2004 GMC safari won't start. The van loses spark. Any help is much appreciated.

Most cases in none spark is the distributor cap and rotor is damaged or old. also the spark plug wires need to be constantly changed as the dampness super affects them. change your wires plugs, distributor cap and rotor runs you about 128$ canadian the last time i looked and it should fix the issue.

There is no spark from the coil to the cap. Changed coil wire, coil, and crank sensor. Sometimes it will start and run fine for a half hour or so and shut off and may not start for a few days. Thanks for your help any other suggestions will be much appreciated.

This sounds like the ignition control module is shot then. The ICM is that little box attached to the coil with the aluminum heat sink. replacing this should fix the issue. ill direct you to a link that should help you solve the problem if this does not work it also tells you how to diagnose with out just throwing the money at it. Also to boot if you ever have problems wher ethe door locks keep going nuts on you such as random locks and unlocks That is your battery gone bad. http://easyautodiagnostics.com/gm/4.3L-5.0L-5.7L/ignition-misfire-diagnostic-tests-1

rockauto.com is your best bet for good priced parts in the states and they offer the widest range of parts for older vheicles.

Thanks much. I will give it a try.