Weird electrical/ ignition barrel problem?

[GRPABT1]

Hey guys I've got a problem with my sierra that is annoying me. It's a 1989 sierra with a 1988 mk1 Gti swift twin cam motor. Lately it has been temperamental in starting. Although the key will turn all the way around to start for some reason I get absolutely nothing. No accesories no headlights, nothing. Then I can try again later and it's all fine. Doesn't seem to relate to cold or hot starting either.

I have recently installed a bigger (700cca) battery and yesterday replaced the main starter wire also. Other than that I have checked all the fuses I could find and traced the wiring where I could and can't find any obvious abnormalities.

So what do you guys think it is? Could it be electrical or simply something like a worn ignition key or barrel (cause is is a fair bit worn looking)?

Thanks in advance for you input guys.

[lump_a_charcoal]

Try to get to the switch on the back of the barrel... I have not seen a suzuki one but I am guessing it is similar to a datsun - just check the contacts are all ok.

[GRPABT1]

So just take the barrel out if I can and give the contacts on the back a cleanup? Sounds easy enough.

[GRPABT1]

Checked the wires coming out the back of the barrel and they look ok, a little dusty but ok. I unplugged the connection to the wiring harness and it looks fine and traced the harness back a little which also looked fine. I guess I will wait till it happens again (probably at 5am before work) and then I'll have a play with those wires again to see if it works.