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 Hi everyone, I am new to the 6 V positive ground system. So I apologize ahead of time for me seem like trivial  questions. I have a 1948 dodge D 24 sedan with the 230 flat head six.  She runs great at idle and all the way up to about 2000 RPM.  Past that she start sputtering and  Backfiring. I have rebuilt the carburetor, installed new points, condenser, rotor, distributor cap  and set the timing.  She honestly runs great at the lower RPMs.  Once I start to accelerate or rev the engine from rest and get to about 2000 RPMs she starts to backfire and sputter. I have  monitored the spark through my timing light And found that it starts to go erratic. I monitor the voltage on the positive side of the coil And at idle I have about 2.4 v.  As the rpms raise the voltage drops and I find that the missing starts once the voltage hits zero and goes negative.  Not sure what this means.  I also used a test light to monitor the pulsing of the signal. The signal continues to grow brighter as the rpm is raised until I hit that certain mark.  Then the pulsing is very erratic. It almost is acting like a rev limiter. But I cannot find one anywhere and my service manual makes no mention of it. I also must mention that monitored the vacuum with a gauge at the intake and have 20 inches at idle.  If anyone has any helpful ideas I would love to here them.  Thanks 

Edited by Mopar Wayne
Typos.

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Sounds like either the coil or the points to me. Most likely the coil. "Point bounce" is more common in engines that turn a lot more RPM's than your flat 6 turns.

Since it is a good idea to carry a spare coil,points,condenser,and distributor cap in the trunk anyhow,and a HELL of a lot cheaper than paying a roll-back to carry you home,why not just buy all that stuff new and try it one at a time until the problem goes away,starting with the coil?

Coils crack and get burnt out from getting too hot from bad grounds,but it's the cracked ones that operate fine to start an engine and then operate at low RPM's. Once they get hot and the demand on this climbs from higher RPM the crack widens from the heat and you lose fire.

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point bounce is suspect, ensure your point spring is properly located when installed...also disconnect  your vacuum advance for a test run and ensure you not shorting out the distributor at the higher RPM as the jumper wire in the distributor if improper positioned can often touch ground as the plate rotates. 

 

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Yup... What Plymouthy said... I once mistakenly connected a set of points and didn't get the spring connected right. above around 2000 RPM it would sputter, cough, and loose a great deal of power. As you said, the timing light would show very erratic spark. Once I found what I did and corrected it everything was fine.

He also mentioned the jumper wire in the distributor... They have been known to have bad insulation and short out against the distributor body, or points plate, when the distributor advances under higher RPM. Inspect that wire carefully.

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Ditto.  Points first, overall distributor condition - to include condition of wiring, then coil.  Not a 6v specific issue you describe, it could happen to anything with points ignition.  6v is just what our cars run on, not much to do with how they run.

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What brand of points did you use?  Most new stuff including from Napa are junque.  Weak springs, crappy can rubbing block, no oil wick for lube, miss aligned points, crappy material for contacts.  Did this condition exist before you replaced points? Do you still have the old ones? I would put them back in and see it it will rev better.  The other thing to check is the thin flexible wire that supplies the points with power from the coil terminal of the dist.  This wire can sometime have insulation fall off allowing an inadvertantly ground before the points, or it will look good on the exterior but be separated within the insulation it is very important to proper running through the full rpm range.  With positive ground make sure your coil is wired ignitionignition to neg terminal, positive terminal to dist.

 

 

 

 

 

 

 

 

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Thanks everyone. As an update I totally disassembled the distributor this morning. My vac advance is totally shot. I knew this and had already block the line to the carb. The bearing plate for the vac advance was gummed up bad. I cleaned it up and verified the mech advance is free and working (as best as I can without a dist machine). The wire inside the dist is very suspect. I actually wrapped it with some electrical tape but plan to make a new one tonight. I did not change out the points yet as I have to run and get a set. I did put is all back together and I still have the same result. Hopefully the points will take care of it. I will keep you all posted. Much thanks for the advice. On a side note, where can one get a vacuum advance. I saw one that was NOS on ebay, but I am unsure if I want to use an NOS one due to the rubber component and I also thought $90 was a bit steep. Here is a pic of my tag on the dist

IMG_31601.jpg

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5 hours ago, greg g said:

What brand of points did you use?  Most new stuff including from Napa are junque.  Weak springs, crappy can rubbing block, no oil wick for lube, miss aligned points, crappy material for contacts.  Did this condition exist before you replaced points? Do you still have the old ones? I would put them back in and see it it will rev better.  The other thing to check is the thin flexible wire that supplies the points with power from the coil terminal of the dist.  This wire can sometime have insulation fall off allowing an inadvertantly ground before the points, or it will look good on the exterior but be separated within the insulation it is very important to proper running through the full rpm range.  With positive ground make sure your coil is wired ignitionignition to neg terminal, positive terminal to dist.

 

 

 

 

 

 

 

 

Thanks Greg. They where actually changed prior to me buying the car. So I am unsure of the brand. The coil is wired correctly. That was one of the first things I checked. As far as I know the gentleman I purchased the car from actually got it running after a long period of being out of service. I do have a question, is normal 18 or 20 ga stranded wire going to be acceptable to replace the existing wire with?

 

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That wire needs to be very flexible to allow the breaker plate to move smoothly through its range of motion.  I had some insulation loss on mine.  I removed the wire and wound some light cotton sewing thread around it, then painted the repaired area with thinned rubber cement.  That was 15 years ago...maybe I should recheck it! Keep a record of that number that starts with IGS.  Then when you order tune up parts order by that number.  I found some good quality U S made points through a CarQuest jobber.  Also heard that Bosch brand were still decent also.  From what you just reported,I would suspect the largest culprit is the vacuum advance followed by the interior wire.

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The wire in question is a special wire and needs to be very flexible. I believe you can get a replacement at most auto parts stores. Also you can use an electric drill and a power supply such as a battery charger to adjust the dwell (point gap) with the distributor spinning on the work bench.

points.jpg

dual_points_1.jpg

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solder wicking wire is a good copper multiple strand braided wire 

 

available in various sizes...this one should work but you make the final if you choose to use it....I have used hundreds of rolls of this stuff.....in various sizes depending on the component being removed from a PCA

http://www.ebay.com/itm/2-0-mm-Desoldering-Braid-Solder-Remover-Copper-Wick-Spool-Wire-Cable-1-5m-USA-/290768708140?hash=item43b32a622c:m:mY7UFS8PnrGItFKQSvj87gg

Edited by Plymouthy Adams

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Hey everyone, first off, you all rock! I have it figured out and done fixed it. Turns out the points the last person put in where missing part of the spring and I didn't even realize it when I took the distributor apart. I installed the new points (all of the included parts) and she runs like a raped ape now! I am not even sure if I need to replace the vacuum advance. I suppose if I come across a good deal I will. All of the ideas, suggestions  and troubleshooting tips where spot on. Special thanks to Don. The drill idea was perfect. I didn't even need to hook it up to electric to find the issue. I know I will have tons more questions as I move along with this ole girl. I came to the right spot!

 

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It has been posted here before that Terrell Machine in Deleon Texas will repair your vacuum advance with new parts . You probably would want to have it running like mopar designed it to run .   

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Mopar Wayne ,  Looking in my Auto-Lite catalog ;  your distributor model number IGS-4207A1 uses vacuum chamber VC- 2082R . Hagen's Auto Parts in Puyallup , Wa . ( 1-253-845-7020 ) shows one at $60 and your core . 

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Hi Wayne, also you can quick check the coil. Using a screw driver, arc any plug wire to ground. If the spark arc is white coil is "ok", Red spark coil is weak ,blue spark coil is like new.

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On 10/6/2017 at 10:59 PM, Jerry Roberts said:

Mopar Wayne ,  Looking in my Auto-Lite catalog ;  your distributor model number IGS-4207A1 uses vacuum chamber VC- 2082R . Hagen's Auto Parts in Puyallup , Wa . ( 1-253-845-7020 ) shows one at $60 and your core . 

Thanks Jerry, I placed my order this morning. :)

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Jumping in, any recommendations in regards to a good 6 volt positive ground  coil product to purchase online? Same regarding the coil and condenser. 

 

Thanks 

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37 minutes ago, Thomba48 said:

Jumping in, any recommendations in regards to a good 6 volt positive ground  coil product to purchase online? Same regarding the coil and condenser. 

 

Thanks 

Believe it or not I was able to get parts off of rockauto.com

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1 hour ago, Thomba48 said:

Jumping in, any recommendations in regards to a good 6 volt positive ground  coil product to purchase online? Same regarding the coil and condenser. 

 

Thanks 

And standard 6 volt coil,condenser,and point sets will work just fine as long as none of it was made in China. You can usually buy this stuff in any auto parts store,but any but NAPA are likely to have to order it after you convince there there is such a thing as 6 volt coils.

Tractor dealers are also a source for 6 volt coils,condensers, and batteries,and MIGHT even have the points

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Thomba..........were'nt early VW's running 6 volts?........the guys may not have seen you are in Germany and US parts shops may not assist you...........have you tried Andy Bernbaum for a NOS coil, points & condenser?............. andyd

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I had a 68 BMW 1800 that was still 6v, had a bosh coil.  But most coils without internal resistance will work on 6v.  Most 12 volt systems contain some sort of resistance, like Mopar ballast resistors, or GM's resisted feed wire to supply 6 to 8 volts to the coil when the ignition switch is in the run position.  So you do note need to look for a 6 volt specific coil, just stay away from the ones marked internally resisted.

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