Ignition problem, could use some insight.

Automotive Stud

Automotive Stud

Well-known member
What I've got is a '47 59ab motor with the stock distributor. I'm running the one piece crab cap, a big old square Mallory coil, and I'm running on 12v neg ground. The car has been on the road like this for about 7-8 years.

Yesterday I had it die on me on the highway. I have two problems that I don't know if they are related. It just shut off at 70 mph. When I costed over I saw it threw the fan belt off, but not the water pump/alternator belt, and I don't think it caused any other damage. It didn't get hot because I was on the highway. After getting it home I tried a test light on the coil, I don't show any juice on either of the terminals. I have a big mallory ballast resistor on the firewall, one wire goes to the stock ignition switch, the other obviously goes to the + coil terminal. With the key on I have power going into the ballast but the test light isn't even dim on the other side of the ballast. I thought I had it nailed down, but I switched in another new ballast from my dad's model a with the same setup and I still just get a ballast that is warm to touch and only shows power on one terminal. I'm at a loss now and welcome suggestions, thanks for reading.
 
Are you saying there is no spark at the plugs? Is the test light intended for 12V and not 115? Do you realize the role the points play in the circuit? Disconnect the wire from ballast to coil and see what the test light does. It could be time for a new coil if the old Mallory is shorted.
 
JWL said:
Are you saying there is no spark at the plugs? Is the test light intended for 12V and not 115? Do you realize the role the points play in the circuit? Disconnect the wire from ballast to coil and see what the test light does. It could be time for a new coil if the old Mallory is shorted.
Click to expand...

Yes I have a good automotive test light, and no spark at all. There isn't power getting to the points. I tried disconnecting the wires from the coil and checked, I still have no power on that side of the ballast that goes to the coil or on the wire that goes from the ballast to the coil. I was sure it was a bad ballast until I replaced it with another and have the same problem.

FlatheadTed said:
Run a fresh hot wire to the ballast from the battery
Click to expand...

I'll try that next but it has power going into the ballast from the key so I'm not sure if that will do anything.
 
Run the jumper straight from the battery to the coil, and see if it starts. If it does, you'll know the problem is somewhere between the battery and the coil (e.g., ignition swith, resistor, or the wiring). If it doesn't, it's probably the coil, points, or a problem in the distributor itself.
 
Automotive Stud said:
Yes I have a good automotive test light, and no spark at all. There isn't power getting to the points. I tried disconnecting the wires from the coil and checked, I still have no power on that side of the ballast that goes to the coil or on the wire that goes from the ballast to the coil. I was sure it was a bad ballast until I replaced it with another and have the same problem.



I'll try that next but it has power going into the ballast from the key so I'm not sure if that will do anything.
Click to expand...


there should not be power to the points, they are ground put your lead to ground to test the points
 
You can not use a test light on the coil, or on the coil side of the resistor. Use a multimeter. The resistor will not let enough current to pass to light the test light. With the distributor points open you will see voltage to ground on the wire of the coil going to ground (in your case - ) With the distributor points closed you will see zero volts there. Check with a digital multimeter what is the primary resistance, in ohms, of the coil. What is the resistance of the "Big Mallory Resistor" in ohms.
 
I had a similar problem that drove me nuts. My '41 would shut off like your '47. It then became a flathead on a flatbed. This happened 5 times over a few months. Finally traced it to the condenser. It was not bolted securely to the block due to another mechanic stripping the threads and a bunch of grease in the bolt hole. The theory is that as the engine got warm on a trip and vibration caused the condensor to lose ground the engine shut off. Next day the car would run fine due to cooling down etc. Have not had the shutoff problem for going on 3 months. I don't know how your condenser is mounted but it is worth a look.
 
Terry said:
You can not use a test light on the coil, or on the coil side of the resistor. Use a multimeter. The resistor will not let enough current to pass to light the test light. With the distributor points open you will see voltage to ground on the wire of the coil going to ground (in your case - ) With the distributor points closed you will see zero volts there. Check with a digital multimeter what is the primary resistance, in ohms, of the coil. What is the resistance of the "Big Mallory Resistor" in ohms.
Click to expand...

I'll do this tonight and post back.

Joe Immler said:
I had a similar problem that drove me nuts. My '41 would shut off like your '47. It then became a flathead on a flatbed. This happened 5 times over a few months. Finally traced it to the condenser. It was not bolted securely to the block due to another mechanic stripping the threads and a bunch of grease in the bolt hole. The theory is that as the engine got warm on a trip and vibration caused the condensor to lose ground the engine shut off. Next day the car would run fine due to cooling down etc. Have not had the shutoff problem for going on 3 months. I don't know how your condenser is mounted but it is worth a look.
Click to expand...

Condenser is mounted to distributor, and I tried another distributor. Also mine hasn't gotten spark at all since it shut off Sunday.
 
Thanks everyone. I bypassed the ballast and got it started. I think the battery voltage was too low. I see now that it's running again my powermaster alternator doesn't have any output. I'm going to try to tighten up the belt first, otherwise I'll have to take it off and have it looked at.
 
I was going to ask about the battery but figured if it started the battery should be OK. G.M.
 
G.M. said:
I was going to ask about the battery but figured if it started the battery should be OK. G.M.
Click to expand...

I thought the same, but I guess with only 11 volts it can still spin the 6v starter with no problem. Odd my volt gauge looked okay until it quit, though it clearly isn't charging at the moment. Hope to have it tested today. When I bought the powermaster in 2010 there was nothing but great reviews, now I'm seeing a lot of not so nice things about them.
 
Hopefully when you get the charging system working it will be fixed....

I stayed out of this discussion from the start up as i just felt we didnt have enough information. But watching it every day i think it came out ok anyway.
However lets discuss the situation and what was said.

Customer said :

What I've got is a '47 59ab motor with the stock distributor. I'm running the one piece crab cap, a big old square Mallory coil, and I'm running on 12v neg ground. The car has been on the road like this for about 7-8 years.

You always need to give the car credit , if it ran ok for 7 years that rules out quite a bit. Coil, ballast and ignition seems to be very functional.

Yesterday I had it die on me on the highway. I have two problems that I don't know if they are related. It just shut off at 70 mph. When I costed over I saw it threw the fan belt off, but not the water pump/alternator belt, and I don't think it caused any other damage. It didn't get hot because I was on the highway.

Another bit of info, the car shut off and threw a belt off the front of the engine. Now after hearing more it could very be that the alternator caused this entire problem, maybe a short to ground causing the ignition to just quit etc.???


After getting it home I tried a test light on the coil, I don't show any juice on either of the terminals. I have a big mallory ballast resistor on the firewall, one wire goes to the stock ignition switch, the other obviously goes to the + coil terminal. With the key on I have power going into the ballast but the test light isn't even dim on the other side of the ballast. I thought I had it nailed down, but I switched in another new ballast from my dad's model a with the same setup and I still just get a ballast that is warm to touch and only shows power on one terminal. I'm at a loss now and welcome suggestions, thanks for reading.

As others stated , you really got to know your test light and the voltages it will light under. Also the use of a test lamp is positional , meaning the position of the distributor makes all the differences in the world with test light testing.
Ex: If the points are closed ( grounded) then current will flow making the voltage drop high in the ignition circuit causing a very dim test light based on voltage drop across the components.
Makes it even tougher to diagnose.....
staying tuned hoping this one is fixed ......with a new alternator etc ????:eek:
 
BUBBAS IGNITION said:
Hopefully when you get the charging system working it will be fixed....

Another bit of info, the car shut off and threw a belt off the front of the engine. Now after hearing more it could very be that the alternator caused this entire problem, maybe a short to ground causing the ignition to just quit etc.???


As others stated , you really got to know your test light and the voltages it will light under. Also the use of a test lamp is positional , meaning the position of the distributor makes all the differences in the world with test light testing.
Ex: If the points are closed ( grounded) then current will flow making the voltage drop high in the ignition circuit causing a very dim test light based on voltage drop across the components.
Makes it even tougher to diagnose.....
staying tuned hoping this one is fixed ......with a new alternator etc ????:eek:
Click to expand...

Thanks, we'll get this sorted out and see where I'm at. I don't think the belt failure was related. The alternator/water pump belt was still in place, just the fan belt. I didn't replace it when I put the other one on so it was old, it probably didn't like the long ride. I've used this test light on coils before and I knew it should be a little dimmer on the ballast and coil. It was clear I was getting nothing at all.

Bassman/NZ said:
I'm confused as to how the fan belt got thrown off..... it must have been very loose...
Click to expand...

The belt actually failed, it was coming apart but still barely flopping around the fan and crank pulley. Again, I think old age and higher rpms were the cause there. I didn't notice any temperature change but being on the highway kept the air flowing, I've never had problems with this one running hot.
 
Tonight I took the powermaster to Napa and it actually reset their machine twice, so I'm thinking it's shorted internally. I'm going to shoot an email to powermaster to see if they will do anything but I doubt it. I still have a local generator shop in town I'll drop it off at tomorrow and see if they can do anything with it.
 
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