Need help...push button start.

Simon T.

Simon T.

New member
I need help ASAP to get a push button start in the car before this weekend.

I need some help figuring out how to wire a push button start, no key, so everything will be on switches. Why? There is no key at all now anyway and I'm pretty sure starting the car with a screw driver won't make track officials happy.

This is a diagram I have.

wiring.jpg


Anyone know what I need to do? Can I just run two switches, one a toggle to switch ignition "ON" then the push button for the actual starter and still have the rest on the ignition switch so I basically turn the ignition switch on for the rest?

Here are some quotes a member on another forum said, maybe you all can help me make more sense of it. I'm not very wire savvy so excuse my ignorance. ;)

"Yes that is the correct diagram. Notice there are three wires powered in the RUN position and one grounded(don't know why). The ACC wire isn't the only one which needs to be powered, depending on what you're running. The numbers in the switch "box" outline designate the switch position. 1 is start, 2 is run, 0 is off and 3 is accessory/backwards. You'll need to trace the wiring outputs from the switch, through the manual to see what is powered through which wire."

"Just to clarify; to just get the car running you need to switch the RUN/blue wire on(send power to it) then pushbutton on the START/yellow wire(send power to it). I would power the input to the pushbutton fromthe output of the RUN switch(blue wire), but it really doesn't matter which way you do it. The lights, radio, etc should get their power from the other wires I mentioned earlier.

This is all from memory, so double check."

"It's not hard to wire up at all. One wire 12v is all that controls the starter solenoid. That one wire gets it's feed from the starter relay. The starter relay is energized by one wire from the ignition switch. The wire from the ignition switch is what you need to put your momentary push button switch on. You need a wiring diagram of the starter relay and ignition switch to make sure it needs either 12v or ground; I don't remember off my head. You need to power all of the other accessories, fuel pump, ASD, PCM, or whatever from another switch. The pushbutton only activates the starter."
 
KISS:

Three toggle switches:

RD switch to DB (1):
This is the motor electronics primary power, this must remain on to start.

RD switch to BK/WHT (2):
This is usually the radio and other things that stay on when in accessory. The factory ignition switch kills this to make sure you start. If you have a low battery leave this one off before you start (same thing as throwing the key quickly to get the motor to start).

PK/BK switch to BK/OR (3):
This is usually things to engage more power circuits like lights etc. Not needed to start, but you will probably want it.


One momentary switch (Start):

If you want to be able to bump your motor over without starting RD to YEL

otherwise DB to YEL. That way you cannot bump the switch without power to the motor.

Here is your power up:
(1) hit the Start
then hit (2) & (3)

You could combine 2&3 on a double pole single throw switch.

Make sure you use good switches, without seeing the rest of the wiring there is a lot of current on those two fuses, specifically the one for switch (3)

Hope this helps.
 
Duc said:
KISS:

Three toggle switches:

RD switch to DB (1):
This is the motor electronics primary power, this must remain on to start.

RD switch to BK/WHT (2):
This is usually the radio and other things that stay on when in accessory. The factory ignition switch kills this to make sure you start. If you have a low battery leave this one off before you start (same thing as throwing the key quickly to get the motor to start).

PK/BK switch to BK/OR (3):
This is usually things to engage more power circuits like lights etc. Not needed to start, but you will probably want it.


One momentary switch (Start):

If you want to be able to bump your motor over without starting RD to YEL

otherwise DB to YEL. That way you cannot bump the switch without power to the motor.

Here is your power up:
(1) hit the Start
then hit (2) & (3)

You could combine 2&3 on a double pole single throw switch.

Make sure you use good switches, without seeing the rest of the wiring there is a lot of current on those two fuses, specifically the one for switch (3)

Hope this helps.
Click to expand...

That helps a LOT. THANK YOU.

A couple extra questions.

When you say "RD switch to DB" and so on do you mean connect them to the same switch? As in one connector has the RD and one the DB?

What about switch two? I connect RD to two switches?

So I need three toggle switches and one push button right? What AMP toggle switch is best? I'm guessing just buy the largest push button one I can find?

Thanks again!!! :023:
 
Last edited:
Simon T. said:
That helps a LOT. THANK YOU.

A couple extra questions.

When you say "RD switch to DB" and so on do you mean connect them to the same switch? As in one connector has the RD and one the DB?
Click to expand...

Each of the toggle switches needs to be a single pole single throw. So the switch will only have two terminals. One wire on each terminal. AKA RD on one and DB on the other.


Simon T. said:
What about switch two? I connect RD to two switches?
Click to expand...
Yes


Simon T. said:
So I need three toggle switches and one push button right? What AMP toggle switch is best? I'm guessing just buy the largest push button one I can find?

Thanks again!!! :023:
Click to expand...

Would need to see the rest of the circuit. Get something that handles the fuse rating is always the safe bet, otherwise the switch becomes the weakest link.

Start Switch

Toggle

These both use screw terminals as well. I have seen quite a few melted switches from soldering. Always make sure all contacts are covered, ideally with heat shrink. And make sure they do not fall out.
 
All the switches are neat, but why not just fix/replace the OEM keyed ignition switch?

My rule for almost everything on an IT car--the OEM manufacturer did a lot more engineering on the problem than I could ever do and it is usually good engineering.
 
Good info already. I just did this on my 240. Look at the wires coming into your key switch. Typically there's a hot wire coming from the engine room fuse box, a wire for the start circuit, a wire for the on/run circuit, and a wire for the accessory circuit. In my case there was a 5th wire that was on the ON circuit to tell the ECU when that was engaged. I used two toggle switches - one for the on/run circuit and one for the accessory circuit. Then there's the push button for the start circuit. You need to run the hot battery wire to the off side of each switch and then the circuit wire to the on side. The on/run circuit has to be in the on position before you can start since that is where the fuel pump typically goes. The accessory circuit doesn't have to be on in order to start. I just got a Moroso switch kit from Summit that had 5 toggles and a push button. Sounds like you don't have time for that.

David
 
The best switches out there is the MIL grade terminal switches.

Like this:



Also BRING SPARES! Watched at Road Atlanta this past ALMS race, one of the prototypes get towed in from turn two. The problem. A bad master power switch. They had that car down in the pits for at least 30 minutes trying to debug the issue.
 
Thanks SO much for all the info! I haven't done it yet but will probably start today. This all def. helps! :023:
 
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