HEI tach input

BooBoo · Post by **BooBoo** » Wed Jun 28, 2006 2:29 pm

I have a MS 2.2 with MSII and a HEI four pin distributer with the MS hooked directly to the tach output on the distributer cap.

In MegaTune when I crank the engine it shows "not cranking" and every few seconds it will flash "cranking" in red. I replaced the HEI module allready with no change. I have also check the wire all the way from the distribter to the MS and it is fine.

BooBoo · Post by **BooBoo** » Sat Jul 08, 2006 12:05 pm

First off we thought the MS was damaged. It appears that was not true. The MS works fine on the stimulator.

I have the MS hooked up directly to the tach output on the distributer (HEI).

It seems to work alot better with the distributer cap removed. I am attaching a datalog with and without the distributer cap installed.

BooBoo · Post by **BooBoo** » Sat Jul 08, 2006 7:28 pm

I just tryed using a 4-pin HEI module as a buffer between the distributor and the input of the MS. Instead of using the tach pin, I connected a 4-pin HEI module to the VR sensor in the distributor, in parallel with the module in the distributor as instructed online. Guess what? it made no difference. I am getting the same results.

TPI 85 Blazer · Post by **TPI 85 Blazer** » Wed Jul 19, 2006 4:39 am

I may not be the best source of info since my engine doesn't run yet, but I tried to connect the VR coil to MS and to the HEI module (the two were in parallel) and I got either intermittent or no rpm signal in Megatune. This sounds similar to the symptoms you describe. Whenever I disconnected the HEI coil, it worked fine. So it could be that the two in parallel loads the coil too much or it could be that my HEI module had gone bad. I know that a lot of HEI VR coils have been made by difference manufacturers over the years, so maybe some work in this configuration and some don't.

Or maybe what you really want to do is trigger off the ignition coil?