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MSD ignition on RENIX 4.0


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I recently installed a MSD Street Fire and remote coil on my 1988 Comanche 4.0 (RENIX). It decreased my 0 - 60 times by 1.5 seconds (yes, that's right...19% improvement), smoothed out the idle and improved the throttle response and acceleration. Not sure if it improved the gas mileage, I've been having too much fun with the new found power to tell. I did the mod at the same time I replaced the water pump (high efficiency, supposed to decrease hp drag) and swapped my clutch fan for electric fans. So I'm not sure how much of the improvement is due to each individual component, but there is a significant improvement over all. This mod is for a 4.0 RENIX with the ignition module and all of my components were in working order (new cap, rotor, wires, plugs, ignition module; coil was operational but I suspect it was on the down hill slide). I'm not sure if the 2.5 engines use the same set up or if this will work on them. If someone tries this on a 2.5 please comment below. With all the disclaimers out there, here goes:

 

 

You do not have to cut the factory wiring and all MSD boxes are wired the same;

 

Configure your MSD box for 6 cylinder, cut the red loop

 

Heavy black wire to battery neg (will probably have to extend the wire to reach the battery, mine was pretty short)

 

Heavy red wire to battery positive

 

White trigger wire (points/amplifier) to the ignition module negative coil terminal. You'll have to remove the factory coil from the module by unscrewing the two small torix bolts. If you are standing at the engine looking at the ignition module on the passenger fender, you want the coil contact on the left. You can solder the white wire directly to the contact (or make a small jumper wire).

 

Small red wire (12+ keyed ignition) goes to the ignition module positive coil terminal. This is will be the coil contact on the right side. So the same as above and solder it to the contact (or make a small jumper wire). 

 

Orange wire goes to the actual coil positive (either a new remote mount coil or reuse the factory coil).

 

Black wire goes to the actual coil negative (same as above, either new remote mount coil or reuse factory coil).

 

Just for clarification all other wires are NOT used. The gray tach wire isn't needed. The violet and green wires (magnetic pick ups) are not used because the white wire (points/amp) is and you can't run both at the same time. The factory tachometer still works, the ECU advance timing is still functional and the MSD multi spark and rpm limiter work as advertised. The RENIX red lines at 5,000 rpm. I set my limiter at 4,800; low enough to keep the engine from red lining, but high enough you don't hit the rev limiter all the time.

 

That's it, pretty simple. It worked best for me to mount the MSD box and remote coil high up on the passenger side fire wall. If you use a remote coil you'll need to make a new coil to cap wire. All of the factory spark plug wires are too short, but Advance Auto carries a single universal spark plug wire for about $15. In the pictures I relocated the ignition module to the passenger fender well close to the fire wall. This was just to make for an overflow bottle and is not necessary for the system to work. Special thanks to Grewsum 2Sum for the help with the wiring diagrams.

 

 

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Ignition module, left goes to white trigger wire, right goes to small red 12v pos wire.

 

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MSD box mounted upside down high on the passenger firewall. This way makes it easier to route the wires and easy access to the rpm switches. It doesn't matter how the box is mounted as long as water can drain out of it. Double check the location to make sure you can still close the hood. Take care not to accidentally drill through the air box, heater coil and a/c lines.

 

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The remote coil mounted high on the passenger side firewall. Make sure you can close the hood and don't drill into anything important inside. You will need to make a longer coil to distributor cap wire.

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16 hours ago, MiNi Beast said:

should be same for h.o. versions..? perhaps.  umm may just need to upgrade myself to this setup..:shhh:

Not the same for HO engines, they don't run an ignition control module. Much easier. On the back of the coil (mounted on front passenger side of the engine) there is a two prong weather pack connector. The ECU side is what you use for the MSD ignition pick ups. Use the same white and small red wires as the RENIX , but I don't remember which is positive and negative on the plug. The output side of the MSD box (black and orange wires) will go to the coil, once again I don't remember which is negative or positive. If you want to make it look nice pick up some GM weather proof 2 prong connectors to wire it up. That way you don't even have to cut the factory wires and you can plug it back into the coil if something happens to your MSD box.

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21 hours ago, 89eliminator said:

Got mine all done tonight. Super easy install. Throttle response is better and tunable rev limiter is nice as well.

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Glad it worked out well for you. I finally got around to doing Cruser's distributor index. My distributor was way off. Strangely it didn't make any difference performance wise, my 0 - 60 times are still the same. My knock sensor went way down (previous 30-50, current 0 - 5) so I assume that means the engine is timed much better now. I'm guessing the ECU was doing a pretty good job of correcting the advance and the MSD multi spark and super coil were making up for the bad factory timing. Lol

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