Weak spark issues

[Tonka Toy]

In my seemingly never ending quest to get my Travelall's 345 to run as it should, I have discovered that the ignition system wasn't providing a very good spark. Even after some electrical repairs to clean up years of hack work on the wiring. So I read through mayben's sticky about upgrading to the msd system, which is my goal eventually. But with a baby due any day, I can't gather all of the pieces yet. So I decided to install an msd blaster 2 coil to provide a bit hotter spark. This worked wonders! Except that it just burnt out my pertronics unit. I had to switch the distributor out and go back to my old prestolyte, just to get home from work this morning. What I need to know is, if I don't install the 6 series control box, (like it says about my pertronics in mayben's write-up), am I at risk for frying the prestolyte as well? I'd hate to go back to the stock coil at this point.

Thanks!

 

[Robert Kenney]

To run that .7ohm resistance coil you need the ignitorii. The prestolite electronic switching module is also designed to operate standard resistance coils. Yes you risk frying that too. There is no reason your IH should need an after market coil. If it won't run on the stock coil there is something wrong in dodge city.

 

[Tonka Toy]

Well after cleaning up and replacing the crap wiring, replacing the ignition switch, and everything in the system, I still had an intermittent miss like the coil was about to die. Suspecting it was dumping too much fuel into the system, I swapped out the Holley 2bbl (that I even rebuilt) with my edelbrock afb. Then it ran great. Except I could barely get it to start. In diagnosing that, I found my spark to be weak at best. So I went for the hotter coil, since it's part of the planned ignition upgrades. Then we were awesome! Until my pertronix burnt out of course. I guess I should get the rest of it and do it right or go back to my dismal stock spark for a bit. Ugh. I'm starting to understand why the guy who had this truck traded it in. Lol!

Are the internal pickup modules for the prestolytes really that expensive? My local napa quoted me over $350 for one. I thought he was talking about the whole distributor until he showed me the screen shot of the part.

 

[Scoutboy74]

Like rk said, the oe design coil is capable of putting out all the voltage that these engines need and then some. I'm running stock coils on both my sv8 engines, one in conjunction with a crane points eliminator module and one with breaker points. Both engines start easily and run smoothly up to max engine speed. Just because the marketing smoke blow for a performance coil says it is capable of outputting 40,000 volts, doesn't mean the engine ignition system will be able to utilize that amount. Granted, you realized some noticeable improvement when you switched, which was quite likely just a compensation that temporarily counterbalanced some fixable weakness elsewhere in the system. Is the battery fully charged? Is sufficient voltage reaching the coil + terminal? Has any consideration been given to the spark plugs and how they're gapped? How about the plug wires? What is your base timing set to?

 

[Tonka Toy]

like rk said, the oe design coil is capable of putting out all the voltage that these engines need and then some. I'm running stock coils on both my sv8 engines, one in conjunction with a crane points eliminator module and one with breaker points. Both engines start easily and run smoothly up to max engine speed. Just because the marketing smoke blow for a performance coil says it is capable of outputting 40,000 volts, doesn't mean the engine ignition system will be able to utilize that amount. Granted, you realized some noticeable improvement when you switched, which was quite likely just a compensation that temporarily counterbalanced some fixable weakness elsewhere in the system. Is the battery fully charged? Is sufficient voltage reaching the coil + terminal? Has any consideration been given to the spark plugs and how they're gapped? How about the plug wires? What is your base timing set to?

Well, here's a quick rundown. Ran like a dream for the first 500 or so miles. All new ignition including coil, plugs, wires, cap, rotor, etc., were on it when I got it. When the sputtering and misfiring started, I found and fixed lots of little things as I diagnosed it. Here's a quick rundown; disasterous wiring under the dash, all now replaced, carefully following the diagram in my vintage mitchell's manual. Bulkhead connector eliminated, though it didn't look bad at all. Ford starter relay conversion. New ignition switch. (it took a couple of tries before I found a good one. Though I'm not ruling out the possibility that this one isn't really that good either) rebuilt the carb. Base timing was at zero, but seemed to run better at 10 degrees. No traces of plug wire arcing, or cracks in distributor cap or coil tower. Coil gets 12 volts. No discernible vacuum leaks, all hoses checked and vacuum port plugs replaced. Power brake booster verified good. Battery verified as good and is kept well charged.

I've been through this thing forwards and backwards and its driving me nuts. The engine appears to be a recent rebuild, and by how smooth it idles (when it runs right), I'd say its balanced. I have no idea if the po upped compression on it, and that it needs better fuel and/or ignition to help it run right, or not. It's a 345-e motor, and the truck shows it was a 304 by the tag under the hood. So obviously not original.

Anyway, after going through this thing, the only two things that got it back to running as it should was the edelbrock afb and the blaster 2 coil. Every other thing I did was either negligible or temporarily better, at its best. So I lean towards increasing the fuel/air flow and sparking the crap out of it with the msd. Once I have it worked out, I'm going to GM TBI. But then again, that might solve my problem too. Argh!!! What could I possibly be forgetting,.. Aside from checking the green wire? Lol!

 

[Robert Kenney]

Quick test for you. Ignition on, ground the negative coil post and read the positive post voltage. Post the results. We'll go from there. I hear you about all of the work you've done but never the less, it ain't right.

 

[Tonka Toy]

I finally got a short break from getting ready for the baby's arrival yesterday to go out and look at the Travelall. I found the battery was low, and the culprit to that. Some idiot (who shall not be named, lol) hooked the radio up wrong and its constantly drawing power. Unhooked that, then got pulled away for what turned into the rest of the evening. (grr!!!) so my question is, if I were to run a ballast resistor, could I leave my hot coil on there without fears of losing the pickup module in the distributor?

 

[Scoutboy74]

Good job! That was simple. Yes, you can add the appropriate amount of ballast and retain your current setup. I think rk mentioned it was .7ohm, so a 1 to 1.2 ohm resistor added to that would be fine. For a points dizz, you'd need to almost double that total. Take your dvom with you to the store so you can measure the part before you walk out with it.

 

[Robert Kenney]

quick test for you. Ignition on, ground the negative coil post and read the positive post voltage. Post the results. We'll go from there. I hear you about all of the work you've done but never the less, it ain't right.

You still need to verify the coil voltage as I posted.

 

[Tonka Toy]

I didn't measure the resistance, but its a single pole ballast intended for an early 70' dodge, so I'm assuming its cutting it down to 8v. Starts better than ever now. Even when mostly cold with minimal choke, I don't think it even rotates 180 degrees before it fires off. The long term reliability is foremost at the moment. I'm getting tired of it not being dependable, when I know it can be.

So if my prestolyte pickup should ever fail, am I looking at having to convert the distributor to something else? Napa quoted me nearly $350 for a replacement, and they seemed to be the only ones that had a listing for one. I, of course, will be replacing the pertronics setup in the other distributor as a backup, or possible primary distributor.

 

[Tonka Toy]

quick test for you. Ignition on, ground the negative coil post and read the positive post voltage. Post the results. We'll go from there. I hear you about all of the work you've done but never the less, it ain't right.

Ok, I'm slacking! so today I went to drive it and had no power so I went to diagnosing. I found my jumper wire on the neutral safety switch came off, so that was a quick fix. While I was there I thought I'd perform this test. I have 8.9v normally, and 3.8v when I ground the coil. I'm not sure what that result will reveal, but I'm feelin I'm about to be schooled on some old diagnosis trick I didn't know before. Lol!

Also, I found something odd to me. When I turn the key on, there's a kind of buzzing noise coming from somewhere. I assume its from inside the distributor, because it stopped when I would ground the coil for the test. It sounds like an old, dying seat belt buzzer hooked to a weak battery. Any ideas?

Otherwise, the truck has been running fantastically since I put the ballast resistor in, and left the hot coil on it. I think the crappy fuels we're running these days are part of the problem. The only issue I've had is timing, if you would call it an issue. Trying to time it with the light isn't as good as using the vacuum gauge. I think I've found the sweet spot, but time will tell.

 

[Scoutboy74]

Yes, today's ethanol-blended fuels make life tougher for older vehicles in a number of ways, but when all is at it should be, they will start and run quite well. I don't know that I agree with your observation about timing is easier/better with a vac gauge versus a good timing light. The vac gauge is an important tuning and diagnostic aid, but a timing light tells you where the timing is. Like mayben always said though, forget the strobe light if it confuses you and power time the damn thing!
Okay, this buzzing noise with key on is definitely not normal or good. I take it as an audible red flag that is telling you the same thing that rk and I have been brow beating you about for weeks now...you have one or more wiring issues. What's this jumper to the nss? Are you bypassing/defeating the original neutral start circuitry in some fashion? If so, why?
Both rk and you have me completely cornfyewoozed about this whole "grounding the coil' deal. Ain't the coil already grounded to the engine block? I know how to measure voltage to the coil and measure primary resistance across the +/- terminals. Hopefully rk will jump back in and shed some more light on what he was wanting you to accomplish. It might just be a simple case of differing terminology for the same process. I'll reserve my response about the voltage numbers you posted since I'm not so clear on the methods used to arrive at them.

 

[Tonka Toy]

yes, today's ethanol-blended fuels make life tougher for older vehicles in a number of ways, but when all is at it should be, they will start and run quite well. I don't know that I agree with your observation about timing is easier/better with a vac gauge versus a good timing light. The vac gauge is an important tuning and diagnostic aid, but a timing light tells you where the timing is. Like mayben always said though, forget the strobe light if it confuses you and power time the damn thing!
Okay, this buzzing noise with key on is definitely not normal or good. I take it as an audible red flag that is telling you the same thing that rk and I have been brow beating you about for weeks now...you have one or more wiring issues. What's this jumper to the nss? Are you bypassing/defeating the original neutral start circuitry in some fashion? If so, why?
Both rk and you have me completely cornfyewoozed about this whole "grounding the coil' deal. Ain't the coil already grounded to the engine block? I know how to measure voltage to the coil and measure primary resistance across the +/- terminals. Hopefully rk will jump back in and shed some more light on what he was wanting you to accomplish. It might just be a simple case of differing terminology for the same process. I'll reserve my response about the voltage numbers you posted since I'm not so clear on the methods used to arrive at them.

As far as the timing goes, I know how it's supposed To run, but it just wasn't. I'm not the least bit confused about it, other than it hasn't been running right until I ditched the light and went to the vacuum gauge. Now it barely rolls 180 degrees before firing, even when stone cold. And that's What I'm after.

I'm wondering if the buzzing is from the hot coil. I've also wondered if I might not need the 12v bypass wire that aids the coil to start. I'll inquire with msd about it. I don't believe there's anything damaging going on, since its been running its best since the upgrade. But it is suspicious none the less.

Other wiring issues? It would not surprise me, though I believe I've gone through it all well enough to have spotted any issues. Unless there's something missing.

The grounding the coil test was something I spotted in the instructions I found online when diagnosing the failed pertronics setup. I don't recall what it was for, but it will be interesting when rk comments again.

 

[Scoutboy74]

Were you trying to hit zero degrees when it wasn't running well? That factory spec of 0*tdc is just a starting point. Most of these engines really wake up with a little of advance to the base timing. For a 345, 10* of advance is often tolerated quite well.

 

[Tonka Toy]

were you trying to hit zero degrees when it wasn't running well? That factory spec of 0*tdc is just a starting point. Most of these engines really wake up with a little of advance to the base timing. For a 345, 10* of advance is often tolerated quite well.

What I have found is that we're probably about 12-15 degrees. Just off of the timing marks. Trying to run under 10 caused me to have the feeling that I ran out of advance before 3,000 rpms. And I believe that not having a vacuum advance on the prestolyte causes an issue there. With my Holley/pertronics set-up, I could run it between 5 and 10, probably due to the vacuum advance. Eventually there will be a GM TBI system in place, and timing will be dealt with by the computer, so for now, as long as it behaves well, I'm happy.

 

[Tonka Toy]

Success! I talked with the msd tech line earlier today, and they weren't much help this time. This afternoon I finally got to go tinker. The noise was the coil discharging when the rotor lined up with a terminal in the cap. If I moved the motor by hand, it would stop when between the terminals. It wondered if it was somehow being backfed power. I started to isolate circuits to find what fed it. First swing was a home run! I had installed a 12v bypass wire for cranking only, from the starter relay to the coil. The dodge system uses this, since 8v to the coil makes for harder starts. And when I added the ballast, I assumed that I would need one in this system. I guess not, because once I disconnected that, all was well. It even fired right up, stone cold, as if I had just shut it down from a long drive. Honestly, I don't think it was hurting anything, now that I know what it was. But if it runs fine without it, I'm fine with leaving it off.

slapped the timing light on it tonight, just for reference, and its as I suspected, 12-13 degrees, right between the timing marks. I might try 10 and see how it goes. There is still a bit more of an rpm drop from neutral to in gear than I think it should have. And if memory serves, that's the effect of advanced timing.

Next up is the msd 6 series spark control box. Then we'll toss in some low resistance wires and just spark the crap out of the thing! I'm wanting the most efficient burn I can get, and I think that this is the way to do it. Once the TBI goes on, I hope to be putting down some good fuel efficiency numbers.

 

[Robert Kenney]

I was going to respond to your grounded coil test results but now I can't say for sure what you have for an ignition system. Ballast on or off? Pertronix or points?

Basically you have some excessive resistance between the battery and the + coil post... If you were to unplug the trigger module and read the coil voltage it has to be 12v or battery voltage... Loaded or with the neg coil post grounded it has to be the battery voltage minus the ballast voltage drop... I don't know why you are hearing the buzzing. Not a normal deal...

A series circuit of the coil primary winding of .7 ohms and the ballast at 1.3 has a total resistance of 2 ohms and a total current of 6 amps @ 12v...... 6 amps x .7 ohms is 4.2v. 6 amps x 1.3 is 7.8v...

You will drop 4.2 at the coil and have 7.8v at the ballast.

You're reading 3.8v grounded and 8.xv or something not loaded... The two are not right... Something else is loading the system or dropping voltage...

Here is a basic battery breaker ignition schematic to use as a reference.....
Trevor, the coil grounding I referance has nothing to do with the coil can being grounded but the manual grounding of the neg coil post normaly grounded through the breaker points.. Since you can never be sure if the points are closed for a loaded voltage test you can manualy ground across them... Makes sure the coil primary and ballast are disipating there share.. If the poinst are open the coil + term must read battery voltage.

 

[Tonka Toy]

I was going to respond to your grounded coil test results but now I can't say for sure what you have for an ignition system. Ballast on or off? Pertronix or points?

Right now I have the prestolyte distributor and the msd blaster 2 coil with an inline chrysler ballast resistor.

basically you have some excessive resistance between the battery and the + coil post... If you were to unplug the trigger module and read the coil voltage it has to be 12v or battery voltage... Loaded or with the neg coil post grounded it has to be the battery voltage minus the ballast voltage drop... I don't know why you are hearing the buzzing. Not a normal deal...

A series circuit of the coil primary winding of .7 ohms and the ballast at 1.3 has a total resistance of 2 ohms and a total current of 6 amps @ 12v...... 6 amps x .7 ohms is 4.2v. 6 amps x 1.3 is 7.8v...

You will drop 4.2 at the coil and have 7.8v at the ballast.

You're reading 3.8v grounded and 8.xv or something not loaded... The two are not right... Something else is loading the system or dropping voltage....

Ok, so now that I see where this is leading, I just went out and tested again. I had some strangely low readings the first test so I did it again. The second test seemed more probable for readings. I had 12.5 at the battery and ballast, then 12.4 at the coil. Grounding, it went to 4.15 at the coil. My initial test was 12.6 battery, 6.9 at coil and 4.2 grounded, in case you were wondering. For giggles, I checked voltages when running and I have 14.4 at the battery, 14.2 into the ballast, and 11.15 out and at the coil.

So if I understand you, I should have 9.4 when grounding the coil. The 12.4 minus the 3v ballast resistor drop, equals 9.4. Or am I still confused? (highly likely, by the way! Lol!)

if I had to guess at the reason for the higher resistance in this circuit, it would be the ignition switch. Because I'm still unsure of the quality of the "new" ignition switch I bought from napa. And it wouldn't surprise me if the resistance issue is coming mainly from that. When my first "new" switch was as sloppy as the one I was taking out, I did some detective work. Any other parts house that had one in my area was also sloppy. Only the premium brand from napa seemed reasonably tight. I don't imagine there's enough demand for these switches anymore for the quality to be tight on them when they're built.

I could also up my wire size to/from the switch for the coil to a larger size I suppose. But I'm wondering if there's an easy way to wire in a relay that would help with this problem? At this point, anything I can do to ease the load on the ignition switch might be a good idea. Since quality replacements May become scarce.

Thoughts?

 

[Robert Kenney]

I might need to post in the morning from a honest computer and not a smart phone.
In short ad the two known resistances . Current = e(voltage) divided by r ( resistance total). The voltage drop at each of the series resistances is let's say r1 = 1.2 ohms. And the current = 6 amps e=I x r. E= 6amps x 1.2ohms. E= 7.2 volts dropped across the 1.2 ohm ballast so you have the remainder (4.8v)to feed the .8 ohm coil. You need to remember that these only work when static not running. That's a complex deal to calculate and subject to average rms power and coil impedence. Not necessary in this case. We only want to see that the system is good and static is fine.

 

[Tonka Toy]

I might need to post in the morning from a honest computer and not a smart phone.
In short ad the two known resistances . Current = e(voltage) divided by r ( resistance total). The voltage drop at each of the series resistances is let's say r1 = 1.2 ohms. And the current = 6 amps e=I x r. E= 6amps x 1.2ohms. E= 7.2 volts dropped across the 1.2 ohm ballast so you have the remainder (4.8v)to feed the .8 ohm coil. You need to remember that these only work when static not running. That's a complex deal to calculate and subject to average rms power and coil impedence. Not necessary in this case. We only want to see that the system is good and static is fine.

Ok, so can we expand this thought a bit? I feel as if I'm missing a couple of the figures I need to calculate this. If something still isn't right, I want to resolve it. It's been running great, but I can't afford to have something creep up on me either. Thanks!