CJ3A Starting Problem - Runs fine once started

[CChris]

Good Morning,
My name is Chris and I’m new to your forum. Over the past eight months I’ve been doing a frame off restoration of a ’51 CJ3A (serial 451-GB1 23480) with the help of the forum as a reference. I’ve now re-assembled the Willys and am having a problem with reliably starting the engine. The starter is cranking but the engine but it’s just not starting. Once finally started, the engine runs fine with good power and acceleration.

Engine: Re-built L-134 (Compression in cylinders ranges between 100 and 110)
Fuel Pump: Facet Posi-Flo EFP-3 (Generating 2 psi of fuel pressure)
Carburetor: Solex 32PBIC single barrel downdraft
Starter: 6V Foot actuated pinion gear
Distributor: Omix 12V Solid State (Kaiser Willys 923068)
Coil: Standard Motor Products UC15T (Resistance checks OK across primary and secondary coils)
Ignition cables: New 7mm High Temperature
Alternator: Delco 12V 3 Wire – I have only used the charging wire in my Willy at this time

In an effort to diagnose the strength of my spark I pulled the #1 plug this evening and grounded it against a head bolt to view the spark color. As I did this, the engine started immediately…3 times with very little cranking (on 3 cylinders?!). When I re-inserted, torqued and reconnected the #1 plug in the head The engine refused to start again.
I’m stumped and would appreciate any suggestions you all may have.

Chris in Spring Hill, TN

[bmorgil]

Welcome CChris! I am guessing maybe the extra cranking speed and voltage available when it was cranking on three, might have helped a low voltage spark situation.

I would start with the basics. Check the voltage at the positive terminal of the coil when the engine is cranking.

[LarrBeard]

A second opinion here. If you are still running the six-volt starter at 12-volts, I'd guess it is spinning pretty fast so cranking speed probably isn't that big of a factor.

I'll second Bob's notion - check voltages around the coil, maybe with three and four plugs installed.

One more thing; you have a SOLEX carburetor and those carburetors have a less than stellar reputation on Jeeps. Some are great, some not so great.

Let us know what you find - it is a bit curious.

[CChris]

Thanks, guys. I measured the voltages at several locations while the ignition circuit was hot:
Battery: 12.42 Volts
Coil (across positive and negative poles of coil): 0 Volts?!?
Coil Positive to Battery Negative: 12.42 Volts

I measured the continuity of my coil neg pole to battery negative pole and found no continuity there.

I do have continuity between the housing of the distributor and the battery negative pole.

I do not have continuity between the distributor housing and the coil negative pole.

Are these the readings you would expect of do I have a damaged ignition module in the distributor?

Thanks for your quick responses and assistance.

Chris in Spring Hill, TN

[CChris]

In addition, I remeasured the resistance of the coil with nothing attached: 3.6 Ohms

[bmorgil]

Thanks, guys. I measured the voltages at several locations while the ignition circuit was hot:
Battery: 12.42 Volts Good with the engine not running. Should be 13.7 with the engine running
Coil (across positive and negative poles of coil): 0 Volts?!? With the ignition module in the distributor hooked up, this measurement doesn't mean anything.
Coil Positive to Battery Negative: 12.42 Volts This is correct with the key on. Now we need to know what it is while the engine is cranking and not starting.

I measured the continuity of my coil neg pole to battery negative pole and found no continuity there. Good.

I do have continuity between the housing of the distributor and the battery negative pole. Good.

I do not have continuity between the distributor housing and the coil negative pole. Good
In addition, I remeasured the resistance of the coil with nothing attached: 3.6 Ohms is OK. 3.2 to 4 ohms is usually max on a 12 volt internally-ballasted coil.
Are these the readings you would expect of do I have a damaged ignition module in the distributor? Once we determine how much voltage is available at the positive terminal of the coil when the engine is cranking but will not start, we can move on from there to the next possible issue.

Answers in red above CC. Get that reading while its cranking and lets see if this isn't a simple voltage drop issue.

[CChris]

Thanks for your assistance. I've got 10.8 volts between the coil (+ ) and the bat (-) during cranking.

[bmorgil]

That's plenty. Most electronic ignition systems wont fire if the voltage drops below 9.5V. The fact that it did start and run with one wire off tells us it may be something in the ignition module inside the distributor.

The distributor is made by Transpolo, LTD out of Taiwan. I was unable to get any specifications to help with troubleshooting the module inside the distributor. I don't think its needed however. If you have 10 or more volts at the positive terminal of the coil when the engine is cranking, it should produce a spark if everything else is in order (Cap, Rotor, Wires and plugs). Your voltage checks indicate everything is correct in the wiring. Be sure all connections are tight and not causing an intermittent connection. Recheck your prior measurements while wiggling the wires. If it checks out with no bad connections, I would send the distributor back. It sounds as if the module in the distributor is bad.

[CChris]

Thanks, Bob

I've ordered a replacement ignition module and will close this thread with how it performs with the replacement once installed.

[LarrBeard]

Of course we get good ideas too late to help - maybe.

A way to check to see if the spark is weak when you crank with all four cylinders under compression would be to pull the wire off #1 and put it on a spare plug. Put that plug on the block and crank the engine. That would let you see the spark you get with all four plugs in place.