Stock-3

What all is needed to install a factory tach on a 91 truck. There is no sensor on the crank and the plug end on the tach is rectangular (89-91 were square). Truck is also non intercooled as it was built late November. Can anyone lead me in the right direction?

RamGuy84

If you can find a Plug from the radio wiring it is the same plug as you will need to plug the tach into the Plug

thrashingcows

You'll have to find a wiring diagram of the factory tach and it's power and signal requirements. Not sure if a magnetic pick up on the crank will have to proper signal...but might?

If it were me I would sell the factory tach for a pretty penny, then take about half what you just made and buy an Isspro unit with magnetic pick up kit and install.

oliver foster

91.5-'93 factory tachs are different than the factory '89-'91.0 tachs.
I think most of it is in the wiring, but I am sure someone who know more will add to my info.
Freightrain knows his factory tach info., maybe he will chime in.

C_conger04

I don’t know what the factory tach runs price wise but I have an auto meter z-series mini diesel tach and and it’s really simple to install, all you have to do is strap the tach pickup to the alternator and move it around a bit till it soothes out, then calibrate it, it runs about $150 give or take depending where you get it but I would assume it’s a lot cheaper and more reliable than a 30 year old factory tach.

https://www.xtremediesel.com/auto-me...sel-tachometer

^ here’s the link to it on the XDP website if anyone wants it

Gunch

Don’t know if this helps but Mine was just the opposite from 91.5 to 92 just got some good spade conne

ctions

Gunch

I know my 91.5 had 2 wires on crank senor and 92 has 3 my guess is that because the 91.5 has voltage regulator on fire wall but don’t know for sure maybe someone else can chime in

thrashingcows

Makes sense about the alternator function in the PCM getting a signal from the CPS, and the 2 vs 3 wires on the CPS is probably because the 92/93 PCM uses the CPS of more functions then the 91.5's I believe.

RamGuy84

If you look in the Sticky you will find tach wiring diagram's