Cottonpicker

Need help from those who have installed the pre-I/C stock tach setup. Okay, I've now found and received an original tach and wiring from an 89 cummins 1st gen. I'm curious how to hook the wiring up. I looked at the isspro tach wiring diagram in the sticky but it dosen't look the same. It (my tach) says nothing about being an isspro either. It came with the magnetic sensor that bolts down by the harmonic balancer and the wiring from the tach but the wiring from the tach dosen't hook up to the pickup sensor. I'll see if I can post some pictures. My truck is an early 91 non I/C too so its not just a plug and go.

Cottonpicker

Here is the link that shows the pics of the wiring I got with the tach. I asked the guy who I bought it from and he said all I had to do was hook the positive and ground but were does the pickup sensor hook to? He swore up and down it worked great on his early 91 and that he pulled it off of an 89 model. I'm just not feelin like frying this tach.

http://cgi.ebay.com/ws/eBayISAPI.dll...#ht_500wt_1154

Redtruck-VA

This is from the distant past, but I'm trying to do something similar, although I can't see what he is really was working with.
The non IC models as I understand it do not have the two grooves in their harmonic balancer needed to fire the oem sensor. The oem sensor is a three wire magnetic pickup. 1 wire would be signal, another a ground and finally a power wire. Here is were my question lays, what voltage does the oem sensor use? This signal wire originally goes to the PCM and then the PCM sends out what I believe is a 5vdc Tach signal. But since this is truly the transitional PCM I don't know what voltage the sensor actually uses. My intention is to use the sensor in the same manner as an aftermarket sensor and connect it directly to the tach.

thrashingcows

Why not get the magnetic tach signal kit? I ran one of these on my 89 motor in my crewcab.

Redtruck-VA

Ahh that would make it too easy, got to mix it up a little and be a little different. I've been told the voltage is 8vdc to excite the sensor and a 8.2v zener diode and a 300 ohm resistor is what I need. This should get me a usable signal. WE will see. Thanks,

Alec

I could never get a decent signal out of the sensor when powering it with an 8v supply . . . but I was very half-"hearted" in my exploration of the problem. If your signal wire run is short enough, the passive pick-up will work off the notches with no magnets & a very tight air gap.

Redtruck-VA

Alec, from the sound of it you might have upped the voltage to get a better signal, did you?

Alec

Sorry I wasn't clear. I never got the stock sensor to work in the truck. I had two sensors that seemed to work on the bench with the ~8v power supply (hold metal object next to sensor, no voltage, move metal away, voltage @ output), but I could not get either to work in the truck. However, I never made the time to fully troubleshoot why the set-up didn't work.

By they way, IIRC the notched damper has a slightly larger pulley diameter.

Let us know how you make out.

Alec

Redtruck-VA

Alec, thanks for the clarification. I'll play with it some and see if I can make it work. As for the two pulleys I'll also compare them.
Thanks,

RamGuy84

Also Tinktach is really reasonable and they run off the Pulse of the injector lines .