Automotive/1979 Lincoln Mark V

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Expert: - 7/6/2007


Question
Hello,
I have a 1979 Lincoln with a 460ci engine. The car starts and runs great until about the 20-30 minute mark then it starts to hesitate and it stalls. It will not start again for about an hour. I was a parts person for 4 years and the only time I had ever heard of this was on a chevy 1500 and it's problem was a cracked dirtibutor shaft. Would you have any idea what the problem could be? The carb is brand new and the fuel pressure is good.
Thanks for your time.
Phil

Answer
Sorry I did not get to you earlier; we have had some issues with dropped connections here lately.

Your problem as described suggests some sort of thermally- triggered break in electrical power or signal.  This could be either a loose connection which expands open in time, or could be a semiconductor junction that is in the early stages of failure.

Intermittent connector problems can happen with any vehicle.  Electronic problems in an 1979 Lincoln would have me wondering about the health of the ignition modulator.

Ignition modulators contain a power pass transistor, and these devices or the devices which drive them can fail very quickly, going open in seconds; that happened in my 1978 E250 the first time, in 1988.  Alternatively, they can take you through a period of questionable and diminishing performance, often running well on first starting, but becoming flaky once one has been on the road for a bit.  That was the case when the unit I installed in 1988 was found to be failing, in 2005 (which is not bad).  My ultimate determination that the modulator was at fault was when I connected my timing light, and found its flashes to be highly erratic.

On both occasions, I had a spare modulator with me!  As it happens, because I drive into remote territory from time to time, I keep a pretty good kit of spares on board, along with good basic tools and a digital multimeter.  Generally, whenever I do a tune-up, I buy the plugs, rotor, cap, etc for my next tune-up at that time, and stow them away in the kit until that next time, at which time I replace those parts again.  Two additional parts I keep on hand are a spare regulator and diode set for the alternator, and a spare modulator.  Having that spare modulator on hand got me home with only a few moments delay in 1988, and saved me making a special trip to get the part in 2005.  Needless to say, I replaced that spare each time on my very next visit to my jobber.

Keeping hardware like that on hand is very convenient and I highly recommend it.  When the ignition failed in 1988, forcing me to the side of the road in less than ten seconds, all I had to do was disconnect the two connectors to the old modulator, and connect up to my new spare to verify that the problem was in fact the modulator.  Bungy-cording my spare to the top of the WS washer bottle allowed me to get home, whereupon I completed the proper installation after dinner.  The next day, I bought the new one on my way to the office, a modulator that stayed in the kit for seventeen years!  Well, you never know ...

Carburetors and mechanical fuel pumps do not suffer from thermally-triggered intermittent failures, so I would certainly start my investigation with that modulator.

Good task for a Sunday.

Cheers ... EGK

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Ernest (Ernie) Kenward

Expertise

The challenges I most enjoy are thoughtful technical questions of a trouble-shooting nature in both electrical, power electronic and mechanical systems, mainly automotive but also machine control and small-machine PLC applications. Please note, however, that I am NOT a walking shop manual! I DO, however, make it a point to have those manuals and other service literature for those vehicles I DO own, and highly recommend that anyone serious about maintenance or modification of their vehicles do the same; MOST of your answers WILL be found there. For that matter, I do NOT go out of my way to acquire shop manuals for any vehicle I do NOT own! That being the case, any general query to me along the lines of "What is the meaning of this code read from the ECU of my 2015 XYZ?" or "Where is the fuse for the windshield washer pump found?" (try your car's electrical distribution panel for a start!) will not go far. What I do offer is a pretty good collection of literature, insights and hands-on experience with 1950s to 1980's Ford products (plus a developing database of information and practice with the Mercedes diesel cars), along with an engineering perspective and the ability to design and implement custom control, electrical and mechanical subsystems for vehicles. For that reason, I am happy to make my thoughts and efforts available to those who are of like mind and/or are seriously making a point of learning about their vehicles. Use the Opportunity to Learn!

Experience

A key skill in my work and hobby pursuits both is STRATEGIC TROUBLESHOOTING. I am a senior instructor in Electrical Engineering Technology at a leading Canadian polytechnic, my areas being Electrical Power and Industrial Control, electrical and electronics design and manufacturing, and AutoCAD and related CAD/CAE software - plus equipment problem-solving and new equipment design and prototyping. Hobby-wise, I have 30-plus years of experience in auto restoration, mostly in electrical and mechanical systems. Ongoing projects include a 1959 Edsel Corsair, my 1978 Ford E250 class-B motorhome conversion, and the care and upkeep of my Mercedes 300CD. My vehicles become engineering test beds for electrical and mechanical upgrades as ideas present themselves. This includes the design and production of circuit boards to restore or enhance features for which no OEM replacement parts are obtainable, or where better specifications or reliability can be had via newer concepts. Regarding the E250 RV conversion, I designed and continue to revise a custom power distribution system, managed by a Programmable Controller (PLC); this has made most revisions as easy as uploading new firmware as I develop it. The "mini" PLC is a powerful device for custom automotive control systems. One good example (there are many) would be the Moeller "Easy Relay"; these offer a wealth of control, monitoring and variable-and-status display options for such projects. A good example project which has worked well is that one for my RV noted above, which has been on the job - revised in firmware only - for a decade now. It is a load management and charging control system to avoid the sulfation-induced early failure that often befalls deep-cycle batteries used in RV power applications. The battery installed in 2003 lasted long enough to more tnan pay for the PLC that contributed to its longer life ... and the PLC will be there for the next battery as well!

Organizations
IEEE - senior member ... past WCC Student Activities; SME - senior member ... past chair, greater Vancouver chapter chair 318; Edsel Owners' Club - have served in various capacities on chapter executive during seventies; have been Power and Driveline resource on the Edsel Owners' Club "E-team" for more than a decade.

Education/Credentials
Graduate of UBC

Awards and Honors
Certificates of appreciation from IEEE and SME for work in student and chapter activities

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