transmission controled spark switch

Hello All:

Working on the wire harness,,,, 1974 CJ I258 T-18 4spd.... what does the Transmission control spark switch do and do I need it. The circuit is fed off the Ignition side of the switch goes through a vacuum switch(missing) then to the TCSS on the trans.

My other 74 with a t-14 3-spd does not have it. Can I leave it out of the wiring scheme??

THX
Dave

 

My 75 does not have it, runs great.

 

Rusty:
Do you have the t-18 in your 75? and is the switch in place on the transmiswsion? I guess what im asking is do have it and its just not connected or you dont have the switch at all.

THX
Dave

 

Look at the '74 TSM. There is a copy here - http://oljeep.com/edge_74_tsm.html - page 4A-27 - You are fortunate that the complete manual is online, and you do not need to buy a copy.

C'mon, Dave - read the manual. The manual should be your first best resource for questions like this. It explains the TCS system in great detail - it would take a long time to transcribe all that info to a reply.

If you leave the TCS switch out, the Jeep will not be emissions compliant. Otherwise, it will run fine.

 

Well Crap Tim,,, when your right your right,,,,,,, I have the damn manual and to lazy I guess to read it. I am on my second glass of wine right now and therefore taking my scolding like a true hero...LMAO..
THX
for the input and direction,
THX'
Dave

 

Never had it on my 75. Worked like a charm. The purist will say you need it.

 

At first I posted completely incorrect info from memory so figure I need to correct. The basic function of TCS is to inhibit vacuum advance to the distributor when one grabs high gear. But sometimes this function can cause driveability issues, so the system receives input from ambient temp sensor, and also coolant temp sensor. So if it's cold outside, or if the engine isn't warmed up, the TCS function is overridden and distributor vacuum advance functions as per normal.

Retarding the timing lowers firing pressure, so also reduces NOX emissions. This is not a performance enhancer. At best you may not notice the lack of vacuum advance when in high gear. If not working properly you might end up completely inhibiting vacuum advance. I recommend hooking distributor ported vacuum direct to the distributor, then plant a tree to offset the environmental impact.