Cranks but will not start

Hi, I have a 1990 ford tempo 4 cyl with a new battery and it was tuned up 5t months ago. When I turn the key to start it nothing happens no click, no turn over, nothing. The lights work and the radio works. Can you tell me where the starter is and any ideas as to what could be causing this.
Also my heater heats up and blows hot air after idling for a few minutes in the cold weather but when I start to drive the temp gauge goes down to cold and it blows cold air.
Any suggestions would be great
thanks

I was originally having a problem with rough idle and occasional stalling at a stop or from switching from drive to park all after the car had reached operating temp.I have replaced, plugs, wires, MAP sensor, Idle air control valve, throttle position sensor. I hadnt drove it in a few days and came out to start it and t wouldnt start, it turns over and cranks but no start.I do not hear the fuel pump hum and I pulled theline off the fuel filter and got no fuel, I also checked for spark by pulling one of the wires and inserting a plug to see if I got spark and nothing. Inertia swith is not triped and I also tried replacing the ignition switch to someones advice to no avail. Somewhere I was reading had suggested a possible culprit being a camshaft position sensor. Well I bought what should be the correct part but can not for the life of me find where it is located on the car. Any insight or help is appreciate

Inertia switch has not been tripped. Would the ignition module or something with th distributor be a potential cause of the problem?

I have a 1990 ford tempo that will not start. It will turn over good but won't start. I have replaced the fuel pump, starter, battery, spark plugs, ignition module, coil, cyclender, what else can I do to get it to run?