I have a 78 351M and I can not get any spark from the plugs. I put a new plug new plug wire the cap and rotor are new. I am getting power to the coil and I have tried two different coils but I am not getting spark from the plugs. The truck has been sitting for a while I drove it to where it sits and it ran great when I parked it. any ideas would be helpful I will try anything thanks for the help.

 

Have you checked the pickup coil in the distributor?They dont die often but seems like they go all at once.

 

What do you mean you are getting power to the coil?
Do you mean you are getting 7 or 8 volts on the ignition coil when the ignition switch is set to ON; and getting 12 volts on the ignition coil when cranking the ignition switch?

Make sure that the rotor on the distributor rotates when you try to turn over the engine. Just remove the distributor cap and ground the ignition coil secondary wire to the engine block and crank the engine for a second and see if the rotor had moved or rotated. If the distributor rotor rotates then you can analyze further by checking the ignition module or swapping it with another one. Check the wires going to the ignition module.

Don't overlook the fuses.

 

when I say I am getting power to the coil I mean that the wires to the terminals on the coil show about 7 volts when the key is on but no spark from the coil wire or at the plugs. I tested the coil wire and it did not spark.

 

You won't get any spark by just putting the Ignition Switch to ON.

The primary winding in the Ignition Coil receives that 7 volts and converts it to thousands of volts in the secondary winding inside the Ignition Coil. The thousands of volts will not be released until the tach/negative wire of the Ignition Coil is (temporarily disconnected). The action of the distributor shaft, distributor rotor, distributor stator assembly or points, Ignition Module determines when to (temporarily disconnect the tach/negative connection to the Ignition Coil) so that it will release the thousands of volts stored in the secondary winding of the Ignition Coil to correspond to each piston at or near TDC.

You have to crank the engine so that it will spin the distributor shaft and that is where the turning on/off of the tach/negative side of the Ignition Coil happens and then the thousands of volts is released in the form of sparks. Use an adjustable gap spark tester with a metal clip when testing for sparks. Just putting the spark plug wire near the engine block, it might be too far for the spark to jump and it is hard to test it by yourself. Having that adjustable gap spark tester allows you put it in a convenient place so you can see while looking from the driver seat while cranking the engine.

 

I was cranking the motor but the starter solinoid is out so I have been jumping the solinoid with the key in the ignition and it turn on. It sounds like my problem is in the distributor. I tested the coil wire with a plug and someone else cranking the engine. From what I have heard so far I am thinking its the distributor. let me know what you think.

 

If you have the orignal style ignition have the ign box checked at an auto store or try a replacement.