I have a 1991.5. I read in the tech section that 1991- 1993 have the factory tach sender. I looked around the crank pulley but I can't see a sender or wires. What am I looking for? Also, I have a black, flat 4 pin connector under the steering shaft that is not hooked up to anything. Is this the gauge hook up? thanks...david

 

You would be looking for a magnetic pickup located on the front timing gear cover. My 91.5 model does not have one.

 

do not waste your time on it.. mine has it and I ave tried getting it to work for months with no luck.. I order the Diesel tach from jegs and 30 min later I have a working tach.

 

so the four prong plug coming out of the bundle of wires that goes to the fuse box doesn't work for the tach or what?

 

'92 and '93 trucks have a tach harness, earlier trucks do not.

 

What color are the wires in that connector. I'll venture a guess it is the Speed Control connector.

 

My Factory Tach wire colors were: red, orange, black and i think brown

 

What model tach did you buy? Or should I say 2888 Autometer?

 

Yes the 2888 autometer is the one..

 

92-93 uses the magnetic pickup as a speed sensor for the computer, so it knows when to turn on the alternator, and a bit of other logic.

I learned that the hard way....( I hate having to dig through schematics for hours)(always ask DTR first)

If you do have the factory tach harness it is nice and works well.

 

Are there any other tachs out there you can use with the factory plug. I know Issopro make s one, does Autometer make one that is a plug-n-play?

 

Isspro is the only one I know of.

 

I got an isspro. Small but works well.

 

I know this has been covered before and it works for some but not all.I was able to use an elcheapo SunPro tach. It is an 8000rpm tach i had about 2 1/2 inches. I just put spade connectors on the correct wires and put those in the factory plug, set it to 4cyl and works just fine. Just thought i would add that SOME other tachs do work.

 

why set it to 4cyl rather than 6cyl? the sunpro tach. and also how accurate is it