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Discussion Starter · #1 · (Edited)
I am trying to get the IMRC's working on my car, window switch (msd pn 8950)by itself wouldn't work so I purchased a tach driver (msd pn 8913), wired it according to the instructions, I used the drivers side coil power wire to splice into, red/green stripe, when I hook my decrepid old dwell/tach to the gray wire it reads correctly, hooked the window switch to the tach driver, and still nothing, it will not open the circut so the imrc's will open, the vaccum switch for the imrc's is working, I went to a&a and purchased another window switch thinking the original was bad, the only other thing I can think of is the module selector I'm using is bad, (msd pn 8670) but I checked it with my ohm meter and all the positions work with different resistance values for each setting, I know its probably something stupid, but you all know what its like to work on somthing simple :rolleyes: for a couple of hours and get nowhere, (and drive 60 miles, buy something you don't really need)
any help would be great

just so there's no confusion my car is a 94 cougar with a 94 mark viii motor
 

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The Parts Guy
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I went had this exact same problem back when I wired up the IMRC's on my XR7. You won't believe this, but you actually have to splice into the power wire for the coils before that wire splits to go to each coil pack. The way you currently have it wired in will not work.

-Rod
 

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I went had this exact same problem back when I wired up the IMRC's on my XR7. You won't believe this, but you actually have to splice into the power wire for the coils before that wire splits to go to each coil pack. The way you currently have it wired in will not work.

-Rod

That's exactly correct, the waste spark system is a real pita to figure out.
 

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Ok well I am hooking up a MSD RPM switch #8950 soon and I need to know what wire to hook into for an RPM signal (the white wire on the 8950). I would expect this wire to hook into a negative trigger wire, not the power wire. Anyone have any good ideas? Do I just need to hook into the tach wire behind the cluster? Thanks
 

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The Parts Guy
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You can try the tach wire behind the cluster. If that doesn't work, get a tach driver and wire it as described in post #4 of this thread.
 

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Damn I hope I dont have to buy another MSD part just to get this to work. I didnt realize I would have to buy a RPM pill until I got the switch in my hands, lol. What is a tach adapter useful for? That is crazy in post #4, do you think the wire cant supply enough current after the splice to run the RPM switch?

Is the fuel injector wire a bad idea to use for a signal since the injector hits only every other turn of the engine? Do people usually mount these RPM switches inside the car or under the hood? Thanks in advance.
 

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The Parts Guy
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It's called "paying to play".

If you wire the tach adapter in after the power wire splits to the two coil packs, you'll only see half of the ignition events. In other words, the tach signal will say you're at 2,000 rpm when the engine is actually at 4,000 rpm. Been there, done that.

I would not splice into a fuel injector wire for this.

When I was running a RPM switch, it was mounted under the hood in my electronics enclosure.
 

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Well, I just hooked this up on my 99 Taurus to control the dual plane manifold on the newer engine. The MSD 8950 switch is awesome because it is already set up for an 8 cylinder, but you can cut wire loops to make it work with the number of cylinders you have. I only had to cut the red loop to make it recognize that it's a 6 cylinder and I tapped into the tan/yellow wire that runs from the PCM to the cluster. Just so everyone knows, there is no need for a tach adapter using the 8950 switch if you have a 4, 6, or 8 cylinder and tap into the wire that run to the tach. Thanks for all the replies.

Oh and I also used a relay to control the valve directly since the paperwork with the MSD 8950 says it can only handle 1.5 amps. I dont want it to burn up anything soon. I mounted the module and relay to the strut tower :)
 

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I went had this exact same problem back when I wired up the IMRC's on my XR7. You won't believe this, but you actually have to splice into the power wire for the coils before that wire splits to go to each coil pack. The way you currently have it wired in will not work.

-Rod


I am VERY HAPPY that I read this before I even began wiring up my RPM switch.

....

VERY HAPPY.
 

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My MSD 8969 is mounted in my cab. No tach adapter needed, but the 8969 is definitely over kill for the task at hand. If I hadn't received it for such a fantastic deal I wouldn't be running it, I would be using a 8950 with RPM pills.
 

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The Parts Guy
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Just so everyone knows, there is no need for a tach adapter using the 8950 switch if you have a 4, 6, or 8 cylinder and tap into the wire that run to the tach.
Sometimes you do, sometimes you don't. If you use the tach wire and the switch doesn't accept the rpm signal, then you'll need to use a tach driver.
 

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Well, we know it will work on a 99 Taurus at least and its also cool since the PCM connector is on the firewall and easy to get to. I would suspect some other fords from the same era would be similar. I havent had the pleasure of getting to play with one on my Bird yet. :( Thanks for the replies!
 
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