No start situation--NOW solved but still a head scratcher

[wegweiser]

I've found modern Bosch condensers to be absolute junk. I won't use them anymore. Many are bad right out of the package. Try a known good one from a few years / decade ago and see if it helps.

[tjones02]

Five things that have caught me up in no spark situations such as this.

 

1. The little breaker plate ground wire inside the distributor being broken. These are a bitch to solder back together.

 

2. A bad condenser. Whether new or not. I’ve seen new Bosch ones bad right out of the package. Here’s a screenshot of RockAuto. Notice that Bosch is the least expensive. They used to be the most expensive twenty plus years ago. There’s something to be said about that. My dad and grandfather used to be fans of Standard Motor Products, not that they’re good now, but they’re worth trying.

 

3. No dwell. I always actually check dwell with a meter. I’ve only ever set points with a feeler gauge one time, and that was an in the road repair/replacement of an electronic ignition.

 

4. Bad coil. It’s easy enough to swap in a known good coil. Just as easy to use a meter to check one.

 

5. ‘74-‘76 inline ballast resistor wire. I’ve seen the resistor go bad, causing an open in the circuit. Running a blue coil with its own built in ballast resistor isn’t a good idea. I’ve even tested the inline resistor wire at 1.7ohms on a ‘74 Tii which is close enough to the 1.8ohm for a Bosch Red coil. I’ve also replaced that wire with a new normal non resistor wire from the fusebox to the coil.

 

HTH

Edited May 11, 2021 by tjones02

[John76]

20 hours ago, John76 said:

The black wire from the Coil - to the Speed Relay tab #2.

Correction....sorry.

Black wire from Coil - to Speed Relay tab #4.

If you are not using the dashpot, you don't need the speed relay. If the relay is defective, the coil could be grounded.

 

 

[1600]

Had same issue on a client's car last week - very similar symptoms - turned out to be a bad tach.  I simply removed the black wire from the distributor post and then ran a jumper from the same distributor post to the negative side of the coil thus eliminating the tach as a potential problem.  Fired right up.

Good Luck

[Mike Self]

2 hours ago, tjones02 said:

Five things that have caught me up in no spark situations such as this.

Good points (so to speak!)

1.We're checking the little ground wire--it looks good but we'll do a continuity check just to make sure

2. We've tried two condensers--and the second one wasn't Bosch

3. There's no spark when we snap the points open with the ignition on, and there's definitely a visible gap, measured to .016

4. We've tried three different coils, all known to be good

5. We soldered in a new, non resistance wire--and even snaked it through the original blue sheath

2 hours ago, John76 said:

Black wire from Coil - to Speed Relay tab #4.

We'll doublecheck this, but IIRC all that stuff has been removed.  But there may be a dangling wire somewhere.  

 

And we'll try disconnecting the tach, but the puzzling thing is that everything was working just fine a couple of weeks ago--well enough for a troublefree 120 mile drive.

 

The mystery continues...we're checking out all the suggestions we haven't yet tried...and will share what we (hopefully) find.

 

mike

[John76]

2 hours ago, Mike Self said:

There's no spark when we snap the points open with the ignition on

Mike,

Test for a spark without the points.

If coil does spark, then it's a ground problem.

My bet is still the connector on the dizzy, or the insulator block on the condenser.

Do you get continuity from the coil (-) to the tach connection (at the dash)?  If no, then there is a broken wire and/or bad connector at the diz. Also check the 5-pole plug under the dash. This connects the tach to the diagnostic plug (pin #9). Anything broken and grounded between the tach and the diagnostic plug can cause a no-tach, no-spark situation.

Your problem is keeping me up at nights!   It's got to be something really easy!

John

 

[Mike Self]

On 5/11/2021 at 5:57 PM, John76 said:

Your problem is keeping me up at nights!   It's got to be something really easy!

Me too--very frustrating to be stumped after you've tried everything you know.  And you're correct--it's gotta be something simple or a true never-before-seen black swan.  Dene and I can't work on the car 'till the weekend, but stay tuned for further developments!

 

Thanks, everyone for your ideas...I'll share results once we've finally located the problem.

 

mike

['76mintgrün'02]

On 5/12/2021 at 8:44 PM, Mike Self said:

stay tuned for further developments!

 

Thanks, everyone for your ideas...I'll share results once we've finally located the problem.

 

mike

 

 

Calling Mike.  Come in, Mike.  Do you read me?

 

Any progress with That X#$&^*@~* '75 ?

 

 

Tom

[Mike Self]

Between other events in our lives for the past couple of weeks, including having to replace the water pump on my '73 and Dene's travels, we haven't revisited Dene's car since late May.  We're both kinda burned out on the whole thing, but will resume our quest for that elusive spark sometime next week.  I'll do a new post after our next attempt.

 

mike

[wkohler]

Does the distributor rotor rotate while the engine is cranking?  Sounds crazy...

[jgerock]

Lots of things to check- my money is on the condenser wire. I’ve seen a faulty crimp that caused intermittent starting issues (on a 73 automatic).

[John76]

12 hours ago, Mike Self said:

We're both kinda burned out

You mean shorted?

[Mike Self]

SUCCESS!!!

Finally solved the mystery, and it was--and still is--a head scratcher and yet another black swan.  

 

Between Dene's and my car's off-the-wall problems and solutions, I'm beginning to wonder if white swans are the rarity.  

 

We finally got together this afternoon, better than two months after we began this quest (but with lots of time in between sessions due to other commitments) and went through the entire checklist again:

• 12 volts at the coil with the ignition on and also when the key was turned to start.
• no spark when (nearly) grounding the coil high tension lead to the cylinder head 
• continuity between battery and block, battery and body, dizzy and head
• Points, cap, rotor, plug wires all new, and we were on the third new condenser
• ran a new hot lead to the coil, bypassing the resistance wire since we were using a blue coil

Still nothing.  And remember, this car ran flawlessly for 120 mile round trip to Columbus and back a week before this ll started.  One more thing to check--which we had checked previously several times--the wire (in the harness) connecting coil to dizzy.  Then it showed continuity.  This time not so much.  In fact, none.  I ran a jumper wire from the - coil terminal to the dizzy and was rewarded by a little spark between the points when I pried 'em open. 

 

Problem solved by installing a new negative lead from the coil to the dizzy--and it started right up.  There must be a break in that wire somewhere inside the harness, as it wasn't at either terminal. We snipped 'em off and tested just the wire with an ohmmeter--open circuit.  

 

Wonder what'll break next.

 

mike

[John76]

Mike,

Congrats on finding the problem!  We can all sleep better now...

Please do an autopsy on the negative coil wire. Where did it break? Near the dizzy or coil? Any unusually sharp bends?

Sounds like you have checked/replaced just about everything, so nothing should break for a long time!!

John

[Mike Self]

1 hour ago, John76 said:

Please do an autopsy on the negative coil wire. Where did it break? Near the dizzy or coil? Any unusually sharp bends?

The wire that broke is inside a blue sleeve that also carries the (no longer used) resistor wire and the "start mode" + wire to the coil.  We did remove the terminals from both ends and checked with an ohmmeter before we ran a new wire to make sure the problem was the wire itself and not a loose/improperly crimped/corroded terminal.  The break is in the wire itself, and it passes through too many sleeves to be practical to remove.  No sharp bends and no damaged spots on the blue sleeve that would indicate trouble beneath, so the wire must have just expired.  

 

It did test good at least once, so my suspicion is there's a break inside the insulation somewhere, and the broken ends touched just enough to complete the circuit when we disturbed it while testing.  Then it went back to being broken.  Dene's car sat outside for around 16 years without being used, so no telling what befell it during that time.  

 

mike