The Stovebolt Site Forums The Shop Area The Electrical Bay all I wanted was turn signals

help....thought I had all the knowledge to figure out engine starting problems with these old trucks, but this one I cannot overcome. Specimen has a 1954 235 engine, and I've had this truck and worked on it as well as driven it a little for 20 years very much original, only converted to 12 volt about 15 years ago. Truck is not a daily driver. Sat up for a week or two while I installed turn signals and then 2 days of heavy fog rolled in, now I cannot get her started. Seems electrical, chased voltage and fire from ignition switch through resistor, down through coil, and into points, where I get a spark when I turn on the switch and hit with a screwdriver. Engine turning over but will not hit...new battery, which I'm slowly wearing down trying to start....Points and condenser and rotor all less than 3 yrs/ about 500 miles maybe. Points gap shows about 0.017" when open. So, my question is if the points show fire, does that mean they are transferring fire through the plug wires? I live alone and have no one to watch a plug wire or plug for me. Maybe there is a way to do this from under the hood with a big screwdriver.....Carb, fuel pump, fuel system good on this old truck, I spray in starting fluid and still nothing...definitely thinking a fire problem...also, coil is new and tested good for Ohms....any ideas? maybe just replace the points which I might have burned up while fooling around with the turn signals. If I burned them up, would I still see that spark when the key is on and I stick a screwdriver in there and poke at it???

JDJ/Charlotte

Sounds like it could be anything. But, if things suddenly break right after I've made some changes, I usually start there...

I had a self imposed problem like this one time when I was trying to install an anti-theft relay to interrupt power to the coil. In the process of wiring up the relay, I only had it powered when the ignition was "on". It didn't occur to me until after a lot of cranking that there were separate voltage circuits for "crank" and "ignition on" in the car I was modifying. Wondering if any of your turn signal wiring and/or 12v conversion wiring might be causing an issue where you get voltage to the coil with the ignition on but not while the engine is cranking? You could try connecting a test light or voltmeter to the positive side of the coil and see if the voltage changes when cranking.

I also work alone most of the time and need to come up with some creative ways to get things done. In order to effectively verify spark to a plug, I've connected a timing light to the wire while pointing the light to somewhere I can see it from the cab. This might help you verify you're getting spark while cranking the engine. I also have long leads on a couple voltmeters that generally allow me to put the meter somewhere I can see it while in the cab of the truck.

If it's wired like original, there will be a main wire coming off the battery post of the starter. Disconnect it. That will remove all 12V connections except the battery cable. Then temporarily run a jumper wire from the battery to the ignition resistor (needed for 12 volts conversion). A truck starter doesn't have a solenoid so all that's left to do is actuate the foot linkage (stomper) on the floorboard. If it doesn't run then the problem is most likely not the turn signal or any other wiring.

It sounds easy to do but I'm not as flexible as I used to be leaning over a fender to get down to the starter. The first thing I would do is disconnect the battery for safety. Then crawl underneath the truck and disconnect the main wire.

An easier option is to buy an inline spark tester to go between the spark plug and wire to see if you have voltage to the plugs. Unfortunately it will require someone to operate the starter while you watch the tester.

Since the 12v conversion was done 15 years ago and likely worked without issue in the 500 miles prior to turn signal install, that's likely not the issue. Same with compression and timing.

Engine turns over, spark at points, ignition control side seems solid.

That leaves fuel and spark at the cylinder. If it doesn't 'catch' with starting fluid, then I wouldn't think it's fuel related (although that may be an issue later due to aging ethanol).

The single point of failure that makes this crank/no start make sense is the new coil. Is the coil wire firmly contacting the coil terminal? Can you swap to a 'known good' coil? Would it be possible to position a mirror or camera where you can see a spark (spark plug removed and connected back to plug wire, spark plug body grounded)? Even a super long plug wire would work for this spark test.

Did you happen to leave the ignition switch on when you were installing the signals? If you did you more than likely fried the condenser and/or the coil.

Don’t ask me how I know!

Make sure it is neutral, park brake on. You can use a pry bar to activate the stomp starter lever to crank. With key on you can crank & check for spark. Did I mention make sure it in neutral?
If no spark a test light is your friend to check primary side of system.

Exactly, when working on turn signals and and you keep the switch on pull the positive wire off the coil!!!!

The signals should be wired up so they work with or without the ignition switch on. The brake lights are wired thru the signal switch and I don’t believe they would work, if it was wired to the ignition switch and the switch was in the off position.

sounds like a condenser, maybe consider jon g's upgraded one?

could also be a shorted dist rotor, I'v see it a few times in my auto shop over the years.

MrVaughan and Fast55, you should be aware that this thread is 2 years old.

The last reply was in December 2020.