alex's story reminds me of the stubborn Texan that I met (while living in Texas no less) who abhored seat belts because Jim-Bob was trapped in a rollover and died. He claimed he wanted to be able to be thrown clear of the wreck...
Alex's story reminds me of the stubborn Texan that I met (while living in Texas no less) who abhored seat belts because Jim-Bob was trapped in a rollover and died. He claimed he wanted to be able to be thrown clear of the wreck...
Exactly! I couldn't get it to trigger even tho I was trying, which is what led to breaking it.
Similar threads
