trouble shooting weak ignition spark !!! Help

[Dave_Kriegel]

Well I have been working on a non starter 1917 for a month Zero compression, no spark Now with valve and ring job, new wiring, rebuilt coils still no start I have narrowed it down to a very weak visible spark when I lay the plugs on the block and rotate the cylinders into firing order . I have read on the forum years past that a weak spark visible on a plug OUTSIDE the block will result in no spark when the spark plug is chambered and under pressure. I am using modern F 11 plugs new, set at 032 I have strong coil noise New spark plug wires, The only thing I may think of since this is a non starter car is I used 12 gauge wire for both the 12 volt battery ground and running up to the ignition switch Could this thin wire not carry enough amperage ?? Any ideas ?

[John kuehn]

How about the mag. Recharged magnets? Were the 17’s equipped with a hot shot battery from the factory? Will the engine cough or spit at all? Carb adjustment? Rings not seated resulting in low compression?

[Peter, Memphis TN]

12 gauge wire should be plenty capable of carrying the current needed to get good spark from the coils. I'd take another look at all the connections, though.

You spoke of the "sound" from the coils. Have they been looked at with the proper equipment? As I understand it, it is not possible to set a coil without it. There are several inter-connected adjustments, as well as the question of having a good capacitor inside.

[Steve Jelf]

"90% of electrical problems are fuel, and vice-versa."

Except for the ground, you seem to have all the electrical bases covered. Install a proper ground, and if that doesn't fix the problem (my guess is that it won't), look into the fuel system.

Twelve volts for the coils is overkill. I've read that running on battery is better with 12 volts, but six has always been adequate for me so I've never tried it. In fact, I'm not sure that when I hand crank on MAG it's generating even six volts.

[Dave_Kriegel]

Thanks for the ideas I did grind frame metal bright to get a good battery ground. I will check voltage at the coil box to be safe. I will put in old fashion champion X plugs and try starting on MAG !~! Never give up

[Susanne]

Something else you might want to check is the condition of the coil box contacts and the coil box switch internals... sometimes they are corroded enough to give you a weak current, or "carbon traced" and losing current there. Then go thru your wiring and find where your current leak is... one place to check is the timer, as if it's leaking there back to the block you won't get much feeding back to the coil box...

that's where I'd be looking first, but also realize it may be something semi-invisible, like a cracked insulator on your coilbox or a semi-broken wire.

One other thing - since it's a pre-starter car, reverse your battery leads. It won't hurt anything, and will actually prolong the points on your coils.

Remember, your coils are designed to run on AC at a HUGE range of voltages (between 3 and 32), so your coils should be hot IF you're getting good voltage to them.

[Dave_Kriegel]

Great idea I will take commutator off and clean it again make sure it is getting good contact ! Thanks you

[AndreFordT]

Steve,

cranking by hand on magneto It will give you between 2 and 3VAC.

The coils are not made for tension but for current.
While testing coils on an HCCT sometimes the coil start to buss and spark at 1.5VAC and there is a gap of about 1/4 inch where the spark is seen.
Photos in the attachment are from a Heinze coil while testing with a HCCT.

Andre
Belgium

[Scott_Conger]

Why exactly does reversing battery leads lead to prolonged point life??

[John kuehn]

Steve J. has the right idea about a fuel issue causing hard starting. T’s with starters sometimes have issues not starting and I have one of those. My 21 Touring will have a starting issue after setting up a while. I rebuilt the engine, carb and etc. and it gets touchy if the carb’s needle valve is slightly off. I have since learned the ‘magic spot’. Anything more or less is a no go! I learned the hard way after 2 attempts of trying to start the car and hours of scratching my head.
My other two T’s are more forgiving on the needle valve setting after they sit up for a while but not the 21Touring.

[Moxie26]

Dave: You mentioned coil sounds..... loud. Suspect bad condensers inside coil unit. When were the coils last rebuilt ??????

[JohnH]

Why exactly does reversing battery leads lead to prolonged point life??

With DC operation, one point will lose material to the other. That is, one point will develop pitting as the material migrates to the other, which starts to accumulate that material. Which point loses material and which gains it depends on the supply polarity. By reversing the polarity after a period of use, the material migrates back. This is why coils run on magneto (AC) only tend to have less pitting on their points - the polarity is constantly changing.
The point material transfer is more rapid when the coils are operated on 12V DC instead of 6V DC.
I rebuilt my coils in 2002 and have only run them on 6V DC. It was more than 10 years before I cleaned the points, which were actually still in very good condition. I've now done about 40,000km with those points. So, in practice it's not something to worry about, at least with 6V operation.

[Scott_Conger]

John

thanks, but I am aware of erosion due to polarity. One would have to be pretty busy swapping polarity to get any benefit...and I think the expectation that the material that piles up on one point will somehow vacate it's place and fill the divot back in with polarity reversed is wishful thinking. Yes, the migration will reverse, but like a road crew, with no one supervising the hole filling, erosion and piling up will happen where it happens, and not necessarily where you expect.

Almost no one bothers to oil their shackles each morining before a drive on tour, so I can't imagine a parking lot full of people pulling their batteries and turning them around. It would be fun to watch though.

I can state with certainty that I have NEVER seen or heard of anyone doing this as a matter of regular maintenance. And I agree with you that it is nothing to worry about one way or another with 6V.