still having this issue and I can not seem to figure it out. I scan the car with Autotap, and when the MSD is hooked up I suddenly lose communication with the PCM when the engine starts. I have communications with key on engine off, and cranking. It's lost whent eh engine starts. When I unhook the plug from the coil and reconnect the stock, everything works fine. I have communications again like that but I now have no tach because I have bypassed the MSD. (stock guage cluster is gone)

I have rerouted the B+ and - to the starter B+ and to the block (exactly how MSD says to do it) and I still have the same problem.

I thought it might be an Autotap problem at first but I tried HP tuners my buddy has and it does the same thing.

I am connecting to the PCM thru the stock ALDL connector. Checking the connector out and it seems that the ground in the ALDL goes funky when the engine is running. So I tried running a new ground to the ALDL and same thing.

So I e-mailed the MSD tech line 2 weeks ago. Never got a response. So I called today and the MSD rep told me that the MSD line is desgined to run with the GM C/D type ignition and that it cant be the box. He said it has to be the way it is installed. I asked what do you recomend then? He said I dont know it sounds like you have it all good. He said to get rid of the MSD harness and just hard wire the box to the coil plug. I dont think thats going to do anything other than force me to cut the connectors off of a perfectly good wiring harness. He also suggested that I run the power wires directly to the battery (trunk mount). I have several redundant grounds so I know the car has good grounds.

Anyway... I am getting a bit frustrated here with this. Anyone ever had a problem like this? Any idea what the problem could be? I am going to test their idea of runing wires to the battery directly tonight, but I dont know if this will fix it.

Any other ideas? Anyone had a problem like this?

 

for anyone who might be intrested it seems like it might be working now... I ran 2 #10 wires to the battery just laying on the floor and it didnt work. But now I do regain communications after I exit the program and reopen it. Never had to do that before but for some reason now I do. I'll live with that for now... at the least I can get this thing to a dyno like that.

I have tried this scenario several time with it wired the other way and it also did not work.

 

This may be a bit of a long shot, but I had problems with a data logger due to a set of ignition wires that were a good quality name brand, but were producing a tremendous amount of EMI, enough to actually cause the computer to lock up.

Sounds like you might be on the right track though with the MSD unit being directly connected to the battery. My Big Stuff 3 system, states over and over again in the manual that the ONLY acceptable way to wire the unit is a DIRECT connection with the battery...no if ,ands or buts!!!

 

Never thought of that... the motor is new but I did reuse the Taylor 8.8's. Maybe I should step up to a 10.4 race wire as a precaution... Might be worth a shot.