I have a question about if I rigged up a kill switch to the fuel pump relay under the dash (BTW, what's the diff between the fuel pump relay under the dash and the one under the hood?). I'm wondering what would happen if the switch were to accidentally engage and kill the relay while driving? Obviously, the fuel pump would die, but I'm wondering if the engine would suffer any damage from a momentary "super lean" condition, assuming the ignition doesn't stop firing. If so, then perhaps I should slave the ignition to the same kill switch too? Or does the ignition sense when the fuel stops pumping and shuts itself off too?

 

I can't imagine really much damage would happen. I imagine it'd be exactly the same as if you flat out ran out of gas. I really can't see how it would hurt the engine from running completely lean, simply because there'd be nothing to detonate, but then again strange things can happen. My guess would be you'd probably be fine and the car would just die as if you ran outta gas.

 

Yeah, you should be fine.

 

you feel a jolt and then you stop moving, i know this because mine went out on me. if your car has a manual transmission remember to pull it out of gear, hehehe

 

There Are Actually 3 Relays, Initial, Oil Press And I Think Something Else

 

yeah, theres 3 of them, all designed to do what a kill switch does if something else goes wrong And if you accidently hit the kill switch while driving, then just flip it back on. You should notice the car dieing before it actually completely craps out.

 

That;d make sense, just like when you pull that connector clip in the back to relieve fuel pressure. The car runs for a few moments before dieing.

 

ya, my old kill switch freaked out on me a couple years ago. I was on the freeway. The engine just suddently died. No damage. I had to rip the wires off the switch and connect them to get home though. Don't go cheap on your switch. Buy a high quality one if you can find one. no Wal-Mart plastic junk.

 

Same thing happened to me going through the Caldicot tunnel. I had a cheapy switch from autozone that crapped out on me and left me coasting through the tunnel with just enough momentum to get out of there after blocking traffic for about 2 minutes and then coast off of the highway.

 

so who here is actualy cheap...the switch...or you.....ask yourself that one...:P!

 

My PCV pipe fuel rail is doing just fine, thank you very much!

 

Gee, the stories about the switch failing is kinda scarin' me. Are you guys using the switch as an interrupt for the power (positive) going through the relay or as an interrupt for the relay's ground?

 

I used to use the switch to interrupt the primary power for the pump. So yes, all the power was going through it. It lasted for daily used for 2 years. Now I have a better quality switch but I'm killing the signal wire to the fuel pump relay. Less amperage so it should last for 20 years.

 

Killing the power to a primary wire can cause a voltage spike. Not a good idea to interupt the power side of things on a primary circuit that's powering anything other than a relay. Either use a ground or do it the way Bleach did it on a relay circuit. Voltage spikes are less likely to damage the relay then they are to damage an electrical comonent like a fuel pump. Remeber, voltage spikes from collapsing a circuit is what powers your spark plugs, so...