Hi guys new here and wasnt sure where to look so I thought I'd start here. so here's what i have 1978 ford supercab 4x4 and I just installed a 95 cummins I have everything wired up but the tach,so here's the question it has the crank sensor on it and i know from the diagram what the wires are for orange 8 volts input, black and light blue ground, black and gray signal. So is it plausable for me to assume that I can hook these up in that order and have the tach work assuming that the signal would go to the ignition terminal on the tach any help would be great and thanks

 

to DTR Alan!

Is this a factory tack you are hooking up or an aftermarket? I don't know if the phord tach operates the same as the Dodge's tach and I've never seen an aftermarket tach that used an 8v input..... But hopefully that info will help someone help you!

 

aftermarket and it's not the tach but the stock crank sensor that use's the 8 volts

 

Ya, got that, just wasn't sure how the signal would be with an 8v input (if your tach would like it or not). There are two types of speed sensors - Analog (Two Wire Magnetic Pulse) and Digital (3-wire Hall-Effect, requires power to operate). Seems like the tach would have to be calibrated to the speed sensor based on the size of the crank damper, but other than that, since this is a 3-wire (digital) sensor, as long as the tach supports a Digital input, it should work fine... I should probably shut up. I've never installed a diesel tach.

 

most diesel tachs i thought ran off of the alternator,or mechanical...i thought,i could be wrong but the last time my alternator belt shat i thought the tach dropped off.good luck,some of the dodge wireing is odd like 12volts to lock the doors and 6volts to unlock,some of the gauges read on messed up voltage,and there is no regulator rectifier assembly in the alternator its in the body control module(computer)so some sensors may read f.u.b.a.r..let us know how you make out with the fordge.

 

You can't hook the wires from the speed sensor straight up to a tach, they have to go though the PCM (computer) to be converted.
There are aftermarket tachs that use a sensor clamped to an injector line.
The sensor actually senses the line expanding with each pulse of fuel.

 

the crank sensor is the speed sensor?????

 

Engine Speed

 

gotcha! can you explain in greater detail I do understand that it goes to the pcm and comes out as a signal for the tach but does it convert to analog or what ? what kind of signal does it convert to? and can i build something to covert it? I have already built a voltage regulator for it. they did why cant one of us