has to cool down before restarts

where is the diagnostic plug on a 1990 plymouth voyager?
is it inside the engine or under the dash?

my email is patrickoverturf@ymail.com

Where is the body control computer located? Is there any other computer modules on this van and where are they located?

I noticed my breaks on my van were getting loose. Then one day they went out. I mean pedal all the way to the floor and nothing. There was no break fluid in there so I had some put in, still nothing. I had the breaks bled all way around, still nothing. I then had a naster cylinder put on and still nothing. I don't know what's wrong...

Tried checking the o2 sensor, fuel pump, fuel filter, fuel injections system, did an oil change.

'89 3.0 engine,repairthecoolanttuberuns through the block

how to replace a fuel on the van taking it a part and putting it back together.. thank you