Can a Factory 1st Gen Tach be Install on a 1991.5 Truck

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Can a Factory 1st Gen Tach be Install on a 1991.5 Truck

Postby Collers9640 » Fri Nov 17, 2017 2:53 pm

I converted a 1990 Gasser to a Cummins. The Dash Harness is still the 1990 Harness, The Motor And engine wire Harness are out of a 1991.5 D250 so I don’t have a crank sensor.

Is it possible to install a Factory Tach on a 1991.5.
O and just to make some people mad. I found the Tach in a D350 in a LKQ junkyard, someone took the motor and trans but left it behind. Lucky Me..
77’ W200 Cummins- Auto, BHAF, 4” Exhaust
91.5 W250 Cummins Conversion- PS I/C, pump maxed, Red Oak Diesel Injectors, Coolertubz, pump advanced 1/8", 3" elbow, 3200 Spring, Piston Lift Pump, KDP fixed, DennyT pin, HX35, 4in Downpipe, BHAF, Heater Grid Delete, Alcan springs, Bilstein Shocks
1984 D350 Crew Cab (Future Cummins Project)
fuel screw!!!!
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Re: Can a Factory 1st Gen Tach be Install on a 1991.5 Truck

Postby thrashingcows » Fri Nov 17, 2017 6:42 pm

I do not believe you can run a 92/93 OEM tach on a 91.5 system. The ECM registers the signal from the CPS on the later system and then sends a signal to the tach. On the 91.5 there is no CPS, and the factory tach system was a dealer add on and was just a magnetic sensor on the balancer.

But having said that I could be wrong. If it were me I would gamble and buy an Isspro magnetic tach sensor kit and then see if I could get the OEM tach to work off that. I say this because I originally had an Isspro tach on my 89 motor with the sensor kit, but when I switched to the 93 motor and wiring I was able to use that same Isspro tach on the factory Tach wiring. ;)
1984/93 Dodge Crewcab, W350, 1 Ton SRW, long box, 330K Km's, M&H spacer, 366 spring, fuel pin to deep side, 14cm housing, Piston LP, PS IC, Isspro Boost, Pyro and tach, NV4500, 29 spline NP205, 3.54's.

Check out the build.... ... 05923.html
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Re: Can a Factory 1st Gen Tach be Install on a 1991.5 Truck

Postby RumbleFish » Sun Nov 19, 2017 12:35 am

There was a different tach and/or install kit for the non-ic trucks. I had a 91.0 with a mopar "factory" tach and it had a oem style crank sensor installed.
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