poor coil spark

[lorny]

poor coil spark when warm - starts good cold
what does the condenser do ????
new coil and wire
orange electronic box
66 plymouth 383 car starts good cold
hard to start warm and sometimes cuts out while driving

 

[lorny]

just checked coil spark cold its strong but intermitent - car started right up

 

[twecomm]

The condenser is there to suppress AM radio interference from the ignition system.. It also softens the inductive kick from coil when the points open and close unto the cars electrical system. Since you have electronic ignition it's less of an issue, however the condensers do go bad. If you have electronic ignition you should have a solid state voltage regulator if you don't already. Just make sure the case of the "orange box" has a good solid ground to the chassis. Or, the orange box itself could be the problem.

 

[Outsider]

So you've pulled the coil wire, cranked it and held it away from ground, or used a spark intensity test tool, and compared the spark strength for length of arc and color, and compared it cold and hot?

 

[DodgeBoy5150]

poor coil spark when warm - starts good cold
what does the condenser do ????
new coil and wire
orange electronic box
66 plymouth 383 car starts good cold
hard to start warm and sometimes cuts out while driving

If your coil is mounted on the engine I recommend (getting a known good coil) moving it to the firewall or inner fender.
A overheated or bad coil always seems to behave the way you described.

 

[lorny]

yes pulled coil wire cold and hot spark is poor jumping to grd if any
does anything else control how hot the spark is??? besides the coil

 

[twecomm]

In a Mopar electronic ignition, battery + voltage goes thru bulkhead connector to ignition key switch. From the ignition switch, out thru bulkhead connector to ECU (orange box) and to the resistor. (it also goes to alternators voltage regulator on the bat terminal) The resistor is in series with the coil only in the RUN condition. The ignition switch electrically bypasses the resistor when cranking in START position, to provide full battery voltage to the coil for a hotter spark for getting engine started. With the ignition switch In the RUN position, the resistor is electrically in series with the coil circuit and coil voltage is reduced and current is limited by the resistor. The one side of the resistor goes to one terminal of the coil the other terminal of the coil goes to orange box connector.
In the most basic terms, the ECU or orange box electronically completes the circuit from one side of the coil to ground, replicating a light switch opening and closing on-off. Or, like the points in the distributor would in a car without electronic ignition. The pickup coil in the distributor sends a small magnetically generated "trigger" pulse to the ECU, in the ECU this pulse will eventually turn on / off a transistor ( the large one on front of ECU) to complete or interrupt the circuit the coil. This transistor is what is actually doing the switching on and off, of the voltage to the coil. This is why it's so important that orange box has a good ground.
Anything mentioned above can be having an effect on spark. The cars ignition switch, ECU, coil, resistor and bulkhead terminals are all at play to make the ignition work. Anything from coil to distributor and plugs is all on the output side of the coil and Hi voltage. Schematics are helpful.

 

[lorny]

In a Mopar electronic ignition, battery + voltage goes thru bulkhead connector to ignition key switch. From the ignition switch, out thru bulkhead connector to ECU (orange box) and to the resistor. (it also goes to alternators voltage regulator on the bat terminal) The resistor is in series with the coil only in the RUN condition. The ignition switch electrically bypasses the resistor when cranking in START position, to provide full battery voltage to the coil for a hotter spark for getting engine started. With the ignition switch In the RUN position, the resistor is electrically in series with the coil circuit and coil voltage is reduced and current is limited by the resistor. The one side of the resistor goes to one terminal of the coil the other terminal of the coil goes to orange box connector.
In the most basic terms, the ECU or orange box electronically completes the circuit from one side of the coil to ground, replicating a light switch opening and closing on-off. Or, like the points in the distributor would in a car without electronic ignition. The pickup coil in the distributor sends a small magnetically generated "trigger" pulse to the ECU, in the ECU this pulse will eventually turn on / off a transistor ( the large one on front of ECU) to complete or interrupt the circuit the coil. This transistor is what is actually doing the switching on and off, of the voltage to the coil. This is why it's so important that orange box has a good ground.
Anything mentioned above can be having an effect on spark. The cars ignition switch, ECU, coil, resistor and bulkhead terminals are all at play to make the ignition work. Anything from coil to distributor and plugs is all on the output side of the coil and Hi voltage. Schematics are helpful.

wow alot for me to register
i'll put another coil and condencer after lunch and check distributor and cap
spark was very poor this morning cold and long periods between

 

[twecomm]

Sorry to ramble on.. Just trying to indicate what items are at play with your issue. Look at you bulkhead connector. At the rear of the terminals on the firewall, check the wires and look for signs of heating or green corrosion where wire meets terminal pins. Also check the other side of the bulkhead connector under the dash as well.. bad connections thru the bulkhead connector can create problems. And yes, you could also have issues with the rotor and distributor cap. Make sure all your plugs and coil to distributor wire is fully seated and making proper connection. Good luck solving it.. and report back here when you figure out what fixes it. It will help others that search these threads for answers..

 

[Outsider]

With the key in the "run" position, measure the voltage going to the resistor. Should be above 12v going to the resistor, except when cranking, that's why there is the "start" voltage bypassing the resistor.

Never really seen a control or resistor that failed partly, either they work or they don't work, complete failure, open. That said, I really don't have much experience with some of the current replacement modules that don't use the original style transistors.

So go to as recommended above, look for bad ground or voltage loss to the ignition set up. Hopefully you don't have a harness/bulkhead issue as mentioned above. Make there is a good ground to the fender/firewall where you have the module mounted, sand the paint off where it's screwed down, use a toothed star washer between the module and the sheet metal

 

[lorny]

put another coil seem to have good spark but not consistant
noticed spark on the firewall when my wife was cranking.
Wire with yellow tag that says fusable link is bare and swollen must have over heated,
i put tape on it

 

[twecomm]

It looks like you have some visible corrosion where the connectors pins crimp on to the wires. After all, these connections are 50 years old. Have you opened up the bulkhead connector to see what condition the pins are in ? If you have a FSM look at the schematics and identify which wires are related to ignition and inspect further. Might want to think about replacing some or all the pins.

 

[lorny]

what signals the coil to spark ??
the coil has lots of spark cold
almost none hot (does not want to start when hot any more) i even put cold coil when engine was hot still would not start
i've been trying all the things suggested!!!
when engine is hot something won't let coil spark !!! hhmmmm

 

[Pops1967GTX]

good article with information ....


https://www.hemmings.com/stories/article/the-lost-art-of

 

[lorny]

spark is not consistant when hot
is 66 383 same distributor as 74 440

 

[HALIFAXHOPS]

No 383 shaft is shorter than a 440 and will not rotate.

 

[HALIFAXHOPS]

OK reading this it seems it is either your pickup coil or ecu getting hot and failing, fine when cold. Typical for mopar. You have to figure out which one. If you have acess to another ECU swap it in when hot and if it runs there is the issue if not prob the pickup in the distributor. FYI the new orange boxes have a pretty good fail rate on them since the transistor is actually buried into the potting compound unlike the OEM Mopar ones that the transistor on the ecu is real and cools off.

How to tell a "fake" ECU from a real one

Look for one of these it will walk you right through it. I have a copied one I can spare for $15

 

[kiwigtx]

You probably need a Dakota Dash and a pinion snubber.

Check your ground on the ECU at the firewall.
Check the terminals at the ballast resistor
Check the connections at the bulkhead connector
Make sure points/reluctor gap is not not closed - adjust gap with either brass or plastic feeler gauge (non-ferrous)
Check/replace condenser if one is fitted

 

[kiwigtx]

poor coil spark when warm - starts good cold
what does the condenser do ????
new coil and wire
orange electronic box
66 plymouth 383 car starts good cold
hard to start warm and sometimes cuts out while driving

...also check that the moulded plug is seated fully on the ECU - a screw is there to secure it firmly.