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Sherlock Ohms

Mystery of the Failing Ignition

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Charles Murray
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Blogger
Amazing
Charles Murray   11/15/2011 4:15:59 PM
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Here's the most amazing part of this story: "The connection was barely touching the edge of the pad." Without any evidence of solder, the fact that it held together for 27 years is inconceivable.

CDP
User Rank
Silver
Same mystery of failing ignition on a 1961 Ford Fairlane
CDP   11/17/2011 4:26:20 PM
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The description of the failing ignition mystery was exactly how my 1961 Ford Fairlane acted.  I was given the Fairlane in the fall of 1971 to use as my wintertime 'beater' so as to keep my 1971 Hemicuda muscle car stored during the Northeast Ohio snow bound season.  And as Lee described, the Fairlane's engine would simply quit running at random.  Quite often I could shift into neutral and turn the key to restart the engine while still rolling - pop back into 'drive' and keep going.  The ignition failure might occur within the next 1/2 mile or not for days.  Much troubleshooting and ignition parts replacement did not solve the problem.  About a year later I gave the Fairlane to my Brother-in-law - he had hopes of solving the problem himself but ended up having the car towed to the junk yard.  Years later, I described the problem to an Uncle, and he knew immediatley what the problem was and how to fix it !  Down on the steering column, under the dash board was a switch mounted with a movable contact attached to the shift rod.  The purpose of the switch was to prevent cranking the starter motor when the shift lever was in any position except PARK or NEUTRAL.  The switch was about 2 - 3 inches long and curved to conform around the surface of the steering column.  The switch was mounted with two screws, one on each end of the switch housing.  The holes were elongated to allow adjustment of the switch position to match the shift lever indicator.  Wouldn't you know that the screws came loose, and the switch would rotate out of position while driving, cutting the ingnition off.  By moving the shift lever to NEUTRAL, (or PARK if stopped) the switch would be pushed back into correct alignment and away we'd go ! - until the next time...

Rob Spiegel
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Blogger
Re: Same mystery of failing ignition on a 1961 Ford Fairlane
Rob Spiegel   11/17/2011 4:49:56 PM
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Hi CDP, I'd like to run your story as a Sherlock Ohms posting. 

Are you willing?

I will need your name, and I will also need a short bio (two or three sentences would be fine.

If you're willing, let me know at rob.spiegel@ubm.com

Thanks.

Amclaussen
User Rank
Platinum
Re: ignition module
Amclaussen   11/17/2011 5:28:37 PM
Timing was adjustable by just turning the whole ignition distributor, while looking a stroboscopic light shining on the crankshaft pulley, which had angle marks ("BTDC", ATDC": before and after TDC (Top Dead Center) and a fixed pointer...

The described module most probably wasn't an ignition computer, but just a Transistor module that served the purpose of limiting the usual breaker points degradation by the multiple sparking, which was supposed to be kept under control by the old type paper capacitor, usually found inside the distributor.  Heat and Ozone from the heavy HV sparking inside the distributor made those capacitors change their value or fail completely, which caused the contact points to become pitted in a short time and causing an ignition failure; and the need to perform a "Tune-Up"... by that time, the carburetor must have been partly fouled by dirt and gum formation from the not-so-good quality (cleanliness) of the gasoline of that era.  Therefore, the usual "Tune-Up" included a partial or complete disassemby and solvent washing of the carburetor on the fuel side, together with breaker points change and "calibration", "condenser" (capacitor) change, timing with the "timing light", sparkplug change (or at least cleaning with an old "Champion" sand blasting machine), regapping them; and a typical air and fuel filters change for complete service.  This was required every 6 months or so, depending on the quality of the replacement parts, and frequently, the knowledge or the Tune-Up mechanic... Good ones carefully re-gapped every spark plug to strict values, keeping a close look with a powerful loupe, patiently adjusting the ground electrode to be correctly bent, and took the extra time and effort to lubricate all the bushings and slide points in the breaker points plate, checking the vacuum diaphagm and finally placing a little bit of high temperature grease on the distributor cam, so that the new breaker points kept their opening gap much longer!

I have a 1967 Ford Falcon left to me by my father, still running fast, but previously had to pay a lot for the replacement breaker points for the much vaunted "Mallory" Dual point centrifugal advance distributor... those lasted even less than 6 months of daily driving, until someone told me about the small transistor box, which was made in Mexico by an old, very knowledgeable Doctor in Physics as a side business, NO MORE need to replace the expensive Mallory dual point breaker points anymore! By lubricating the distributor cam, the last points set I bought has lasted more than 15 years! (That box used a rugged Toshiba TV horizontal transistor, rated for high voltage, and has endured all these years without a hitch, reducing the current jumping through the breaker points from several amperes to less than 4 miliamperes, which keeps the surface of the contact points clean and as good as new!).

By the way, my father had both an International Scout-800 (a kind of 'jeep') AND a Ford Bronco, both of 1966 vintage... the Scout by International proved to be a much better, rugged, durable and trouble free vehicle, even at a lower sales price! I Actually learned to drive on it.  The closed cabin was much more comfortable than the canvas cover of a Jeep, and the overall quality of the Scout was a notch above the others. The only inferior aspect were the front wheel "locks" which required the driver to come down the vehicle to be able to engage the 4-wheel drive in order to turn both front wheels "locks" manually.  Fond memories!

laserdudephil
User Rank
Iron
Re: Same mystery of failing ignition on a 1961 Ford Fairlane
laserdudephil   11/17/2011 7:32:58 PM
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CDP, that wasn't the problem.  That switch only caused the starter to cut out, not the ignition.

laserdudephil
User Rank
Iron
Re: ignition module
laserdudephil   11/17/2011 7:44:59 PM
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Wade,

    there are actually four ignition timing advance schemes that have been implemented -sometimes in combination- over the years.  (1) A manual lever on the steering columns (any octogenerians out there?), (2) vacuum advance, (3) mechanical (centrifugal) advance and (4) electronic delay line.

laserdudephil
User Rank
Iron
Re: Oldie but goodie
laserdudephil   11/17/2011 8:25:04 PM
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Beth,

    I must agree with Jacob ('73 AB3A DE KC2FHZ) while there were some microprocessors like the 4004 > 8008 > 8080 > Z80 (anyone remember dual clocks?) they were seldom used in mobile applications.  Keep in mind that back then, computers were mostly analog.  Analog circuitry would receive data as potential differences and pulse timings, and output "computed" data as voltages, frequencies and pulsewidths.  Think summing (/difference) junctions, analog multipliers and log amps, variable reference comparators and PWMs.  I (and a quarter of a million other people) owned early '70s Volkswagen Type IIIs and IVs (Fastback/Squareback) which included a very sophisticated Bosch analog high pressure fuel injection engine management system.  The stock 1600cc Type I (Beetle) with a Solex carbureator developed 82 HP.  The type IIIs with the same engine block developed 128 HP with about the same emissions and fuel consumption.

Amclaussen
User Rank
Platinum
Re: ignition module
Amclaussen   11/17/2011 8:47:05 PM
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Ohh, I forgot to tell that about after five years fo using that transistor box with my Dual-Points distributor, it was the box that failed during a very wet weekend driving at high speed in highway...  The culprit was the epoxy potting becoming cracked and allowing water to enter and corroding the TO-3 Transistor socket on the two terminal pins.  As I became friend with the Physicist that fabricated it, he was kind enough to replace it at no charge, but it was interesting seeing HOW he solved the failure: He traced the failure to the Epoxy potting compound shrinking over time, and developing deep cracks. The thermal expansion of the components cycling, plus the epoxy clinging to the walls of the aluminum housing facilitated this.

The solution was elegantly simple: heat the aluminum housing to a temperature slightly above the upper limit of the operating range, change the epoxy to a different type that cured with heat, and let the potted housing cool down as the Epoxy hardened. Thus, the potting compound and assembly were left in a slight COMPRESSION state, which eliminated the tendency of cracking altogether.  The second unit has been working for more than 10 years and I can't see the slightest trace of cracking!

Derby66
User Rank
Iron
More ignition system problems
Derby66   11/18/2011 11:50:49 AM
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Some years ago I drove a 1968 Pontiac 4-dr hardtop with the regular fuel 400 cid engine.  I drove these cars for more than 30 years.

I bought my first one in 1969 near Pontiac, Michigan.  All of these cars were extremely reliable.  Maybe the second or third car I drove started to stall out with about 70K or so on the odometer.  I would be driving along and the engine would just stop.

I would get out, open the hood and move the wires around, looking for a problem.  When I got back in the car to try to start the engine, it would start and run fine until the next time.

This happened for a period of maybe 3 months.  Finally, at home, I decided to take a closer look.  The primary ignition wire had been draped over a clip on the firewall and over time the wire insulation was worn away so that under just the right conditions the wire would ground itself and the engine would stop.  When I reached under the hood and wiggled the wires it was just enough to move the wire away from the clip and remove the short.

The worn insulation was hidden behind some tubes that were also supported by the clip.  A piece of electrical tape fixed the problem for good.  I wish today's cars were as simple.

Rob Spiegel
User Rank
Blogger
Re: Oldie but goodie
Rob Spiegel   11/18/2011 2:43:37 PM
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Hi focusembedded,

I'd like to use your comment here as a Sherlock Ohms posting.

Are you willing?

If so, please send along your name and a short bio (two or three sentences wojuld be fine).

You can let me know at rob.spiegel@ubm.com

Thanks.

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