Roll my own FAS switch

[pcs0snq]

Was thinking of how I would make a FAS switch for my Fit an have an idea. I suspect someone has tried this but would like to get opinions on it before I do it. With 100's and 100's of ignition switch moves, I'm going to modify my Fit with a FAS switch of some kind.

[Shan]

If you do this I expect a step by step guide with pictures of everything. Then I can attempt it!

[abcdpeterson]

Is there a fuel pump relay? You may want to kill the low switching voltage to the relay instead of the higher voltage to the pump.

My car has a relay that supplies power to the injectors. I chose to do the same thing your looking to do, but at the injector rely.

I like to go over board on safety and back up systems.
With that in mind here is what I did.

Short story..
-I put a switch on the switching voltage to the injector rely.

Long story…
-Found what side of the rely switching voltage was power and what side was going to ground.
-I put my Normally closed momentary switch’s on the ground side of the switching voltage.
---By switching the ground side, if my wiring shorts to ground it will keep working.
-I put in 2 sets of parallel wires and switches. In parallel BOTH must be pressed. If one is pressed the other keeps the injectors switched on.
---if something goes wrong with one switch the other will keep me going.
---if I bump one switch the other keeps things going.
-Switching voltage is lower, so I am not as worried about getting heavy enough switch’s or wire.

I went to radio shack and bought wire and connectors. Found 2 normally closed switch’s at the hardware store.
I un-plugged the rely.
Made 3 short wires to connect 3 of the wires back to the rely socket.
The 4th contact is for the switch.
Connected 2 wires (double for safety) to the rely into the dash.
Hooked each wire to a switch.
From the 2 switch’s I ran back 2 more wires to the relay port.

Doing it this way I have not spliced into any wiring. I can unplug my wires and plug the rely directly into it’s socket.

[Right Lane Cruiser]

I wouldn't leave the injectors firing if there is no fuel to push. Additionally, if you introduce a bubble of air in there you are going to have a harder time getting the engine started. I'd just stick with the injector kill if I were you.

[hobbit]

I have a fuel-pump killer in the Prius now, which I've used on
rare occasions when it's keeping the engine running for no reason
and I'm outside the EV-switch range. It takes *forever* for the
thing to finally stumble and die. There's no specific fuse for
the (+) to the injectors so it's buried in the engine harness
somewhere, but probably killing injector power directly is the
right [and quickest-acting] way to do it. I suppose also killing
the fuel pump would be a bonus, why keep shoving fuel through
the regulator bypass [and probably wasting some 12V energy] if
nothing is asking for it...
.
Liberal use of back-diodes to absorb inductive spikes is probably
a good idea, too.
.
_H*

[JusBringIt]

My experiment with cutting the fuel pump was a waste of time for me, injector cut works best

[Shan]

Excellent Paul!!!

Now, I need the idiots guide on how to make this. I do not have a solder gun but I think I know some one who does. I have a few questions:

- The fuse used was that the stock one or just a spare?(I am assuming I can get one from an auto parts store)
- Switch, where can I get one from and what should I look for(remember this is for dummies)
- what kind of wires did you use?

I might have more questions

[hobbit]

Excellent and elegant! I wish more people were doing it this
way instead of key-off FAS.
.
Check carefully for arcing in your switch, though, if you can.
If it's having to break the inductive kick from whichever injector
is on at the time it may not last too long. If you're lucky
you'll always break during times when none of them are powered;
you'll increase the chances of this if you're at idle or even
DFCO when you kill the power.
.
_H*

[Shan]

Let me make sure I understand how this works:

you click the switch and it kills the pump(FAS)

Do you need to click the switch again or do you need to pop the clutch/bump start to get the fuel flowing?

Paul, I might buy one if the price is right. I don't like messing with wires on cars.

[jhu]

Will this work on any car with the pump fuse in the cabin? I just my try this in my car. Also will this cause unwanted and unexpected results (ie damage somewhere vs. normal wear)?