Turns out my tach sensor failed between installing and testing it, and hooking up the tach. I used the frequency setting on my fluke meter to read the output of the tach sensor, it's almost a 1 to 1 relationship between frequency and rpm, about 750-800 Hz + 700 rpm, I ran the numbers but I cant find the paper it is written on so the range will have to do for now, and about 250mv output. then I hooked up the tach and nothing so I tested again at the tach and no frequency output.

Here's how I rebuilt the sensor, Local ford dealer didn't have one and I didn't want to pay that much for a new one so I went shopping at the u pull it. I had previously drilled out the original sensor to gut it and now I'm looking for a sensor that will fit in the old housing. after pulling several sensors to see if they were the right size I found that the ford 4.0 V6 in the rangers and explorer had what I was looking for. But you have to tear it apart to get just the coil from it.

Here it what it looks like


and after pulling the guts out

It was a little to big to fit in the old sensor housing so I chucked it in the lathe and opened it up a touch. I ran a 9/16" drill bit through it and that fit the tip fine but the body further up was a little bigger so I bored it out a little bigger then put the step at the opening to fit the plastic housing. I think it could have been done without the steps by filing or sanding the plastic body down but that could be a pretty tight fit on the wires, have to be real careful to not short them to the housing.

Now the new guts fit in the old housing snugly. I put the housing in the truck so I could mark the direction I wanted the plug facing and some 5 minute epoxy with the mix tube so I could just squirt it in as I put it together and some tape to keep it from oozing out and I have a rebuilt sensor.



a couple days later I installed it and wired in the pigtail to match the new sensor and I have a working tach.





there was a tab on the sensor that I sanded off on the belt sander to make it mostly round but other than that it was glued into the bracket but had a screwdriver slot that popped the glue joint rather easily, I don't know if the aftermarket ones will pop out as easy though.
Rock auto has the replacement sensor for under 10 bucks. or it was $10.00 from the u-pull-it as well.
Rock Auto