Is there a way to bench test a tach?
Dealing with a car that came in running a FITech 30002 EFI with a MSD 8920 tach adapter wired in under the dash. There is no MSD box presently in place, though I wonder if there may have been one prior to the FITech installation. Lots of taped off abandoned wires, some added, some stock.
Tach will not indicate with the adapter connected or when bypassed and re-connected as stock to the negative pole on the Ford e-coil it is using.
Downloaded FITech instructions show no way to tie in a tach or indicate that the 8920 adapter is required. The FITech wiring diagram I show is one of several options provided and is how I think the system was installed, being the only layout that shows using the black wire to the coil with no MSD 6AL box.
Downloaded MSD 8920 instructions all show them connected to MSD boxes with no reference for use with the FITech or other systems.
Without a pretty obvious solution, like a bad tach, I have advised the operator to continue enjoying his ride this season without a tach until the creative wiring and fusing in place can be unraveled and rearranged over the winter. There are literally 30+ fuses installed throughout this car, along with a few circuit breakers too. Its confusing.