9 replies to this topic

[D3nch]

Hi There...

After reading a few posts re fuel systems, i have decided to get an inertia switch on the car..

Any ideas where to get them, how they work, and where and how to fit them????

Thanks Guys...

Add

[Scruffs]

Hi There...

After reading a few posts re fuel systems, i have decided to get an inertia switch on the car..

Any ideas where to get them, how they work, and where and how to fit them????

Thanks Guys...

Add

want another picture?!

This is exactly the one I have on mine... 270162101554 (ebay item number)

seems to work quite well when messing about with it off the car!

I have my pump wired through two relays. One relay switched by the ignition and the inertia switch, and another relay which cuts fuel should the oil pressure get low enough to trigger the idiot light.

[Sprocket]

The inertia switch should only ever be wired in the direct power feed to the fuel pump!!

It will not function as it should wired to control a relay

Its a safety feature!!

[Scruffs]

The inertia switch should only ever be wired in the direct power feed to the fuel pump!!

It will not function as it should wired to control a relay

Its a safety feature!!

Could you explain this a bit more please sprocket?

cheers!

[Ethel]

I got mine out of the scrappers.

I think it would work on a relay but as sprocket says it's not the best way - if the relay fails the switch would have no effect on it.

The switch is operated by a ball bearing inside it (a bit like inertia seat belts) give it a slap in any direction and it should break the supply direct to the fuel pump. The have a reset plunger, in case your driving is bad enough to trip it without crashing, so it'd be a good idea to mount it in reach of the driver's seat. If it's out of sight you can also use it to flummox any would be car thieves.

[Scruffs]

I think it would work on a relay but as sprocket says it's not the best way - if the relay fails the switch would have no effect on it.

I guess I see what you are saying - I wasn't aware relays had a habit of failing in the 'ON' position though? I didn't want to mount it in the fuel pump circuit as I wasn't sure how much current it could take at the time. It does work absolutely fine operating a relay.

Still, if the relay were to fail ON then I would have a problem on my hands, if they can take the current (which, thinking about it, they must do...) then I agree it would be better placed in the fuel pump circuit!

cheers!

Edited by Scruffs, 09 September 2007 - 11:26 AM.

[Ethel]

If you were to have a major bump then who knows how a relay would fail if it got battered or toasted? I think that's the logic.

[Sprocket]

If you use a relay switched by the inertia switch and you are involved in an accident where the wiring is crushed against the body many many short circuits happen and all sorts of things start to flash flicker and spark. Who's to say that the relay wont short and weld closed or just the wires themselves. Also imagine this condition with a fuel pump pushing fuel out of a ruptured pipe into the engine bay at a rate of 70 litres an miniute, wher ethe said wiring is still shorted and sparking. It will empty the tank in a few seconds.

I witnessed an accident and was first on the scene. The battery had no fluid in it because it was crushed, yet ther wiring was still melting, lights flickering and smoke rising from the shorted wiring. Bottom line is you do not know what will happen in these events and the inertia switch is the last thing in the circuit to cut power to the pump and remain switched off.

Thats how all manufacturers wire them and for good reason.

[biggav]

i wired mine inline between the fuse box and the fuel pump..... and it didn't cost anything, they fit nicely in your pocket at the scrapyard......

[Scruffs]

If you use a relay switched by the inertia switch and you are involved in an accident where the wiring is crushed against the body many many short circuits happen and all sorts of things start to flash flicker and spark. Who's to say that the relay wont short and weld closed or just the wires themselves. Also imagine this condition with a fuel pump pushing fuel out of a ruptured pipe into the engine bay at a rate of 70 litres an miniute, wher ethe said wiring is still shorted and sparking. It will empty the tank in a few seconds.

I witnessed an accident and was first on the scene. The battery had no fluid in it because it was crushed, yet ther wiring was still melting, lights flickering and smoke rising from the shorted wiring. Bottom line is you do not know what will happen in these events and the inertia switch is the last thing in the circuit to cut power to the pump and remain switched off.

Thats how all manufacturers wire them and for good reason.

Word to that!

This is why we use forums I guess!...I also guess I shall be a moving it at the next opportunity...

PS 100 posts!