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William K.
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Re: Distributor Cap: 1990's, but still a good choice
William K.   1/23/2014 6:10:52 PM
While the new systems use six coils, or possibly 8 of them in one nonservicable block, the old distributor did have a bit going for it in that the mechanical portion almost never failed, and the whole system was repairable. The change came about to reduce space and assembly costs, with no concern about the customer's repair costs. 

As for the condensation in the cap, it must have been iin a quite humid locality. I had to do some research on the Chrysler 360 engine and in the area of the distributor, located on top of the V8 engine, the temperature would climb to over 200 degrees F after a fully warmed engine was shut off and the vehicle was parked in a garage. As the engine cooled  over the course of an hour air would indeed be drawn into the distributor, but it would be the air heated by the engine. So usually condensation would not be a problem, since every time the engine ran it would get really hot and dry things out. 

Possibly this is not true for other makes of vehicles.

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Re: Diagnosis, false codes and possible frauds?
Amclaussen   1/21/2014 2:39:40 PM
Good post CRITIC.

I have seen some false codes too. In my 1991 Dodge Spirit R/T, from time to time the car sets a code 61 ("Open Or Short In BARO Read Circuit") that is not real (wiring and contacts are OK, and it resets randomly.

In my Stratus R/T sedan 2002, the code P0601 is set most of the time since a year ago, clearing itself for short periods occasionally, and then returning. But even when the code appears to be serious matter ("Internal powertrain control module fault condition detected (failed memory checksum" or simply "Checksum error"), the car runs perfectly and passes emissions with very good numbers. If someone more knowledgeable than me could please explain in simple terms what does this mean, please help me!

As there was a recall in 2003 ("Customer Satisfaction Notification No. C30 PCM Electrical Connector Seals") that I was never informed by the dealer or factory, related to a misplaced or "rolled" seal in the Powertrain control module, I performed the inspection myself but found it was not the case, but still cleaned all the numerous contact points -around 60 some- using my old good CRAMOLIN (still made in Germany, which is stronger and more effective than the actual product from CAIG)... and I cleared the P0601 code, but it returned, nonetheless, the car performs perfectly OK. So I believe it is a false code. At one discussion forum, someone expressed that some "car computer failure" codes were not real ones, but fraudulent moves by the manufacturer done in order to send the customer to their service center and promote the unnecessary replacement (at a heavy cost) of the computer of the vehicle. I'm not sure, but it could be a possibility, as fraudulent schemes are nowadays more and more frequent.

I have seen at least three ones: A) the infamous Panasonic Viera Plasma TVs that have a malintentioned firmware installed in the factory, that reduces the outstanding initial contras of the picture in several steps after a few months of use. It was denied by Panasonic but consumers fought back and a Class Action Suite followed. Panasonic lost a large sum of money, but the numerous customers received very little each one. B) The false messages displayed by some printers, that stopped the printing and required the user to take the printer to the authorized service shop, where it was given a quick cleaning and reset, received new toner supplies and made the owner wallet a little slimmer. A dissatisfied repair technician told me he only had to clear the code to reset the printer and it was ready, as it was never really in a true need for service and most still had plenty of toner remaining. C) The bogus messages displayed by a Sony Vaio laptop from a friend, who was ready to order a new battery for his laptop because the messages were popping on the screen after only five minutes of use, after having recharged the batteries for hours and having tried other chargers to discard a possible bad charger issue. As I heard him he was ready to dispose of the battery, I begged him to give it to me, and after carefully opening the halves of the clamshell battery pack (careful here, as some metal straps joining the cells inside were ready to touch themselves as the design only prevents their shortcircuiting by means of some ribs molded in one of the shell halves, ready to break hell if the cells still have enough charge. And to my surprise, I found all the cells having about 79 to 82% of the full charge voltage in them. As my friend was convinced the pack to be worn out, he bought a new one. I used the popular "18650" (18mm in diameter and 65mm length cylindrical Lithium cells) in a heavily used hand drill that previously used Nicads, and continued to use them almost three full years after I removed them from the Sony Laptop pack! Then I asked myself what was the purpose of the three different Integrated circuit chips placed on the small circuit boards inside the pack... apart from monitoring and cell balancing, would the circuits include a cycle or operating hours counter, or some date code in order to make the pack appear as defective and worn out, when in reality its cells were almost full of charge in still in excellent shape? Amclaussen.

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Re: Non-Optimal design. Good enough for "Made-by-Monkeys"
bobjengr   1/7/2014 5:40:39 PM
Turbineman--That's just about the coolest fix I've heard in a long while.  I hope he bought you lunch and a beer for diagnosing that one.  Wonder how many mechanics could have performed that quickly and in such a very short period of time?


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Critic   1/7/2014 10:01:59 AM
Thanks, Mark, for an interesting article.

I have learned that a bad PCM/ECM can cause random diagnostic codes.  I had an ECM in an F-150 fail, and various different codes appeared, although there was nothing really wrong (except the computer itself was bad).  The connector to the engine wiring harness protrudes through the firewall of this truck, and a gasket was supposed to protect the computer from splashes.  However, when the computer was installed (carelessly), the gasket got pinched, so the computer got soaked repeatedly and corrosion eventually killed it.  The moral of the story:  sometimes codes are wrong, so verify the problem/complaint first, if possible.

Other ways to find a misfire:

1. Use an engine oscilloscope.  This is probably the fastest and easiest way, but not everyone has a 'scope.

2. Disconnect one spark plug wire at a time and see if it makes a difference in the way the engine runs.  Be careful not to shock yourself, and remember that a test like this can damage a weak component (sometimes a good thing)!

3. Inspect the spark plugs.  One that is wet with fuel or a different color than the others indicates a problem.  An experienced mechanic can determine a lot from looking at the plugs.

I had a Ford engine that would constantly oil foul one spark plug, about every 200 miles.  I knew that the engine was mechanically sound, so it was a mystery why there was so much oil in the one cylinder.  I ultimately discovered that someone had mistakenly installed two PCV valves on the engine, and one was bad, so lots of oil was being sucked into the intake stream.  The geometry of the plenum is such that most of the oil ended up in one cylinder.

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Distributor Cap
RobLewis   1/6/2014 6:19:33 PM
Distributors are so 1990s, don't you think? 

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Re: Cooling down time?
JimT@Future-Product-Innovations   12/30/2013 10:17:17 PM
When I was in High School, the standard tune-up mantra was ALWAYS; "Points, Plugs & Condenser".  If a car really needed help, you would throw in a new distributor cap. That was pretty much all you ever needed to make a V8 scream, unless you got more sophisticated and borrowed a timing-light from the Auto-Shop tool crib.   Condensation and corrosion was pretty much an expected thing you had to deal with.  Plugs & Points were ALWAYS burnt and corroded; it only stands to reason the distributor points would be, too. So I'm not too surprised to head the distributor points had a corrosion bridge.

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Re: Another GM experience...
Amclaussen   12/30/2013 3:56:58 PM
Your comment made me remember a demostration at school: I was studying Chemical Engineering around 1974, and at a Physics Lab class the teacher was demonstrating the dielectric properties of different materials with a high voltage generator.  It was very enlightening for me to actually see how badly some common plastics behaved under the high voltages around 100KV that the demo was using. For example, vinyl (PVC) insulation on common jumper wires and alligator clips was completely useless above one or two KV...  and some pieces of "lucite" plastic withstood easily the full output of the test rig. A couple of years later, I built a small scale Electrostatic Precipitator using a two inch diam. copper pipe, about 18" long, with a metal guitar string along the center of the pipe. Under the pipe I placed a plastic cup where they used to sell 8-piece sets of Autolite sparkplugs during those years. That package made of good quality High Density Polyethylene.  That plastic cup withstood the 3 KV easily and served to receive a small duct where I connected a very small centrifugal blower from a miniature vacuum cleaner.  A pair of fellow students kept blowing cigarrete smoke one after the other so to provide an almost continuous stream of an extremely fine dust or smoke flowing into the precipitator.  At the top, a common F14Y Champion sparkplug served as the top insulator, once the bottom electrode was removed.  A strong light from a 100 W bulb illuminated any smoke exiting the apparatus.  Switching On and Off the high voltage to the guitar string provided an electrostatic field strong enough to completely precipitate the cigarrete smoke, chalk dust from a blackboard and every conceivable dust!  This project was reviewed by the same Physics teacher and won his approval.  In that exercise, the HDPE plastic of the Autolite brand sparkplug package withstood many Kilovolts with easy, even at a thickness of less than 1/32"!

bob from maine
User Rank
Re: Memories...
bob from maine   12/30/2013 12:04:49 PM
I've had VWs and Volvos exhibit this problem. I also had a boat with two brand new 307 GM engines with Mallory low-profile distributors that had similar problems. The issue was the engine got hot when running (a good thing) and when shut-off the non-vented crankcase would cool and draw relatively cool air in from the outside through the distributor vent hole and moisture would condense inside the distribtor. Subsequent starting would cause arcing between the coil input and one or more spark-plug outputs inside the cap; this arcing seemed to cause breakdown of the bakelite and leave carbon tracks which would eventually create a permanent leakage path. The boat issue actually would cause the engines to quit during cold weather operation (<40 degrees) and required re-designing and sealing the entire distributors.

User Rank
Another GM experience...
kf2qd   12/26/2013 12:53:17 PM
Years ago we had a Chevy Monza Spyder with the 305 V8. Never did change the sparkplugs on the drivers side, but that's a different story...


Had the High Enewrgy Ignition with the coil as part of the cap. I was in college at the time. married with 2 toddlers so money was very tight. My wife had driven into town and the car just quit. I was able to get a friend to drive me to the car between classes and I figured out te spark was jumping through the rotor to the distributor shaft. So I looked in the car and found a candy wrapper and put it under the cap and fastened it back down. Drove the car for several days until I could connect with one of the instructors from the Automotive Department and got the advice to change the sparkplug cables. Seems that the in center of the cap was an area of low desity because of the design of the mold they were made in. A thin candy wrapper had better dielectric properties that the much thicker plastic in the rotor.


One area where GM did a good job was in the ignition points with the hex socket adjusmant screw. Should have hired more engineers like that one.

William K.
User Rank
Cooling down time?
William K.   12/26/2013 12:37:35 PM
My experience with distributor caps has always been that at engine shutoff they are a bit too hot to hange on to for very long, although they cool fairly rapidly. On my Chrysler products with the slant six they seldom had problems, and somight be replaced once at 60,000 miles on general principles. On my Horizons and Neon they did not ever seem to develop problems. Of course, all of those caps were as close to symetrical as possible.

Plug wires were a different sory, as they usually had to be replaced a bit more frequently, I never did figure out why some failed and some didn't. I did come up with a cheaptrick for checking plugs, which is to use a DVM multimeter to measure resistance between plug top and engine block. Anything less than open circuit meant time to either clean or replace that plug.

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