need help engine shutting down

[Durb]

I have an 86 GT with small performance upgrades. While driving the engine will just shut down with no lights on in instrument cluster but if you turn the key off the back on you will get instrument lights and it will restart. I have replaced key cylinder and ignition switch with no change. Is there a relay or something that i should be looking at. Any help or suggestions would be great.

 

[08GT500]

Hi, Sounds like an EEC Relay issue to me. If you’re losing 100% percent power, (engine stall & Dash Power) while Driving, Key-switch replaced, I’d be looking that direction.
Take the opportunity to clean your Battery terminals and verify all of your Grounds are solid, Battery to EEC, Battery to Block, Block to Chassis Strap.
Replace wiring/connectors that you may have been putting off (if any) or appear any less than optimal. T.Moss drafted up an easy to understand layout of the basic electrical System. I’d added the link below.
Any questions, don’t hesitate.
Good luck!

http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

 

[Durb]

Hi, Sounds like an EEC Relay issue to me. If you’re losing 100% percent power, (engine stall & Dash Power) while Driving, Key-switch replaced, I’d be looking that direction.
Take the opportunity to clean your Battery terminals and verify all of your Grounds are solid, Battery to EEC, Battery to Block, Block to Chassis Strap.
Replace wiring/connectors that you may have been putting off (if any) or appear any less than optimal. T.Moss drafted up an easy to understand layout of the basic electrical System. I’d added the link below.
Any questions, don’t hesitate.
Good luck!

http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Thanks you very much

 

[08GT500]

You are very Welcome!