Intermittent Spark

[newbaufish]

All -

I installed a pertronix Ignitor III system on a reman'd distributor and have been pretty happy overall on my stock (?, I bought it) 383. Ran great for a while and now has developed an intermittent spark pattern. This means the car starts great, idles just fine, then while hammering on, or cruising it has a noticeable pause or surge.

Going deeper, I found the spark pattern from the Coil to the Distributor to be consistent and just faster when adding RPMs. The pattern is noticeably inconsistent from the disti to the sparkplugs...

Based on this, I believe it's the disti/pertronix combination but wondered the following:

1. Am I right on my suspicion? Other thoughts?
2. Would a failed Pertronix unit be inconsistent or just go "dead"
3. Any other areas where spark might be jumping? (bad ground, jumping from spark plugs to motor)
4. suggestions on how to fix it. I'd like to keep the stock look but if billet makes it go away...I may be swayed

Thanks gang,
Tim

 

[Meep-Meep]

Not sure what you mean by spark pattern. I check for spark and when I see a good one I move on.

 

[70rr-brian]

The symptoms you describe sound fuel related. Like it is possibly running lean or erratic fuel pressure. Could be your advance is off.

 

[RustyRatRod]

Spark pattern. Haven't heard that in a while. I assume you're talking about an oscilloscope pattern. Have you had a scope on it?

 

[bigmanjbmopar]

The coil match the pertronix unit? I have heard from some e-body guys that the wrong coil cause's problems. This is why I run MSD

 

[newbaufish]

I'm sorry I should clarify. The spark pattern as shown with a timing light as you would adjust the timing the car. When I tried to set timing, noticed the pattern was not regular or consistent at revvs as the light would cut out at times. Suspecting a bad plug wire, I changed the timing indicator to other wires to see it was one bank on the rotor, disti or such. Happens to all wires at some point when revving the car. Maybe this is a bad test.

I tried running the car without vacuum advance and that did not improve. Had a shop change jets up 2 on primaries, also did not improve.

Thanks for listening and the feedback so far.

 

[RustyRatRod]

I certainly wouldn't trust a timing light in that manner. That's not what it's made to test. Could be a loose connection in the light itself.

 

[blackblazer717]

Interesting... Heres and idea, pull the dizzy cap and make sure your retrofit is still tight and the reluctor on the shaft is not contacting the pertronix pickup, and/or any damaged teeth.....

 

[68 Sport Satellite]

How does it feel when driving?

I did a points to pertronix II swap on a '67 motor years ago and I seem to remember two things from that -

1. the pertronix requires slightly different timing than the points. Check with Pertronix on this for the pertronix III version. (from another website forum: "The fitting of the Pertronix unit can change where the spark occurs compared to the points, it may be different by 10deg.")

2. with the pertronix it is key to get the reluctor pickup gap under the distributor cap set correctly. Check before and after tightening.

You also need to make sure you have 12V from the ignition switch and don't hook up a stock resistance wire that may have a lower voltage.

I didn't like my pertronix. It ran OK, but overall I felt like my points setup when new was a lot more snappy when I got on the throttle.

This is not the case with the mopar chrome box ECU's. I love those!

 

[RustyRatRod]

Great point. ...and to the OP. You know....the distributor does sling around just a little. You DID use red locktite on all the screws...right?

lol

Interesting... Heres and idea, pull the dizzy cap and make sure your retrofit is still tight and the reluctor on the shaft is not contacting the pertronix pickup, and/or any damaged teeth.....

 

[440roadrunner]

I certainly wouldn't trust a timing light in that manner. That's not what it's made to test. Could be a loose connection in the light itself.

^^THIS^^ I have two lights, neither of them flash consistently and also depending on RPM. This "test" is not conclusive.

Sorry, I don't know anything about the pitfalls of Pertronix

I use a Mopar (Accel replacement) breakerless dist. and GM HEI module. No ballast, stock coil, works great.

 

[newbaufish]

Thanks again for the info. I did use Loctite but will re-examine the inner parts to ensure something hasn't moved around the reluctor.

I will also see if there's a different way to look at spark pattern as it's clear when the stumble happens the spark pattern as I was viewing it was inconsistent.

 

[Sixer]

I had enough of a consistent timing issue with a PIII that I said to hell with it and returned it. It triggers off of the original points cam, which is gently rounded as opposed to most if not all reluctors which are sharp and distinct, more so on racing units. Could never quite get the thing to both idle and perform. Went back to points until I can score the complete Mopar conversion. And I was using the Pertronix recommended coil.

 

[68 Sport Satellite]

^^THIS^^ I have two lights, neither of them flash consistently and also depending on RPM. This "test" is not conclusive.

Sorry, I don't know anything about the pitfalls of Pertronix

I use a Mopar (Accel replacement) breakerless dist. and GM HEI module. No ballast, stock coil, works great.

Would love to hear details on your HEI module install. Is it fairly involved or an easy swap? I have been considering this myself.

 

[RustyRatRod]

Thanks again for the info. I did use Loctite but will re-examine the inner parts to ensure something hasn't moved around the reluctor.

I will also see if there's a different way to look at spark pattern as it's clear when the stumble happens the spark pattern as I was viewing it was inconsistent.

...and the timing light may WELL be picking up on something there. I was simply saying that's not a good method to check it by. An oscilloscope WOULD be. Of course, not everybody has one. lol

 

[440roadrunner]

Would love to hear details on your HEI module install. Is it fairly involved or an easy swap? I have been considering this myself.

Simple. You can go through all kinds of stuff upgrading the coil, but for my mild "was a 360" now a 318, it works fine.

All you need is a working Mopar or compatible distributor (I use an Accel / Mopar look-alike)

A quality 4 terminal GM module from the mid--70's like Standard / Blue Streak LX-301, or NAPA/ Echlin TP-45.

Looks like this one:

The module has a "tit" on the bottom and this must be broken/ filed off or a clearance hole provided. It must be mounted flat on some sort of heat sink. The previous owner of my Dart had mounted an ECU with sheet metal holes on a "flat spot" on the firewall under the wiper motor, so I mounted the HEI there.

Use the supplied thermal grease, and a good ground to the mounting screws.

Very easy to wire, no ballast needed: Hook your blue run and brown bypass wires together (in other words bypass the ballast and you can hook the original coil POS wire to the POS on the coil Tach goes to coil NEG. Pay attention to the drawing of the dist. connector, the "bare" terminal of the connector is at the top in the drawing. You can get these connectors at any parts store by buying a 2 terminal rubber "trailer" style connector.

Here's an "emergency" ignition I built into a box, hook up dist, ground, and battery, and coil wire:

and an engine I test fired using the "emergency" ignition while hanging off the hoist. So far I've done this twice already

 

[newbaufish]

I got back to the garage and finally pulled the distributor. The pertronix unit had shifted slightly and I re-tightened everything down and double checked the Loctite...runs like a champ now. Thanks for your help and guidance in this area.