My 351 F250 has hardly any spark the only time it tries is when I stop cranking it. I have replaced plugs wires distributor cap and rotor, had the ignition module checked and it is fine and I put a new coil in. What could my problem be?

 

If I understand your issue right you might want to check the ignition switch itself.

Power to coil key in "run" position but week or no power to it in the "crank" position, not an uncommon problem with that year.

 

Okay where is the ignition switch located and what are the instructions on replacing it

 

You need to check at the + (POS) side of the coil while someone cranks the engine. If the test light lights with the same intensity as if you hook it to the battery while cranking then the Ignition switch is OK in the start position. If not the Ignition switch is located on top the steering column down near the floor board. You remove its plug and then it has two screws holding it on. You may want to drop the column down while you do this to get at it better.

If the test light lights OK then check on the other side of the coil and see if you have power there. If so you may have a bad PIP sensor inside the distributor.
If not you may have a bad plug that plugs onto the coil.

 

What exactly is the PIP sensor and what do you ask for at the auto parts place, and how do you replace it

 

the PIP is the pickup coil, its located in the distributor itself and you have to take out and disassemble the distributor to change it ( at least you do on a 1990 with a 351)

 

It stands for Profile Ignition Pickup. You have to remove the distributor from the vehicle and disassemble it to replace the PIP. I had the Ford garage replace the PIP in my '88, they charged me right a hundred dollars parts and labor when I carried just the distributor in to them. That was about 8 years ago, it would be higher now. The Ford garage should be able to test the distributor before tearing it apart to see if the PIP is bad, they did mine.

Many people would just tell you to get a rebuilt distributor, I wouldn't as rebuilt distributors have a terrible reputation.

 

The PIP or CMP sensor is made up of a hall device and the permanent magnet and is inside the Stator Assembly that replaced the old Pick-Up coil in the old Duraspark II Ignition system. There is not a coil in the Distributor of the TFI Ignition system.
To replace the PIP sensor you have to replace the Stator Assembly. As said above you have disassemble the distributor to replace the Stator Assembly.

PIP: Profile Ignition Pickup.
CMP: Camshaft Position.
TFI: Thick Film Ignition. An ignition module comprised of a custom integrated circuit, Darlington output device and associated thick film integrated components.


The Stator Assembly:


A setup for testing the PIP Sensor:




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Okay I used the test light on the coil and I have power the the positive side but on the negative side with the key on the light is very dim and it stays the same when key is turned on the only time it gets a little brighter is when you let off of the key. What could this be

 

Do you mean by the second "on" that this is the state while it is cranking?

 

Yeah while cranking the light is still very dim until the second you stop cranking it flashes bright

 

Try unplugging the plug on the distributor.
Turn on the key.
Does the test light now show bright on both sides of the Ignition Coils plug while plugged onto the Ignition Coil?

 

What plug on the distributor are you referring to? Just the one going from the cap to the coil?

 

This Plug:


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Okay the plug didnt look the exactly the same but it was the only wires going to the distributor so I figured it was the right thing so I unplugged it and the light was bright after it was unplugged, so what does this mean?