Need help understanding Mopar ignition…no spark

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Sdriche

Sdriche

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I have a 68 Dart which the previous owner replaced the ignition components. New Mopar electronic distributor, new orange box, new coil. it’s been running fine until yesterday. Moved the car out of the garage and wouldn’t restart. Seems to be lacking spark to the plugs. I confirmed spark out of the coil and coil wire when cranking, but no spark past that. Cap center terminal has continuity, rotor looks good, what would stop the spark from transferring to the plugs? I know There’s a pickup in the distributor that feeds the module but unclear how that works. Any suggestions?

cleaned the ground o the module, cleaned the cap/rotor although they look new, new wires…
 
If you have spark out of the top of the coil and in to the cap, but nothing at the plugs it’s only one of 4 things. In this order
1.cap
2.rotor
3.plug wires
4.plugs
 
If I remember correctly there’s two wires that power the ignition. One when the key is on “start” and one on “run”. My car is has been rewired for a while but I think they go to the ballast resistor.
 
Sdriche said:
I have a 68 Dart which the previous owner replaced the ignition components. New Mopar electronic distributor, new orange box, new coil. it’s been running fine until yesterday. Moved the car out of the garage and wouldn’t restart. Seems to be lacking spark to the plugs. I confirmed spark out of the coil and coil wire when cranking, but no spark past that. Cap center terminal has continuity, rotor looks good, what would stop the spark from transferring to the plugs? I know There’s a pickup in the distributor that feeds the module but unclear how that works. Any suggestions?

cleaned the ground o the module, cleaned the cap/rotor although they look new, new wires…
Click to expand...
Try holding the key in START and see if it starts up and runs. It won't hurt it for just a couple of seconds. If it starts with the key all the way in START and will not keep running when you release the key, put a ballast resistor on it.
 
I put a new cap and rotor on and didn’t help. I get 11v to the + Side of the coil and 4v on - with key on. I’ll measure while cranking. It looks like the ballast is bypassed on this car.
 
Understand that there are two conditions for power, and they can lead you down a rose colored path

In "run" the key feeds the ballast which feeds the box, and with key in "run" but engine stopped, the coil should be drawing current. This causes the voltage to coil + to drop and should be somewhere around 6-10V or so, maybe a bit higher or lower, but certainly not 12, which means the box is not causing the coil to draw ---by properly grounding the coil neg

I "start" the key KILLS the "run" voltage, and the ONLY starting power is from the bypass, IGN2 circuit, so when using the KEY in start (NOT jumpering the start relay) the coil + should be close to battery voltage. So if the starter drags the battery down to 11.5, then the coil _+ should be close to that voltage

It is IMPORTANT, therefore, to evaluate coil spark with the key in "start" rather than jumpering the relay. "Rig" a solid core wire-even a low voltage wire hung "in the air" and to a spark gap, either tester or widened plug, and hook that to the coil tower

You should get rhythmic sparks nice and hot and blue at least 3/8" and typically 1/2" long
 
Is the rotor button actually making contact inside the cap's center terminal?

Could be a defective button or simply the incorrect one.

New means nothing these days!
 
I did some further testing and actually had a weak spark to the plugs with the Mopar ignition. I had on old GM HEI here and did the conversion. Now I have a strong spark to the plugs and the car still wont start, just cranks. I can see fuel squirting when i move the throttle so now I'm stumped !! I pulled a plug and grounded it out to verify spark. Ugh!!
 
Are the plugs wet fouled? You may have flooded the cylinders and plugs. I've seen new plugs work wonders .
 
i can try new plugs but was getting spark when i grounded them out. They didn't look wet. Do you think new plugs are the next step?
 
well if yo
Sdriche said:
i can try new plugs but was getting spark when i grounded them out. They didn't look wet. Do you think new plugs are the next step?
Click to expand...
u been cranking it and no start Id think the cylinders loaded up but if you say they are dry, I dont know Id look at all 8 keep em in order. How about timing is the distributor hold down tight? you could try spraying a blast or two of carb cleaner down the carb see if it fires off than youd know you have no fuel...mechanical pumps crap out suddenly...sounds like you have sparkk. Ive always understood 4 things cause an engine not to run, spark, fuel, timing and internal damaged components causing no compression etc. Technically if you check for all 4 of theos ethings you should find the problem sounds like spark good now go after fuel quickest way I test for fuel is to spray carb cleaner down carb see if she fires...but dont flood it just a fey quick burst of carb cleaner. you could be ou tof gas regardless f what the guage says...:)
 
You can clean oil/ gas off plugs with anything that evaporates fast. Aerosol parts cleaner, carb cleaner or starting fluid. Use the snorkel, give a blast or two directly into the plug AWAY from you and let them dry.

A plug that sparks in open air MAY NOT spark under compression. I don't suppose you are old enough to remember the old sandblast plug cleaner / testers. You screwed the plug into a test chamber with a window, and pressurized it with air as you supplied spark voltage. At some pressure the plug would stop if bad
 
Take a new spark plug of any type and open the gap to .080" to .100" on spark plug wire and grounded. Have someone crank engine. If you have a good spark that isn't your problem. If no spark hook it to the coil wire and test again. KD used to make spark testers that look like a spark plug with an alligator clip attached to the shell. I always use them to test ignition. If you have spark then fuel, timing or compression.
 
Sorry, ^^^^ is incorrect.


You can get a spark in open air, but no spark under compression because of a faulty coil.
 
do you have a cheap box laying around that you can change out that garbage orange box with for ***** and giggles? those orange boxes do some goofy **** sometimes
 
Sorry to resurrect this thread but I'm at the end of my thread so to speak and could use the wisdom of this group. To recap, 360 motor, with Mopar HEI distributor which is now paired with the GM HEI conversion (wiring exactly to the image below). The coil is a brand new FD-478 and I have a GM HEI module and just replaced it with another to rule out any module issues. Still no start. I have power at key on and at crank to the coil and module (12v). The module is grounded properly. Cap and rotor are new as well. On cranking, i get one shot of spark then nothing. The distributor was new last year so not that old. The only thing I can think of at this point is the pickup in the distributor isn't telling the module to ground out the coil and generate spark. Any advice on where to go next ? Thanks in advance

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1695905129238.png
 
You can test the pick up in the distributor. Pull the distributor out and clamp it in a Vice. Chuck the dist shaft in a drill. Hook a multimeter to the pickup wires, polarity makes no difference. Spin the drill/distributor and measure AC voltage on meter. Depending on how fast you spin it you’ll see 1-4 volts AC if good.
 
TT5.9mag said:
You can test the pick up in the distributor. Pull the distributor out and clamp it in a Vice. Chuck the dist shaft in a drill. Hook a multimeter to the pickup wires, polarity makes no difference. Spin the drill/distributor and measure AC voltage on meter. Depending on how fast you spin it you’ll see 1-4 volts AC if good.
Click to expand...
Can i do that same test on the car with the engine cranking vs pulling it and doing on a bench?
 
Not familiar with that coil. Is it designed to be [a] used without a bal res & with a GM module?

Check p/up air gap. Should be 0.006-8". If the p/up touches the pole piece, you get no spark.
 
Bewy said:
Not familiar with that coil. Is it designed to be [a] used without a bal res & with a GM module?

Check p/up air gap. Should be 0.006-8". If the p/up touches the pole piece, you get no spark.
Click to expand...
Yes, that is another style of E core coil.
I don’t like that style because it uses blade type pins.
Even if you use the factory connector it doesn’t seal up around them.
 
There are E core coils.......& there are E core coils.

It HAS to be compatible with the ign system with which it is being used. The MSD #8251 is an E core coil, but it has a primary resistance of 0.04 ohms & is designed for MSD 7 CD ign. Not for inductive ign, like HEI.
The GM HEI module has an inbuilt current limiting device to limit current to about 5.5 amps; the original GM coil had a pri resistance of about 0.6 ohms.

The coil needs to be compatible with the ign system it will be used with. Not a case of pick-a-coil.
 
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