[62131]

I have replaced my coil for the forth time now in three years. I just made a trip to the nationals in Knoxville and on my return trip my car started to develop a miss and after a few  minutes it cleared up. We traveled another thirty to forty miles and it started missing again after a few minutes it cleared up again. After I got home I thought I would check all connection and found nothing loose. As I was checking voltages across the coil and from the ignition switch I noticed a drip from my coil wire as I investigated it was oil coming from the coil. I have a Mallory Unilite system with the coil and ballast resistor mounted in a horizontal position. I have always thought that the heat from the engine caused the coil to over heat but I have raised the coil well above the manifold to let air circulate around the coil.
Can anybody tell me why a coil would over heat or if they experience this problem. I understand how a coil works the only thing I'm not sure of at this point is what my plugs are gaped at. 

[themoose]

I have a Mallory Unilite system and I have been using the 29219 coil which does not require a ballast resister and have not had any problems with it getting hot. As for oil leaking out I have seen that condition on horizontally mounted coils on a couple of occasions but replacement but not any repeated failures. Not all ballast resistors have the same value so make sure you have the correct one for your coil or better yet just get the coil I'm using and do away with the resistor.
http://mallory-ignition.com/ignition-electrical-and-wiring/ignition-coils/electronic-canister-style-coil.html

Moose

[62131]

Moose


I used the 29219 coil when I first finished my car. It lasted about 8 months, it would over heat and then the engine would not start very easy, after it cooled down  it would start just fine. You can put a new coil on it and it starts first time every for a while then the coil starts to break down and is hard to start again.
I was broke down on the road and purchased an after market coil with internal ballast resistor just get me home from Advance and it lasted about 6 months, I picked up a cheap coil from the swap meet with a ballast resistor attached to it and that's what I just changed out.  Mallory says use a coil that has 1.4 ohms on the primary with ballast resistor of .75-1.0 ohms or their coil with a internal resistor. They also told me to run their coils on a 45 or a 90 degree angle to keep the oil where it was designed to be.

[themoose]

Have you ever considered an epoxy filled coil? If your eating coils on a regular basis and your sure that the input voltage on the primary side is within the range of the coil requirements  then you need to start checking the secondary side of the system. High resistance on the secondary side of the ignition system could be caused by incorrect spark plugs,  plug gaps that are too wide or faulty spark plug wires with high resistance or even a cap or rotor. Any one of these conditions or a combination of them could definitely cause a coil to overheat.

Moose

[EDNY]

Kinda curious...have you monitored the voltage going into the coil after the ballast?   Not sure but I think the coils only need about 7 or 8 volts...anything more & continuous could cook it.  The ballast is bidirectional but maybe yours is not dropping the voltage correctly?

Moose....could he mount a separate voltage meter (digital) specifically to monitor coil input voltage while driving around?

Ed

[themoose]

Moose....could he mount a separate voltage meter (digital) specifically to monitor coil input voltage while driving around?

Yeah that's a good idea Ed. That way he could monitor everything that's going on like spikes in the charging or fluctuations that might indicate a intermittent engine/distributor ground which could also cause changes in resistance at the coil and cause it to heat up.

[62131]

I've only checked it with a test light so far, tomorrow I plan on hooking up my digital meter and checking the voltages again, and testing my module, checking the resistance on my ballast resistor. What's you're opinion a coil laying horizontal?   

[themoose]

What's you're opinion a coil laying horizontal?

A number of production cars back in the day had oil filled coils mounted horizontally without problem so it really shouldn't be an issue...Of course parts aint what the used to be    

Moose
 

[62131]

That's what I think. It really should not matter what position It's mounted at?

[cocobolo]

Sorry to hear of your coil troubles.

Trying to remember back when I actually used to use a coil, and I think the factory engines - from what I recall - always had the coil mounted vertically.  They were usually mounted on the back of the intake manifold somewhere so I don't think it would be heat from the motor that would be the root cause of your difficulty.

I would call Mallory directly if I were you and get them to email you everything they have on your system so you can check it out correctly.  I always find it best to go directly to the source in a case such as this.

I cannot remember ever having had coil troubles in all the years I have messed with cars.  Just about everything else has gone wrong electrically, but not a coil.

[themoose]

Ford (bite my tongue) has often mounted them horizontally and I have even seen some cars with them mounted upside down. There really should be no reason for them to leak if they are constructed properly.

Moose

[EDNY]

Ford (bite my tongue) has often mounted them horizontally and I have even seen some cars with them mounted upside down. There really should be no reason for them to leak if they are constructed properly.

Moose

Which brings out a good point, is the coil mounted in a high vibration area, weak clamp...or is the hold down clamp too tight & crushing the coil.

[cocobolo]

Ford (bite my tongue) has often mounted them horizontally and I have even seen some cars with them mounted upside down. There really should be no reason for them to leak if they are constructed properly.

Moose

Yes, I think they had coils mounted horizontally way back when I had a '50 Meteor (Canadian Ford).  And as you say, if the coil is built well, why should it fail?

Just checked on my original '35 Chevy, and it's mounted upside down!  For all I know it's probably still perfectly good.

[62131]

Well I checked the resistor today with my digital meter, a reading of 3.8 ohms the coil 1.8 ohms, went and ordered a 29217 Mallory coil and a  Mallory #700 resistor. I hope I didn't damage my module, I guess I should have checked all my component's before installation. Learned another lesson I guess.

[cocobolo]

Well I checked the resistor today with my digital meter, a reading of 3.8 ohms the coil 1.8 ohms, went and ordered a 29217 Mallory coil and a  Mallory #700 resistor. I hope I didn't damage my module, I guess I should have checked all my component's before installation. Learned another lesson I guess.

Well honestly if you bought them new you shouldn't have to check them, should you?  That's the job of the QC department at Mallory.