Could a bad tachometer make a Model A hard to start?
 

I’m still learning about the Model A ignition system (and tachometers, for that matter), and I’m wondering if a bad tachometer could make a Model A hard to start. Here is some background information.

Around the beginning of November, I noticed that my tachometer (https://www.westach.com/product-page/2ct32-6v), purchased new in May of 2020, was acting flakey from time to time. (From May to October, the tachometer worked fine.) While idling at a stop light, sometimes the needle would “float” high, but there was no corresponding change in the engine sound, and then the needle would eventually drift back to 500-700 RPM or so, again without any change in the engine sound, meaning that the RPM sounded constant, but the tachometer erroneously indicated a change in RPM. Also, while driving at what was likely to be 1500 to 1800 RPM, the needle would sometimes waft up to 2200 to 2500 RPM, with no perceptible change in the engine sound. Apparently, the tachometer sometimes has a mind of its own and displays whatever it wants to display. The unit appears to be under warranty; so, I need to call about it.

However, I’m curious. For the last couple of weeks, the car has been uncharacteristically hard to start. (https://www.fordbarn.com/forum/showthread.php?t=289945) I’ve jumpered the junction box posts together to take the ammeter out of the equation as a potential problem. I’ve tried a number of different coils (two oil filled coils and one Ford script coil) and two condensers. I’ve thought I had the problem solved a number of times, but the car would continually “backslide” into hard starting over the course of a couple of days.

I have observed the following while working through this issue.

1. I‘ve used a Sparklite (https://www.brattons.com/ignition-sp...il-tester.html) a number of times when cranking the engine, and I’ve noticed that the engine does not “catch” unless there is a fairly bright LED flash at some point from the Sparklite. (A weak spark sends no flash to the LED or just a faint flash to the LED.)
   
2. When the car did “catch,” I would always see a strong LED flash from the Sparklite as the engine "caught," and a strong LED flash would continue while the engine was running.
   
3. The engine is hard to start with or without the Sparklite connected. So, the Sparklite does not seem to be causing any of the problem.
   
4. Not considering that the tachometer could be a potential problem (until now), I’ve always connected the tachometer to both terminals of whatever coil I’ve had in place.
   
5. Regardless of the coils and condensers, the car would still be hard to start at some point, regardless of whether the engine was hot or cold.
   
6. I’ve checked the points a number of times, and they are set at .018.
   
7. The distributor shaft does not appear to have any lateral play in it.
   
8. For the entire episode of hard starting, I seemed to be getting poor spark to the points.

Yesterday, I installed a Pertronix 40111 epoxy coil (https://smile.amazon.com/gp/product/...?ie=UTF8&psc=1), and the car began to start reliably again (hot and cold), even with the tachometer connected to both sides of the coil. Installing the Pertronix coil was the final change I made. So, it's higher output appears to be allowing the engine to start reliably again.

So, I’m wondering if a bad tachometer could make a Model A hard to start. Could the tachometer be robbing the other coils of enough of their power so that the points do not get enough spark to fire the engine?

Re: Could a bad tachometer make a Model A hard to start?
 

With all this missing around, did you consider checking the Battery? Does not matter if new or not, still could be bad. If battery load test good, then check all the grounds. Set the points at .020-.021. If the car is still positive ground, are you connecting the leads to the correct terminals? How many volts are you getting to the points cold, if 6 volts, that is what the cold reading should be.

Re: Could a bad tachometer make a Model A hard to start?
 

Unless it's defective and shorting stuff out, then I really doubt it. Disconnect it and see if it helps. I think your issue lies elsewhere. Colder weather will make it harder, and require a little more choke on a cold start than summer.

Re: Could a bad tachometer make a Model A hard to start?
 

I keep the battery on a trickle charger, so the battery has good charge (6.3 volts or so, according to my test meter) every time I try the starter. The starter turns freely when engaged. I can try setting the points wider to .020-.021, maybe tomorrow. The car is positive ground. The leads are connected to the correct terminals. With the points open, the movable arm gets 6.3 volts.


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Re: Could a bad tachometer make a Model A hard to start?
 

It’s disconnected from the Pertronix coil at the moment. (It didn’t seem to make any difference with the tachometer connected or not with the Pertronix coil. I didn’t think to question the tachometer until after I installed the Pertronix coil.) I was thinking about putting one of the other coils back in the car with the tachometer disconnected to see if it made any difference.


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Re: Could a bad tachometer make a Model A hard to start?
 

Am I understanding correctly? Widening the point gap should create stronger spark, correct?


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Re: Could a bad tachometer make a Model A hard to start?
 

Yes because it increases the dwell time.

Re: Could a bad tachometer make a Model A hard to start?
 

Check the battery water level because you always have it on your charger, clean the points ( they can get a coating on them) and open the gap! My A likes the point gap closer to .022 @ .018 the starts to run a little funky.

Re: Could a bad tachometer make a Model A hard to start?
 

Thanks. I really appreciate your feedback.


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Re: Could a bad tachometer make a Model A hard to start?
 

I recently checked the battery. The water level is good. I recently cleaned the points (several times). I plan to try widening the gap.


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Re: Could a bad tachometer make a Model A hard to start?
 

Dwell is the time the coil is energized and saturating, meaning the points are closed. The reason the spark is “hotter” with a wider gap, is because the coil is putting out more voltage(up to its maximum design). If the gap is too wide, you’ll over work the coil and it will fail.

Re: Could a bad tachometer make a Model A hard to start?
 

Thanks for the feedback.

The higher output from the new Pertronix coil “fixed” the hard starting for the moment, and my wife and I were out in the car yesterday because it turned out to be a warm day. The car has fired up on first crank multiple times all day yesterday and the day before on the Pertronix coil.

I plan to put one of the other coils back in the car and adjust the points wider to see if that makes a difference with either of those coils. I'd like to determine what caused the issue in the first place.

Could a bad tachometer make a Model A hard to start?
 

Several days ago, I disconnected the tachometer, and the car started right away, with no other changes. I also swapped the Pertronix coil with the two other coils I had on the shelf that I have been using for testing, and the car started right away with each of them as long as the tachometer was not connected. (Those two coils were really struggling to get the car started when the tachometer was connected to them.) So, apparently, the tachometer is robbing enough power to keep the car from having sufficient spark to start easily. I called the tachometer vendor, and the the guy (who was extremely nice and knowledgeable) said that can sometimes happen if the tachometer’s inducing coil (I think that is what he called it) starts to go bad. The tachometer is under warranty; so, I’m shipping it back for repair.


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Re: Could a bad tachometer make a Model A hard to start?
 

I would use a battery maintainer in place of a charger, Less apt to damage the battery

Re: Could a bad tachometer make a Model A hard to start?
 

I received the repaired tachometer from Pete Cornelius yesterday. (Wow, that was a quick turnaround. Shipping was probably 3 days each way. So, he must have repaired it on the same day that he received it. He seems to be a great guy, and he was very helpful on the phone.)

I plan to reinstall the tachometer as soon as I can. The car has been starting consistently on the first crank without the tachometer installed.


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Re: Could a bad tachometer make a Model A hard to start?
 

Thanks for the feedback. The charger I’m using is a charger/maintainer.


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Re: Could a bad tachometer make a Model A hard to start?
 

I just wanted to report back on this issue.

I got the repaired tachometer installed today. The car starts on first crank with it connected now. I’m now using the same coil and condenser that I was installed prior to starting becoming an issue.

I’m glad to put this issue to bed. Thanks, everyone, for your feedback.


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