Re: low voltage causing starting problems and rough idle?
[Re: 68charger440strk]
#1645388
07/11/14 07:03 PM
07/11/14 07:03 PM
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Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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With electrical issues especially strange ones like this start at the beginning (the battery), sub another one in & see how it performs. With nothing on you will have system voltage everywhere just like in a college dorm, all the toilets have equal water pressure till someone flushes one of em & the pressure drops which is why someone in the shower may scream from being scalded when a stool gets flushed in an antiquated system. When running you are going to have system voltage available except each connection will have a slight voltage drop (hopefully only several tenths per connection) & the device (coil/ecu) used will drop the voltage further from the amount of current (amps) it uses. If the batt is OK then unhook the coil & see what the voltage does then hook it back up & unhook the MSD & see what the voltage does. Holler back with any news.
live every 24 hour block of time like it's your last day on earth
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Re: low voltage causing starting problems and rough idle?
[Re: RapidRobert]
#1645390
07/12/14 06:40 PM
07/12/14 06:40 PM
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Joined: Apr 2013
Posts: 16
colorado
68charger440strk
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Joined: Apr 2013
Posts: 16
colorado
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Quote:
With electrical issues especially strange ones like this start at the beginning (the battery), sub another one in & see how it performs. With nothing on you will have system voltage everywhere just like in a college dorm, all the toilets have equal water pressure till someone flushes one of em & the pressure drops which is why someone in the shower may scream from being scalded when a stool gets flushed in an antiquated system. When running you are going to have system voltage available except each connection will have a slight voltage drop (hopefully only several tenths per connection) & the device (coil/ecu) used will drop the voltage further from the amount of current (amps) it uses. If the batt is OK then unhook the coil & see what the voltage does then hook it back up & unhook the MSD & see what the voltage does. Holler back with any news.
The voltage at the feed to the positive side of the coil is 10v today(the gremlins are feeling generous today). That is the same when I disconnected it from the coil, and when the MSD dizzy is disconnected or connected also. I swapped the battery with no effect last week. The coil is an MSD blaster 3 which has .7 ohms primary resistance and 4.7 k ohms secondary resistance.
Is there something behind the dash that would keep the voltage down with the key on? Am I correct that I should have at least 12v to the coil since I have bypassed the ballast resistor?
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Re: low voltage causing starting problems and rough idle?
[Re: Challenger 1]
#1645392
07/12/14 08:28 PM
07/12/14 08:28 PM
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Joined: Apr 2013
Posts: 16
colorado
68charger440strk
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OP
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colorado
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Quote:
I'd check the heavy red wire that goes through the bulkhead connector. It's worth checking or bypassing the connector in the bulk head connector instead of waiting for it to cor road and over heat.
I have solid wire red soldered in passing through my bulk head on my one car. Been that way since 1985 when "I fixed it" lol  It's known to melt down.
I did that bulkhead bypass also for both the feed to and from the ammeter. I didn't connect the two wires to one side of the ammeter thus bypassing the ammeter altogether though. I am starting to wonder if the ammeter is where I am getting the inconsistrant voltage from.
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Re: low voltage causing starting problems and rough idle?
[Re: 68charger440strk]
#1645396
07/13/14 11:26 PM
07/13/14 11:26 PM
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Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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Incredible  I've never known an ammeter to act like that. We coulda been chasing that one for a long time
live every 24 hour block of time like it's your last day on earth
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Re: low voltage causing starting problems and rough idle?
[Re: RapidRobert]
#1645397
07/14/14 12:14 AM
07/14/14 12:14 AM
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Joined: Jan 2007
Posts: 401
Norway
General 68
mopar
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mopar
Joined: Jan 2007
Posts: 401
Norway
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Hi Robert. I believe this is a sympthom of an ampere meter about to burn if not taken care of. They are simple by design so I can not see many other things that can fry them. From the start the studs are fit tight through the U-shaped piece and held tight by the inner nuts. But after thousands of cyclings and temperature changes the fit and connection between the stud and nut and this U-piece get affected causing excessive heat. Robert: When I am on here I would like to say that you are doing a great job and putting in a lot of work by helping so many on here! Thank you for your positive attitude and will to share your knowledge and experiance!  Lars
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Re: low voltage causing starting problems and rough idle?
[Re: 68charger440strk]
#1645399
07/14/14 11:53 AM
07/14/14 11:53 AM
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Joined: Jan 2008
Posts: 1,213
Minn
SportF
pro stock
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pro stock
Joined: Jan 2008
Posts: 1,213
Minn
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I am coming on this a little late, but you say you are running MSD ignition? If so, then both wires on the coil come from the box, right? And if so, you don't get battery voltage there. In fact, as I recall, when running, it will be a high enough voltage that you don't want to measure it, and I believe the instructions imply or state that (+200 vdc). If your battery isn't up to full charge, MSD really doesn't want to work. Charge your batter fully, then see how it goes, but with MSD, I wouldn't be checking that coil voltage with anything. I did read that coil voltage with an "O" scope with an inductive pick up years ago and I seem to remember some +350 volts or something (running engine). But whatever it was, it was surprisingly high hence the huge spark at the plugs.
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Re: low voltage causing starting problems and rough idle?
[Re: SportF]
#1645400
07/14/14 12:36 PM
07/14/14 12:36 PM
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Joined: Apr 2013
Posts: 16
colorado
68charger440strk
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colorado
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Quote:
I am coming on this a little late, but you say you are running MSD ignition? If so, then both wires on the coil come from the box, right? And if so, you don't get battery voltage there. In fact, as I recall, when running, it will be a high enough voltage that you don't want to measure it, and I believe the instructions imply or state that (+200 vdc). If your battery isn't up to full charge, MSD really doesn't want to work. Charge your batter fully, then see how it goes, but with MSD, I wouldn't be checking that coil voltage with anything. I did read that coil voltage with an "O" scope with an inductive pick up years ago and I seem to remember some +350 volts or something (running engine). But whatever it was, it was surprisingly high hence the huge spark at the plugs.
Let me clarify... I am running an MSD HEI all in one dizzy without the separate ignition box hooked up. With that setup the dizzy does get the coil power directly.
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