Intermitent Starter issue Options

[914itis]

My starter was fine, until the weekend.

The weather was nice and I decided to take a drive; started fine. when I got to my destination, I turned the key and it attempted to start the car and the battery cuts off.
I have a 60 amp fuse on the red wires going to the battery, check the fuse it wast toast. I replaced the fuse and it blew it instantly as soon as I turn the key on.
Since there is a wire coming from the the main fuse that I installed from the battery to my amp and air horn, I isolated the wire and replace the fuse again the car starts fine.

When I got home, I installed a dedicated fuse for that amp wire.

Since then, the starter becomes a hit and miss. sometimes starts on the first try, sometimes i have to turn the key on and off before the starter spins. Sometimes it would start spinning for a short time and stops before the engine can start.

The starter positive wire is straight from the battery.
I know that there is an issue with the 74's where a relay is installed, but why would it burn the fuse to begin with?

All my grounds are intact.

Any ideas??

[timothy_nd28]

I'm not familiar with the Djet start circuit setup. The start wire still runs thru the relay board via the 14 pin connector and out the 12 pin connector. It may be worth removing both connectors, and re-seating them 20-30 times each. This way, the connection will self etch thus eliminating any problems (if you have any here).
I think you already isolated your problem, by putting the amp on its own circuit. But, I think the damage is already done with the ignition switch. To verify, pull off that 14 pin connector, and measure for 12vdc at pin 1 on the connector (not pin 1 on the relay board) while the key is in the start position. If you do see 12vdc while in the start position, try jiggling the key or whacking on the steering column, while watching for any voltage drop at the meter. It would also be good to ohm out the relay board, pull off the 14 pin and 12 pin connectors, and put one meter lead on pin 1 (on the 14 pin socket on the relay board) and the other meter lead on pin 6 (on the 12 pin socket on the relay board) you should measure close to 0 ohms. You may wanna double check the bypass job on the seatbelt interlock circuit. I have seen PO's use a wire nut to tie the 2 yellows together. I'm not a fan with this type of repair, just for the fact that the wire nut could come off and cause a short. I know it is a pain in the ass to solder these two wires, due to their size. Also, if it is soldered, it's easy to have a cold solder joint if the soldering iron was undersized. It's worthy to take another look at that connection. All and all, I'm leaning towards the ignition switch being the culprit.