Electrical Problem

Robert/Texas

Robert/Texas

Well-known member
I’m having an electrical problem with my ’28 roadster. The car has an almost new 6-volt battery which cranks the engine over well, but the engine won’t start. The voltmeter stays at zero while cranking with the ignition switch on or when turning on the lights or blowing the horn. As I get 6.3 volts on both sides of the terminal box, I don’t think that there is anything wrong with the ammeter.

The car has a new diode style cutout. The BAT side of the cutout shows 6.3 volts and the ARM sideshows zero volts with the ignition both off or on. With the engine not running, I think that this is what it should be.

With the ignition off and a piece of thin cardboard slipped between the points, I only get voltage (6.2 volts) on the movable side with the ignition on.

Both the plus and minus sides of the coil show 6.3 volts with the ignition off or on.

The problem started some weeks ago. My wife and took the car for a long ride. The next day the battery was dead, and I replaced it with a new one. I also replaced mechanical cutout with another old mechanical one. We went for another ride and all was fine.

Sometime later, when we went for another drive, we didn’t get far, and the engine shut down. It started back up while I was coasting down a hill, so I turned around and headed home. Again, it stalled close to our house and we pushed it into my workshop.

I installed a new diode style cutout, thinking that this second old mechanical cutout had failed but that didn’t help, and here’s where I’m at now.

I’m having trouble thinking this through, (probably due to my age).

All help and suggestions will be greatly appreciated.

Thanks, Robert
 
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I think the earlier cars were wired on the 'wrong' side of the ammeter so the ignition draw doesn't show like the later cars.

I don't see anywhere that you checked for spark out of the coil and to your plugs?

Robert/Texas said:
With the ignition off and a piece of thin cardboard slipped between the points, the moveable side shows 2.45 volts and the non-movable side shows 6.3 volts with the ignition on. With the ignition off, both sides show 6.3 volts.
Click to expand...

This does not make since to me. With the ignition off, you sgould have no voltage at the points.
 
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If I'm reading the problem correctly, it sounds as if there is a problem somewhere from the ignition switch to the points.

Key on there should be battery voltage [6v] at the open point arm and no voltage to the ground side of the points. When points are closed there should be no voltage.

Key off there should be no voltage to points.

It seems like the switch may be grounding against the tank. The insolation in the primary cable could be bad.
 
Thanks Ruth and Patrick.
I just re-checked the points and they are behaving as they should. I don't know why I got those bad readings but I've corrected my original post. The points are much too close, so I'll correct that. I'm surprised the car ran as good as it did until all this happened.
Robert
 
Do you have a pop out switch or just a cable with a wire running through it? The cable with the wire inside will short out inside with age. Shake the cable and see if it starts,also make sure the Spark rod is not hitting the cable.
 
Voltage to both coil terminals - switch on or off - is normal. Wiring to the ignition switch and to the distro merit further investigation.
 
Thanks Wick and Mulletwagen.
I re-set the points to .018 and it still won't start. It has an after-market ignition switch disguised with an armored cover. I'm ready to drink a beer and hope to get back to it tomorrow morning.
Robert
 
To help you with your testing remember that current only goes one way thru a diode cutout. The Model A is positive ground. The Model T is negative ground. It follows that a Model A cutout and a Model T diode cutout look alike but they do NOT replace each other.
 
Remove sparklers, place a plug wire/strip about 1/4" from the good ground source, turn key on, hit starter and see if there is a spark to the ground.
 
The old spark check as previously mentioned is a good first start in troubleshooting. I always do the easiest thing first. The condenser is the next thing to easily replace with a no blow & check. If still no spark, a volt/ohm meter set on Ohms resistance can be used to check the ignition circuit for opens or high resistance in the switch to breaker circuit or switch to coil side. The power side of the coil can be checked for voltage easy enough since it's hot all the time. Coils can go bad too but I check everything else before changing it out. The coil should have about 1.5 ohms from small terminal to small terminal.

The model A is somewhat unique in the fact that the ignition switch is connected in the breaker side of the circuit. More modern cars switch the hot side of the coil on the power in feed and the breaker side is just connected from the distributor to one of the coil primary terminals. Which side of the two small coil terminals is connected to what is where the polarity comes in. Positive ground systems use the positive terminal for the breaker as a general rule but it's usually best to have a polarity tester to make certain the coil will function properly.
 
Ruth said:
I think the earlier cars were wired on the 'wrong' side of the ammeter so the ignition draw doesn't show like the later cars.

I don't see anywhere that you checked for spark out of the coil and to your plugs?



This does not make since to me. With the ignition off, you sgould have no voltage at the points.
Click to expand...


https://www.fordbarn.com/forum/showthread.php?t=251629&highlight=ammeter+wiring



In this string the wiring change on the ammeter wiring is discussed. If wired this way the ammeter has a slight wiggle from the points opening/closing. Very useful if your car does not start/fire, the wiggle indicates that the points/ignition switch/coil/wiring are somewhat functioning correctly.
Does not give status of the high voltage. That can be checked by taking a lead off the spark plug, placing it 1/4 inch to 1/8 inch away from the spark plug, and using the starter rod with the ignition switch on . You should see a nice blue spark.
 
Thanks to all of you for your help.

barnstuff
I'm sure that the diode is positive ground. I bought it from Snyder's and the box it came in and the sticker on the bottom of it say so.

Patrick L.
I just tried this and didn't get a spark.

rotorwrench
I don't have a new condenser but I'll get one when I order some parts. It's always good to have a spare one. The volt/ohm meter shows 1.6 ohms and 6.3volts.
Closed Cab PU
The ammeter used to wiggle when I cranked the engine as it still does on my other A, a March '28 open cab pickup with most of the early features.

Thanks again to all of you, Robert
 
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So far no one has mentioned the wire going between the upper and lower plate in the distributor. I know you said you are getting voltage to the movable point arm with the ignition on but it may be intermittent. Try moving the retard leaver while you are checking for voltage at the point arm. Maybe using a test light might make it easier to see.
 
OK, the problem seems to be primary side of the ignition.

Check to make sure the switch and ignition cable are working as they should all the time [wiggle while cranking]. Then as mentioned check the upper/lower plate wire. Then comes the condenser and finally the coil as mentioned.
 
Try a new coil wire before you start taking things apart. This fooled a couple of our members last summer and they towed it in because of an old coil wire.
 
I agree with Jack. If you have 6V at the points you should at least get a pop or a sputter. Have you also tried cleaning the points? It's unlikely that's the problem since you were driving recently but stranger things have happened and it's a quick test.
 
The model A is the ONLY car I know of that has the ignition switch wired between the coil
And points.
A simple...sure check
Remove the two parts of the distributor cap.
Turn the engine so the points are closed
Turn on the key.
Open the points with a wooden or plastic pointed object. Did the coil spark when you did that?
 
Thanks to all of you. I think that I’ve found the problem which now makes me feel kind of foolish. I’m farsighted and use reading glasses when looking at things up-close. I had misplaced the glasses and was using an old pair while testing the distributor and re-gapping the points.

This morning, after reading your posts, I started rechecking things. I found that the movable-side point was completely worn out. I’m surprise that it ran so well up to the point of failure.

I remembered that I had rebuilt this distributor some time in the past. Looking through my receipts, I found that I bought the parts from Bratton’s on 2/26/2001. The condenser on the receipt was noted as Short-Proof.

Although I should have figured this out sooner, I’ve gained a lot of knowledge from your posts. I’m going to order point-set and a spare condenser.

I’ll let you know if this solves the problem.

Many thanks again to all of you, Robert
 
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