gadam05

G

gadam05

Junior Member
I am looking for some help to solve a problem with my 1930 model A. I've owned the car for 26 yrs.and never had this occur.
The car was running in my driveway while I was doing some yard work. The car stopped suddenly, and I could not get it to start and run more than a few seconds. I have checked the following: gas flow, 0k, carberator, ok but swapped to another to be sure. Ignition: starter engages, car tries to start, turning over rough, but runs for only a few seconds. checked point setting,ok,,timing-right
on., rotor and distributor body and cap ok,, spark plugs gaped ok. I have not checked the coil, How can I do that? Is that a possibility? I need some ideas, please.
 
Check the condenser first by changing it with a known good one. If that don't work, change the coil to a new one.
 
I like to do the easiest checks first. Just hold the coil wire 1/4" from a head nut and see if you have a good blue spark while cranking the engine with the key on.

Pull the choke for a couple revs. Do you have gas dripping out the carb intake?
 
Well, with all the coil & condenser guess, it should be easy enough to pull the coil wire while cranking it over to see what the spark looks like. When you say it is turning over rough, my initial thought was timing gear. If it had jumped a tooth or two, it could create some symptoms as you are suggesting.
 
Hello,and thanks to my respondents. I appreciate your ideas. Checked my gas cap venting----ok. changed my condenser--- no change. checked my coil spark--spark was good but not blue in color,so I changed the coil. now have a blue spark, but no change to my problem. Because this problem began when the car just stopped while it had been running at idle just sitting in neutral in the driveway, I would Question the thought of the timing gear jumping a tooth.
I do appreciate the ideas---and welcome any other thoughts. Thanks
 
I don't know about conditions in the States, but here in NZ, since converting to non lead fuel, it's quite often the case that after idling a vintage engine for a length of time, that the plugs foul up.
For almost all running problems, the plugs were the first thing to check with running problems?
Keith
 
One of our club members had something similar happen. It turned out to ne a frazzled coil wire that only made intermittent contact. Try replacing it.
 
I was wondering if you have 10% ethanol crap gas and it got so hot just setting at idle that the crap gas started to boil and give trouble?

How is the running when the engine is cold?
 
I now have an authentic used old stock Model A coil. It works fine in its mount and also works fine when held in hand and disconnected entirely from the car except for the wires. It does not need to touch the firewall at all. BUT... earlier I had a replacement coil of uncertain vintage in my new restoration. It used a clamp mounting screw and nut to tighten the firewall mounting bracket around the coil. The clamp and firewall mount assure a good full time ground for the outside case of that coil and it did reqire grounding. After about 350 miles of initial running, vibration loosened that screw, the coil slipped down just a bit and the fresh paint on it eliminated the electrical grounding. The car stopped running suddenly and completely till the coil was repositioned and the clamp tightened. Finding that was a real mystery. The symptoms you list could be a variation of this anomaly.
By the way, I have never been clear on the wiring logic for the high voltage coil component of the coil. Wiring diagrams do not show a current source. Can anyone explain this? Rancho
 
The black wire from the terminal box supplies the voltage to the coil primary. The red wire runs from the coil primary through the switch and grounds at the points to complet the coil primary circuit.

I don't know of any coil where the metal can is connected to the coil primary circuit, and the coil mounting should not need to be grounded. You only need a feed wire and a ground wire to complete the coil primary circuit, and if either one is through the can, the points can't do their job.
 
last i knew the coil secondary grounded via the can; the other end of the secondary is obv. the high voltage coil wire. An automotive coil is in essentially a DC transformer, with 12 v in and 10-15 K volts out. Of course, DC voltage doesn't fluctuate so this violates the principles of a transformer. BUT add the points to make and break the primary and voila you have fluctuating voltage after all
 
tbirdtbird said:
Of course, DC voltage doesn't fluctuate so this violates the principles of a transformer. BUT add the points to make and break the primary and voila you have fluctuating voltage after all
Click to expand...

Like you said the points make and break so the voltage goes from 0 max 0 max 0 max similar to AC.

circ_ic.gif
 
Notice in Mike's picture the secondary is tied to the primary winding, and not the can. This is the typical coil practice.
 
I just experienced a similar situation with my 31 SW, and after a long list of tests it was the condensor that was the problem. I replaced the coil, distributor body and cap, did compression test, ,checked oil for sign of water, insulated dash light wire completely, checked timing, made sure intake manifold was torqued properly, changed distributor. Now the A RUNS GOOD. And I am Hot and Tired after a 105 degree day. Good luck ,hopefully this will give you some ideas.

Jim from Kansas
1931 SW FORDOOR
 
No wonder condensers die so fast & points burn out without them, the secondary voltage goes straight through them! If the secondary was grounded through the can would it make the condenser & points last longer?
 
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