Question about 1987 Ford F 250
I HAVE CHANGED EVERY ELECTRICAL PART I COULD FIND ON THIS TRUCK EXCEPT THE DISTRIBUTOR AND IT WILL STILL NOT FIRE. WHEN THE MOTOR IS TURNING OVER THERE IS NO SPARK BUT WHEN YOU LET UP ON THE STARTER IT SPARKS. WHAT AM I MISSING HERE?
If module is fine try replacing pick-up coil located in distributor.
Posted on Nov 11, 2008
Try connecting the ignition system's B+ straight to the battery's positive terminal. Possible reasons are:
1. starting drawing too much current nothing left for the ignition system;
2. ignition switch/connectors, joints corroded/loose.
The ignition system's B+ is the switched +12 when the IGN switch is turned to ON. When you crank the engine this normally would go down. If for any of the 2 reasons above this could go to zero hence no spark.
If you are using the contact point style, the IGN B+ is the + terminal of the IGN coil. If you are using the electronic module type, then the IGN B+ would be one of the wires going into the module. To verify, a DVM would be effective. This would also display if the IGN B+ goes down when cranking. When where the IGN B+ is connected to your system, hardwire an insulated auto wire from that point straight to the battery. This would simulate IGN ON condition, as if the ignition switch is set to the ON position. With the system's IGN B+ tied directly to the battery's positive terminal, crank your engine and verify that there is spark. If yes then the solution could be:
1. defective ignition switch;
2. loose/burnt connectors/junction joints.
An easy way around is to use a relay to switch/provide the IGN B+.
Hope this be of initial help/idea. Pls post back how things turned up or should you need additional information.
Good luck and kind regards.
Thank you for using FixYa.
Posted on Jun 04, 2008
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Posted on Jan 02, 2017
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