Bad condenser

MarkB_MI

Well-known Member
Location
Motown USA
I had heard that a open condenser can prevent an engine from starting, but I had never proved it. I'm a believer now.

My Ford 4000 had been idle for several months due to a blown rear tire; last month I finally got around to replacing the tires. Not surprisingly it wasn't running well, having not been run. So I decided it was time for new points and condenser. My visits to the local auto parts stores (which in the past always carried points for the Ford) got me nothing. Even when I gave them a random Ford car model and year (just about any Ford made in the fifties or sixties uses the exact same points), nobody had them in stock. So I took a trip to TSC and picked up a tune-up kit (points/condensor/rotor) for the Ford.

After changing out the parts, the Ford didn't want to start but I eventually got it going. But it quit the next day and I couldn't get it started again. It would sputter a bit, but then quit. Interestingly, it appeared to have good spark: I pulled the plugs out and verified they would fire outside the engine. Compression was good, about 195 psi. I pharted around with it off and on for the past couple of weeks with no improvement.

Finally this morning I was driving by the local CNH dealer and stopped in and bought a Motorcraft tune-up kit. ($55 for points, condenser, rotor, spark plugs and the infamous Ford rotor clip) I changed out just the points and condenser, gapped the points and bumped the starter. It fired up instantly and ran perfectly!

I did a capacitor check of the TSC condenser with my multimeter. Sure enough, the brand new TSC condenser was open. Next time, I'll check the condenser first!
 
Condensers going bad is common and even more so with the brand new ones from the land of almost right.

I always keep my old known to be good used condensers as it is a quick and easy troubleshoot a tractor that quits.

Many a time I have gotten an old tractor that quit out of the field with one of my dad's old small block chevy condensers from the 60's and finish the day's work.

Bad condensers get the wire cut from it and thrown in scrap metal bucket so no chance I can use it again.
 
Had a brand new condenser fail on my 69 Plymouth sport satalite when i was 18. Acted like it was starving of fuel and just plain jerking badly.Narrowed it down to the condenser.
 
An open condenser will not prevent an engine from starting (shorted will) but it will not run well and the contacts will quickly pit.

Dean
 
Typically if the condenser isn't even in the circuit or bad/open, "MANY" ENGINES (if all else was in good shape???) WOULD STILL START but the spark will be weaker. HOWEVER a dead shorted condenser will obviously kill the spark completely. With an open or no condensor at all the points will burn up fairly quick. If an engine isn't in good shape or there are other weaknesses or defects I can certainly envision how an open condenser could prevent one from starting !!!!!!!!!!!

John T
 
I can see how a motor with 195 psi compression might need all the spark it can get. 10:1 compression ratio? 10.5? In a Ford? Probably needs av gas.
 
Agreed, John.

I probably should have said "An open condenser alone will not prevent an engine from starting.

Dean
 
John T & Dean essentially covered it. My experience parallels that, in that some will run without a condenser & others will not, because spark is very much weaker without condenser (energy is going into the arc across opening points) & if the rest of the system is on the weak side, those will not run without condenser.
 
Years ago (about 1980) my older brother couldn't figure out what was wrong with his 68 chevelle...so he called the junk yard to come get it...I ask him if I could have the distributor out of it,he said go ahead and take it.So I put that distributor in my 77 Camaro...and guess what?...it wouldn't start so I put a condenser I had sitting around and it started up and ran perfect.....boy was my brother mad....lol.
 

If you keep confirming good spark by looking at the spark jump a standard plug gap you will waist right much time diagnosing spark issues. Invest in a spark checker one that is adjustable not a blinking light spark checker tho they do have there place.

The process of elimination is EZ a bad condenser makes you go thru the whole damm process :(.. This year I have seen 3 new condensers bad and 3 new sets of points that had to be cleaned to get them to WORK all top name brand parts ...

Be happy its not have a P.O.S. front mount coil... :)
 
Testing a condenser is tricky. An ohmmeter test will show a open on a good condenser. A analog ohmmeter will show a quick movement of the needle when first hooked but may not do it again until the condenser sits for a while. A short is easy to tell as an ohmmeter will show continuity which you don't want . We used to have a old time condenser tester at the shop that checked resistance, microfad capacity and something else that escapes me. I never ever found one test bad on that thing and it wasn't until after the tester went AWOL did I ever confirm that a condenser was the cause of an engine problem. I would even take discarded condensers and reinstall them in a different engine just to prove they were not the cause of the problem. It usually was something like a wire grounded out or dirty points that were corrected when the condenser was replaced. Now days is a different story as I know several have failed for the boys down at John Deere.
 
Well, John, it did run with the bad condenser for a short while. The points were burned a bit, but certainly no worse than the set they replaced. At any rate, changing points and condenser fixed it. My guess is the combination of marginal points and open condenser resulted in a spark too weak to do the job.
 
Mark, Sounds like a good guess to me. If you ever bench test a coil with and without a condenser I swear your eyes can tell the difference in how much weaker the spark is if there's no condenser at all. If a condensor is too big there's no spark at all but if to small its as you described. The picture (I think Mr DeMaris may have posted it once) shows the results of incorrect condenser values, if its sized to match the coil and you end up with a balanced LC circuit you get the same result on BOTH point surfaces but if its out of balance one side has a pit and the other a mound. Electrons are particles with a mass and they get thrown back n forth against the point surfaces (sorry that's oversimplified a bit lol).

Fun sparky chattin with all of you

John T
a175899.jpg
 
(quoted from post at 17:34:59 10/21/17) >I can see how a motor with 195 psi compression might need all the spark it can get.

How about 95 psi?
nless there's some mitigating factor, I generally condemn a cylinder at 90. Below that it might not fire no matter how good the spark is. When you checked it, did you have the throttle wide open? Can make a huge difference. Also compression test will show low if valves are too tight. If those don't bring it up, put a tablespoon or two (no more) of oil in the low cylinder(s) and retest--if it comes up more than 5-10 psi, the extra oil sealed up the rings; they'll need replaced soon.
 
My memory says .01 microfarad capacitance but it is old and rusty. DMM input impedance is in the multi meg ohms. 9 volt battery. Don't expect a suitable answer. You are down in the millijoules or less and they don't register to the naked eyeball.
 
Long story short. 6 cyl AMC that had been in four different shops and nobody figured it out.
You could pull ANY 4 PLUG WIRES and it would run,but missed with the wires on. I did take a second look to realize there was no condenser.
 
As an ex Navy ET , very ex, a condenser goes in front of the radiator and a capacitor goes in the distributor.
 
> My memory says .01 microfarad capacitance but it is old and rusty. DMM input impedance is in the multi meg ohms. 9 volt battery. Don't expect a suitable answer. You are down in the millijoules or less and they don't register to the naked eyeball.

I'm not sure what your point is, Mark. You can certainly test an automotive condenser for an open condition with a DMM. The input impedance of the DMM is irrelevant on the ohms scale. If the resistance goes negative when you reverse the leads, the capacitor is not open. I did compare the suspect condenser with the orginal one, which tested good.
 
> As an ex Navy ET , very ex, a condenser goes in front of the radiator and a capacitor goes in the distributor.

I have a BS in Electrical Engineering, so I call them capacitors as well. But try asking for a "capacitor" at an auto parts store and you'll get a blank stare. Of course, these days you'll get the same blank look if you ask for a "point set", so I suppose that's not the best argument for using the archaic terminology.
 
Ok. I never had luck with them. Would get out my old Simpson analog and if lucky on a small uf cap would get a squeak out of it.
 
John, I remember seeing that picture (or one just like it) in old Motors manuals from the sixties. I wondered then, as I do now, "what the heck do you do with that information?" It's not like you can go down to NAPA and buy a different value condenser.
 
(quoted from post at 13:49:43 10/22/17) > My memory says .01 microfarad capacitance but it is old and rusty. DMM input impedance is in the multi meg ohms. 9 volt battery. Don't expect a suitable answer. You are down in the millijoules or less and they don't register to the naked eyeball.

I'm not sure what your point is, Mark. You can certainly test an automotive condenser for an open condition with a DMM. The input impedance of the DMM is irrelevant on the ohms scale. If the resistance goes negative when you reverse the leads, the capacitor is not open. I did compare the suspect condenser with the orginal one, which tested good.

I think his point is testing a condenser with a run of the mill meter that most mechanics have in their toolbox is not a good enough test. Back in the day there was a test rig to thoroughly test all aspects of a condenser instead of just one aspect but it was expensive. Not sure why anyone would want to invest in one of those rigs today to evaluate such outdated technology. Could even be why so many brand new ones from the land of almost right do not work well. Simple meter test shows them to be good.

I do not even fool with testing them. Quicker to install another known to be good one instead. If I am lucky I have an old one of proper spec in my bucket of old savaged units. If I do not have one of the original spec then it does not really matter all that much. I simply pick one that will physically fit where it needs to be in the distributor and put in in there. If it fixes the issue then I pick one up of proper spec next time it is convenient for me to do so - usually within a couple weeks. In the mean time, the tractor is a running and I am using it.
 
How do you know what the "proper specification" is, or do you just mean proper part number?
 
For me ones I have taken out of the tractor before and put it back in the same box so I have the proper part # if I want to get nit picky.

When I do not have a particular one available in a spare, my experience tells me the actual spec of the condenser does not really matter all that much. If it will fit in the disributer physically it will likely work.

I have put many of the run of the mill chevy small block condensers that were 12V in 6 volt tractors and they worked fine. 6 volt condensers usually have a bigger gage diameter wire on them compared to 12 volt units, but those old chevy small block condensers are awesome cause they have a long wire on them so you can get creative on fitting it in the distributer when needed - especially the ones where the condenser case slides in the clamp as that gives you even more options for fitment inside the disributer.
 
> I think his point is testing a condenser with a run of the mill meter that most mechanics have in their toolbox is not a good enough test.

No, a multimeter test won't tell you if a capacitor is "good". But it will definitely tell you if it has failed either shorted or open. In my case, the test confirmed my suspicion that the condensor was the root cause of my problem. I diagnosed my first bad capacitor (in a the radio of a '55 Ford) about 45 years ago, and I've replaced dozens since them. I can't recall a single case where a capacitance bridge was required to determine the part was faulty. (I have used a bridge to verify a capacitor was GOOD on a few occasions.)

> Quicker to install another known to be good one instead.

I'm not sure, based on your criteria for "good", how you know a random used part is good. In my case, the defective condenser was brand new.
 
I keep all my known to be good condensers and I covered that explanation in an earlier post: Most I inherited from my dad when he died as he always saved his old known to be good ones and it is a practice I have continued. I have a gallon bucket full of them. Bad ones get the wire cut from them and tossed so no chance they will ever get re-circulated again by me.

In my dad's era it was common to tune up vehicles with otherwise relatively good points and condensers as preventative maintenance. If the vehicle was running very well when it was tuned up then those were all assumed to be good parts to be saved. Same for tractors.

Additionally I have brand new parts that dad well never got around to getting installed before he died. These are brand new parts but made in the 1970's and not in the land of almost right so having a failure right out of the box is nearly unheard of like the poor quality ones you buy today.

In your case, when the tractor would not run right or at all with all the new parts, then I would have left all the new parts installed and simply put the old condenser back in there (assuming tractor ran great before). If it ran good again well I would know my new condenser was bad.
 
(quoted from post at 23:04:58 10/21/17) As an ex Navy ET , very ex, a condenser goes in front of the radiator and a capacitor goes in the distributor.
he term condenser, when speaking of electronic components, dates back the the "electrical fluid" theory. It has simply stuck in the automotive industry, something like calling it a "battery" even if it only has one cell.
 
Condenser: "To condense", from my Apple's desktop dictionary: "make (something) denser or more concentrated".
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The capacitor absorbs the energy of the coil's discharge that otherwise would have risen up at a rate and amplitude (as the points were opening) sufficient to cause arcing of the points and destructive pitting, thus condensing it and releasing it at a slower rate and lower amplitude; thus preventing the arc and preserving the points for a longer service life.
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Probably back when points were first used in such circuits the designers figured that the general public didn't know what a capacitor was (and didn't care) but knew what condense meant...aka Borden's Condensed milk for one, so they named if for what it does, (adjective) not what it is (noun)............sorry for the diversion here but I can't believe that back in parochial school, first few grades, I actually learned something about the English Language.....amazing......and it took me 76 years to figure that out....working crossword puzzles to keep your mind active does that.

That's my take on it.
 

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