The car runs fine, in the morning it will start right up but if I turn the engine off and take the key out I have to wait a good 10 to 15 minutes before it'll start again. Today I discovered if I turn the key one notch over but don't take it out the car will start up just fine. Not sure what this means, if anyone can help or give advice as to what I need to replace to fix this problem it would be very much appreciated.

Also I want to increase my MPG as much as possible, here soon I'll be commuting pretty far so saving gas would be great. I've looked into turbo's but I'm not sure the engine can handle it. It currently has a D15B2 engine 1.5 everything stock. Recently changed the head gasket and all the valves, timing is spot on, needs a valve adjustment but I'll be taking care of that next pay check.
Thanks.(:

 

Resolder the main relay (see the DIY forum).

Check the key switch by pulling the brake handle up and watching the "BRAKE" light on the dash while you're trying to start but it won't. The light should stay lit all the time while cranking.

 

I had the same issue & installed a new Main Relay. A lot of guys are repairing them But it was easier for me to just buy a new one & install it. I guess it depends on your money situation. One thing I know is NEVER install an AIRTEX electric fuel pump. Mine lasted a few months.
On our 90 with the same engine with an automatic we get 29-37 mpg. Depending on how hard we push it. But avg about 32 mpg. I'm not sure you can get much more from this engine vs cost. If you find a way please PM me.
These are great little cars that run pretty good. Our 90 Civic will run over 100 mph on the flat. That is moving for a small engine. They handle like a Go Cart solid & stable.