Hello all! Hope you all are heathy!

I recently purchased and installed an ISSPRO R8508 tach. I have a '93 so I went right off the factory tach plug. I always like testing everything first so my connections all are wire nutted. The gauge lights up and flutters when i switch to key to on, but does not show any RPM with the truck running or revving. I have connected everything per the sticky's and instructions from ISSPRO. I know I have good ground and switched 12vdc b/c the gauge light works/dims and I have metered the 12vdc switched. Does anyone know what kind of voltage I'm supposed to have from the signal wire? I don't have any other charging or PCM problems you would suspect if the Crank Positioning Sensor would be faulty, and I did recheck the spacing of that magnetic sensor to the crank pulley (.050"). I also verified the dip switches in the back of the gauge, and it is on the 6 cylinder setting. Nothing ever easy with this pig, any ideas would be appreciated. Thanks in advance!
v

 

I had purchased an Isspro Tach to use on my 89 motor, so it was the kind with the magnetic pick up off the harmonic balancer. When I converted the truck to 4wd I went wth the 93 wiring system and swapped the same tach over using the OEM tach wiring. It did the same thing you are experiencing and I had to purchase the adapter wiring harness from Geno's, which has two possible wiring configurations, and one of them got things working properly.

 

Is this what you're referring?

https://www.genosgarage.com/product/...ge-accessories

Ive seen these, but just assumed they were just the wires with the needed female blade connectors. I made my own but there could be something special about them?

*EDIT*
As I read the fine print, it does state its required for '92 and newer trucks. Duh.

As always, thanks for your help!

 

Check out this thread " Tach wiring in my 92 w/a isspro r8503" . If you didn't buy the wiring harness, you need microfarad capacitor on one the wires

 

Does that pickup use a magnet glued to the harmonic balancer? My 89 doesn't have a Crank Position Sensor which is why the Autometer tach uses a magnetic pickup strapped to the alternator.

Edwin

 

Yes the kit required two small magnets glued to the balancer 180* apart, then mount the pick up where you can, I mounted it off the a couple of the bolts on the oil pan.

 

I managed to get my used Isspro (R85215 w/hourmeter) to work on first hookup without any fancy harness. I set the DIP switches to 2 pulses per rev because that's what the 2 notches in the crank balancer deliver.

I just ran wires down into the stock tach connector. IIRC, there's 4 pins... V+, two grounds, and signal. It flutters a little at low revs, but steadies up with engine speed.

AFAIK, if the signal is dead, your alternator won't juice up either.

 

I couldn't find this thread. Can you tell me more about this capacitor? Mine functions but if the harness uses a cap to smooth it out, I'd like to add one to my wiring. I just ran wires.

 

https://www.dieseltruckresource.com/...highlight=Tach

Or go to the thread search box at the top of this page. Enter the word "tach" into the search box. After the search pulls up, go to page three and it is near the bottom of the page.

 

I bought a cheap digital tach and wired it up to the factory harness but it read 1350 rpm at idle