Correct Coil Resistance

[Old Henry]

I have been chasing an intermittent stumbling of my engine when under load and have replaced or checked out all ignition components and am now to the coil. I got this diagram from some authoritative source and have always suggested it to others. Primary coil is in the range of the diagram. But when I just checked the resistance of my secondary coil in my stock 47 Ford coil that Skip Haney rebuilt I only get 6,130 ohms, not the 10-11,000 ohms per the diagram. Is that low enough to affect the spark or not? Is the coil bad and needs replaced or just marginal?

[fourfords]

Call Skip.

[G.M.]

Originally Posted by fourfords

Call Skip.

You got it. Get the correct coil rebuilt and forget these abortions. G.M.

[Lawrie]

Henry, I chased a miss or skip as you call it on the 33 for ages,turned out to be two loose valve guides and those two let oil into the cyl and fouled the plugs ,ran like a train while burning along at 50mph but slow and speed up and the miss was there.
Lawrie

[Old Henry]

So far I've replaced all of the spark plugs, the points, condenser, rotor, and coil resistor. All I can think of that's left is the coil so I'll call Skip tomorrow and see what he thinks. I'll also PM Bubbas Ignition since he hasn't commented to see what he thinks of the low resistance secondary coil.

[Terry,OH]

Sponsored Links (Register now to hide all advertisements)

Using the resistance of the coil Sec./Pri. will give you the approx. turns ratio. For both of the pictured examples it is about 13,500/1 . If Skips coil has a primary resistance of 0.5 Ohm you wind up with 12,300/1 . With 3 to 4 volt input, that's an approx. max. output of about 35,000V should be hot enough for a flat head.

[Old Henry]

Originally Posted by Terry,OH

Using the resistance of the coil Sec./Pri. will give you the approx. turns ratio. For both of the pictured examples it is about 13,500/1 . If Skips coil has a primary resistance of 0.5 Ohm you wind up with 12,300/1 . With 3 to 4 volt input, that's an approx. max. output of about 35,000V should be hot enough for a flat head.

Thanks. Bubba also said it was OK. So, I'll put the coil back in and continue looking elsewhere. Sure hope I can fix it before my 5 day trip on the Pacific Coast Highway next week.

[Bored&Stroked]

Originally Posted by G.M.

You got it. Get the correct coil rebuilt and forget these abortions. G.M.

He got the coil from Skip in the first place.

[keith oh]

Henry, Is this the same problem that you said leaving the hood open a bit while moving helped some?

[Old Henry]

Originally Posted by keith oh

Henry, Is this the same problem that you said leaving the hood open a bit while moving helped some?

Not really. It is a very minor form of that same problem that has plagued me for many months. It never stops me dead like the other problem did, just "flickers" or "stumbles" with a slight loss of power with hard acceleration or hill climb. And the worst part, of course, is that it is intermittent, not always, just once in a while. That's what makes it hard to diagnose and fix. Fortunately, most of the time when I'm just going along at any speed with normal throttle it is either hardly noticeable or doesn't exist.

Right now I'm driving with my timing light taped to the cowl so I can see its flashes through the windshield while I drive. The pickup is on the high tension wire coming out of the coil. I mainly did this to confirm that it is a spark problem, not a fuel problem. Sure enough, when the engine stumbles so does the light flashes.

[flatheadmurre]

Originally Posted by Terry,OH

Using the resistance of the coil Sec./Pri. will give you the approx. turns ratio. For both of the pictured examples it is about 13,500/1 . If Skips coil has a primary resistance of 0.5 Ohm you wind up with 12,300/1 . With 3 to 4 volt input, that's an approx. max. output of about 35,000V should be hot enough for a flat head.

Pri/sec resistance doesnt give you the secondary voltage.
To be able to calculate output voltage you need the turns ration of the coil.

[JSeery]

Sounds like a loose wire or connection unless it is heat related. Or a vacuum / carb issue on the advance. Are you running the original vacuum only advance distributor?

[Old Henry]

Originally Posted by JSeery

Sounds like a loose wire or connection unless it is heat related. Or a vacuum / carb issue on the advance. Are you running the original vacuum only advance distributor?

Yes, stock distributor with centrifugal advance retarded by vacuum brake.

It certainly acts like a loose wire so I bypassed all wiring from the battery to the coil with a jumper from the battery to the coil. Didn't help.

[FlatheadTed]

Check the spring loaded contact in the distributor if its a crab ,Ted

[47COE]

Originally Posted by FlatheadTed

Check the spring loaded contact in the distributor if its a crab ,Ted

That spring loaded contact was causing problems for me. Took it out and cleaned both halves of the connection.

Any '47 distributor (rabbit ears or crab) can have that problem.

[Old Henry]

Originally Posted by 47COE

That spring loaded contact was causing problems for me. Took it out and cleaned both halves of the connection.

Any '47 distributor (rabbit ears or crab) can have that problem.

Originally Posted by FlatheadTed

Check the spring loaded contact in the distributor if its a crab ,Ted

I guess I'm not sure what spring y'all are talking about. Is it the strip spring that pushes the contact points together that I just replaced with the contact points? Isn't that the only spring in my distributor other than the one in the vacuum brake. This is the kind of distributor I have:

[Old Henry]

I think I figured out what you're talking about - the terminal that the wire from the coil connects to that has a spring loaded post that pushes against the points plate? If so, I can take that out and check it. I just removed that plate to replace my points and twisted the plate against that post to position it so hopefully it's OK. Distributor was built by Bubba a year or two ago.

[47COE]

Yes, it is the post for the coil wire.

The only reason I found the problem is that it finally quit totally and I found it was open circuit between the coil wire screw and the inside brass plate.

Unscrew the post and then polish the end of the spring loaded pin with emery cloth. You can probably clean up the brass plate with emery cloth too without taking the distributor apart again.

My distributor was serviced by Bubba too and he cleans and checks that connection. But for some reason it still failed. See more (and Jim L.'s response) at:

https://www.fordbarn.com/forum/showth...52#post1152852

[47COE]

Looking at your distributor photo again, it looks like that pin is way off to one side and hardly making contact. Perhaps the photo is of a different distributor?

[Old Henry]

Originally Posted by 47COE

Looking at your distributor photo again, it looks like that pin is way off to one side and hardly making contact. Perhaps the photo is of a different distributor?

That is an old photo of my original distributor that was worn out, not the one Jim built for me. It isn't even all together. You won't find the retaining ring around the points plate. That was the one Jim got in exchange for the one he sent me.

[V8COOPMAN]

Way off.......good eye! DD

[keith oh]

Kinda "smells" like a defective condensor(capacitor)at least if it were on my 35 distributor.

[Lawrie]

I can see a problem in the bottom pic,the split pin on the left points looks like its touching the copper strip on points.
Lawrie

[Old Henry]

Originally Posted by keith oh

Kinda "smells" like a defective condensor(capacitor)at least if it were on my 35 distributor.

Thanks. I thought that too, so have discussed with Bubba's since I got the condensers from him. They test within specs and he said they're fine.

[keith oh]

Good eyes Laurie, it even looks like some discoloration, maybe from a short there.

[Old Henry]

Sponsored Links (Register now to hide all advertisements)

Originally Posted by 47COE

Looking at your distributor photo again, it looks like that pin is way off to one side and hardly making contact. Perhaps the photo is of a different distributor?

The problem with that old original distributor was a worn shaft that allowed the rotor to hit the contacts in the cap. That's why I traded it in to Bubbas for the rebuilt one I'm now using. I just posted that picture with my question in that post to illustrate the type of distributor I was using, not to illustrate the actual current one.

[Bored&Stroked]

If this is your actual distributor, then check the following . . .

Here is the area that Lawrie mentioned - the cotter pin looks loose and could intermittently be grounding out the points - which would cause this sort of issue:

21A-Dist.jpg

[Old Henry]

Originally Posted by Bored&Stroked

If this is your actual distributor, then check the following . . .

Here is the area that Lawrie mentioned - the cotter pin looks loose and could intermittently be grounding out the points - which would cause this sort of issue:

Attachment 243764

That is 47COE's distributor that somehow got from the post he referenced back in September to this post. It's not my distributor although it looks more like the one I'm currently using than the picture I posted that I previously explained.

So, there is no picture in this thread of the distributor I'm currently using in its current condition.

[FlatheadTed]

Henry ,I have at leased on one occasion drilled a hole beside it and ran a wire by passing it ,or pull it out and rubber grommet the hole with a fresh wire ,its the internal spring were you can get problems also .Ted

[FlatheadTed]

Lawry's catch is definitely a potential problem ,Ted

[Old Henry]

Please, people.

What Lawrie saw was a picture of 47COE's distributor in his post back in September, not my distributor. I don't believe that the cotter pin position is causing him any problems as I expect he's been driving his truck for almost two months since then without a problem.

My cotter pin does not hang over the fiber lever as in that picture.

[Floyd]

Before you go crazy, try another coil. Beg or borrow one if you don't have a spare (spare coils and condensers should be part of your tool kit). The remote mounted coil like you have could not be easier to change. I have seen this problem before.
Just an opinion

[Old Henry]

Originally Posted by Floyd

Before you go crazy, try another coil. Beg or borrow one if you don't have a spare (spare coils and condensers should be part of your tool kit). The remote mounted coil like you have could not be easier to change. I have seen this problem before.
Just an opinion

Thanks Floyd. I did that. It didn't help. According to several who have replied to my resistance readings, my coil is OK. It was built by Skip Haney a year or so ago.

[Bored&Stroked]

Another idea hit me - how about the grounding of the engine to the frame? Do you have a dedicated ground strap from a head bolt to the firewall (or something similar in your year car)? If there was an intermittent or dirty ground, these types of problems can occur - especially with rust over the years.

[Old Henry]

Originally Posted by Bored&Stroked

Another idea hit me - how about the grounding of the engine to the frame? Do you have a dedicated ground strap from a head bolt to the firewall (or something similar in your year car)? If there was an intermittent or dirty ground, these types of problems can occur - especially with rust over the years.

Thank you for the suggestion. I actually had starting problems for a long time a year or so ago that I finally traced to that very thing - my ground strap from the engine was loose on the firewall. It's been plenty tight ever since. I checked it again recently with new starting problems that turned out to be a bad solenoid.

[JSeery]

You have the engine grounded to the firewall, might try a ground from the engine to the frame directly, the closer to the battery the better. The best would be the same connection the battery is grounded to. Might at least try a temporary ground connection to eliminate that possibly. If it is starting ok that is most likely not the issue, but it is intermittent, so who knows!

[jake197000]

it seems its not your coil but.over the years ive seen many bad coils that ohm out just fine.make sure your plug wires r plugged in the cap real good they can b tricky.hope u find it.

[meric42]

Just a thought, have you checked you ignition switch for resistance or worn contacts. I have heard of this dropping the low tension voltage to the coil and causing missing problems.

[George/Maine]

You could use a 6 volt coil from and Chevy ply buick any 6 volt coil to test that problem.
Any 6 volt coil doesn't need a resister. only ford used them. You could see if you can pull off the end of dist wire maybe held only a few strands, jump direct to coil from battery. check see if you have a loose shaft in dist, and good air gap of .015

[Old Henry]

I found something tonight that could certainly be my problem.

I took a drive moving my timing light pickup between each sparkplug wire (heretofore it was on the coil output wire). The timing light was firing way more than it should have on the first two wires. As I was moving the pickup from the 2nd to 3rd wire with the engine running I got shocked! I thought, "I shouldn't have got shocked. I didn't touch the spark plug." I finished my drive checking the rest of the plugs that all fired way more than they should have and erratically. So, I had the idea that just maybe it was the spark plug wires. They're fairly new but I put a lot of miles on everything very fast and things wear out.

When I got home and pulled into the garage I left the engine running with the hood up and turned off all of the lights. Sure enough, there were little just barely visible sparks jumping from each plug to the block and from each wire to the conduit where they exited. It all makes sense to me now. All symptoms now seem consistent with leaking spark plug wires.

I'll have a set flown to me tomorrow to put on and bet good money that will fix my problem.

Let's all keep our fingers crossed.

[flatjack9]

Sounds like you've hit the solution.

[Lawrie]

Henry.I got a couple of GOOD shocks from my snap on timing light ,if the pickup slips down on the spark plug wire and touches the top of the plug were the wire goes on,man you get a big shock,
Lawrie

[BUBBAS IGNITION]

Originally Posted by Lawrie

I can see a problem in the bottom pic,the split pin on the left points looks like its touching the copper strip on points.
Lawrie

Not really a side view would show clearance. We ran it on a tester for some time as a final inspection...

[BUBBAS IGNITION]

Henry , WD40 will help insulate those wires , might try it before replacement. Just spray them down and wipe off the excess......
Worth a try.....

Jim

[Bored&Stroked]

Good news - have had that issue before . . . forgot all about it!

[Old Henry]

Sponsored Links (Register now to hide all advertisements)

Originally Posted by BUBBAS IGNITION

Henry , WD40 will help insulate those wires , might try it before replacement. Just spray them down and wipe off the excess......
Worth a try.....

Jim

Thanks. I'll give it a try. I absolutely loath the thought of threading new wires through that conduit, the rubber boot, into the upper distributor cap and plug into the inner cap and get the upper cap to close. Not fun.

[47COE]

Originally Posted by Old Henry

I absolutely loath the thought of threading new wires through that conduit, the rubber boot, into the upper distributor cap and plug into the inner cap and get the upper cap to close. Not fun.

I agree. It is a real project to replace the ignition wires in a rabbit ears distributor.

Once upon a time I knew a guy with a Lotus Europa that wouldn't start in wet weather. He fixed it by cleaning the wires and then coating them with corona dope such as:
http://www.alliedelec.com/gc-electro...4702/70159781/

Unfortunately in this case, the wires could still be arcing inside the conduits or outer distributor cap. But I'm a believer in trying the easy option first. It might be all you need.

Tom

[Old Henry]

I sprayed the wires down with WD40 before starting this morning. When I started up and pulled out of the garage and down the street the timing light was exactly right and engine running smooth. Unfortunately, that only lasted for a minute before all returned to bad. So, unfortunately, WD40 wasn't even a short term solution.

My recollection of the WD40 trick is when water is a problem, not so much on the wires as the distributor cap. The WD40 displaces the water and eliminates it as a path for spark to short cut. Water wasn't my problem so the WD40 didn't help. Even if it did, as 47COE said, there is still a lot of wire in the conduit that I couldn't spray and could be leaking to that thing.

I just ordered the wires to replace them. Gonna have to put on my favorite music to keep me calm during the ordeal of replacing them. But, if it fixes the problem, it will be well worth the effort.

[Steves46]

Originally Posted by Old Henry

Thanks. I'll give it a try. I absolutely loath the thought of threading new wires through that conduit, the rubber boot, into the upper distributor cap and plug into the inner cap and get the upper cap to close. Not fun.

If originality is not a concern you want to consider replacing your existing distributor cap with (IMO) the more user friendly crab-style cap that was used on the 42 models. My 46 has one and I have been very pleased with it. I believe the only modification is replacing the clips to secure the cap (as per the photo in post #27). I hope you are able to soon resolve the issue. Steve

[Old Henry]

Originally Posted by Steves46

If originality is not a concern you want to consider replacing your existing distributor cap with (IMO) the more user friendly crab-style cap that was used on the 42 models. My 46 has one and I have been very pleased with it. I believe the only modification is replacing the clips to secure the cap. I hope you are able to soon resolve the issue. Steve

Thanks, Steve. I certainly consider switching to a crab cap every time I have to replace the spark plug wires but I'm afraid that I am very passionately committed to originality and authenticity. It's the thing that keeps the "time machine" working so well. So, I continue to suffer. Fortunately, the suffering is only for and hour or two. Then I get to enjoy the authenticity for at least a year or two. I figure I'm no worse off than those that drove this car in the 40's and 50's every time I experience an "authentic" mechanical problem.

[Steves46]

Hang in there and hope the new wire set will resolve the problem. I know you are looking forward to your road trip and we are looking forward to reading about it with some photos.

[FlatheadTed]

At night I think you will get color (static ) of the wires even new ones .Ted

[Old Henry]

Originally Posted by FlatheadTed

At night I think you will get color (static ) of the wires even new ones .Ted

You may be right. It may be that new wires aren't going to fix my problem and I waste my time and money changing them but it's my best hope at the moment. It's the only thing I have found that clearly looks broken that could cause my symptoms. Nothing else has manifested itself in all of my testing. I hope for the best and prepare for the worst.

[47COE]

Originally Posted by Steves46

If originality is not a concern you want to consider replacing your existing distributor cap with (IMO) the more user friendly crab-style cap that was used on the 42 models. My 46 has one and I have been very pleased with it. I believe the only modification is replacing the clips to secure the cap (as per the photo in post #27). I hope you are able to soon resolve the issue. Steve

I went from the rabbit ears cap to crab cap because of the minimal space in a COE. It was very difficult to pull the distributor with the deeper rabbit ears cap with the truck fan and fan shroud in the way.

Besides the clips, the crab cap requires a different rotor with a larger radius: 21A-12200 instead of the usual 59A-12200.

[Old Henry]

Looks like something's not quite right here. What do you think?

I got the new spark plug wires in and took the old ones off with the inner distributor cap. Here's what the inner distributor cap looks like.









There are all of those metal flakes all over that looks like metal from the distributor posts. And the posts look like they've been worn down by the rotor hitting them. All of those cracks around the posts can't be good either.

Here's what the rotor that I just put in looks like:



It looks like it has pounded on the distributor posts.

So, I checked for play in the distributor shaft and here's what I found: (Video) https://youtu.be/F04Ran7T2MY

I've actually had this before, a worn distributor shaft letting the rotor his the cap posts. That's the distributor I traded in for this one from Bubba's. Looks like I need to do it again.

What do you think?

[47COE]

It's hard to see from the video. Best would be to pull the distributor and measure the end play. I have a distributor with more than 0.05" of end play vs. another one with less than half that.

I don't know what amount of end play is normal.

Tom

[George/Maine]

I think with 250,000 miles its time for a different dist. and spring for a new cap and rotor.

[tubman]

After reading all of this, I'm starting to appreciate the "Load-a-matic" on my '51. I hope you can get this solved; it'll be good to know what the actual base problem is.

[Old Henry]

What a relief! What a blessed relief! - to have Old Henry's heart ticking again just as it should and hasn't for months. It passed the stress EKG with flying colors - no arrhythmia, no tachycardia, no stumbling nor stuttering of any kind. And more power than I've had for months.

The biggest problem I had I didn't notice 'till I got working with that old inner distributor cap some more. See if you can see it.



The button that's supposed to be in the middle of it for the rotor blade to run on isn't even there! There was nothing for the rotor blade to run on to get the spark except just sliding over what was left of the base of the button. Add that to all of the other problems with the worn terminals and cracked terminal bases and I think we have the biggest problem there was. I replaced that along with all of the spark plug wires and the engine runs fantastic and powerful in the most harsh acceleration and up the steepest long climb - like it hasn't done for months.

Thanks to everyone for all of your help.

[ccnelson]

Glad you found the problem and Old Henry is ready for another road trip.

[Old Henry]

Originally Posted by ccnelson

Glad you found the problem and Old Henry is ready for another road trip.

Thanks. I would have gone on the trip the way it was but it wouldn't have been near as fun. Now it's going to be a blast. Leave Tuesday for 5 days on the Pacific Coast Highway, Highway 1.

[JSeery]

Good to hear and have fun on the trip!

[Old Henry]

Originally Posted by FlatheadTed

At night I think you will get color (static ) of the wires even new ones .Ted

You were right. Even after installing brand new spark plug wires there were still some flashes in the dark, not as much as before, mostly around the spark plugs, but they were still there.

I'm thinking my problem was really that broken inner distributor cap way more than bad wires. But, the little bit of effort added by threading new wires through the conduit is nothing compared to the effort to get them all plugged into the inner cap then get the outer cap to close on it. So, I might as well have replaced the wires as long as I was replacing the cap. That's what I did and will do in the future when I more routinely replace that inner cap, or, at least inspect it for damage. That's hard to do without at least loosening the conduits so the cap can be turned up to inspect. That's why I haven't done it more routinely in the past. We lives and we learns.

[koates]

Hi Craig, That dist cap sure was a mess with cracks and tracking on many cylinders and on whats left of the centre contact too. There is some side play in that front dist bush and it should be replaced. It should have no side movement at all. Also it is generally usual to see a small light show around the leads and plugs at night. Make sure all your spark plugs are really in good condition. If plug centre electrodes are worn away and not square then the spark will have resistance in jumping the gap and will then want to find weak places in the cap and leads to go to ground. Fit new plugs and check that the gaps are correct before fitting. Some spark plugs don't perform very well once they are physically cleaned or sandblasted and seem to fowl up much quicker than new spark plugs. In years past I would clean plugs several times over but now I would maybe only clean them once before replacement. Keep the outside of your spark plugs and leads very clean, wipe them down now and then. Like wise wipe the inside of the dist cap and the rotor now and then. On electrical items "CLEAN IS GOOD". There is no requirement for "HOT" or "PERFORMANCE" ignition coils on standard touring car engines. All they do is place extra voltage pressure on all your high tension components and do nothing to increase power output of the engine. Good luck on your coming trip. Regards, Kevin.