The main fuse blows every time the engine is shut off. The one by the rad under the hood.

I was installing a Tach. I used the white on the coil furthest from the dash. for the tach wire. I grounded my black wire, used my ECM IGN (on the fuse block) fuse for the Ignition and GUAGES (on the fuse block) for my lighting The car started and it worked fine. I turned it off and the main fuse blew ( i didnt know this) had it towed to a shop and they did some work on it.. they couldnt figure it out, they narrowed itdown to a few things.. I'll get the wiring diagrams and elaborate on this in a later poset, i need some help, the car runs amazingly the fuse never blows on startup only on turning the key to the "off posistion" if the car stalls it doesnt blow..

could anything in my fuel system be surging>?

Thanks in advance

 

btt

 

btt

 

That fuse by the radiator is not the "main fuse." It is the fuel pump fuse. I don't know how close to 20 amps the draw on the fuel pump is and I don't know what the draw on the tach is, but I would unhook the tach, and see if the problem goes away. If it does, hook your tach to a switched on power source elsewhere. You might need to run a relay that the ignition switch turns on. Then power up the tach by the relay with an inline fuse for protection.

 

So could it be the fuel pump relay causing the surge? or the fuel pump itself