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Pertronix Ignitor issues
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Author:  Mack McCormack [ Sat Aug 04, 2018 9:05 am ]
Post subject:  Pertronix Ignitor issues

I suppose that the Pertronix Ignitor could be considered an electronic gadget so I will post this message here.

Over the years I have had Pertronix units fail. My experience has been that they either work or they don't work, for no apparent reason. This past weekend at NJMP-Thunderbolt I had a new experience. My engine was running rough with a poor idle and loss of power above 5000 rpm. I thought it it may have been a fuel starvation issue so checked the fuel filter, carb floats and all the jets, all of which were fine. Graham Long helped me and we also measured fuel pressure which was OK. He did find that my carburettor was a little loose on the intake manifold which could have caused an air leak but fixing that did not fix the problem.

So then on to ignition. I had a slight misfire at Thompson which prompted me to replace my distributor cap and wires before NJMP. But now all of the symptoms were much worse. I checked all of my electrical connections to make sure they were tight and that all ground wires were secure, and they were. Because of my past experience I always carry a spare Pertronix unit and so replaced it but not the magnetic collar because the new one did not fit my distributor shaft. My distributor had been built with internals from a Lucas electronic distributor which doesn't have a cam for points on the shaft. Just on a whim I removed the Pertronix magnetic collar from the distributor shaft. For some reason I decided to shake it and to my surprise it sounded like a rattle. Clearly, one or more of the magnets were loose inside the collar. Well that would certainly give me a misfire.

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After combing the paddock to find a collar Pete Carroll said that he had bought a Lucas electronic distributor at a flea market for $15 that might have one inside. Sure enough, someone had replaced the Lucas electronics with a Pertronix unit that had the same magnetic collar. We put it in my distributor and the car ran better than it had in months! In retrospect, the minor problems that I had at Thompson were caused by the same loose magnets.

The magnetic collar in question was identified with the number "LU-141-3" on it, which I could not find anywhere. The Lucas electronic distributor is a "45DE4". But as it turns out the Pertronix unit for that distributor is a "LU-147A" for an Ignitor (or 9LU-147A for the Ignitor II models) and the collar part number is ""LU-147A-3" the "-3" indicating the magnetic collars in all the Pertronix units. So I have ordered replacement collars from Summit Racing and after they arrive I will open the defective collar with the loose magnets and let you all know what I find. I will also be interested to see what number is on the new collars, LU-141-3 or LU-147A-3.

And oh yeah, I am well aware of Tivvy's opinion of Pertronix ignition systems.

Author:  Ian Wisbon [ Mon Aug 06, 2018 11:22 am ]
Post subject:  Re: Pertronix Ignitor issues

Excellent post Mack!

Dare I say something we should also put into a newsletter/website Blog post.
Certainly makes the case for carrying a spare collar, Pertronix, and points!

Glad you got it sorted.

Author:  Mack McCormack [ Sat Aug 11, 2018 8:23 am ]
Post subject:  Re: Pertronix Ignitor issues

But wait, there's more.

I got two new spare collars from Pertronix, one of which was defective. Of note is that the new ones were marked LU-141-3 despite the fact that the part number I had to order was LU-147A-3...go figure. After talking to the tech guy at Pertronix I learned that the little magnets inside must be positioned with the correct polarity, south pole facing outward. I dissembled my old collar with the rattle. After a look inside it is clear that there is no where that the magnets can go so they must have been rattling in their respective slots. I rebuilt the old collar and used a compass to make sure that the south pole of each magnet (which I marked with red) was facing outward in its respective slot (see pics below).

So now I am thinking that it must have been the Pertronix pick-up that failed at NJMP. Since I replaced both the pick-up and the collar at NJMP I won't know until I put the old pick-up back in with a new collar. I also found a head gasket issue so I won't be able to run the test until the engine is back together.

Stay tuned for part 3.

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Author:  Mack McCormack [ Sat Aug 18, 2018 7:44 am ]
Post subject:  Re: Pertronix Ignitor issues

OK. Part 3. Now that the engine is back together I tried all the different combinations of new and old magnetic collars and ignition modules. The bottom line:

There was nothing wrong with the magnetic collar in the first place, despite the rattle sound. Those magnets can't go anywhere unless the collar is obviously broken apart. All of my problems were from the Pertronix module pickup unit. This is the first time I have had one fail "incompletely". Usually it is an all-or-none proposition. With this one I had a misfire at idle and loss of power at revs over 5000. Everything is back together and running the way it should. Spare Pertronix module on order. Live and learn.

Looking forward to VRG @ Pitt-Race.

Author:  Mark Palmer [ Sun Aug 19, 2018 9:38 am ]
Post subject:  Re: Pertronix Ignitor issues

Old trick I learned a long time ago, for electrical spares ... more than once, I've seen someone have a problem at the track (commonly a misfire). They replace the coil, for example, with their brand-new spare -- and still have the misfire (or it gets worse). So they conclude, logically, that the problem can't be the coil because they just installed a new one.

Problem is, a brand-new electrical part occasionally will be defective. So when you purchase a "new" electrical part to carry as a spare, it's a good idea to test the part on your car for a race session or two, to prove that it's good. Then take it off the car, put your "regular" part back on, and put the now proven-good spare in your spares box.

With a mechanical part, you can usually tell if it's bad by visual inspection. With electrical parts, not so much.


Author:  Mike Clifford 2 [ Sun Aug 26, 2018 10:59 pm ]
Post subject:  Re: Pertronix Ignitor issues

We've moved away from Pertronix on just about everything. Just like you've mentioned, Mack, we struggled with pretty frequent and always-mysterious failures. Lost sessions, lost hair... Now we either use points or we've started putting Jennings distributors in some of the Ford-powered cars. More expensive (~$500?) but they've been bulletproof. They also have measurably less timing float at racing rpm than the Pertronix distributors do.

Author:  Nial McCabe [ Sat Sep 01, 2018 7:05 am ]
Post subject:  Re: Pertronix Ignitor issues


Thanks for writing up your experience.

It's interesting to hear that one of the Pertronix collars you ordered was defective. Not a good sign.

As others may not know, I talked to Mack about all this at NJMP , partly because I was having a similar issues with my 1275 Spridget.
I also wondered if the problems were caused by my Pertonix.....but was also unsure about my two SU carbs.

In my case, the plugs were sooting up and fouling so that my car was very hard to start but would keep running if I kept it revving to at least 4000 RPM.

Between sessions I kept swapping plugs and eventually I went down to Auto Zone and got a cheap set of Champion RN14Ys (which are super hot plugs intended for a Chevy 6). These hot plugs were a "band aid solution" but at least allowed me to get the car started (albeit still with difficulty). With my car, all four cylinders were showing fouled plugs, so it seems unlikely (but not impossible) that one of my two, stock HS2 carbs was out of kilter. I made it through all sessions in the weekend but probably down about 25% on power.

I was running a Pertronix unit that was about 10 years old. Previous to this I had a Pertronix that lasted about 6 or 7 years, so I really have no gripe about these units. When I got home, I inspected the Petronix collar-ring that Mack had suggested might have loose magnets. On mine, the two main pieces of the collar had started to separate...there was a clear opening where the part had been assembled. But no discernable rattle of the magnets.

The coil in my car is probably 5 or 6 years old. Same thing with the cap, rotor and wires. So all this stuff was due for a change anyway.

Fuel pressure seemed OK and I could not see anything wrong with the SU carbs. Switches and measured voltage were OK.

In the end, I took the "shotgun" approach and simply swapped a bunch of parts.

Here's what I replaced:
New Pertronix pickup unit and magnet collar ring.
New cap and rotor.
New wires
New Pertronix 3.0 ohm coil
New fuel pressure regulator
New carb floats
New carb needles and seats
New platinum plugs (I normally swap these a few times a year anyway)

Reset valve lash (0.015") and ignition timing (in my case, 32 degrees total advance).

I set the carb mix with one of those little Gunson looking-glass spark plugs (I know.....old school). Both at idle and at 5000 RPM, the Gunson showed a nice, blue flame on #1 and #4 cylinder so things are at least close.

The car idled much better and overall it seems improved. But there is only so much one can do setting things up in a suburban driveway. To be honest, the new plugs could easily disguise any fouling problems temporarily.. So I won't really know until I run it next week at Pitt-Race.

It's worth noting that if you are using a Pertronix pickup unit for a Lucas 4 cylinder distributor (25D) you have a choice of Pertronix Flamethower canister-type coils. I'm running the 3.0 ohm Flamethrower coil with no ballast resistor. This is what I ran previously with good results. Pertronix recommends this application of 4 or 6 cylinder street engines but suggests the 1.5 ohm coil is better for 4 cylinder racing engines (typically used with a ballast resistor). My engine is much closer to a street engine and I keep RPMs modest; so far the 3.0 ohm coil seems to be able to keep up.

One other comment: if you are buying spares for these cars it's really worth looking at the UK vendors, even with the shipping costs. Prices are better in the UK (I think it may be related to Brexit but not sure). Also, Moss-USA offers much less choices (or no choices) as compared to Moss-UK. I just bought a bunch of gearbox internals from Moss-UK that are not offered in the Moss-USA catalog. Other UK vendors such at MiniSpares are good too.

Like Mack, I bought my new Pertronix unit from Summit.

Author:  Stefan_Vapaa [ Fri Sep 07, 2018 8:23 am ]
Post subject:  Re: Pertronix Ignitor issues

I too have had a checkered past with Pertronix points-delete conversions. Up until recently, they've all been Ignitor 1 products, not the much improved Ignitor II or III.

For the Ford V4 (Bosch distributor) I had one be DOA and another turn to smoke when I accidentally left the ignition on while checking valve clearances.

On the 3 cylinder two-strokes (also Bosch distributor) I have never gotten one to run well. Many many other folks have had zero issues with them on their two-stroke SAAB engines, so I don't know what my problem is, but after trying to run several different units on several different cars and motors, I've given up. I suspect that the successes of others are on street driven and tuned cars and the demands of the racing engine are just too much.

My problem is that there are so very few options for these 3 cylinder two strokes. The original points have been unreliable and temperamental when we tried them. Generally no better than the Pertronix. The problem is that there are so few options for these cars, especially ones that look period from the outside.

At the moment, all three of our cars are running on custom built solutions that were commissioned by the great driver and Skip Barber instructor Duck Waddle when he owned a Bobsy SR3 with a SAAB two-stroke fitted. They utilize a custom machined shutter wheel welded to a Porsche 6 cylinder rotor and wired to yet more custom wiring spliced into a ignition controller from some Bosch fitted car of the 80's or 90's. We have maybe one of these kits left out of the parts we got from his stock. After that, I don't know what we'll do? Pertronix doesn't offer a kit for the two-stroke in their much improved Ignitor II or Ignitor III versions, even if I thought that would work.

Author:  Mack McCormack [ Sat Sep 29, 2018 8:34 am ]
Post subject:  Re: Pertronix Ignitor issues


I am sure that you have checked this but just in case...make sure that the main jets on your SU carbs are fully up on the seats. The "choke" mechanism for the SU carb is not really a choke at all but rather a fuel enrichment mechanism achieved by lowering the jet on the tapered needle. If the jet tube does not fully return to its seat you will run rich and foul plugs.


I have also heard that the Pertronix units don't like to powered up (ignition on) without the engine running. So now, every time I switch on the ignition for any reason that does not result in starting the engine, I disconnect the 12V+ lead to the distributor. I guess the only time I have the Pertronix powered without the engine starting immediately is when I pressurize my oiling system from the Accusump prior to starting the engine (electric solenoid valve powered by ignition on). It is only a few seconds until I get oil pressure from the Accusump but I wonder if that is enough to cause Pertronix failure.

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