spark seems weak

[moparbud66]

I'm still waiting to hear my newly rebuilt 440 run for the first time. Everything has been checked and double checked but she won't start. I pulled number one plug out and grounded it and it gets a small orange spark but nothing that looks like it will knock you on your butt or fire under compession. I have a NOS ignition box and electronic distributor, new forward conversion harness and new Accel coil, wires and plugs. Any ideas???

 

[moparmarks]

Ya orange is a weak spark. Should be purple to white-ish.

 

[67 B-body]

Check your body ground, engine ground, Ign module case ground, verify spark plug holes are free of engine paint. Use a good meter and measure all of this, not just say "yep it's grounded good"...
Verify coil power with volt meter on + terminal. Test coil itself by supplying 12v to + terminal, hold the negative side to ground and let it saturate for a second, release -terminal from ground and watch for good spark from coil lead to ground or across a spare spark plug gap that is held to GOOD ground. Measure the resistance across the primary and secondary coils of the ign coil.
Report findings here...

 

[bigmanjbmopar]

Yeah Grounds!!!! If not then ignition box replace.

 

[moparbud66]

Check your body ground, engine ground, Ign module case ground, verify spark plug holes are free of engine paint. Use a good meter and measure all of this, not just say "yep it's grounded good"...
Verify coil power with volt meter on + terminal. Test coil itself by supplying 12v to + terminal, hold the negative side to ground and let it saturate for a second, release -terminal from ground and watch for good spark from coil lead to ground or across a spare spark plug gap that is held to GOOD ground. Measure the resistance across the primary and secondary coils of the ign coil.
Report findings here...

Will check your suggestions over the weekend. Thanks!

 

[67 B-body]

Will check your suggestions over the weekend. Thanks!

Yeppers,,,,, Hope you find something that doesn't take a bunch of money to resolve!!

 

[440roadrunner]

Some of that is incorrect. Paint on the plug holes don't mean squat, other than gumming up the threads. What DOES mean squat is if you painted the engine with the plugs in place, and got paint all over the insulators

You cannot test a coil by the method indicated. It WILL make a spark, but NOT a good spark WHY is that? Because these types of ignition systems MUST HAVE a condenser (capacitor) in the circuit. If you for example, remove the condenser from a points type distributor, the car generally will not start. The Mopar ignitions basically have a condenser built into the box.

Most of the rest of the suggestions were good.

It is IMPORTANT to understand that you CAN NOT check Mopar spark with a stock ignition using a ballast resistor by jumpering the starter relay. YOU MUST check the spark by using the KEY to crank the engine.

WHY is this? Because on Mopars, Unlike Ferds/ GM, the resistor bypass circuit is IN THE ignition switch. This means that with the key in "run" and by jumpering the relay, you are NOT getting much voltage to the ignition system.

Put your meter on the coil+ terminal and crank the engine USING THE KEY. You should get VERY close to battery voltage and NOT below 10.5 volts.

Certainly scrape, clean, the ECU mounting, and use star lock washers for a better ground.

Have you checked the spark by eliminating the coil wire? When I have "suspect" spark, I ALWAYS use a grounded probe to see the spark at the coil tower. With only one person, you will have to rig a gap. You can buy spark testers, or make one from a good plug---just open up the ground electrode wide, or break it off. You can use a clip, wire, etc, to "rig" this up to the lip on the cowling, so you can see it looking under the hood, etc

Like this:

In addition, disconnect all connectors, the distributor, the ballast, the ECU. Examine them for corrosion, and "work" them in / out to scrub them clean and to "feel" for a tight connection

Check the distributor reluctor gap, using a brass .008" (that's inches, not mm) feeler gauge. Last time I needed one, O'Reallys had them

Put your meter on low AC volts, hook the probes to the distributor connector, and crank the engine. The distributor pickup should generate about 1V AC when cranking

Check the ballast resistor. These vary a little over the years, but the coil side is around .5 (1/2) ohm, the ECU side (if it's 4 terminal) is about 5

You can also try running a temporary clip lead to the coil+ terminal and see if this improves spark. Do not leave this connected for too long and watch the coil for overheating.

 

[SwedCharger67]

The coil and the electronic box should be matched to each other. A high performance coil will not be high performance if you cannot feed it with the current it requires to output the power it is designed to output. Note that a high performance coil will draw a big current and an electronic box designed for standard low current coils may not survive the test.

I'm still waiting to hear my newly rebuilt 440 run for the first time. Everything has been checked and double checked but she won't start. I pulled number one plug out and grounded it and it gets a small orange spark but nothing that looks like it will knock you on your butt or fire under compession. I have a NOS ignition box and electronic distributor, new forward conversion harness and new Accel coil, wires and plugs. Any ideas???

 

[67 coronet]

double check the two wires to the distrib as well.if they get reversed it can cause a week spark.

 

[67 B-body]

Some of that is incorrect. Paint on the plug holes don't mean squat, other than gumming up the threads. What DOES mean squat is if you painted the engine with the plugs in place, and got paint all over the insulators

You cannot test a coil by the method indicated. It WILL make a spark, but NOT a good spark WHY is that? Because these types of ignition systems MUST HAVE a condenser (capacitor) in the circuit. If you for example, remove the condenser from a points type distributor, the car generally will not start. The Mopar ignitions basically have a condenser built into the box.

Most of the rest of the suggestions were good.

It is IMPORTANT to understand that you CAN NOT check Mopar spark with a stock ignition using a ballast resistor by jumpering the starter relay. YOU MUST check the spark by using the KEY to crank the engine.

WHY is this? Because on Mopars, Unlike Ferds/ GM, the resistor bypass circuit is IN THE ignition switch. This means that with the key in "run" and by jumpering the relay, you are NOT getting much voltage to the ignition system.

Put your meter on the coil+ terminal and crank the engine USING THE KEY. You should get VERY close to battery voltage and NOT below 10.5 volts.

Certainly scrape, clean, the ECU mounting, and use star lock washers for a better ground.

Have you checked the spark by eliminating the coil wire? When I have "suspect" spark, I ALWAYS use a grounded probe to see the spark at the coil tower. With only one person, you will have to rig a gap. You can buy spark testers, or make one from a good plug---just open up the ground electrode wide, or break it off. You can use a clip, wire, etc, to "rig" this up to the lip on the cowling, so you can see it looking under the hood, etc

Like this:

In addition, disconnect all connectors, the distributor, the ballast, the ECU. Examine them for corrosion, and "work" them in / out to scrub them clean and to "feel" for a tight connection

Check the distributor reluctor gap, using a brass .008" (that's inches, not mm) feeler gauge. Last time I needed one, O'Reallys had them

Put your meter on low AC volts, hook the probes to the distributor connector, and crank the engine. The distributor pickup should generate about 1V AC when cranking

Check the ballast resistor. These vary a little over the years, but the coil side is around .5 (1/2) ohm, the ECU side (if it's 4 terminal) is about 5

You can also try running a temporary clip lead to the coil+ terminal and see if this improves spark. Do not leave this connected for too long and watch the coil for overheating.

Painted spark plug holes DOES mean "SQUAT".... how do you think the plug obtains a GROUND in order for the spark to jump the gap?????? That's why you have to hold a spark plug against a grounded source while observing a spark jumping the plugs gap when your testing for spark in an ignition system.... THINK ABOUT IT!! A good clean thread will provide one of the required conditions for your ignition system to operate at its fullest potential, hens the reason I provided one of the many things for the OP to check.
A coil can be tested as I indicated... A condenser/ "Capacitor in modern terms" is not intended to conduct current between a source + & - fields.... It does however "STORE" a short duration of current and is measured in capacitance "a value of Micro Farads" This is accomplished by two plates of metal "typically aluminum" lying parallel to each other and separated "insulated" from one another using a thin piece of paper type substance "could be plastic or any other NON-conductor material". The two plates of metal with insulator are rolled up and inserted into a can. One of the two plates are "in typical automotive application" is connected to the cans body. The other is attached to the lead exiting the can. A certain amount of current is absorbed into the capacitor when the points are no longer providing a source of ground "points closed". This does not mean that it "conducts current" but rather each plate will absorb its own potential in form of + or - electrons to its respected termination. In simple terms, the lead/plate that is hooked to the + source will store + electrons and the opposite plate will store - electrons.
How does this apply to a cars ignition some might ask? Well, lets step back and look at what's going on in a typical points ignition system.... Keep in mind that everything in a modern electronic system is simply replacing the mechanical items in the points system in all practical purposes....
Most of you reading probably already understand the function of a rotor in the distributor and the dist cap, so I will write with these assumptions and speak only about how we create a spark, since my methods of doing a simple test of coils operation is in question.
The ignition coil has two sets of coil winding's within its case. The number of winding's or ratio between the "primary" and "secondary" winding's dictates the coils potential for "stepping up" the supplied ignition voltage to a point that provides the ability to jump a gap. The function of this process is possible because we can predict how electricity will act! When we supply current to the + terminal of a coil, we are actually sending power to one leg of the primary winding. The other leg of the primary winding is attached to the - post on your coil. The negative is then ran to your points and also "pigtails" paralleled to the condenser wire. Remember a capacitor in working order will not conduct current from the wire to the ground.... it will only store SOME electrons, and only when we are not already providing a source with low resistance to ground "points closed". When the points are in the closed position, current is rapidly flowing through the primary winding's of the ignition coil. When the cam lifts the points open, all of that flowing current has to go somewhere "as we can predict with how electricity typically reacts". This is Saturation and the breakdown of a field of electricity within the coil. When this happens, the inducted current from the primary to the secondary winding's will exit the coil through the high tension coil lead as long as there is a ground at the other end of the lead.... This ground is actually across a gap, and since we have stepped up the voltage through an increase of winding's in the secondary winding's of the coil, we have provided the "power" for this current to arc across the rotor gap and spark plug gap. Now that the field has collapsed within the ignition coil we have to charge everything back up again and start over.... so we close the points again. The condenser aids in the sequence by providing a momentary storage of the current that would normally want to arc or bridge across the points gap as they open, thus controlling this action and preventing "or at least aiding in the prevention of" transferring metal from one point contact to the other point contact. You can see this in some points ignition systems and looks like a nice built up point on one of the contacts and a depression in the other contact. This is NOT it's only function, so don't stop reading yet... The condenser also "it's primary function" causes the immediate opening of the circuit when the points open by absorbing that "what would be arc" between the points as they open... This is a big benefit for a consistent operation of this process, but not necessary for "testing a coil" manually. A bad capacitor typically shorts out internally causing the points system to effectively never open the ground side of the ignition coil and as a result, no spark is generated... If it losses its ability to sustain capacitance, it could prevent a coil from saturating and collapsing its field in time before the next cycle of open close sequence giving a "weak spark" condition....
End of class.....:glasses12:

I'm just trying to help....

 

[moparbud66]

This is what I diagnosed this morning. With the key turned on, I'm only getting a little over 6 volts to the coil. When disconnected from the coil, I get 13 volts at the positive lead. I scraped all the grounds to bare metal. I have good continuity from coil negative back to the box and from the box frame to engine ground, but open between the coil negative and engine (body) ground (with key on). This leads me to believe that the control box is faulty, maybe fried it by using Accel coil? Now I realiize I skipped a step and will check from the box terminal through the box to ground. The box is new but 30 plus years old.

 

[nothingbutdarts]

This is what I diagnosed this morning. With the key turned on, I'm only getting a little over 6 volts to the coil. When disconnected from the coil, I get 13 volts at the positive lead. (The reading you took for the key on is a good voltage. You are seeing that the ballast resistor is in good working order. The reason the voltage goes up to battery voltage when disconnected is that you opened the circuit when you disconnected the coil) I scraped all the grounds to bare metal. I have good continuity from coil negative back to the box and from the box frame to engine ground, but open between the coil negative and engine (body) ground (with key on). This leads me to believe that the control box is faulty, maybe fried it by using Accel coil? Now I realiize I skipped a step and will check from the box terminal through the box to ground. The box is new but 30 plus years old.

I have a spare electronic distributor lying around that I will hook up to a system and turn by hand to check spark.

As mentioned previously by others, make sure it's getting full battery voltage to the + side of the coil when CRANKING! (key in the "start" mode). It would be beneficial to your non (broken-in)
engine to take the wires off the starter while checking in the start position voltage, till you make sure the spark is good. You don't want to wipe out the new cam.

 

[440roadrunner]

Painted spark plug holes DOES mean "SQUAT".... how do you think the plug obtains a GROUND .............................................
A coil can be tested as I indicated... ................................................ It does however "STORE" a short duration of current ...................................

You sir, have a HUGE misunderstanding of "how stuff works."

First of all, you don't think that the many many kilovolts of ignition voltage cannot punch through a little ol film of paint? Tell ya whut. Pull your coil wire, and hold it near the PAINTED engine block, and notice !!!!! Just how well the spark travels from the coil wire, THROUGH THE PAINT to the block

Condensers. Condensers, and by the way I can REMEMBER when they were called that, BEFORE the term "capacitor" had come along, do IN FACT conduct current!!!! You don't think there is current flow in a

photo flash? A great big cap is charged up and DISCHARGES it's energy through a flash tube. That is REAL measurable CURRENT flow

CD ignition? A great big cap is charged up, and in the same way, DISCHARGES it's energy through the coil. REAL current flow.

Read up, do some Googling on "Kettering Ignition" This is the term used to describe breaker points ignitions. Condensers (capacitors) are a VERY necessary part of the spark energy and voltage in a break points ignition, AND in a switched ignition such as the Mopar ECU

Haven't you ever looked at a primary scope pattern? What do you think all those wiggly lines are? THEY ARE the "ringing" oscillations caused by the seesaw effect of the coil and the capacitor EXCHANGING ENERGY between the energy stored in the cap and the magnetic energy in the coil, which oscillate back and forth until the LOSSES of the two components cause the energy to finally die out.

A DEFECTIVE CONDENSER will cause the coil output to decrease dramatically, and a BAD condenser will cause the engine (generally) to not start.


Now I COULD go out and screw around and record some scope patterns of a factory coil, with and without a condenser in play, but I'm not gonna do that. I don't have time to "school" you.

- - - Updated - - -

This is what I diagnosed this morning. With the key turned on, I'm only getting a little over 6 volts to the coil. When disconnected from the coil, I get 13 volts at the positive lead. I scraped all the grounds to bare metal. I have good continuity from coil negative back to the box and from the box frame to engine ground, but open between the coil negative and engine (body) ground (with key on). This leads me to believe that the control box is faulty, maybe fried it by using Accel coil? Now I realiize I skipped a step and will check from the box terminal through the box to ground. The box is new but 30 plus years old.

6v is about normal. You are measuring the supply voltage, then DROPPED BY the ballast resistor, cause by the load of the coil. All you are doing when you disconnect the coil negative you are removing that load.

I assume you are measuring the "open" with power off, with your ohmeter? Not a legitimate measure, as the transistor path in the box will be "off"

To check your supply voltage, you need the loads on the system "as normal." So hook everything up, turn the key to "run" with engine off, and measure between battery POSITIVE (or starter relay stud) and the blue field wire on the alternator, or the switched ignition wire "ignition run" on your ballast. You should read VERY low voltage, the LOWER the better, as you are measuring voltage drop through from the battery, all through the harness, and out the bulkhead to the regulator, alternator field, and ignition system. Over .3V (three tenths of one volt) means you have a drop problem.

BUT THIS should not prevent a good hot spark during cranking, because the ignition is powered from the IGN2 lead coming from the ign switch.

To check that, as I said earlier, hook your meter to coil+ and crank the engine using the KEY. You should read very close to same as battery and in no case below 10.5V

I don't know if aftermarket boxes work the same, but Mopar boxes should trigger by grounding one of the two distributor terminals in the ignition harness.

 

[67 B-body]

Wrong again I'm afraid...
I can tell you how a capacitor is used for photo flash, and how a large cap discharges..... It STORES ENERGY and discharges that energy from the two polarities of the capacitor.... This high discharge of stored energy gives you the ability for your photo flash to work.... Just charge a capacitor and place a screw driver across the two terminal and you will see the stored energy released....
BTW,,, and education from YOU is something that I'm far beyond.... I hold several degrees and my profession as an ELECTRICAL ENGINEER provides me the opportunity to design crap like this for you to BELIEVE you understand it better than I....
I'm through discussing **** with you,,, and if the moderators don't flag you for causing trouble or interfering with a member trying to help another then why the hell are we here??!!
Just move on and don't bother trying to impress anyone else with your shameless attempt to belittle someone...
BTW I said current doesn't flow through a capacitor not from a capacitor..... Big difference pal...

 

[daredevil]

I think though irritating the dialouge in this thread is interesting. I dont know enough to know who,s innoquivicably right but I would not let internet disagreement get to me. As long as the language is civil and we dont degrade to name calling I dont step in in these matters. I think everyone here stands to learn more when we see information proving posters points and disproving bad info. Please understand that though some info may not be correct its what others have accepted as truth and may be hard to have them reconcile.

 

[moparmarks]

Nothing wrong with a good debate as long as those involved can be adult about it. As a retired sparky I too find this thread interesting.
I worked in the parts house back in the 70's and we had a spark plug tester. Would put out about 5KV. We would charge up a condenser and set it on the counter.
Then tell the new delivery girl to take it over to the service station across the street. She'd pick it up touching both the housing and lead and Bammmm.
Made for some good times.

 

[67 B-body]

I think though irritating the dialouge in this thread is interesting. I dont know enough to know who,s innoquivicably right but I would not let internet disagreement get to me. As long as the language is civil and we dont degrade to name calling I dont step in in these matters. I think everyone here stands to learn more when we see information proving posters points and disproving bad info. Please understand that though some info may not be correct its what others have accepted as truth and may be hard to have them reconcile.

Simple enough,,,, everyone interested can go out to the car hold a wire to batts positive to the + terminal of a coil. Then hold another to the - terminal to ground. Stick your finger in the coil lead hole and release the - wire while leaning against the car.... Let me know if you get one heck of a jolt up your arm or not....
Then report back with your findings.... I can't wait to hear all about it...lol!
Btw,,, just because I can measure something with an scope, doesn't mean that is its purpose... That's like saying tires rolling down the rode are meant to make noise not roll..... Lol! Things measured or observed aren't always what they seem at first glance.

 

[daredevil]

Simple enough,,,, everyone interested can go out to the car hold a wire to batts positive to the + terminal of a coil. Then hold another to the - terminal to ground. Stick your finger in the coil lead hole and release the - wire while leaning against the car.... Let me know if you get one heck of a jolt up your arm or not....
Then report back with your findings.... I can't wait to hear all about it...lol!
Btw,,, just because I can measure something with an scope, doesn't mean that is its purpose... That's like saying tires rolling down the rode are meant to make noise not roll..... Lol! Things measured or observed aren't always what they seem at first glance.

That hurt thinking about it. I would probably report a knot on my head too.lol

 

[67 B-body]

That hurt thinking about it. I would probably report a knot on my head too.lol

Yep,,, used to illustrate this a lot while working through college at the parts store that I was asst manager of.....

 

[moparmarks]

Got hit with 50KV DC while Hypot testing 15KV lines and terminatons. Threw me 15'. Hurt like hell.
Does that count?