Poor Spark?

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Calipag

Calipag

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We've installed the 318 from our 1974 Dart donor car in to our 1970 Dart. It was running when removed and the distributor was not removed. I cleaned up the electronic ignition and installed the GM module and Ram Truck coil.

I'm trying to start the engine after the swap and I have a strong spark from the coil wire.

I have very weak almost no spark at the plug wire.

It has a new cap and new rotor.

The engine does not want to start, and is back firing. I've checked the firing order and made sure TDC and the distributor are correct.

The Spark is the only thing that I feel could be the problem but don't understand why the spark is so weak.

Am I missing something?
 
Eliminate the plug wires through an ohm test. Suspect the new modification.
 
Bodyperson said:
Eliminate the plug wires through an ohm test. Suspect the new modification.
Click to expand...

If the modification was the problem, wouldn't the coil spark be the problem?

I have a strong coil spark.

I don't know if the mod would affect the spark at the plug wire.
 
Calipag said:
If the modification was the problem, wouldn't the coil spark be the problem?

I have a strong coil spark.

I don't know if the mod would affect the spark at the plug wire.
Click to expand...
Good point. You still need to remove the plug wires from the equation.
 
Look at the wear on the cap and rotor to make sure it is ok easy first might have cracked. The new stuff sucks. I have seen the rotor gap way off new especially if two different brands, have the old ones still throw them in and see what happens, doubt all 8 wires went bad.
 
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You said weak spark at "the" plug wire. How many did you check his way?
If you got a hot spark going into the cap, you should have a hot one coming out. Pop the cap and find out where it went. In the meantime put a shot of oil in every cylinder and let it sit for a couple of hours, overnight is better. You may have just washed all the oil off the rings by now.
Also, the new module might have affected the engine timing. She will likely start better with some extra timing thrown at her. You can back it down to "normal" after she's all warmed up.
Good luck.

Oh yeah; you said you removed and replaced the engine without pulling the D. Did you pull the engine with the trans attached? This is a tricky thing to do and not bend/break the D. You might want to pop the cap and make sure the advance system is still operative and that the center shaft is spinning nice and true. Also check the rotor is the same as the one that came out. Sometimes the firing tips are shorter/longer. Look for damage inside the cap to the tower contacts.
One more; you said you replaced the cap, and checked the firing order. What yo did not say is that you replaced the wires one by one or sync'd the #1 plug wire to the Correct tower with the rotor under it, with #1 cylinder at TDC compression. . Just cuz the cap has #1 on it does not guarantee that the rotor is gonna be there when it's supposed to be.
 
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This SHOULD be pretty simple, the way I see it the possibilities are:

1...Coil wire. If you checked spark using the coil wire, that is "run" in the car, then you eliminated that

2...Cap and rotor. If they are not new replace them. Inspect the rotor for "punch through" IE carbon tracking/ damage that allows the spark to conduct down through the rotor and ground to the shaft. Inspect cap for dirt, debri, metallic tracking, etc Make certain you actually have the correct cap/ rotor combination, and that some oddball combo of parts has not created a big gap between rotor contact and cap coil tower contact. I can't imagine what that might be

3...Wires. As said above, measure them end to end with an ohmeter. "Shake" them to see if they are intermittent. The "old standard" for old style resistance wire was a max. of 1000 ohms per foot of length. I've never seen a good one anywhere near that high

4...ROTOR PHASING. When doing this conversion, it is IMPORTANT to get the distributor pickup wires in the correct polarity, as it offsets the spark timing in relation to the contacts in the cap/ rotor. Google it

5...Related to (4), reluctor installation. This is just something to check while you are making certain things are "right." The reluctor has TWO keyways, and an arrow beside at least one. This same reluctor is used in both SB and B/RB engines and the distributors of which rotate opposite directions

The one below shows BIG block. On a SB you want the pin next to the CW arrow

20170518_102034-jpg.jpg
 
67Dart273 said:
4...ROTOR PHASING. When doing this conversion, it is IMPORTANT to get the distributor pickup wires in the correct polarity, as it offsets the spark timing in relation to the contacts in the cap/ rotor. Google it
Click to expand...

Betcha this is it.:D
It would only take a minute to swap the distributor pickup wires and see.
Good spark at the coil and not at the plugs is a dead giveaway.
 
Calipag said:
We've installed the 318 from our 1974 Dart donor car in to our 1970 Dart. It was running when removed and the distributor was not removed. I cleaned up the electronic ignition and installed the GM module and Ram Truck coil.

I'm trying to start the engine after the swap and I have a strong spark from the coil wire.

I have very weak almost no spark at the plug wire.

It has a new cap and new rotor.

The engine does not want to start, and is back firing. I've checked the firing order and made sure TDC and the distributor are correct.

The Spark is the only thing that I feel could be the problem but don't understand why the spark is so weak.

Am I missing something?
Click to expand...
On my car with the same symptoms it turned out my original firewall to block ground wire was bad. The connections at both ends were clean and tight and the wire tested good for continuity. Ground wire from battery to block was new and both connections clean and tight. Replaced firewall ground and problem solved. It drove me nuts.
 
AJ/FormS said:
You said weak spark at "the" plug wire. How many did you check his way?
If you got a hot spark going into the cap, you should have a hot one coming out. Pop the cap and find out where it went. In the meantime put a shot of oil in every cylinder and let it sit for a couple of hours, overnight is better. You may have just washed all the oil off the rings by now.
Also, the new module might have affected the engine timing. She will likely start better with some extra timing thrown at her. You can back it down to "normal" after she's all warmed up.
Good luck.

Oh yeah; you said you removed and replaced the engine without pulling the D. Did you pull the engine with the trans attached? This is a tricky thing to do and not bend/break the D. You might want to pop the cap and make sure the advance system is still operative and that the center shaft is spinning nice and true. Also check the rotor is the same as the one that came out. Sometimes the firing tips are shorter/longer. Look for damage inside the cap to the tower contacts.
One more; you said you replaced the cap, and checked the firing order. What yo did not say is that you replaced the wires one by one or sync'd the #1 plug wire to the Correct tower with the rotor under it, with #1 cylinder at TDC compression. . Just cuz the cap has #1 on it does not guarantee that the rotor is gonna be there when it's supposed to be.
Click to expand...

I'll try a the oil in the cylinder.
I did pull the motor and trans together.
I checked the spark at a few different plug wire ends and still weak.
I pulled the #1 spark plug and checked for TDC and made sure I was on the compression stroke (even pulled the valve cover to look at the rocker arms) and matched the rotor tip to the #1 plug wire. I have moved the distributor around to see if it was a timing problem and it still not firing off. It acts as if I had the timing off 180 but I've check and check and had someone check my check and I believe it's TDC and everything is lining up the way it should.


It did sit for a while prior to me buying the donor car and someone else mentioned it may be stuck valves. I have not checked each cylinder for compression. I'm going to do that tonight.
You mentioned the distributor center shaft. How touchy are they? I was very careful when removing the engine but when we separated the transmission from the engine ( out of the car) I had the cap off and the rotor hit the cap as I spun the torque converter to get to the bolts.
It does spin freely and nothing appeared to be damaged in the distributor.
 
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TrailBeast said:
Betcha this is it.:D
It would only take a minute to swap the distributor pickup wires and see.
Good spark at the coil and not at the plugs is a dead giveaway.
Click to expand...

I remember you telling about that when I did the install and I checked, or should I say I've switched to see if the spark was better, worse or non at all and when the wires to the distributor leads are switched it really made no difference at the spark plug end.
 
67Dart273 said:
This SHOULD be pretty simple, the way I see it the possibilities are:

1...Coil wire. If you checked spark using the coil wire, that is "run" in the car, then you eliminated that

2...Cap and rotor. If they are not new replace them. Inspect the rotor for "punch through" IE carbon tracking/ damage that allows the spark to conduct down through the rotor and ground to the shaft. Inspect cap for dirt, debri, metallic tracking, etc Make certain you actually have the correct cap/ rotor combination, and that some oddball combo of parts has not created a big gap between rotor contact and cap coil tower contact. I can't imagine what that might be

3...Wires. As said above, measure them end to end with an ohmeter. "Shake" them to see if they are intermittent. The "old standard" for old style resistance wire was a max. of 1000 ohms per foot of length. I've never seen a good one anywhere near that high

4...ROTOR PHASING. When doing this conversion, it is IMPORTANT to get the distributor pickup wires in the correct polarity, as it offsets the spark timing in relation to the contacts in the cap/ rotor. Google it

5...Related to (4), reluctor installation. This is just something to check while you are making certain things are "right." The reluctor has TWO keyways, and an arrow beside at least one. This same reluctor is used in both SB and B/RB engines and the distributors of which rotate opposite directions

The one below shows BIG block. On a SB you want the pin next to the CW arrow

View attachment 1715251361
Click to expand...

The cap and rotor are new but we are going to buy another set to compare (we threw away the old set).
The wires are the only thing in that system that we have not replaced, so I may just do it to cross it off the list of suspected items.
We never removed the the reluctor but I will check for proper installation.

Thank you
 
67dodgedartconv said:
On my car with the same symptoms it turned out my original firewall to block ground wire was bad. The connections at both ends were clean and tight and the wire tested good for continuity. Ground wire from battery to block was new and both connections clean and tight. Replaced firewall ground and problem solved. It drove me nuts.
Click to expand...

Now that you mention this. I don't think there is a ground wire from the firewall. I have one from the battery to the block. One from the ignition module to the battery. One from the block ground back to the frame and one to the Rad support. But none from the engine block to the firewall.

Could it be that ?
 
Electronic ignition pickups don't need a ground actually. Al they do is prioduce a low voltage that is amplified by the ECU/module. Your problem is you have coil spark no wire spark seriously look at the distributor and cap and rotor. A bent dist advance shaft can do weird things. Spark in no out, hmmm.....Think about it for a few.
 
Calipag said:
Now that you mention this. I don't think there is a ground wire from the firewall. I have one from the battery to the block. One from the ignition module to the battery. One from the block ground back to the frame and one to the Rad support. But none from the engine block to the firewall.

Could it be that ?
Click to expand...
I don't think that has anything to do with it, for three reasons; 1) you say that you have a hot coil spark, and 2) you have plenty of redundant grounds, and 3) the distributor does not need to be grounded, only the ECU needs to be grounded, and of course the spatkplugs,lol. If she cranks, then the plugs will have adequate ground.
As to the strength of the distributor driveshaft,at the reluctor end, it is stronger than the cap or rotor, so the little knock you spoke of should be a non-issue as well.

Wataminute! How are you testing for spark at the plug wire ends, versus at the coilwire?
 
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AJ/FormS said:
I don't think that has anything to do with it, for three reasons; 1) you say that you have a hot coil spark, and 2) you have plenty of redundant grounds, and 3) the distributor does not need to be grounded, only the ECU needs to be grounded, and of course the spatkplugs,lol. If she cranks, then the plugs will have adequate ground.
As to the strength of the distributor driveshaft,at the reluctor end, it is stronger than the cap or rotor, so the little knock you spoke of should be a non-issue as well.

Wataminute! How are you testing for spark at the plug wire ends, versus at the coilwire?
Click to expand...

I'm just holding the lead near a ground and looking for the color and intensity of the spark.
 
Calipag said:
I'm just holding the lead near a ground and looking for the color and intensity of the spark.
Click to expand...
Are you expecting the spark to jump from the plug-clamp about 5/8 inch up inside the plugboot, and another 1/2" to ground? Few coils can pull that off, and some systems can be irreparably damaged. You may be forcing the electricity to take an alternative path inside the cap.
 
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UPDATE:
So I came home tonight and checked compression in the cylinders. I have compression so I check the distributor leads and switched them again, and it sounded much better.

I cranked it over and it started but as I release the key it turns off. I had this issue prior to doing the engine swap and it was recommended that the ignition switch was bad. The donor car ran fine and the ignition worked as it should. So I removed the ignition switch from the donor car (74 dart) and installed it in the 70 Dart but now the ignition is doing the same thing. When in the run position it kills the engine but when in the start (starter engaged) or turned forward almost to the starter is engaged it runs.

So I think switching the distributor wires helped it fire but I still have another problem.
 
AJ/FormS said:
Are you expecting the spark to jump from the plug-clamp about 5/8 inch up inside the plugboot, and another 1/2" to ground? Few coils can pull that off, and some systems can be irreparably damaged. You may be forcing the electricity to take an alternative path inside the cap.
Click to expand...

I push the lead out of the boot and take it close to a frame bolt or something similar.
 
Ballas
Calipag said:
UPDATE:
So I came home tonight and checked compression in the cylinders. I have compression so I check the distributor leads and switched them again, and it sounded much better.

I cranked it over and it started but as I release the key it turns off. I had this issue prior to doing the engine swap and it was recommended that the ignition switch was bad. The donor car ran fine and the ignition worked as it should. So I removed the ignition switch from the donor car (74 dart) and installed it in the 70 Dart but now the ignition is doing the same thing. When in the run position it kills the engine but when in the start (starter engaged) or turned forward almost to the starter is engaged it runs.

So I think switching the distributor wires helped it fire but I still have another problem.
Click to expand...
The ballast resistor check it one side is crank the other run, common issue.
 
Either the ignition switch is bad or you have it wired incorrectly, or the wiring has generated a problem

There are TWO switched ignition sources, IGN1 and IGN2 off the ignition switch. IGN1 is "run" BUT GOES DEAD during cranking. IGN2 is hot ONLY in carnking and feeds ONLY the coil + side of the ignition

When you run something like HEI with no ballast resistor you must tie them together

Problems can be in the bulkhead connector, the ignition switch connector, or the switch itself, or of course a wiring mistake

Since you have made this modification the most logical problem is that you did not get thet two wired together
 
67Dart273 said:
Either the ignition switch is bad or you have it wired incorrectly, or the wiring has generated a problem

There are TWO switched ignition sources, IGN1 and IGN2 off the ignition switch. IGN1 is "run" BUT GOES DEAD during cranking. IGN2 is hot ONLY in carnking and feeds ONLY the coil + side of the ignition

When you run something like HEI with no ballast resistor you must tie them together

Problems can be in the bulkhead connector, the ignition switch connector, or the switch itself, or of course a wiring mistake

Since you have made this modification the most logical problem is that you did not get thet two wired together
Click to expand...

Should the IGN1 and IGN2 be tied together at the coil? I lost/trashed the diagram that @TrailBeast sent me. I know I have them on separate leads at the coil. I hope that is my mistake.

Thank you to everyone for being patient with me.
 
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Calipag said:
Should the IGN1 and IGN2 be tied together at the coil? I lost/trashed the diagram that @TrailBeast sent me. I know I have them on separate leads at the coil. I hope that is my mistake.

Thank you to everyone for being patient with me.
Click to expand...

Either at or preferably well before the coil, so you only have one 12v wire running to the coil and ignition module.
But yes, ign1 and ign2 have to be connected together to power the coil in "Start" and "Run" both.
 
TrailBeast said:
Either at or preferably well before the coil, so you only have one 12v wire running to the coil and ignition module.
But yes, ign1 and ign2 have to be connected together to power the coil in "Start" and "Run" both.
Click to expand...

The problem is me! I wired it incorrectly. I will change it tonight and report back with my results.

Thank you again and Happy Thanksgiving!
 
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