Car ran fine yesterday but today ran on three cylinders. We run an 009 Bosch so no nasty comments please. We were the fastest flat-head T at the Lincoln NB hill climb in 2013 and it is a known performer. Anyway, today it runs on one four and three and two is dead. So, new distributor cap, rotor, ignition wires . . . full set. and new plugs, full set installed. Still a dead # two.
Zero ohms resistance on rotor cap, distributor cap and all ignition wires zero resistance piece by piece or connected on all. Ran engine with #2 wire off and just very close to ground and no spark jumping. Plug was wet so cleaned, connected to #2 wire and laid plug on head to observe. Started engine and no spark at plug. Plug has continuity from top to tip. The electricity will simply not travel down the pipe to the combustion chamber.
What I had was full connections with continuity everywhere. So I changed out # two spark plug and it runs like a top. So here's the question . . . . Why would I have continuity to the plug but no short with sparking with a screw driver but changing the plug fixed it. One would assume that an open circuit would spark with continuity to ground.
Any suggestions ?
What difference does it make ? That car ain't no good fer nuttin. Cain't haul nuttin wit it. Run it into a ditch and get you a truck !
Did you do anything to the points. If gap is very close, you might not be opening on #2. The points need to open in order to get a spark. Try new points and condenser. Also could be worn bearings in distributor causing the cam to wobble. Again a close gap could aggravate the problem. If so, new bushings would be the best fix, but a temporary would be a wider gap.
Get back to basics. Compression, fuel spark, plain and simple. I vote for a stuck valve.
In the real world if it drives in and then won't start or runs poorly, it most likely is internal(stuck valve) or burnt valve from your last run. Electrics just don't happen over night.
Burger, It now has a trunk on the back to carry Mary's lady things, hats , jackets, and water bottles. Before, we had a cigar box under each seat and a wrench in my pocket. See pictures below of its new boat tail. By the way it weighs the same and is just as fast.
The problem was a bad brand new spark plug. My question was why didn't the spark jump off of the wire to the head when the plug was taken out of the equation ?
The spark could have been following a carbon track down the insulator on the combustion chamber end of the plug, where it wasn't visible?
Brass car guy, the plug failed over night. Just had a valve job and new gasket. Again, my question why no spark when ignition wire touched to head ? That's what drove me nuts and put me on the wrong trail. I even changed rotors and caps. still no bang.
Worked on a Jeep 30 years ago that did something like that. I would adjust the points with dist cam on #1 and engine ran on 2 cyl. Adjust the points with dist cam on #2 and it would run on the other two cyl. Finally dawned on me the breaker plate was jumping all over the place. An unauthorized 2 hours from civilization repair got it running on all 4.
Ed, but when removed from plug and shorted to ground, still not spark on that wire.
breaker plate in good order Bill. It was the plug. Again the question was why no spark when #2 was grounded.
By grounded, do you mean the end of the plug wire held a bit away from ground so that a spark could jump the gap?
No gap, no spark.
One possibility is a defective wire. Held one way for testing, it opens (or shorts, or both) internally. Held another way for a different test, it reacts differently. I have had ignition wires burn a carbon track through one spot in the wire (usually where it is touching, or very near, a ground). The same wire had a broken spot in the wire after the carbon track (probably part of why the carbon track formed in the first place. Hold the wire one way, it measures good (break touches itself inside). Hold it another way, it reads bad. Connect to the spark plug, but keep the carbon track clear, it sparks okay. set it slightly different? No spark (carbon track grounds).
Drove me nuts for awhile.
I won't even talk about the right rear wheel of the boat-tail.
Drive carefully, and enjoy, W2
Mark, if you read my first post you will see that I tried it all ways. Spark wire connected to plug and resting on head. Wire held in an insulated clamp and holding it at all distances from ground, no spark at any time and that is why I am asking this question again and again but folks are not reading my post carefully. I tried every possible thing and no spark. The brand new plug simply failed over night while I slept. .
Grounding or holding the wire close to ground gave no spark in any set-up yet changing the plug fixed it. How can one plug on a dead wire fire and another one not fire ?
I'm with Wayne. To totally eliminate the plug install it in another cyl.
Sorry about missing that detail in your first post, Frank. I'm mystified why replacing the plug would fix it when there was no spark from the plug wire when it was held a short distance from ground.
Thank you Mark, it really was strange ;~)
Still with Wayne. New cap & rotor. The first new plug didn't fire because it had no spark going to it. Bad wire. You had no spark with the wire alone held to ground. How can it be the plug? A worn dist bushing might be the cause but not on one plug/wire constantly. Usually that involves high speed missing. A worn lobe also. But why would only one lobe be worn? Highly unlikely. The only thing you didn't do was stick a philips screwdriver in the #2 cap terminal and check for spark at the cap itself.
Charlie, there was continuity between the wire and ground and from the cap to ground, and from the cap to the ground. Read my first post carefully.
after a large amount of time and contiplication followed by a few drinks I realized that Frank's problem is directly related to the quality of the caulking on his rear deck.
I can see that there is a small section near the center that is not straight or uniform.
If hisT was in a wooden boat competition it would be sunk
If nothing else, I would try the bad plug in another cylinder or at least on another plug wire just to positively confirm it's bad. I suspect some sort of variable between the dist. and the plug.
Frank I've seen a similar problem many times with older V-dubs and Porsches, usually running Bosch 009 or derivatives thereof.
Here is what I've found in most of those cases. A high resistance crust forms on one or more distributor cap contacts inside the cap. If one of the wires or plugs has a little higher resistance than normal, no spark! If you check for the spark at the wire to ground, the resistance is higher still (since your holding it away from the ground farther than the plug gap) and you get nothing.
I have seen this happen with new caps and old caps alike, and it wouldn't surprise me if tomorrow when you start your engine you'll be back to three cylinders again.
The fix was to take my pocket knife and scrape the rotor contact and the cap contacts inside the cap to shiny metal.
This problem was especially common near the beach, which I attributed to condensation that formed inside the top of the cap over night causing slight oxidation to form on the contact.
I have seen the crust so bad that you can actually see the chunk of oxidation pop off the contact when you scrape it.
It could be that when you replaced that plug the resistance was low enough to allow that circuit to fire again, but if I'm right, not for long.
Charlie, there was continuity between the wire and ground and from the cap to ground, and and from the cap to the ground. Read mt first post carefully.
What you are describing is a short in the plug. Electricity follows the path of least resistance, thus no spark even though there is continuity. Check resistance from center electrode to contact.
Now to be argumentative Frank I read your first post a number of times. You state there was continuity through the #2 plug circuit but no spark from the wire when held to ground. With spark from the other 3 wires. If there's no spark from the wire when held to ground it's not the plug.
Unless I am missing something here - you in fact "measured the problem" but didn't chase it. You have continually stated you had "continuity to GROUND" (the definition here is that CONTINUITY means DC resistance path) at the plug wire connection at the cap. If your car is not running then the rotor is not touching anything but air inside the distributor cap unless this is a different sort of distributing device. On the other end the plug porcelain should insulate the other end totally from ground so all you had to do was find out where the "continuity to ground" was coming from. When you took it all apart I am guessing the "continuity to ground" path was broken and is now not there. What you are insisting should be happening is what often happens and makes electrical debugging often difficult. The problem in the first place may have been an intermittent and as such can and often will go away as soon as you touch something. I have chased intermittent problems many times and they can lead you out into tall grass if you insist that something CANNOT be the issue. Think about it. If you indeed have a good cap, good wire, good coil, good plug, good grounded head, good points, good condenser, good battery, good wiring supplying the coil...etc then there by definition can be NO PROBLEM. I get calls sometimes from someone with a problem and they go down a list of everything that it cannot be and in that list is everything that could cause the problem. I tell them to "keep testing" and when they have totally given up and are willing that the problem "can be" something they have already tested - to call me back and we will start over.
DC continuity to ground anywhere along a spark plug wire from cap to plug end IS A PROBLEM that you must find and locate. If I misunderstood your statement then of course I am then a lost ball in tall grass but you lead me there ha ha. I can appreciate your frustration. Been there many times.
Charlie B, It was the plug and the engine runs beautifully today. Some said it would run on three today but today it runs well on all four. It was a brand new plug that ran well for about an hour and then went bad. I have not looked at it carefully to see if a bit of carbon is shorting out the new plug in some manner or if the ceramic failed. I still have continuity from the top of the plug to the central electrode.
I have worked in the aircraft after market turbocharging business (RAYJAY) for many years and worked with drag racing supercharging with up to 65 pounds of boost. We burned 12 gallons of nasty stuff in under five seconds 20 years ago. I also taught auto shop in the Community Colleges before being kicked up stairs to the Dean of Curriculum and Instruction in a college with 25,000 students and 108 trade and technical programs. I am well trained and still remember a lot of technical stuff although the technical stuff has changed and I have not. Never the less my problem was a 1920's issue and not a digital one of modern times. So I posted my issue because my problem just did not sound reasonable and all of the comments proved that it could not be. Even yours proved me wrong and impossible. Yet, it was the spark plug. While chasing the miss-fire all wires, cap,and rotor were replaced. It was only when the #2 plug was changed out that it cleared the problem.
I would like to put the (bad) plug in another engine to see if I can create the same issue in another engine. That would end this issue. Thank you and all of our other responders for your interest and comments and I too am not sure how the plug change fixed the issue. Again I posted my problem because it was impossible but it happened. Thank you all again for your interest.
I just want to add this.
I think you just had bad luck as I had a few years ago.
I was working on a Austin 3000six cylinder to make it ready for a 1000 miles rally. It was running good before I started but for performance there was a ring and valve job and all the ignition parts were changed (plugs , points, capacitor, rotor, distributor cap, wires and coil)
Distributor was rebuild with new bearing, in a word everything was done to make it run as well as it could be. Instead it run as crap, the 5th cylinder was missing. I went over the job three times but couldn't found what went wrong till, on the morning the day before the start of the rally, I start working on it at 6 am. It was still dark in the workshop as I fired up the engine. Still running on 5 cylinders I saw a spark between the distributor cap and the spring that hold the cap down. The spark was that small it became invisible in daylight.
I changed the new cap with the old and all was done. The car finished second of his class.
Hope you find the reason