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What would damage ignition condensers?
#1423590 Fri Sep 10 2021 10:36 PM
Joined: Mar 2014
Posts: 154
G
'Bolter
I'm back again with a new question, after many hours of diagnosis and thinking I might know what my problem was/is. I originally posted a question about whether my distributor was the problem because I had an erratic dwell. https://www.stovebolt.com/ubbthread...-need-a-new-distributor.html#Post1422088 I'm starting a new thread because that one strayed well away from the original question.

I'm working with a 1949 216 that I believe is 100% stock (still 6V) and has a Carter W-1 carb. After looking more closely (and using my brain!) I realized my distributor is just fine. The shaft internal to the distributor has almost no play. The distributor moves around in the engine block a little, but not much. That was definitely not the problem causing my erratic dwell. As I was in the process of diagnosis, the truck got to where it wouldn't even start. So with the help of my son, who's a Peterbuilt certified diesel mechanic, we diagnosed everything possible related to the ignition system and concluded it must be the condenser. I was very reluctant to believe that could be the problem because I had one of Jon's new design condensers installed. Today I went and bought a "Blue Streak" condenser at the FLAPS and after installation, she started right up with absolutely no other changes. It ran great for about 15 minutes while I adjusted the timing, checked the dwell and adjusted the idle. I went to clear everything from around the truck so I could take my victory lap around the neighborhood, and it died before I could get back in the driver's seat. It won't start again. This is now the second time I've had the truck running really well, and it just dies after about 15 minutes and won't start again. Almost exactly the same scenario each time, months apart. I assume it must be the condenser yet again.

Is there anything that could be damaging my condensers? It wouldn't seem so, but it's hard to believe I've now had 2 condensers that only lasted about 15 minutes out of the box, including Jon's.


Greg Brown
'49 Chevy 3100
Re: What would damage ignition condensers?
Greg Brown #1423595 Fri Sep 10 2021 11:31 PM
Joined: Mar 2010
Posts: 639
B
Curmudgeon
Heat and/or overvoltage will kill a capacitor. I would rule out engine heat for now. The condenser and coil work hand-in-hand. Talk to your son and see if he can get access to a diagnostic scope. Install another new capacitor. See what the primary and secondary coil voltages look like.

Last edited by buoymaker; Fri Sep 10 2021 11:31 PM.
Re: What would damage ignition condensers?
Greg Brown #1423596 Fri Sep 10 2021 11:45 PM
Joined: Aug 2018
Posts: 607
2
'Bolter
I’ve experienced heat sensitive bad coil before and it took a lot of careful observation to diagnose but once observed was so obvious in hindsight
Good luck and let us know your testing progress
-S

Re: What would damage ignition condensers?
Greg Brown #1423597 Sat Sep 11 2021 12:15 AM
Joined: Mar 2014
Posts: 2,525
J
'Bolter
Greg I have no idea what caused that...but obviously something. Possibly something with the coil? Do you have a handheld multimeter?


Jon

1952 1/2 ton with 1959 235
T5 with 3.07 rear end
Re: What would damage ignition condensers?
Greg Brown #1423598 Sat Sep 11 2021 12:23 AM
Joined: Feb 2004
Posts: 23,022
H
'Bolter
Change the coil. If there's a short circuit between the primary and secondary windings, the condenser will get hit with tens of thousands of volts every time the points break. That will blow holes in the dielectric of the condenser, and short it out in a matter of minutes, causing the engine to stop.
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Re: What would damage ignition condensers?
Greg Brown #1423607 Sat Sep 11 2021 01:37 AM
Joined: Mar 2014
Posts: 154
G
'Bolter
Thank you guys for all the great suggestions. You wouldn't believe how frustrating this has been... or maybe some of you would.

I've asked my son about the diagnostic scope. He was actually telling me about the capability to graph voltages the other day. Not sure if he'll be able to swing that.

I didn't mention this before, but when I first had engine problems 6+ months ago, the first thing I did was replace the coil with a new 6V coil from Napa. When that didn't fix the problem, I did the full tune-up, using the condenser from Jon, and the new coil. That was when the truck ran great for 15 minutes the first time.

My son tested the primary/secondary resistance of both coils the other day and they were pretty close to the same. This was on the workbench, not while in use or in a warm/hot environment. Short of having the scope, is there a better way to test a coil?

Now I'm wondering if my original condenser went bad, causing my initial problems. And the new coil I installed is also bad, killing both condensers I've used since putting it in.

If I can't get the scope, I'm thinking I may go back to using the original coil with another new condenser and see what happens.


Greg Brown
'49 Chevy 3100
Re: What would damage ignition condensers?
Greg Brown #1423612 Sat Sep 11 2021 02:36 AM
Joined: Mar 2014
Posts: 2,525
J
'Bolter
Let me know what you do. I'm happy to send you another condenser.


Jon

1952 1/2 ton with 1959 235
T5 with 3.07 rear end
Re: What would damage ignition condensers?
Greg Brown #1423614 Sat Sep 11 2021 02:59 AM
Joined: Feb 2004
Posts: 23,022
H
'Bolter
A resistance check will not show up a high voltage pathway between the primary and secondary windings. It's basically a hole in the insulation that allows a spark to jump beteween the two windings. Early HEI systems for the odd-fire Buick V6 were notorious for burning a hole in the distributor cap under one of the coil attaching screws and making one cylinder miss intermittently. It was impossible to duplicate on a scope unless the car was on a chassis dyno so the engine could be loaded in the shop. The repeated flashover would cause frequent failures of HEI ignition modules. GM solved the problem by making the cap thicker in the area that was prone to burn-through. One cause of burn through on a conventional coil is a dangling plug wire that allows the secondary voltage to go to 25-30 KV or more without firing a plug.
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Re: What would damage ignition condensers?
Greg Brown #1423634 Sat Sep 11 2021 02:57 PM
Joined: Mar 2010
Posts: 639
B
Curmudgeon
I totally forgot the basic first step. With an analog meter, do a resistance check, at X1 scale, to see if you have a sweeping deflection (meter movement) as the condensor charges. If the condensor is open, no deflection.

Last edited by buoymaker; Sat Sep 11 2021 02:57 PM.
Re: What would damage ignition condensers?
buoymaker #1423767 Sun Sep 12 2021 11:03 PM
Joined: Mar 2014
Posts: 154
G
'Bolter
Originally Posted by buoymaker
I totally forgot the basic first step. With an analog meter, do a resistance check, at X1 scale, to see if you have a sweeping deflection (meter movement) as the condensor charges. If the condensor is open, no deflection.
Unfortunately I don't have an analog meter. I found a procedure for testing with a digital multimeter, but I'm not confident it actually works.

Regardless, I figured out what the problem was this time, without any doubt. I was about to say $#!= it, after installing yet another new condenser and getting no start, when I decided to re-check a few things with my meter. I immediately discovered that the hot side of the points were grounded. What the heck?? I had used a piece of rubber to insulate the stud coming thru the side of the distributor and apparently after it got hot, it allowed the stud to short to the base of the distributor. Obviously no fire with this situation. I put a nylon spacer on the stud outside of the distributor and re-checked everything. All good and the truck fired right up. I took my victory lap around the neighborhood successfully, came home, shut it off then restarted. It's going to take a few successful runs before I'm confident, given what I've been thru, but it all seems good.

The question now is whether this was my problem all along. There was a cracked bakelight washer on that stud that I replaced with the rubber. It looked like it would have worked as an insulator, but now I'm not so sure. Was it shorting after getting warm? After my frustration wears off, I may go back and try the 2 condensers, and the old coil, all one at a time, to see if in fact any of them are bad. I'm not so sure now.

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Last edited by Greg Brown; Sun Sep 12 2021 11:24 PM.

Greg Brown
'49 Chevy 3100
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