sparks around spark plugs...

P.S. said:
It's pretty obvious (to this electrical engineer) that the ground connection is the problem. The blue sparks around the base of the spark plugs and the sparks up the armoured cable were the giveaways. This is NOT a carburetor issue, guys.
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Ground may be an element of this problem... but I've since cleaned the plugs and ensured that where they mate up with the head is good and clean too... I think I've resolved the sparking around the base of the plugs issue...

However, the fact that the engine will only rev when it choked seems to indicate an overly lean condition... I just can't seem to pinpoint the cause of the overly lean...
 
It will rev only when choked because a richer mixture will srill explode even with a weak spark.

The grounding issue is somewhere between the coil low end (at the points) and the ground return, through the block to the chassis to the battery terminal. Do you have the pans? Do you have a ground cable between the engine block (or transmission housing) and the frame? What kind of condition is your battery ground strap? Those are the kinds of things I suggest checking.

I'm admittedly very new to this exact type of car, but very experienced with electrical systems. If the model A contains some special kind of electrical science, then please disregard my suggestion.

Oh, FYI: a condenser IS part of the grounding scheme for the HV spark. Its connections and condition shouldn't be overlooked.
 
P.S. said:
It will rev only when choked because a richer mixture will srill explode even with a weak spark.

The grounding issue is somewhere between the coil low end (at the points) and the ground return, through the block to the chassis to the battery terminal. Do you have the pans? Do you have a ground cable between the engine block (or transmission housing) and the frame? What kind of condition is your battery ground strap? Those are the kinds of things I suggest checking.

I'm admittedly very new to this exact type of car, but very experienced with electrical systems. If the model A contains some special kind of electrical science, then please disregard my suggestion.

Oh, FYI: a condenser IS part of the grounding scheme for the HV spark. Its connections and condition shouldn't be overlooked.
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I've checked the ground strap... cleaned and tightened the connection. Also the whole distributor was cleaned to include the condenser.

There does not appear to be any other ground strap anywhere. I would've thought that if it were a ground strap problem, it would have showed up before now... I'll hook up another ground cable just to check.
 
Hold the coil wire 1/4" from a head nut and check for a hot blue spark. If that's OK, then I'd rev the motor and slap your hand over the carb intake. Just before the engine dies, remove your hand and let it rev up and do it again. This may pull some junk through the carb and help. I still think it sounds fuel related.
 
Ground for the bottom of the coil proceeds as follows:

Through the lead on the + side, down the inside of the armoured cable, through the connection to lower plate, (through condenser for HV) through connection to flexible wire, through flexible wire to points, through the points to points block, through points block to upper plate, through upper plate to distributor housing, through distributor housing to head and block, etc. ALL of those connections have to be clean and tight with no paint, oil, dirt, etc. between them. Points especially have to be clean and touch squarely, not on edge. Clean the points with isopropyl alcohol, not brake cleaner. You don't want any trace of oil between the points or any other electrical connection.

Then lastly, the engine block has to be grounded to frame, etc.

Your HV is finding the return path through armoured cable, etc instead of proper path. I am guessing a problem with grounding based upon that clue.
 
Tom Wesenberg said:
Hold the coil wire 1/4" from a head nut and check for a hot blue spark. If that's OK, then I'd rev the motor and slap your hand over the carb intake. Just before the engine dies, remove your hand and let it rev up and do it again. This may pull some junk through the carb and help. I still think it sounds fuel related.
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Did the 1/4" check... blue spark. Also did the momentary cover of the carb intake... and disassembled verified all the passage ways clear... I've done the momentary cover of the intake many times...

BILL WILLIAMSON said:
Some moisture "may" be trapped in the distributor itself?? Bill W.
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I went through it pretty well when I replaced the lower plate and put new points in... they are clean and dry.

P.S. said:
Ground for the bottom of the coil proceeds as follows:

Through the lead on the + side, down the inside of the armoured cable, through the connection to lower plate, (through condenser for HV) through connection to flexible wire, through flexible wire to points, through the points to points block, through points block to upper plate, through upper plate to distributor housing, through distributor housing to head and block, etc. ALL of those connections have to be clean and tight with no paint, oil, dirt, etc. between them. Points especially have to be clean and touch squarely, not on edge. Clean the points with isopropyl alcohol, not brake cleaner. You don't want any trace of oil between the points or any other electrical connection.

Then lastly, the engine block has to be grounded to frame, etc.

Your HV is finding the return path through armoured cable, etc instead of proper path. I am guessing a problem with grounding based upon that clue.
Click to expand...

I think I've gone through all of that... but I'll go through once again...
 
I too feel that right now the issue is fuel. That said, an electrical problem could happen if the distributor isn't well grounded to the block, thats thru its contact and the set screw.
Back to fuel, have you removed the line at the carburetor and checked for proper flow ? Does the fuel line extend too far beyond the ferrule into the carburetor ?
What carburetor are you running ? Where are the adjustments set ?
 
robw said:
I think I've gone through all of that... but I'll go through once again...
Click to expand...


OK, sounds good.

As a side note, after gapping points the very first time on the Model A, I had problems. I had used the feeler gauge to set the gap and the barely noticeable oil on the feeler gauge obviously left some behind on the points and was enough to make the points work poorly. After soaking the edge of a thick business card in isopropyl alcohol and cleaning the points, she purred like a kitten.

Also discovered through tiral and error that the points have to close absolutely square for best results. Using a magnifier, you can reposition the points block or bend the points themselves slightly to make them land square.

I started using a scope, power supply, and load resistor, and spinning the distributor with an electric drill to "tune" the distributor while on the bench before installing in the car, and it's amazing how much very small problems can cause the waveform to go scattered and not be perfectly square.

Since adpoting the electronics engineer approach to setting up distributor and points, our car is running better than ever. This last week, the guy who owns the body shop in town (whose dad is an old Model A guy) told me that his dad said our Model A is the best running car he's ever heard in his decades of working on them. Quite a compliment!

The drill/scope method will also uncover a condenser that isn't yet bad, but will be soon. I had to buy 4 different condensers before getting one that works exactly right.
 
Do you have a known good carb to try on your car? That should let you know if your carb has a problem. As mentioned, you also need to check for good fuel flow to the carb.
 
Patrick L. said:
I too feel that right now the issue is fuel. That said, an electrical problem could happen if the distributor isn't well grounded to the block, thats thru its contact and the set screw.
Back to fuel, have you removed the line at the carburetor and checked for proper flow ? Does the fuel line extend too far beyond the ferrule into the carburetor ?
What carburetor are you running ? Where are the adjustments set ?
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fuel flow is great... fills a cup up very quickly. No, it doesn't extend too far in...

P.S. said:
OK, sounds good.

As a side note, after gapping points the very first time on the Model A, I had problems. I had used the feeler gauge to set the gap and the barely noticeable oil on the feeler gauge obviously left some behind on the points and was enough to make the points work poorly. After soaking the edge of a thick business card in isopropyl alcohol and cleaning the points, she purred like a kitten.

Also discovered through tiral and error that the points have to close absolutely square for best results. Using a magnifier, you can reposition the points block or bend the points themselves slightly to make them land square.
Click to expand...

Ok, starting at the coil I went step by step... removed the coil, scuffed up the firewall and the coil mount to make sure there was good metal to metal contact. cleaned out the coil tower... made sure it was good and dry. expanded the contact just a bit so the coil wire would fit in good and snug...
Pulled the distributor... cleaned it, made sure no oil anywhere. scuffed the spot where the condenser screws in. buffed up the metal on the condenser to make sure it had a good ground. buffed the hole in the head to make sure the distributor made a good ground there.

Pulled every plug. gapped at .035. buffed the hole in the head to make sure there was a good ground. cleaned all the plugs.

retimed the distributor. points open on 2d click.

added a ground strap from the transmission to the frame.

no change. I'll check tonight to see if my sparkler show is still there. I think it is gone now.

Tom Wesenberg said:
Do you have a known good carb to try on your car? That should let you know if your carb has a problem. As mentioned, you also need to check for good fuel flow to the carb.
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Nope, no other carb to use. I'm fairly certain the carb is ok... it was recently rebuilt by a professional... and was working great until the great washing.

It starts very easy. almost as soon as you press the starter button. The engine turns over about a 1/4 turn and is running.

anyway...
 
When it's dark look carefully at the coil tower for any sparks.

I've also seen the distributor body have an internal short (usually between 3 & 4) and this will cause a miss, especially at higher speeds, where more high voltage is required to fire the plugs.
 
Tom Wesenberg said:
When it's dark look carefully at the coil tower for any sparks.

I've also seen the distributor body have an internal short (usually between 3 & 4) and this will cause a miss, especially at higher speeds, where more high voltage is required to fire the plugs.
Click to expand...

Yep, I checked for that... seems to check out ok on an ohm meter... no continuity between 3&4...

Also did lots of continuity checking between various components looking for other possible shorts besides what Les has you look for in his book... no luck there either.
 
robw said:
Yep, I checked for that... seems to check out ok on an ohm meter... no continuity between 3&4...

Also did lots of continuity checking between various components looking for other possible shorts besides what Les has you look for in his book... no luck there either.
Click to expand...

Continuity means nothing when dealing with high voltage that can jump large gaps. Be sure to try a good distributor body and cap.:)
 
Tom Wesenberg said:
Continuity means nothing when dealing with high voltage that can jump large gaps. Be sure to try a good distributor body and cap.:)
Click to expand...

Ok, well, I've tried two different bodies... the one that was working well enough before, and this new one, which fits much tighter. Since I'm using different rotors for each cap... it is easy enough to jump between the two...

other than running them... how else would you test them? Even when running them... how would you test them to know that #3&4 were shorting out?
 
My friend's was shorting between 3 and 4, even at idle, so I could short the plugs and found the fault to be the distributor body. If it only misses at higher speeds on the road, then changing the part is probably the easiest way to check it.
 
Ran it in the dark again... light show is almost gone... only appears at high revolutions and is not nearly as bright as before. Nothing by the coil. One small blue spark between the armored cable and the retard lever, which is almost impossible to see... but it is there. The other part of the light show is at the spark plugs... very faint, but the spark creates an illusion of the spark plugs being transparent.

At any rate... it is still there, so I've still got something not right. I'm done for this weekend... back on it next weekend.

rob
 
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