FBO systems issues

[68HemiCharger]

I installed the HRR688 ECU and distributer for my 1968 Hemi Charger. I followed the install instructions and was running great for awhile. As I was driving and accelerated around 3000 rpm the engine shut down and wouldn't start back up. The ECU lit up when the key was on and flashed as it was cranking like its supposed to but still wouldn't start. I ended up getting towed home.

I was reading the troubleshooting article on the FBO site. I disconnected the tach wire on the negative side of the coil and it started and ran great again. I then tried hooking up the tach wire again and it wouldn't start. Disconnected it again and it started. Why did it work with the tach wire before but not now? FBO says its a problem with the tach wiring or the tach itself. Why would the tach not make the car run? And why did it work for a little bit and then stop?

And I'm not sure if its related but when the car was running after installing the FBO systems and before it broke down I had 14 volts at the battery. Now when its running and the tach wire is disconnected I only have 12.3.

It doesn't appear that any wires for the tach or alternator are damaged or shorting out.

Anyone else have a similar issue?

 

[67charger383]

An FBO is just a GM HEI unit in a Mopar Performance housing...

 

[steve340]

The tacho wire must be going to ground somewhere.
My wiper linkage rubbed through the insulation and was earthing mine out.

 

[Nacho-RT74]

An FBO is just a GM HEI unit in a Mopar Performance housing...

That was the HR688 box which replaced the A688 original box, but not the newer HRR688 box... as far I know

 

[Dale Lucy]

I installed a FBO ECU in my GTX in May, and it worked great, right until I had to be towed home during the test drive. Like yours the LED came on and blinked when the engine turned over, but it would not start. Turns out that they had a ‘bad batch’. Got a new one shipped to me, and no further issues.