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Discussion Starter · #1 ·
I am trying to finish a starter circuit to work with a start button. I want to have the button turn the car off as well as on. I also want the circuit to reset itself to the off state automatically if the engine dies.
So, the question is....

Is there a pin coming out of the computer (EEC-IV from a 1994 cobra) that would signal whether the engine is running or not?
I want to identify a wire that is at a high voltage when the engine is running and a low voltage (or vice versa) if the engine stalls, even if the key is still in the run position.

Thanks.
 

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Blue Oval Scribe
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You might be able to use the fuel pump relay output. If the computer does not see a crank signal (engine not turning) it shuts off power to the fuel pump relay...

Just a thought...

HTH...
Mark
 

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Discussion Starter · #3 ·
That is what I had hoped. From the schematics and pinouts I've seen I was not sure if that relay shut off when the engine quit, or when the key was off.
Thanks.

If I can use that wire, I think that I can build a start button circuit that works like the new cars, except that you have to hold to start the engine. The circuit would let you press and hold to start, press to stop, and self reset after a stall so you can just press to start again.
I thought about a timer circuit so that you don't have to hold the button to start, but it seems like you would want to be able to run the starter sometimes, like priming the engine.
 

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Discussion Starter · #4 ·
Mark,

One question. Are you referring to pin 8 or pin 22? Or did I miss the boat completely?

Thanks,
 

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I was working on something similar and posted about it here: http://www.ffcars.com/cgi-bin/ultimatebb.cgi/ubb/get_topic/f/1/t/094631.html?

I was planning to use the FP feed as Mark described and yes it does turn off in the event the engine stops since it is triggered by the PIP signal from the TFI. This is the start side of the circuit and I haven't had time to work on the stop side since I have been busy getting tit fired up.



Cheers, Rod
 

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Discussion Starter · #6 ·
Rod,

Interesting. I am using a feedback loop circuit. It uses a relay and a MOSFET in a loop with a switch in between. The switch powers the MOSFET which triggers the relay and the relay then powers the MOSFET to latch the relay on. Pressing the switch again drains the MOSFET gate and unlatches the relay. That toggles the engine on or off. If I can finish the circuit this weekend I will post a diagram.
 

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When you turn the key to run the EEC powers the Fuel Pump for a few seconds and then turns this circuit back off until it recognizes a PIP signal from cranking.

Something to keep in mind if the button sets up the run signal for the EEC. I'm not sure how the EEC will behave if it comes to life while the engine is cranking, although I guess most people don't wait before they crank.
 

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Narve is correct. In my circuit you will not be able to crank until the pump has pressurized the system. It's only a couple of secs so I don't have a problem with that. One of the issues is that it has to operate to separate circuits. On start it has to energize the starter relay and on shut down it has to kill the ignition. I still have the key in mine, which will allow me to start or kill the engine in the conventional manner. I don't plan to wire this in until the winter months since getting on the road is my priority before the driving season ends. I'm not an electrical expert so I'm trying to stick with what I know. I'm sure someone who knows what a MOFSET is can come up with a more elegant circuit. ;)

Cheers, Rod
 
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