Firing from coil to cap

Tiny
THRACING
  • MEMBER
  • 1994 DODGE DAKOTA
  • 5.2L
  • V8
  • 2WD
  • 120,000 MILES
My vehicle listed above Magnum will not start or fire when cold if the coil wire is all the way pushed down on distributor cap, but if I pull the coil wire off the cap and have it just hovering above the post that it goes on it will fire and start right up. But if I push it back on it will shut right off. Now after it warm up a little I can push the coil wire on and it will run fine start up good, but let it sit couple hours and it will backfire, sputter act like it going to fire but no start. Take coil wire back off the cap leave just off post on the cap and it will start right up run perfect. Will not start if coil wire is all the way on cap. Changed wires cap distributor coil. What is causing this to happen?
Thursday, March 4th, 2021 AT 8:36 PM

6 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,700 POSTS
Hi,

This may sound crazy, but what I think is happening is this. When the spark has to jump (partially removed), it creates a hotter spark. I have a feeling the coil is weak.

Here are directions for checking the coil. The attached pic below includes the resistance specifications.

__________________

1994 Dodge or Ram Truck Dakota 2WD V8-318 5.2L
Component Tests and General Diagnostics
Vehicle Powertrain Management Ignition System Ignition Coil Testing and Inspection Component Tests and General Diagnostics
COMPONENT TESTS AND GENERAL DIAGNOSTICS
NOTE: The ignition coil is designed to operate without an external ballast resistor.

PROCEDURE
1. Inspect the coil for arcing. Test the coil according to coil tester manufacturer's instructions.

- Arcing at the tower will carbonize the nipple, which if it is connected to a new coil, will cause the coil to fail.

2. Test coil primary and secondary resistance. Replace any coil that does not meet specifications. Refer to the Coil Resistance chart.

3. If the ignition coil is being replaced, the secondary sparkplug cable must also be checked. Replace cable if it has been burned or damaged.

4. If a secondary cable shows any signs of damage, the cable should be replaced with a new cable and new terminal. Carbon tracking on the old cable can cause arcing and the failure of a new coil.

___________________________________

If the coil is bad, here are the directions for replacement. Pic 2 correlates with these directions.

__________________________________

1994 Dodge or Ram Truck Dakota 2WD V8-318 5.2L
Procedures
Vehicle Powertrain Management Ignition System Ignition Coil Service and Repair Procedures
PROCEDURES
Ignition Coil Location

pic 2

REMOVAL

1. Disconnect ignition coil cable from coil.
2. Disconnect engine harness connector from ignition coil.
3. Remove ignition coil mounting screws. Remove coil.

INSTALLATION

1. Install ignition coil to bracket on cylinder block with mounting screws.
2. Connect engine harness connector to coil.
3. Connect ignition coil cable to ignition coil.

_______________________________

Let me know what you find or if you have other questions. Also, note there is a pickup coil in the distributor that may be going bad as well.

Take care and God Bless,

Joe
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Friday, March 5th, 2021 AT 8:50 PM
Tiny
THRACING
  • MEMBER
  • 4 POSTS
Okay, I got a pick up coil and distributor from lkq but it could be bad too. I will get new coil and pick up coil. Hope this fixes it don't know what else do. It will all be new then except crank sensor.
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Saturday, March 6th, 2021 AT 6:07 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,700 POSTS
Hi,

Are the coil and pick-up already new? If they are, let me know. Also, the title of your post says firing between coil to cap. You aren't seeing any spark jumping between the two, correct?

Let me know.

Joe
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Saturday, March 6th, 2021 AT 6:18 PM
Tiny
THRACING
  • MEMBER
  • 4 POSTS
Yes, I see fire but the only way it will start is if the coil wire is out the cap but close enough to the cap where it goes on at to spark to the cap. It will run but put it all the way on the cap it won't run period at all are even try to start.
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Thursday, March 11th, 2021 AT 11:26 AM
Tiny
THRACING
  • MEMBER
  • 4 POSTS
It will start and run like the picture, but put it on it will not start or even act like it will. But after it warms up and runs for awhile you can put it on and it will keep running and cut off, start right back up. Let sit for hour start right up let sit over night are few hours wont do anything unless you put coil wire back like picture. I don't get it going to test coil now and after warms up see any difference.
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Thursday, March 11th, 2021 AT 11:31 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,700 POSTS
I know you replaced the distributor, but has the rotor been replaced as well? Making it jump like that creates a hotter spark. Something is shielding the power at some point.

I have another question. Does the coolant temp gauge work properly? We may have an issue where the ECT is causing the fuel mixture to be too rich which would require a hotter spark to burn. It's a theory at this point.

Joe
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Thursday, March 11th, 2021 AT 2:54 PM

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