87 22r carb, sr5 cluster swap tach issues
 

Hi all, a newbie to the board- searched and did not find anything too helpful other than

https://www.yotatech.com/forums/f2/2...nal-out-16982/

sorry if this is a cross-post but that topic appears to be in the wrong forum by model year.
Details:
87 22R carb with base model cluster, no tach wire.
I connected a wire to the (p) terminal on the tach and tried to pick up the tach signal two places:
1. igniter check/ign terminalper several post on this board ( single capped wire at ignitor used for diagnostics). This did run the tach UNTIL the motor went closed loop. At that point the motor died and would not restart and idle. I disconnected the tach lead and it fired right up( hopefully no damage). I also tried to use a diode on that wire to protect the systems but it did not operate the tach. Does this indicate a problem with the closed loop system?
2. As per my haynes wiring diagram I connected the tach lead to the yellow aire that becomes the black wire at the igniter to body wiring harness. This did not run the tach. Confused why it didn't run the tach. Check the connection with a VOM and it read continuity.
3. my last choice appears to be the black wire to the coil. The schematic does not show this as a connection and it will put load onto the igniter($$ to replace) that may load it down or shorten it's life. how do I safel test fot the pulsed ground(?) that the tach needs to operate?

Who else had this problem and how did you get the tach to work without damage?

Thanks
Scott

okay- an update-
got the truck running without the tach and took it for a spin. Noticed the speed got stuck at 30 mph. crap. Take the cluster out again. When I did I noticed that the tach wire i added to the P terminal slightly nicked the neighboring trace on the back of the cluster. This was giving the tach wire 6v when it was not connected to the igniter. fixed the connection and plugged it into the igniter check wiring. Works fine( even hot).
And the needle on the speedo was in too far so it was binding on the face of the gauge.
All better now. Still is a knda freaky water temp gauge9 even with tuner cleaner in there).
thanks
Scott

i have the Green Plug right by the coil so im basically wired for a tach...all i gotta do is get the tach wire off the parts truck when i find one with a GOOD SR5 cluster..lol..i have my tach wired into some random green wire by the coil..it works..and will continue to work until i can get my dang'd 'ol cluster..right now i also have a oil pressure gauge just laying on my shifter boots...im too lazy to mount it because i know i'll have to take it right back out whenever i get my SR5 cluster..lol