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Mallory Ignition vs. Battery... Strange but True!

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tahoe36c Avatar
tahoe36c Paul Hruza
Panama City, FL, USA   USA
1969 MG MGC GT "Little Red Rocket..."
1972 MG MGB GT "Tiny Dancer"
2002 Harley-Davidson Dyna
Here is one for all the electronic whiz kids... Strange but true! I posted this on the C forum and here due to the increased exposure.

A few months ago I took a friend out for a ride in the 69 C/GT. We drove approximately 5 miles and then stopped at a red light. The engine just shut down... No lumping, no funny noises, no nothing. It was as if I turned to key off. A quick check proved I had fuel pressure but ignition was barely there. When cranking the engine the #1 plug wire was just barely sparking about every 5th crankshaft rotation. Called a friend to come get us. We towed the car home and put it in the garage... I left it for about a week because I had other things to do and surely wasn't too happy since I've never been left by this fine running engine previously.

I finally began troubleshooting the ignition system which includes a Mallory Unilite Distributor (installed by one of the previous owners) and found three things:

The coil seemed fine but was a 3 Ohm and Mallory recommends 1.5
The ignition ballast was also 3 Ohm, and again, Mallory recommends 1.5

Neither of these two deficiencies seemed to affect the ignition system performance prior to this failure. The car has been running just fine since I purchased it... More to come on this however.

I performed the Mallory check on the ignition control module and found it bad (but don't you points lovers get all excited just yet!!! LOL)
The checkout for the module is to remove the distributor cap, power the system, then check for 12volts at the negative side of the coil. If that is good then you place a credit card sized object (I used a small piece of cardboard) to block the photo optics of the module. This is when the distributor fires. Voltage should drop to 2 volts or less. If so, it is good...

I was getting crazy crap like only 6 or 7 volts at the positive side of the coil and 1 or less on the negative side BEFORE blocking the optics!!! Then I'd walk away and come back to find 12 volts at the positive side and still only 1 or 2 at the negative side. It seemed to be ridiculous!!! I checked the battery connections for cleanliness but found nothing because I have always been a stickler of keeping the posts cleaned and lubed with Vaseline. Battery ground was also perfectly clean. I know because I removed and cleaned it again....

So in the end I got on eBay and ordered another module figuring it was bad... I connected the battery to the Battery Tender again as usual and just left it for two weeks waiting on the part.

In the meantime, I got to thinking about that ignition ballast and wondered why it was even there. I thought it was only required for points to help them last longer so I removed it... I was wrong about that too!

Anyway, the new module shows up, I install it and Vrooooommmm. She fires right up! Heck yea... Go to go. Then about 5 minutes into the warm up; dies again. Now I'm really confused so back to the Mallory test. I read through it and finally noticed the BOLD lettering; WARNING: this distributor requires a ballast. Not using one can shorten the life of the module. Shorten? Well yea! It lasted 5 minutes!!!! LOL $$$$

So that is when I called Mallory tech support, explained the entire situation, and was told to use the 1.5 Ohm coil and ballast. So I ordered a new coil, new ballast and another module. No warranty on the first replacement since it came from China (from a guy who actually was the Mallory supplier!!!).

Are you ready for this? All parts come in. I replace them. Turn the key and.... Nothing. Engine spins, no start. Now I am ready to pull out the C4 and really fix this car!!!! Grrrrrrrr

I do the Mallory Module test and guess what? Same crap as before. 1.5 volts at the negative side of the coil before I even block the optics... Now I'm thinking there must be an ignition switch problem. Not letting enough juice get to the coil. OK then, before I do that I decide to install my spare battery (the one for the B/GT rebuild) just for shits & grins. And now...

Engine cranks right up and runs like a charm... Really? Was the battery really the cause of all this from the beginning? Well... Yes. I reinstalled the original and first ignition module replacements (just wired in to make the check, not put into the distributor). They are both fine!!! So now I have two spare modules.

Car has been running fine ever since replacing the battery. The battery was found to be "low" when we performed a battery load check but still cranked the engine just fine.

OK, enough electrical insanity for this year. Hopefully all will remain operational for a while! LOL...

So there you go. Another electrical mystery solved. Mallory Ignition System; just fine, no problems. Battery was the culprit! Hmmmmmmmmm

Just took another ride today. Runs like a dream!! smileys with beer

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Steven 67GT Avatar
Steven 67GT Steven Rechter
Jackson, CA, USA   USA
No doubt that the old battery had sulfated.

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tahoe36c Avatar
tahoe36c Paul Hruza
Panama City, FL, USA   USA
1969 MG MGC GT "Little Red Rocket..."
1972 MG MGB GT "Tiny Dancer"
2002 Harley-Davidson Dyna
Steven,

I forgot to mention the battery was 8 years old... LOL I had no idea since it was in the car when I purchased it just 5 years ago. Never thought about the age of it since car was always on a Tender and never gave any problems previously.

It just amazes me how the car ran just fine and then all of a sudden... crap. Specifically with the ignition system. You'd figure ignition would work just fine if the starter was still spinning normally!?!?!?

Oh well... You live and you learn.spinning smiley sticking its tongue out

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Fred Winterburn Avatar
Ripley, ON, Canada   CAN
But, If the battery spun the engine, it wasn't bad. Most likely a bad connection between the battery and ignition switch to the ignition module. A connection in that series string must have been disturbed and brought back to life somehow by replacing the battery. Dead batteries don't turn engines over very well, so I think you've got a time bomb on your hands as it will happen again. Fred

In reply to # 3909379 by tahoe36c Steven,

I forgot to mention the battery was 8 years old... LOL I had no idea since it was in the car when I purchased it just 5 years ago. Never thought about the age of it since car was always on a Tender and never gave any problems previously.

It just amazes me how the car ran just fine and then all of a sudden... crap. Specifically with the ignition system. You'd figure ignition would work just fine if the starter was still spinning normally!?!?!?

Oh well... You live and you learn.spinning smiley sticking its tongue out



'Anyone who likes liver, can't taste it'
'If you want to repair car electrical systems successfully, learn Ohm's Law'.
'You can't shake hands with a snake'

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tahoe36c Avatar
tahoe36c Paul Hruza
Panama City, FL, USA   USA
1969 MG MGC GT "Little Red Rocket..."
1972 MG MGB GT "Tiny Dancer"
2002 Harley-Davidson Dyna
Fred,

That's my point exactly... How was it spinning the starter but not powering the ignition system properly?

Then again, the battery did check bad during a load test... I guess it was teetering on the edge of failure.

All connections are clean. No corrosion found anywhere. I was thinking intermittent ignition switch but never found anything wrong there either. I'd almost always get 12V at the positive side of the coil, though a few times it only showed 6 or 7 on the meter (which could have been me). It was the negative side that gave most of the weird readings during the troubleshooting.

Everything changed in the blink of an eye when I installed the new battery... Now she fires right up!

I guess Lucas & Mallory are friends once again.

Guess I'll just drive the crap out of it and see what happens next!!! smileys with beer

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Lonwuff Gerald Beach
NAMPA, ID, USA   USA
Electrical problems the worst when I rebuilt boat electricals (especially the trailers) since salt water really does a number. It's all Benjamin Franklin's fault.

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Gerald O Avatar
Gerald O Gerald O'Docharty
Wake Forest, North Carolina, USA   USA
1978 MG MGB
The starter can crank the engine with low voltage just fine so long as it has sufficent current. A points type ignition tend to be more forgiving of this. Try measuring battery voltage sometime while cranking and you'll see that it drops noticably. So the starter is not a good measure of a battery's condition. This is why I have a volts gauge in the dash.

What I find troubling about this story is that the car stalled after it was already running. Usually the charging system will hold the voltage at a good level even when the battery is weak while the motor is runninng. So this points to a possible problem in the charging system as well. A brand new battery can mask that for a while.

Should be measuring around 13.5V while running and 12.7V stopped, after the battery has rested a while



Edited 2 time(s). Last edit at 2019-03-15 07:06 PM by Gerald O.

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tahoe36c Avatar
tahoe36c Paul Hruza
Panama City, FL, USA   USA
1969 MG MGC GT "Little Red Rocket..."
1972 MG MGB GT "Tiny Dancer"
2002 Harley-Davidson Dyna
Gerald,

Alternator checks good... Battery 12.7 engine off, 13.8 engine on. And the "ignition light" which we all know is actually the alternator field excitation light goes off when revs go just over 900 or so and it stays off...

Told you man... This is a strange one. But I am not surprised considering the car is a 50 year old car. Hell, I am 57 and I know my starter wakes me up every morning, but sometimes my ignition system refuses to work too!!!!!

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Fred Winterburn Avatar
Ripley, ON, Canada   CAN
The problem with the logic is that a starter will draw at a minimum 200 amps even with a low compression engine. This will drop the battery voltage for sure. However, you had bad voltage readings off-starter without the engine running. Your tests of the ignition system with the engine not running should have been fine even with a compromised battery providing it would produce 12.4V or so without a load. A bad battery, and I mean a really bad battery can be loaded down by the 3 or 4 amps that an ignition system draws. However, it is impossible for a battery in such poor condition that it will not supply the ignition, to spin the engine too. You must have an intermittent connection between the battery and the ignition system. Further proof for this is that the engine just shut down while it was running. Assuming your charging system was doing its job, the engine would have stayed running despite the battery getting weak. Fred
In reply to # 3909418 by tahoe36c Fred,

That's my point exactly... How was it spinning the starter but not powering the ignition system properly?

Then again, the battery did check bad during a load test... I guess it was teetering on the edge of failure.

All connections are clean. No corrosion found anywhere. I was thinking intermittent ignition switch but never found anything wrong there either. I'd almost always get 12V at the positive side of the coil, though a few times it only showed 6 or 7 on the meter (which could have been me). It was the negative side that gave most of the weird readings during the troubleshooting.

Everything changed in the blink of an eye when I installed the new battery... Now she fires right up!

I guess Lucas & Mallory are friends once again.

Guess I'll just drive the crap out of it and see what happens next!!! smileys with beer



'Anyone who likes liver, can't taste it'
'If you want to repair car electrical systems successfully, learn Ohm's Law'.
'You can't shake hands with a snake'

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tahoe36c Avatar
tahoe36c Paul Hruza
Panama City, FL, USA   USA
1969 MG MGC GT "Little Red Rocket..."
1972 MG MGB GT "Tiny Dancer"
2002 Harley-Davidson Dyna
Fred,

I am not disagreeing with you at all... Everything we (you & I) understand about automobile electronic systems is in total agreement. Specifically ignition and charging systems.

That still doesn't change the fact that in the end there was only one bad component; the battery. Every other item tested fine.

The only other items that were "not correct" were the coil and ballast. Engine ran fine even though they were the wrong Ohms units for the distributor... Or should I say not the "recommended" Ohms.

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Fred Winterburn Avatar
Ripley, ON, Canada   CAN
Well, I still say you have an intermittent bad connection. For example, I had a CDI customer want to return a CDI because it stopped working. I talked him through some basic tests for continuity and they all passed. And then I finally asked the question I should have asked immediately and that question was: Does the engine run with the switch on the CDI selected to STD? He replied that it didn't work in either mode. Yet, he had voltage where he should have had voltage and continuity with his ohmmeter where it needed to be. The only conclusion was that it was a bad external connection despite the voltage and ohm readings being correct. After more encouragement, he cut off a connection on the coil that had been crimped and soldered and re-crimped the connection. Lo and behold the ignition worked in both modes, CDI and STD (Kettering). The supposedly bulletproof crimped and soldered connection had been done badly. It still had enough contact area to pass the minimum current that a low voltage supply ohmmeter provides and still had low enough resistance that with the ignition off, the voltage reading were correct with no load (no current) . So, a lesson learnt yet again, check the connections even if they appear or even measure fine. Fred

In reply to # 3909459 by tahoe36c Fred,

I am not disagreeing with you at all... Everything we (you & I) understand about automobile electronic systems is in total agreement. Specifically ignition and charging systems.

That still doesn't change the fact that in the end there was only one bad component; the battery. Every other item tested fine.

The only other items that were "not correct" were the coil and ballast. Engine ran fine even though they were the wrong Ohms units for the distributor... Or should I say not the "recommended" Ohms.



'Anyone who likes liver, can't taste it'
'If you want to repair car electrical systems successfully, learn Ohm's Law'.
'You can't shake hands with a snake'

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tahoe36c Avatar
tahoe36c Paul Hruza
Panama City, FL, USA   USA
1969 MG MGC GT "Little Red Rocket..."
1972 MG MGB GT "Tiny Dancer"
2002 Harley-Davidson Dyna
Fred,

I think we need to consider this electrical system is 50 years old... Then work our way up from there!! LOL... With this in mind I had some other thoughts you might consider.

Could it be that there is a connection somewhere in the circuitry that has built up enough resistance over the years (most likely through corrosion I have not yet identified) which caused this to occur only because the "failing battery" didn't have enough "punch" to push it through as good as the new one is now doing?

Which would mean it will happen again once the new battery reaches a certain level below that which is considered "normal"...

Just something to consider.

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Bill Morris Avatar
Nor Cal, USA   USA
1971 MG MGB
Paul,

My guess is that you have/had 2 different probs. I think the main culprit is the ign switch. When turned to crank, those connections are just fine and the motor cranks well. When moved to the run position, there may be some resistance in the switch which could decrease the available voltage to the motor. Slightly decreased voltage (the bad battery part) may be just insufficient enuf to keep the sparks happenin.

Or maybe I'll just take door number 2...
Bill



Home of the wayward cars...feel free to drop one off anytime.

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dickmoritz Avatar
dickmoritz Platinum Member Dick Moritz
Philly 'burbs, PA, USA   USA
The coil seemed fine but was a 3 Ohm and Mallory recommends 1.5
The ignition ballast was also 3 Ohm, and again, Mallory recommends 1.5


This doesn't compute. I'm not familiar with a 3 ohm ballast resistor, since it is my understanding that 12 volt ignition systems, old-school points systems, want a total of 3 ohms resistance through the ignition primary circuit when running. This can be achieved with a 3 ohm coil or with a 1.5 ohm coil and a 1.5 ohm ballast resistance in the primary circuit.

Can someone ed-you-kate me on a 3 ohm ballast?

Dick



Errabundi Saepe, Semper Certi
(Often wrong, but always certain)

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Rick Fawthrop Avatar
Rick Fawthrop Richard Fawthrop
Langley, WA, USA   USA
Paul do you have access to a graphing multimeter?

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