Mk111 turbo won't start

[Anushamoon91]

Ok here's the deal. 1987 mkiii turbo won't start. We got this car a few years back and it ran just fine but needed a few parts suspension wise so was parked until we could afford it. So pulled it out a few weeks ago. Replaced the battery = nothing. So jumped it off and starter was bad so replaced that but now still won't crank and we tried to manually crank and nothing. Disarmed the security system that was recommended by a friend but still nothing. When you depress the clutch and turn the key you hear a thunk and that's it. Any suggestions?