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Ignition Troubleshooting on the Road

May 26, 2019 | Troubleshooting & Repair

Ignition Troubleshooting on the Road Note: This article has a photograph and a diagram. How do I insert them in this article?

If you own a 356 "driver" and drive it on trips as I do, the most crucial problem you can run into is a failure of your car to run. You want to solve this problem so it can bring you home with the least amount of effort, time and cost. The problem can be solved if you carry the right parts so if one fails, you have a spare. However, to isolate the failed part, knowledge is critical—if you cannot isolate the problem, you cannot fix it. While many parts can fail, only a very few can prevent your car from returning home. This is a brief tutorial on how to appropriately prepare for your trip (an ounce of prevention is worth a pound of cure) and how to find out what is causing your 356's inability to run.

Over the years we have had two 356Cs in our family from a new one in 1964 for twelve years to a pre-owned one over the last 25 years. They are 26 serial numbers apart so were built on the same or adjacent days. Both coupes are identical with the same interior but red outside, Ruby and Signal. We have had three road breakdowns, one a broken crankshaft (obviously not fixable on the road), one a broken points cam follower, and the last, a faulty connector in the back of the ignition switch. We've never had a fuel or mechanical failure and hence this article is about how to isolate and repair ignition electrical problems. The ignition can be more prone to failure than other parts of your 356 and can usually be easily fixed on the road. Other kinds of failure can occur too, but when your engine shuts down in a fraction of a second, you know it's ignition. Hence this is a primer on how to identify engine ignition problems and fix them. Obviously, there can be many types of electrical problems, lights, turn signals, starter, etc. which will not prevent you from returning home. If the starter fails, one can always "pop-the-clutch" and start the car this way. This is about the ignition system which must operate or your engine will not run.

356s, like many other cars of this vintage employ a Kettering ignition system, which includes a battery, coil, distributor and points, generator, voltage regulator, and spark plugs. If any of these parts go bad or any connections between them go bad, your engine will not run or not run correctly. Kettering was a prolific American inventor, engineer, businessman, and the holder of 186 patents. He was a founder of Delco, and was head of research at General Motors from 1920 to 1947. Among his most widely used automotive developments were the electrical starting motor and leaded gasoline. While the starter is technically not part of the ignition, Clyde Coleman and he invented it and it first appeared in a 1912 Cadillac. The Kettering ignition system first appeared in a Cadillac in 1910.

Many people who are skilled at solving problems like those occurring on your 356 follow some simple but effective guidelines. Look for the simple ones first. These take less time to find and are easier to fix. Follow a logical sequence. Be familiar with what you troubleshoot. Luck often rewards the well prepared.

As a general rule, to solve ignition problems you can be greatly helped by having an electrical schematic and one does come as part of the owner's manual. It is very small and very detailed and knowledge of electrical circuits is important but not required. There is also an excellent 356C 24" X 18" color version mentioned in the 356 Registry, page 66issue 40-5 or 1-2/2017 available at gfyryan@aol.com.Since this article restricts itself to only the ignition system, the following is a physical diagram of the parts, cables, and connectors—a better way to visually troubleshoot.


First, it is important to know how the ignition switch gets and delivers 6 volts to the rest of the ignition system. 6V from the battery goes directly to the supply side of fuses 2, 3, 4. A red wire goes from 4 to the light switch (labeled 30) and then to 30 of the ignition switch. This is power to the ignition switch even when the key is off.When the key is turned on, 6V. is supplied to 54, the radio, and to the three connections labeled 15. From here one black lead goes to fuse 1, one, colored blue/yellow goes to the combination meter and then on to 61 of the voltage regulator, and one, black/grey goes to the + on the coil. At 50 a black lead goes to the starter solenoid and is activated when the spring-loaded key is turned further CW.

Of importance to us is the coil which, with the key on, must have voltage at + connection. If the points are open, that same voltage will appear at the – connection of the coil. There is a lead (yellow in my case) from the – neg. of the coil to the 6V. connection on the side of the distributor. If the points are closed, that connection will read zero voltage since the points ground the – connection of the coil. Also the middle high voltage connection from the coil goes to the center of the distributor which distributes the high voltage to the 4 spark plugs.

Your engine dies on the road. What now? First, get out your electrical kit with these instructions, knee pad, 356 tool kit, and open the engine hood. Check the fan belt and the high voltage leads from the coil to the distributor and plugs. It won't solve anything but it will make you feel better.

To trouble shoot follow these steps and referring to the diagram above.

1.Connect the negative lead of your voltage indicator (it is easier to probe with than a volt-ohm-meter) to any convenient ground which is anything attached to the metal part of the engine or chassis.

2.Set the parking brake and put the transmission in neutral. Turn on the ignition key and probe with the positive lead of the voltage indicator to the + connector of the coil. It should have voltage. If not, you have a problem upstream toward the battery. Logically you should now test the back of the ignition switch, but an easier approach is to open the bonnet, and test at the fuse area. With the key off, fuses 2,3, 4 should all have voltage since there is a direct connection to the battery. If not, you have a dead battery (unlikely) or a bad connection in that area. If all proves well, now it the time to test the back of the ignition switch. See picture below.

Photo of the ignition switch looking rearward from under the dashboard. The connectors are of the bullet type.

3.With the key off, test for voltage at the red lead labeled 30. If no voltage, you have a connection problem from the 4 fuse to the back of the ignition switch. If voltage is there, turn the key on and test for voltage on all 3 connections labeled 15. If all 3 have no voltage you have a bad ignition switch. If voltage is there, you have a problem between here and the + connector of the coil.

4.If you have a bad ignition switch, meaning that there is no connection from the 30 terminals to the 15 terminals, there is a way to get voltage to the two 15 connections of importance. It involves moving two leads from the 15 position to the 30 position. You don't want any hot wires when doing this, so disconnect a lead from the battery. Now move the blue/yellow bullet connector wire (going to the voltage regulator) to one of the open 30 connections. Move the black/grey bullet connector wire (going to the + of the coil) to the remaining open 30 connection.The remaining bullet connector on 15 is not crucial as it only goes to fuse 1 which supplies voltage to the back up light, the stop light, and the flasher, none crucial to the ignition system. When you have reached your destination don't forget to unplug a battery connection so the battery does not drain.

5.Go back to the coil and test the – neg. part of the coil. It should read the same as the + connection if the points are open. If the points are closed, use the generator pulley wrench to visually move the distributor cam so the point's cam follower is on a high lobe of the cam. The voltage at the -neg. connection of the coil should have voltage. If not, you have a bad coil or connection.

6.Assuming the coil is good, continue probing at the back of the distributor where a lead comes from the -neg. of the coil. It should also show voltage. If not, the lead from the -neg. of the coil is bad or either of its two connections. Another problem which could cause no voltage at the side of the distributor is a bad condenser. Since a good condenser will be an open circuit, a faulty condenser will show up as a short circuit causing the lack of voltage. If this is the case, replace the condenser.

7.Assuming all is good going downstream from the coil, a good and simple check for spark at the points and with the car in neutral, is to turn on the key, and with the generator wrench, turn the generator and engine pulley CCW so top dead center indicator is at about 11 o'clock. Now turn the wrench CW slowly so the top dead center indicator just passes by the engine mark. You should hear and see a spark jump across the points at 3° before top dead center. This procedure is, of course, how you time the engine. If the spark jumps, you should have an operating engine. If no spark, it could be a totally untimed engine or a problem in the distributor. If it is timing, do the test again going further CCW to start and further CW past the timing mark and hope to hear a spark but one off the mark. If a spark exists the solution is to time the engine by loosening the distributor clamp nut and turning the distributor a small amount to find the correct position of the distributor. This is of course, 3° before top dead center.

Another interesting article from the 356 Registry about the ignition switch explains how a faulty switch can manifest itself in several ways. Volume 18 No 1., May/June 1994 was a repeat of Volume 8, April/May 1982. This 356 experienced starter problems and strange lighting intensity on both the generator light and the oil pressure light located in the dashboard combination meter. The owner was ready to get dirty and look at the starter but realized the combination meter is connected to the ignition switch as is the starter solenoid. Hence a bad ignition switch caused these symptoms.

The spreadsheet at the end is what parts I carry for electrical ignition problems, as these are the most critical. My complete list is larger but probably not that much better. You only want to carry parts which can be installed on the road or in a remote repair shop. There is also a trade off in what you carry so your parts do not occupy too much volume in your small car. Additionally, there is a cost consideration which will limit what you can carry. None of these should limit you carrying a reasonable amount of parts and have a good chance of effecting a repair. The whole complement of parts should be divided into containers, such as electrical, fuel, mechanical, and tools. I actually carry more than the ignition parts, but frankly the ignition is where trouble is most likely to be found.

356C Parts and Tools

1996 prices

Electrical Ignition

Stoddard

Extended

Description

Qty

Part No.

Cost

Cost

Spark plugs

4

999.170.001.90

$2.20

$8.80

Voltage regulator

1

616.603.203.00

$153.00

$153.00

Coil

1

547.602.101.00

$29.60

$29.60

Coil to Distributor High Voltage Wire

1

Generator

1

616.603.101.01XXX

$122.00

$122.00

Generator Woodruff key

1

N.012.705.1

$0.90

$0.90

Generator brushes (3/4" across and black)

1

616.603.904.02

$9.35

$9.35

Distributor clamp, clip set

1

NLA.602.954.00

$4.50

$4.50

Distributor insulator kit

1

NLA.602.936.00

Distributor hold down plate

1

539.09.313

Distributor cap - black

1

616.602.215.00

$9.50

$9.50

Distributor rotor

1

616.602.221.00

$5.85

$5.85

Distributor condensor 280 nF

1

616.602.907.02

$6.85

$6.85

Distributor condensor bracket

1

NLA.602.900.00

$6.40

$6.40

Distributor points

1

616.602.226.01

$4.95

$4.95

Bullet connectors

4

999.652.102.10

$0.85

$3.40

Hub for pulley

1

547.09.304

$18.18

$18.18

Inner pulley half

1

539.09.315

$10.75

$10.75

Outer pulley half

1

539.09.316

$7.87

$7.87

Pulley spacer

4

539.09.314

$0.90

$3.60

Pulley nut

1

547.09.303

$13.99

$13.99

Electrical Tape

1

Alligator line, clip on each end

2

Generator V Belt

1

999.192.006.50

$6.00

$6.00

Fuses, 4 Red, 4 Blue, 7 White

Feeler gauge

1

Voltage Indicator from Walmart

1

Small bright flashlight or forehead light

1

Emery paper and QD Electronic Cleaner

1

Needle Nose Pliers for bullet removal

1


Other General Tools:

Metric sockets

11

9mm to 27mm

Spark Plug socket

1

Metric open end wrenches

7

6mmto24mm

Metric box end wrenches

7

6mmto24mm

Ratchet and extensions

4

356C Tool Pouch

1

356C Factory Manual

1

Knee pad

1

Wiring diagram + Joe Leoni books

1

NLA.612.001.00

$10.05

$10.05

1 Comment

Profile missing thumb
Bill Mcbride
July 13, 2019 at 6:13 PM
What size crescent wrench for the fan pully? And the direction should be clockwise for loosing and counter clockwise for tightening , if memory serves me correctly. And does all of this relate to a 12 V system conversion with a VW alternator since the refurbished generators use Chinese brass bearings instead of the Canadian copper ones . I’ve burned out 8 generators in succession and rapidly . Thus the alternator .Better safe than sorry .Especiall in long trips