The Stovebolt Site Forums The Shop Area The Electrical Bay Mysterious sudden death of ignition system

My '57 235 engine has slightly over 200 miles on it since being refurbished. The ignition system is basically new i.e., new coil, leads, distributor, points, plugs, condenser, wiring, etc.

This afternoon about one block from home the engine suddenly died and would not restart. After getting the truck home I started my investigation. Here are the findings and things done:

• I am lacking a ballast resistor so 12 volts is being supplied to coil from key switch. This will be corrected tomorrow, but engine has been firing right up and running well prior to todays problem.
• Checked wiring from switch to "Bat" terminal for continuity and ground - OK
• Filed and regapped points to .017
• Points making and breaking. Checked manually by just opening by hand and using ohm meter between ground and condenser terminal on distributor base and then between ground and "-" terminal on coil while cranking and ignition switch on
• Coil primary resistance ~ 1.5 ohms. Secondary resistance ~ 8-10 ohms if I recall
• Coil secondary wire will not throw a spark from distributor end to good ground, but will give me a wakeup jolt should I decide to act as ground
• Of course, keeping the forgoing in mind, no spark from plug wire to ground
• I've tried three different coil to distributor wires with same results
• Rotor contact to cap looks good
• Battery fully charged or on charger when performing test

So... What's going on? could the coil be fried from running on 12 volts even though primary and secondary resistance is within specs? I initially thought that due to the sudden death nature of this problem that it was a grounded our open wire. I think at this point I have ruled that out. Right now I'm leaning heavily towards fried coil. Even is condenser is bad that wouldn't affect coil voltage would it? Hmmm, perhaps if condenser was grounded? But then again, I'm not getting any real fire from coil to begin with if my troubleshooting is correct. Any help would be appreciated.

Oh, here is a link to one of the best Ignition System 101 that I have seen.

down2sea,

Without doing lots more troubleshooting, I would install a new set of points...the full 12 volts probably didn't help them, and a new condenser.

If your resistance readings of the coil are accurate, it sounds like it's OK.

Stuart

Yep, my experience with running points without a ballast resistor has been that they can run so hot they not only burn, but can end up 'floating' simply because they get so hot the metal warps the points open too far. In the middle of a drive, this manifests itself as a 'sudden death' situation.

Pertronix has a great point eliminator with a collar that slips over the point cam and a sensor that mounts in place of the points for under $100. running it on my '54 sedan for 4 years daily strong...

I've had too many experiences where I was so damned sure the points were closing and conducting when they weren't... only to be proven wrong by installing a new set.

Don, if you pull the coil wire off the cap and turn the motor over while holding the wire close to ground, does it spark?

It will not throw a spark but will wake me up. See bullet 6 in my initial post.

As far as the points go.. I'm sure that they have overheated as indicated by the discoloration of the active side contact arm. Doing this troubleshooting tonight I decided to file the points and regap as a prelude to buying new ones tomorrow. They actually look good now and do function properly.

One interesting thing and it's something I'll check again tomorrow (today actually) is the secondary high tension lead from coil to distributor tower. Although I tried three different wires, including the one installed when the engine died, none of them show continuity when using a digital ohm meter. I say no continuity but it was actually something like 4 meg-ohms. I'll look into that when I get up later this morning. This sounds weird but will check with analog meter tomorrow.

This isn't rocket science and shouldn't be all that difficult to diagnose. Just a little memory cell realignment going on as it's been a few years since I've tuned and timed an engine.

Later,

Don

yep no resister fryed your ignition i had a 440 once that i had to run 2 resitores or replace my point cap and wires every month it got spendo i would replace everything again to avoid setting along the road

Could you have broken down the insulation/resistance between the primary and secondary in your coil from the hi current? Three meg. can't be right. Is that the wire resistance with just the DVM connected to the ends of the wire? I have had a condensor go bad on a nailhead motor that killed the spack then after cooldown measured ok. Condensors are electrolytic type capacitors. They have a wax or oil type dielectric which can "heal" itself it to lower testing voltages such as DVMs and removed from heat.

my vote is fried condensor

Okay, heading out to the garage to do a little more trouble shooting prior to heading to NAPA. Going to get new points and condenser and will pick up a ballast resistor. I am still pondering new coil with internal resistor vs mounting external resistor. The installed coil clearly states for use with external resistor which it didn't have.

Due the fact that this coil is in 6V/12V converted system (6V starter with no "starting voltage lug" for by-pass while starting)and simple on/off key switch I will have to live with lower coil voltage during starting. One reason I'm considering internally resisted coil is PO had a metal clad ignition wire switch configuration (original to '41?). What I mean is the fabric covered wiring from the switch to the coil is encapsulated in flexible metal conduit (similar to what is used on speedo cable.) This makes it problematic to install a ballast resistor on the firewall.

Anyway, better stop bs'n and get popping!

Don

Don,

If my vote counts, I would lean toward the internally resisted unit...cleaner, less wiring and just as reliable. If the engine is even in a moderate state of tune, reduced juice will easily do the trick.

I wouldn't get lost in the meg-ohms maze...sometimes these things confuse the basic issue. Points and condenser is a good starting point, and probably the solution.

Stuart

Don,
My vote on this is the condenser.
Also with Stuart on the internally resisted coil.
Regards,Steve Sr.

Try opening and closing the points and watch the spark. If it is a small crisp and sharp spark, I would say the condensor was OK.

If the spark is more of a flash and bright blue in color, most likely it is the condensor.

Many times I have replaced the old condensor because the new ones were faulty.

Everyone's vote counts but you all lose. The coil was fried. Rather than shotgun it I installed the new points and condenser first. No fire. I then installed new $16.95 internally resisted coil and Viejo fired right up.

This has been a good refresher course for me BTW, and I appreciate the input as always.

Don