My car keeps killing coils. Many years ago it was upgraded to a Duraspark 2 ignition system. The original coil had been on there for a least 10 years, and it failed because it leaked. At the time I was on the road far away from home, and the parts store only knew the coil that was stock, so I went with that. I got two of them and each of these only lasted a few days, which was enough to get me home. I noticed that there was molten metal on the ends of the terminals when they failed. I put on a Duraspark compatible Taylor coil (718205), and it just failed the other day. It lasted around 4 months. All of these coils had printed on the canister that they need a ballast resistor. I hadn't put one on because of lack of time, unfamiliarity with the wiring, and a lack of knowledge about electronics. I've started to dig into the wiring and I found that the wiring pretty much matches the diagram I attached. The ignition module is the one with the blue grommet. The white wire is cut off and doesn't lead anywhere. The wiring is different from the diagrams that include the ballast resistor, and it's not clear to me how I'd add one. Another issue I'm running into on parts sites, is that's there is almost no information on what coils require a ballast resistor and which ones don't. A few have it printed on the coil, while others show nothing. I'm also confused about which coils and ignition modules are meant to go together. If anyone has any input into this, or suggestions of how I should go at this problem, it would be appreciated.
I'm not sure how your first coil lasted 10 years. It must have been a type of coil that did not require a resister. All Ford OEM 12 volt ignition systems require a ballast resistor. Based on your diagram your resister wire has been eliminated. If your ignition system had the required resistor in place your Taylor coil 718205 as well as the others would have lasted longer. I have attached a correct Duraspark wiring diagram for 1974. The resistor should be between the run side of the ignition switch and the battery side of the coil. When the ignition switch is in the run position, the voltage via the ballast circuit drops to approximately one-half the charging circuit output. Good luck with your repair.
Virtually any coil for stock system will require a ballast resistor. Coil resistance does vary from system to system but most are interchangable. A Duraspark coil used on a points system would likely cause premature points failure. A points coil used on Duraspark will not deliver full spark potential. The E-core coil does not require a resistor, BUT that's when used with the complementing system that limits coil dwell time. Your coil failures are almost certainly due to over heated coil(s), no doubt due to lack of current limiting(ballast) resistor.
I've been sitting around waiting for the parts to arrive. I talked to my dad since he did the install, and said it was based on instructions from this page: https://fordsix.com/ci/DizzyCompare.html So, the diagram I posted is correct. The distributor is a Duraspark with a magnetic pickup. The coil was stock. I guess I was just lucky that it lasted something over 10 years. I have an MSD 0.7ohm ballast resistor and I'm not sure where to put it along the red wire. According to the diagram, when running the current is coming from the ignition switch. I was thinking before it gets to the junction, maybe? The diagram for the painless Duraspark wiring harness looks very similar to arrangement I have: https://www.painlessperformance.com/Manuals/30812.pdf They have it between the coil and the junction. Would this be more correct?
I would not put any form of coil current limiting device before the switch.. ideally it should go between the switch and the coil itself as that's where the voltage limitation is required. Why all this OEM coil resister requirement hubbub? Just buy a hotter aftermarket non-resister coil and your wiring/resister issues will disappear. The duraspark disty is a decent unit for the price(I and many others have beaten the snot out of them many times over) but any OEM box or coil connected to it is only going to limit the parts interchange and overall tuning capability once the timing curve is better optimized for that particular engine/chassis. Add hot coil and fine wire platinum/iridium plugs and forget about it for a while. Engine efficiency and overall power will improve.
Well, for now I just want to get the car up and running and on the road again. I would be interested in a hotter non-resister coil for later. Do you have any suggestions for some good brands to look at?
Had the resistance wire remained in the circuit, coil(s) would have been fine. The brown wire feeding from I terminal on solenoid provides full battery voltage while cranking, should remain connected to coil +. As wired coil and module receive full battery voltage at all times.
I finally had a chance to replaced the coil and add the resistor, and it still isn't getting any spark. So I took a closer look at the distributor and I found the real problem. The purple wire has detached from the pickup coil. I'll have to see if I can reattach it, or replace the pickup if that fails.
Chances of a successful(at least long term) reconnection to pickup are approx zero & none. Wire was probably dragging inside of dist, so it had to flex/move when vacuum advanced. Seen a few condensers in points system suffer same fate.
A word of caution regarding that plastic fuel filter; I had one deform at the base of the nipple where it connected to rubber and spray fuel all over engine bay. The car stalled coming over a bridge n left me stranded. Lucky I was only few blocks from home -- had to go on the hook home. I was fortunate the car didn't catch fire. Not intending to "Jack the Thread" -- Along w/ getting the Dizzy issue worked out -- Consider dumping that filter for metal unit.
I got the pickup coil replaced, and now the timing appears to be way off. I've been struggling to get a good reading with a timing light. Between the alternator and the water pump, there's almost no room to see the balancer and get the light down in there. I think I may have to take off the alternator to get a good view. One thing I did do was to crank the engine until the rotor was pointed directly at the terminal for the #1 cylinder wire, and the balancer was at 25 degrees BTDC. This will be my first time messing with timing. I'll take note of the fuel filter.
Yeah it's a bear seeing timing marks. If you've marked balancer with white paint on timing marks(10, 20 etc), then stick your ear down on the battery hold down bolt while viewing, you might just get a glimpse. For a stock engine, old time method of advancing timing till it pings on light acceleration, then back off slightly is often as good as any method.
I've done some adjustment now that it's stopped raining. It was impossible to see the balancer with the light when I was just cranking it over. I just couldn't register 1 flash every few seconds or so. So, cranked it to TDC and rotated the distributor to point to the #1 wire. This brought me to 12 degrees BTDC and the engine would finally idle. It didn't like 12 degrees, and it would die when I gave it some gas. I gave it some test rides at 6-8 degrees. It has more power at 6 degrees, but the engine has a slight stumble in drive at idle for some reason. It seems somewhat worse at 6 degrees. I need to do something about mounting that coil. At one point it slid back and jammed the throttle open.
