Cold Start

[GunnersWillys]

Ok, I’ve tinkered and searched for answers, time to bring in the big guns, you guys.

‘58 3B.  Doesn’t want to fire when cold. It’s not fuel, it won’t fire with starting fluid either.  After turning over off and on for about 5 minutes, suddenly it fires and runs great.

One hint:  I’ve hooked up my timing light when it won’t fire and sure enough, there doesn’t appear to be any spark.  Then, there is.

New points, plugs, condenser.  Wires are pretty new.  I can’t find any busted wires.  Battery is strong enough I think.  Doesn’t turn over super-fast speed but seems fast enough.  Hooking up to a jump doesn’t seem to matter.

Suggestions?  Thanks.

[Rus Curtis]

Ok, I’ve tinkered and searched for answers, time to bring in the big guns, you guys.

‘58 3B.  Doesn’t want to fire when cold. It’s not fuel, it won’t fire with starting fluid either.  After turning over off and on for about 5 minutes, suddenly it fires and runs great.

One hint:  I’ve hooked up my timing light when it won’t fire and sure enough, there doesn’t appear to be any spark.  Then, there is.

New points, plugs, condenser.  Wires are pretty new.  I can’t find any busted wires.  Battery is strong enough I think.  Doesn’t turn over super-fast speed but seems fast enough.  Hooking up to a jump doesn’t seem to matter.

Suggestions?  Thanks.

GW,
You've hooked a light and noticed "no spark" when it won't fire.  Have you opened the distributor and with a wooden stick (popsicle, chopstick, bamboo skewer, etc) lifted the points - when closed between lobes - to see if there's a spark when the engine doesn't want to start?

If it starts after roughly 5 mins of cranking, i.e. there's no fire then there is, makes me wonder if there's a component that's intermittent. 

How old is the coil? If 12V, internal or external ballast? 
How old is the condenser?
Wire connections good (including wire to terminal ends)?  Using a meter to check when engine doesn't want to crank.
Do you have a spare condenser? This was one of my first start issues:  Bad right out of the box.

Other ideas bouncing around but I need to actually reference some resources.

[GunnersWillys]

Points and condenser are new.  The cold start issue didn’t change after I changed both.  But it runs great once it starts.  Coil is one with internal resistor.  Not too expensive so I may just change it out to rule it out. 

I agree on the intermittent failure theory.  Could be as something gets a little current running through it, it heats up enough to close a gap.  Visually I can’t see a thing.  I’ve tired removing and reinstalling most of the wires, in case there is some corrosion.  I’ll try the points test next. 

[SteveKfl]

Have you checked the "start position" on the key switch for continuity, and then follow the run circuit too from the key location.  Just wondering out loud what I would check.  Old parts can get touchy with wear.  Good Luck.

[Rus Curtis]

Points and condenser are new.  The cold start issue didn’t change after I changed both.  But it runs great once it starts.  Coil is one with internal resistor.  Not too expensive so I may just change it out to rule it out.

I agree on the intermittent failure theory.  Could be as something gets a little current running through it, it heats up enough to close a gap.  Visually I can’t see a thing.  I’ve tired removing and reinstalling most of the wires, in case there is some corrosion.  I’ll try the points test next.

When it's acting up, that's when I would check most of it.  I have noted a jump in the amp needle when I cut the key on.  Then again, when I hit the starter.  Then a swing to positive when it's running.  Old parts (and cheap ones!) can be touchy.  There is a test I found for the coil using an ohm meter (from Chilton's):

Ohm across the +/- (primary) test should be (with internal resistor) should be 4.0 ohms.  If far from this = bad.
Ohm across distributor terminal (-) and tower (secondary) should be 4,000 - 10,000 ohms.  If considerably higher, e.g. 40,000 ohms = bad.

HTH

[GunnersWillys]

Okay, round two.  I tried opening the points as suggested by Rus with the key on.  No spark.  After maybe the 15th opening, one spark, then no spark again.

Tried to start it.  Nothing.  Turned it over for 5 - 8 seconds maybe 8 times, then checked for spark again at the points.  And, spark!

Gave it a little shot of ether to speed up the process.  Fired and stopped.  Turned over again and it fired right up.

So it's something upstream.  Condenser (new) or coil.  Or maybe the key switch connection as mentioned before.  Or a broken wire.  I re-inspected all the wires for breaks and don't see anything.  My meter is out on loan and I won't see it for probably a week.  May just order a coil.  Can't hurt to have a spare.

I'll be back with either a fix or a request for more suggestions.  Thanks.

[SteveKfl]

Til your meter comes back, you could try bypassing the key with a hot wire to the coil directly from the battery.  If it runs like that consistently, either the key or the wire from it is the potential culprit, or one of them maybe.

[GunnersWillys]

I’m intrigued.  That’s a pretty creative bypass test.  I’ll try it tomorrow. 

[GunnersWillys]

LOL!  Well, I learned that wasn't a workable test, or at least the way I did it. 

Checked for spark at the points.  Nothing.  Connected a wire to the terminal on the coil closest to the distributor, then touched the other end to the positive terminal on the battery.  Instant Fusible Link!  Apparently I haven't thought this all the way through.

But, checked spark again at the points, great spark!  And jeep fired right up.

I should have my meter back late tomorrow.  I'm waiting on that to test the coil. 

Pretty entertaining.

[Rus Curtis]

ouch!

The jumper should connect where the hot wire comes from the switch (closest to the firewall).

https://cj3b.info/Tech/IgnitionSpark.html

This has a diagram showing the wiring.  Added:  Actually has some good tips on troubleshooting - some that we've been discussing already.

[GunnersWillys]

Got my meter back. Coil tests out pretty far beyond the numbers noted above, so I ordered a new one.  I'll comment back as to whether it fixed things.

Thanks.

[GunnersWillys]

Update:

The new coil showed up.  For fun I checked the ohms on it, right in the sweet spot.  I pulled the old one, installed the new one, checked the points for spark first.  Great spark!

Jeep still wouldn't fire.  After a few tries I hit it with some starting fluid, which I hate doing, and it stumbled.  Then choked it and it fired right up.  Runs great.

I thought about it a bit and realized I may not have been fully pulling the choke when starting cold.  Just now (a day later) I tried it where I normally start it and it wouldn't fire over.  So I pulled extra hard on the choke lever, and sure enough it moved a bit further and fully closed the butterfly.  After a few seconds it fired right up.  Maybe that is part two of my starting issue.

Thanks for the tips.

[SteveKfl]

You are narrowing it down now.  Every vehicle has its starting quirks it seems.  We have to learn them little by little.  Keep up the progress, and the progress reports too, so we all can learn from it.  Thanks!

[GunnersWillys]

Hey, final comment I suppose.  So over the past week, for 3 or 4 days straight I started the 3B using full choke.  Started right up.  I then let it go for three days, didn't want to start.  Full choke, no fire.  Backed off choke and could smell a little fuel, flooded I suppose, no fire.  4 or 5 tries kind of messing with choke location and it fired and ran fine.  This morning, a little hesitant, full choke for 8 or 10 seconds, no fire, backed off a bit and it started.

Bad news is it is finnicky.  Good news is it will start with some effort!  At this point I'm taking what it is giving me.

It mostly just sits in the barn at the moment as I need to bleed the brakes before I take it out on the highway.  They are mushy, a little air in the lines.  I had some brake work done outside and the guy shredded the reservoir cap and I can't get it off.  Good project for next weekend.  After that, steering slop!

Thanks for all the tips!

[GunnersWillys]

One more update.  Turns out the cold start issue did not go away.  I'm thinking now it may be a vacuum issue.  Kind of struck me while considering possible causes, so I read up a bit. 

Correct me if I'm off.  Since the engine uses vacuum to draw fuel into the cylinders when starting and running, if there is low vacuum at the carb with a cold start no fuel will make it's way into the engine.  If I hit the carb with some starting fluid it starts right up, then runs fine. 

There is really only one vacuum line, from the distributor advance to the carb.  I checked at the carb, all was tight.  I checked at the vacuum advance, pretty darn loose.  I tightened it up last weekend, and now every day it has started pretty quickly on full choke when dead cold.  This morning was in the 30's.  A little slow, but started about 15 seconds into the crank cycle.

What do you think?  Could this be the issue?