MTFCA Forum

I have been picking away at this project for a couple of years and I finally get to the first start stage, and I am having issues. It was a running and driving engine, had the head rebuilt, and put it back together. Changed from a distributor set-up using one set of plugs to a Bosco ZR-4 to fire both sets of plugs at the same time.

the most I got out of it was a sequential four pops in the last two months. that was long ago. this is where I am at:

* got plenty of fuel, fuel pump, pressure regulator set at what it was for the last time it ran as a complete car.
* plugs are wet and smell like fuel
* get spark to the wire when placed near the head
* no spark at a plug when laid on the head.
* wrapped a wire around the plug for better grounding, nothing different
* tried a good plug out of a car, no spark on this car laid exactly the same way.

I am stumped....

The pics are below. Please ignore the long spark wires, it will all get cleaned up when running

Does your magneto have an impulse coupling?

What is the condition of the mag? Rebuilt? Recharged magnets? Appears as if it's weak, (spark from wire to ground, but not through plug electrodes.)

Timing correct? TDC compression versus TDC exhaust?

Reinstall the distributor. Dual propagation adds zip.

Yes it has an impulse and I can hear it click off and it was rebuilt by marks this year.

I also have I hooked to a battery connection and grounded

What are your spark plugs gapped at? Some Bosch magnetos want the plug gaps at about .020, not the usual distributor setting of .032.

A lot of the "antique style" spark plug wire has had some cross firing leakage issues in the past decade or more. So much excessive length will exacerbate the issue, and could cause misfiring problems. Often, such problems will fire okay at slow turnovers making one believe there isn't a problem. But once rpm surpasses about 10? Spark begins landing anywhere but where you want it. It is often interesting to look at the wiring in a dark shop at night with the engine running. The amazing thing is how well an engine might run with ignition going every which way. And sometimes they don't run.

"I also have I hooked to a battery connection and grounded". ??? The mag should not be hooked to a battery or voltage source. There should be a ground wire connection on the point cover. To kill the mag, this wire gets shorted to ground. Otherwise not connected when running. \How did you time the mag? The impulse should trip slightly before TDC on the compression stroke. Just popping might be the case of really late timing. What do you have for a mag coupling to adjust the timing? FYI, the mag should fire when the points just break open.

Thanks for all the suggestions!

I have an adjustable coupler, using 4 set screws. Been all over the place around the timing at TDC. I have a boroscope that look at the bore. It is timed right now for when the piston is just over TDC the impulse clicks off.

Keep all the suggestions coming! I’m trying them all

Hi John,
How far will the spark jump from the wire to the engine? Any chance you have resistor plugs? I was once told to test a magneto you wet your
finger & press it firmly to the kill terminal, grab the engine with the other hand. Then have someone turn the engine over as fast as they can,
wait 2 minutes then check how far down your leg the wet stream is. If it's past your knee it's a good mag.
Craig.

Craig L, You so BAD! (Me, Laughing!)

I once bought a very incomplete mag at a swap meet. Thinking it wouldn't work with missing pieces, I absentmindedly walked around the swap meet flipping over the armature. Turned out it was quite hot! I worked with all sorts of electrical systems my whole life, including high voltage systems. I know what areas of voltage and power that are harmful and even maybe fatal, what hurts harmlessly and what to be careful of, I often am willing to touch harmless high voltages as a quick test, or even as a joke! (It isn't the voltage that kills, it is the current!) (Although there are some voltage areas that can be deceptively dangerous!!!!) (Household 110V is deceptively dangerous by the way!)

I once had a good and wonderful friend adjust a few coils for me on his HCCT. I turned his joke on me back onto him when he told me to "touch this" as he cranked (sorry Dan!), and I quickly reached to actually touch the hot connection! I had touched enough spark plug wires over the years (including model Ts while running) that it just doesn't bother me anymore.

I am not sure he ever forgave me for that?

John- if the impulse is tripping after TDC, your timing is late- try advancing the mag a small amount at a time. An impulse will delay your ignition a small amount.

I agree about the timing. I googled my plug that is on it and it is in fact a resistor plug. When I went to the auto parts store I had them cross reference and they must not have thought this was a big deal.

I will get some plugs shipped from Langs today, they have the 14mm adaptors. I know they wont be resistor plugs.

Keep the ideas coming, even the smallest nugget is helping.

Are you getting 14mm plug from Lang's? The last set of those I got from them a few years ago were Autolite 66, a 4K ohm resistor plug.

I'm curious what they are selling now, NOS plugs off ebay were the only source I found at the time for appropriate non-resistor 14mm plugs.

I see the wires are old style, but are the wires copper or steel core wire? I know magneto dont like modern fiber plug wires, just something to check,

The 14mm spark plug adapters may not fit.
I believe the BB had 18mm plugs on both sides.

Yes, just like Fronty. However the plug adapters for a Model A work to let you use modern plugs. You need a deep reach modern plug, I use a NGK BKR5EGP, the less expensive BKR5ES or BKR5E would likely work. Not certain why I chose the platinum version. Oh, recommended by a friend whose Porsche likes the spendy ones.

I run Autolite AP5405 platinum plugs in my BB.
There are long reach. Extend well in npt adapters.

the auto parts store has them in stock, will update tonight's progress after dinner and before the yankee game!

If your spark is nice and hot, that resistor plug won't interfere at all. Keep looking.

Impulse mag timed a little ATDC, is just rite, in my book, sposed to keep you from kickback.. Dave in Bellingham, Wa

Changed plugs, timed just after TDC, checked with a bore scope and we made some progress

https://youtu.be/voxxbIMXpL0?feature=shared

Now I’m Not sure what it’s telling me.

Good news is we heard it sing

Hi John, Is that a BB1 or BB2 carter? they tend to like a rather rich mixture to start. Sounds like you are close!
Craig.

Yes, it is the BB1 that I ran on ot previously. I think it is rich. I am going to start with Fuel pressure and work my way forward making adjustments.

John- your timing is late- that why it will almost start. (In my opinion).

Dan McEachern wrote: ↑

Thu Oct 31, 2024 1:49 pm

John- your timing is late- that why it will almost start. (In my opinion).

Mine too. I went through the same thing. I would have sworn I had the timing set right. Fussed with it for 2 days. Finally, my wife said, "why don't you just check the timing again to be sure." In my mind, I screamed, but my voice said, "okay why not." Yup. Timing was way too late. Before resetting it, it chugged a bit, just like yours.

Good News! we are up and running. Fussed with the fuel pressure and carburetor settings and we are all started. I have to find the middle of the range of my spark adjustment as it will start when advanced and quit when retarded, but all is happy is the world of Rajo BB land. Thank you everyone for all the advice!