I have heard of wiring a kill switch up to the main fuel relay so you don't have to alter the wiring harness (Cut any wires). I know most people like to put 1 or 2 relays in the circuit, is it ok to wire the switch directly into the main fuel relay? I am just afraid of burning something out, figured I better ask first

Also, if I have a fuel cutoff switch, and I forget to turn it off when I leave the car, will it continue running it even with the car off? Will it cause any damage to the car in anyway?

Thanks

 

Yes you can put a switch directly on the fuel pump relay, [PGM-FI Main Relay], the switch can be installed on the ECU/ECM ground control lead to the fuel pump relay to cut power to the fuel pump or, [a better way] you can install it on the ground for the injector relays coil, to cut power to the injectors, fuel pump, one of the powers to the ECU/ECM and a few sensors, [both relays are in the PGM-FI Main Relay, bot the control lead to the fuel pump relay and the ground for the injector relays ground are low current and require only a small 1A switch, [making it easier to hide] and of coarse you are not dealing with 12V+ but a low current ground.
No, there are no bad "side effects" of installing a switch on either one of the leads, other then the car not starting if you forget to turn it on, and no the car will not continue to run if you leave the switch on.
When the switch is on, the circuit is closed like it would be if there was no switch. 94

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fcm &raquo;</TD></TR><TR><TD CLASS="quote"> Yes you can put a switch directly on the fuel pump relay, [PGM-FI Main Relay], the switch can be installed on the ECU/ECM ground control lead to the fuel pump relay to cut power to the fuel pump or, [a better way] you can install it on the ground for the injector relays coil, to cut power to the injectors, fuel pump, one of the powers to the ECU/ECM and a few sensors, [both relays are in the PGM-FI Main Relay, bot the control lead to the fuel pump relay and the ground for the injector relays ground are low current and require only a small 1A switch, [making it easier to hide] and of coarse you are not dealing with 12V+ but a low current ground.
No, there are no bad "side effects" of installing a switch on either one of the leads, other then the car not starting if you forget to turn it on, and no the car will not continue to run if you leave the switch on.
When the switch is on, the circuit is closed like it would be if there was no switch. 94 </TD></TR></TABLE>

i can't wait til someone do a write up on this infamous kill switch and relocating the main relay so that it be out of reach.

 

g2tegsown: you probably heard it from fcm himself. He's been telling people to do this across many forums for many years.

fcm: that's going into a sticky somewhere someday.

JLEK: didn't you just quote the write up? That's a write up if I've ever seen one. I also have a write up on my site on the fuel kill tab all the way at the bottom. wrx-killer-etc has at least one post on relocating the main relay.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fcm &raquo;</TD></TR><TR><TD CLASS="quote">...the switch can be installed on the ECU/ECM ground control lead to the fuel pump relay to cut power to the fuel pump or, [a better way] you can install it on the ground for the injector relays coil, to cut power to the injectors, fuel pump, one of the powers to the ECU/ECM and a few sensors, [both relays are in the PGM-FI Main Relay, bot the control lead to the fuel pump relay and the ground for the injector relays ground are low current and require only a small 1A switch, [making it easier to hide] and of coarse you are not dealing with 12V+ but a low current ground.
</TD></TR></TABLE>

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fcm &raquo;</TD></TR><TR><TD CLASS="quote"> Remove the relay and the wiring install a small 1A switch on the black lead going to PGM-FI Main Relay, it will cut your fuel injectors, some sensors, one of the powers to the ECU/ECM and the fuel pump, it's a low current ground for the injector relays coil.
And if you want to double up install a switch on the ECU/ECM control lead to the fuel pump relay, also a low current ground, no 12V+ to deal with at all, no relays, and very little wiring. 94</TD></TR></TABLE>

Do I have this right for each option mentioned? Read some other FP kill and MR kill switch articles and got a little confused.

1. G101 = ground for injector relays/pump/sensors/ECU

2. GRN/YEL to A4 and A17 = ECU/ECM control lead to FP relay? (Bigger circle)

I wanted to make sure you're not talking about the BLK/RED coming off A26 ---&gt; G101 (third pic, red rectangle)

As for G551 (smaller circle)--this would be an un-related kill at the marked location right? Basically a ground side version of the in-line fuel-pump kill--still requiring a 20A switch--w/ limited hiding spots?

Thanks,
Oh these pics are from 92-95 EG non-VX BTW. I didn't shrink em to maintain legibility.


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The only one you need it the black, [2 red squares] installing a switch on that lead to open the circuit will shut down the fuel injectors and the fuel pump, it is a low current ground.

If you just want to shut down the fuel pump install the switch on the green/yellow, [big circle] fuel pump relay control from ECU/ECM, it is also a low current ground.

The black coming from the fuel pump, [small red circle] is the fuel pump ground , it is "high" current ground, and should not be used for a fuel pump kill without a relay.

Not even sure what the black/red is, [red rectangle] ground for ECU/ECM maybe, I wouldn't put a switch on it. 94

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fcm &raquo;</TD></TR><TR><TD CLASS="quote">The only one you need is the black, [2 red squares] installing a switch on that lead to open the circuit will shut down the fuel injectors and the fuel pump, it is a low current ground... 94</TD></TR></TABLE>
The Helm Inc. Manual for the 99-00 EX Coupe shows the PGM-FI Main Relay (C443) very close to the Ground (G402) associated with this section of the Main Wire Harness (Right Branch, sect. 23-38). Does this severly limit the choices I have regarding where I interrupt the Ground Wire coming off of the PGM-FI MR? Or does the Ground wire from the PGM-FI MR (Black, from terminal #3 (for 99-00 EX Coupe)) terminate at some point other than G402?

I've read a post where you mentioned we could extend the wiring for the PGM-FI MR Ground interrupt. Are there any concerns regarding the length of the extension, or could we use a very long wire if we wanted/needed to (hypothetically, 100' total extension)? I just want to be sure that I'm not confined to the area immediately surrounding the Passenger side kick panel, and that moving too far from that area won't adversely affect the Kill Swtich or the PGM-FI MR's function.

Lastly, I was thinking of finding a new Ground point to use for this switch. With one end of my low-amp switch connected to the PGM-FI MR Ground, I'll be able to simply connect the other end to any clean Ground point on the Chassis, right? Will doing so require me to remove the original (cut) wire that leads to G402 (or wherever it ends)?

Thanks for the tips and guidance. You guys here are helping a noob along very quickly!
JasonGhostz

 

What's the difference between putting a switch on the main relay as opposed to the fuel pump?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by menappi &raquo;</TD></TR><TR><TD CLASS="quote">What's the difference between putting a switch on the main relay as opposed to the fuel pump?</TD></TR></TABLE>Among potentially other things (that I'm hoping others will point out), the Current that runs through these wires is different. You'll have to match the contact ratings on your Switch to ensure that it won't burn.

The PGM-FI MR Ground is low current, while the Fuel Pump Wire is not. You'll need a bigger switch for your Fuel Pump (one that can handle more Amps), but if you disable your PGM-FI MR's Ground Lead (using a smaller switch) you will, effectively, be disabling power to your Fuel Pump anyway. This is what fcm has been preaching for years.

Furthermore, you may have to employ the use of your own Relay if your "Fuel Pump Only Kill Switch" wire is extended by more than 5 feet (total wire added, not the distance from cut).

Again, there are other differences that may exist out there, and I haven't done this yet. I'm sure others will chime in as they peek in over the weekend...

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<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JasonGhostz &raquo;</TD></TR><TR><TD CLASS="quote">...Does the Ground wire from the PGM-FI MR (Black, from terminal #3 (for 99-00 EX Coupe)) terminate at some point other than G402?</TD></TR></TABLE>The Helm Inc. Manual for the 99-00 EX Coupe (sect. 23-75 & 11-238) shows the Ground Distribution/Identification for the PGM-FI MR terminating in the Engine Bay, at G101 (via the Main Wire Harness and Engine Wire Harness link).

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JasonGhostz &raquo;</TD></TR><TR><TD CLASS="quote">Lastly, I was thinking of finding a new Ground point to use for this switch. With one end of my low-amp switch connected to the PGM-FI MR Ground, I'll be able to simply connect the other end to any clean Ground point on the Chassis, right??</TD></TR></TABLE>Sect. 11-39 shows that this Ground is somehow connected to two of the Grounds from the ECM/PCM (from terminals B2 & B10 (both Black) on the 25 pin connector). Anyone know where/how this occurs on the 99-00 EX Coupe? How might this affect where I choose to interrupt any of these Grounds?

As always, thanks!
JasonGhostz

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JasonGhostz &raquo;</TD></TR><TR><TD CLASS="quote">

Are there any concerns regarding the length of the extension, or could we use a very long wire if we wanted/needed to (hypothetically, 100' total extension)? JasonGhostz</TD></TR></TABLE>

I was thinking about this myself. Both leads in question are low current (1amp or less)--doesn't this make them more sensitive to increased resistance in the circuit? I'd prefer to run a good 1-2 feet of wire on each, but I'm not sure how much resistance an in-line switch and wire is going to add to each lead.

I don't think it is a big worry unless you're leaving the dash area and traveling far from the main relay, but w/ this sort of thing its always better to play it safe and ask right?

 

Although the load, injector relays coil is low current, [under 200mA] the ground lead itself is as high as the wire used will handle, [15A min.] as long as the lead you add can handle 200mA your good to go.

However, although the fuel pump relay coil load is the same, [under 200mA] the control output from the ECE/ECM may also be "low current" as that is all that is required to control the relay, extending that lead too long could be a problem.

I have never run into a problem with either, but then again with the fuel pump control lead my extensions have never been longer then 4 feet total as you can install the switch anyplace along the control lead between the ECU/ECM and the PGM-FI Main Relay.

I use the coil ground for injector relay in my 94LS and there is a total of 10-15 feet of lead added, I depined the ground "opened" the terminal up and replaced the ground lead, [same gauge wire] ran it through the stock harness to my hidden spot for the switch and back to the dash harness ground point on the A piller.

Yes JasonGhostz you can run the injector relays coil ground lead to the switch anyplace you want and ground the other side of switch at any good ground point, it is pretty much what I did, I am not using the original ground at all, it is tucked away in the dash harness, my ground is at a dash harness ground point, it may or may not be the same place the stock coil ground goes, there is more then one.

The other main differance that exists, the two ways I recommend are low current grounds any others will be high current 12V+, my way there can be no short, any other way the potential for a short is there. 94

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fcm &raquo;</TD></TR><TR><TD CLASS="quote">[a better way] you can install it on the ground for the injector relays coil, to cut power to the injectors, fuel pump, one of the powers to the ECU/ECM and a few sensors, [both relays are in the PGM-FI Main Relay, bot the control lead to the fuel pump relay and the ground for the injector relays ground are low current and require only a small 1A switch, [making it easier to hide] and of coarse you are not dealing with 12V+ but a low current ground.
No, there are no bad "side effects" of installing a switch on either one of the leads, other then the car not starting if you forget to turn it on, and no the car will not continue to run if you leave the switch on.
When the switch is on, the circuit is closed like it would be if there was no switch. 94 </TD></TR></TABLE>


I read on another forum that a switch like this that cuts power to the ECM/ECU will basically reset your vehicle's computer every time you leave the car (and presumably arm the kill switch)? Thus the performance may be slightly affected for those running mild bolt ons like I/H/E until your computer recalibrates for the breathing mods. Can you shed any light on this?

 

No it will not harm anything.

 

It does not reset the ECU/ECM as that ECU/ECM power is off, [along with injectors and fuel pump] each time you turn off the ign. switch anyway. 94