Ignition Woes - DON'T Jump to Conclusions!

[KiwiTR6]

Hi all.

For some time now I've noticed that my car hiccups occasionally when moving away from standstill but thought nothing of it.  Also it always took quite a while to fire up which it always did eventually with full enrichment which, being relatively new to the PI system, I again thought was normal. 

However, a couple of days ago I went for a spirited drive on the back roads and started pushing the motor hard up into the rev range (which I've never really done before) and found it was starting to misfire well short of the red line.  After a bit more sedate driving I moved off swiftly from an intersection onto the main highway and the engine cut out completely for a period before it recovered and allowed me to get home, misfiring occasionally along the way.  Once home I got out the timing light and checked for misfires which were pretty obvious. 

Yesterday I went to start the car to confirm the timing as I'd pretty much determined the Pertronix unit was faulty and I had a brand new Powerspark item as a spare (it was cheaper ).  The car wouldn't start at all and I could smell raw fuel so gave up and and switched out the igniters.  First turn of the ignition switch and the car fired straight up!  At this point I need to pull the plugs as I've obviously fouled at least one when I flooded the engine.

I've read mixed reports about the Pertronix unit over the years and for obvious reasons won't  be buying another (the car has a Flamethrower coil which I'm sure is fine).  Instead I'll invest in a second Powerspark kit and cross my fingers that I won't need it.

I hope this is helpful.

Gavin

[Mike C]

To be honest, I've had no problems with my Pertronix since I fitted it in 2006.  Was there any possibility you left the ignition system on but not running for a long period of time - the old Pertronix fitting instructions warned this could cause the component to fail.

[KiwiTR6]

1 hour ago, Mike C said:

To be honest, I've had no problems with my Pertronix since I fitted it in 2006.  Was there any possibility you left the ignition system on but not running for a long period of time - the old Pertronix fitting instructions warned this could cause the component to fail.

Anything's possible, although the fuel pump would be running as well which would drive me nuts.  I'm the second owner since it was restored so could it have happened before my time if that has actually caused it to fail.  No sign of overheating either and 0.0 ohms from the distributor plate back to the battery, two issues to check for apparently.  It also has 12V from the ignition switch, the ballast has been bypassed.

 

[Mike C]

Mine looks  much older than yours- the box is stamped P/N LU-166A.

It's been a long time since I installed mine but the leaflet that came with mine says to connect the red wire on the Ignitor to the ignition switch wire prior to the ballast resistor. The ballast resistor stays in series. You should be getting 12V at the red wire while running.

The leaflet also says you need a minimum of 1.5 ohms across the coil primary terminals. Note I've had a fair few misfiring/shut down problems over the years due to  coils failing when they get hot.

Good luck- I hate intermittent electrical faults. Hope others may be able to  help you  further.

 

[Waldi]

Hi Gavin,

I note you have a riveted black rotor; some of these riveted rotors (not all) are prone to short-cutting. If you have another one I would try that first.

The red rotors (no rivet) from Distributor Doctor, which should be stamped with DD, are preferred by the UK based forum members, so I have a couple of these too.

You will find it.

Waldi

[KiwiTR6]

17 hours ago, Waldi said:

Hi Gavin,

I note you have a riveted black rotor; some of these riveted rotors (not all) are prone to short-cutting. If you have another one I would try that first.

The red rotors (no rivet) from Distributor Doctor, which should be stamped with DD, are preferred by the UK based forum members, so I have a couple of these too.

You will find it.

Waldi

Hi Waldi.

No signs of any arcing from the rivet that I noticed inside the distributor and that's the same rotor that I'm now using with the Powerspark which fired straight up after the Pertronix failed.  The Powerspark came with a red non-riveted rotor (definitely not from DD) but my understanding was that the plastic contact plate retainer was the potential weakness on the cheapie versions, hence why I reused the riveted one.  Perhaps I have that wrong?

Gavin

[Waldi]

Hi Gavin,

Good you found the cause, so it was the Pertronix that failed? 

I’m not familiar with the “other” red rotor and its quality.

Waldi

[Casar66]

I also had problems with the pertronix from time to time. At first I thought it was the contact ring under the rotor. Some are not well made and it might be helpful to change that or at least see if the ring is seated properly.

But in the end, the cause of the misfires was never the pertronix. "Misfires at high RPMs could be because the MU isn't delivering enough fuel.  

Or a bad rotor (even if you don't see any signs of it) or a cap. Also the ignition wires and plugs are often not the best anymore. As is the wiring of the electrical connections, maybe you have a loose connection. I would want to rule out all of the above possibilities first.

I also have Powersports as a replacement, in my eyes they are lousy compared to the Pertronix.

Cas

[KiwiTR6]

On 3/13/2023 at 7:44 PM, Waldi said:

Hi Gavin,

I note you have a riveted black rotor; some of these riveted rotors (not all) are prone to short-cutting. If you have another one I would try that first.

The red rotors (no rivet) from Distributor Doctor, which should be stamped with DD, are preferred by the UK based forum members, so I have a couple of these too.

You will find it.

Waldi

Top marks Waldi!  After your comments and in the process of swapping out the riveted rotor for the new red Powerspark item I noticed a decent crack which undoubtedly will have been playing some part in this saga.  My next move is to reinstall the Pertronix unit and check if that was indeed my problem.  I'll report back in due course.

ps.  Excuse the dirty fingers.  I was in a rush and had omitted to wash my hands first

 

[KiwiTR6]

12 minutes ago, Casar66 said:

I also had problems with the pertronix from time to time. At first I thought it was the contact ring under the rotor. Some are not well made and it might be helpful to change that or at least see if the ring is seated properly.

But in the end, the cause of the misfires was never the pertronix. "Misfires at high RPMs could be because the MU isn't delivering enough fuel.  

Or a bad rotor (even if you don't see any signs of it) or a cap. Also the ignition wires and plugs are often not the best anymore. As is the wiring of the electrical connections, maybe you have a loose connection. I would want to rule out all of the above possibilities first.

I also have Powersports as a replacement, in my eyes they are lousy compared to the Pertronix.

Cas

I certainly have a bad rotor all right as noted to Waldi.  Even if the Pertronix is OK after all, I may revert to the Powerspark as I now have two and being able to swap them out same for same means I wont have to adjust the distributor in the process.

[Waldi]

Good news Gavin,
A crack in the rotor and/or in the distributor cap can be sufficient to result in short-cutting.

I friend has a Teal Bugatti, also fitted with a TR6 engine. His riveted rotor failed as well, but that one had clear signs of burns from the current/ sparks.

Cheers,
Waldi

[KiwiTR6]

Well, I'm now positive that the Pertronix was definitely not guilty as charged!  In addition to the cracked rotor found earlier I've also found several failed ignition leads.  They are all labelled TRF Suppression 16K Ohm/m and the readings from each are (rounded values):

Coil to cap = 7M Ohm, #1 = 6.8K, #2 = 2.7K, #3 = 4.1K, #4 = 3.7K, #5 = 21M and #6 = 3.8K.

How the car ever ran as well as it did is beyond me.  Anyway, a new set of leads are on the way from the local classic car parts supplier and the good news is the the coil checked out OK and the cap was brand new a short while back.  I'm now left with three sets of electronic igniters but I'll probably go with the Powerspark for the reason stated earlier.

Thanks for the suggestions.

 

[Waldi]

Wow, that is a large spread in resistance.

A related question:
Can you measure ignition leads (copper core or modern ones) with a standard multi meter (eager to learn).

Cheers,
Waldi

 

[RobH]

3 minutes ago, Waldi said:

Can you measure ignition leads (copper core or modern ones) with a standard multi meter

Yes you can. It's a straight-forward resistance measurement. 

[Mike C]

1 hour ago, RobH said:

Yes you can. It's a straight-forward resistance measurement. 

Yep, just take out both ends and measure them one at a time.

[Waldi]

Thank you Rob and Mike, 
I achieved my target for this day (learnt something).

Cheers,
Waldi

[KiwiTR6]

14 hours ago, Waldi said:

Wow, that is a large spread in resistance.

A related question:
Can you measure ignition leads (copper core or modern ones) with a standard multi meter (eager to learn).

Cheers,
Waldi

 

Yes, it's hard to comprehend as the motor was fully rebuilt around 18,000 km earlier and the leads look to be in good condition as you'd expect.  I tested, retested and tested again as I couldn't believe what I was seeing.  Those that are bad are really bad.  I used the same multi meter as in the earlier photo, set to Ohms and on autorange.

The sparkplugs are going to get a wake up call in the not to distant future, I have a Mallory CDI unit on the way and a CB Performance Black Box map-able ignition following not far behind.  These parts are really for a performance engine I'm planning to build up and swap out for the current one (which will go into storage), but I've decided I may as well fit them to my current setup and see how they go.  And, before anyone mentions the 123 distributor, I want to retain the existing mechanical tacho drive.

Cheers

Gavin

[mattyb]

Hi Gavin

 

Glad you got to the route of the problem - My personal experience - fitted a Pertronix ignitor to my 1958 MGA 15 plus years ago and its still working well today - I believe that the newer manufactured are perhaps more prone to failure ? - I still carry a built up DM2p4 distributor with contact breakers and condenser as a spare - just in case ! 

 

Happy motoring 

 

Matt

[KiwiTR6]

Now all sorted, new leads fitted and she runs like a dream

[Don H.]

Hey Gavin -- maybe you could change the title a bit to reflect your current knowledge?  There's good info in your thread, but the title doesn't do it justice any more.

[KiwiTR6]

10 hours ago, Don H. said:

Hey Gavin -- maybe you could change the title a bit to reflect your current knowledge?  There's good info in your thread, but the title doesn't do it justice any more.

Hi Don.  I'd like to do that as I feel a bit bad about crucifying Pertronix, but someone will need to give me instructions as to how I can do that.

[Don H.]

3 hours ago, KiwiTR6 said:

Hi Don.  I'd like to do that as I feel a bit bad about crucifying Pertronix, but someone will need to give me instructions as to how I can do that.

I send a note to our capable form moderators using the "report" option at top right of a post, Gavin, and I'm sure they'll get it sorted.  This is a useful thread and deserves to be found by folks in the future with similar issues.

[KiwiTR6]

4 hours ago, Don H. said:

I send a note to our capable form moderators using the "report" option at top right of a post, Gavin, and I'm sure they'll get it sorted.  This is a useful thread and deserves to be found by folks in the future with similar issues.

Done!

[KiwiTR6]

Took the car for a quick jaunt tonight after work and what a difference a new set of leads has made!  Smooth power all the way to the red-line (where it has never been before during my ownership) with no hint of a misfire or pinking.  However, as often happens with these old vehicles, the safety catch on the bonnet fell apart when closing the bonnet after adjusting the idle on my return.  Never ending, but that is part of the joy of owning a classic car!

Gavin

Edited March 22, 2023 by KiwiTR6
grammar

[astontr6]

9 hours ago, KiwiTR6 said:

Hi Don.  I'd like to do that as I feel a bit bad about crucifying Pertronix, but someone will need to give me instructions as to how I can do that.

Pertronix do fail as I had one fail. I had it tested by Pertronix here in the UK as they are not far from where I live. I was given another one and that was 8 years ago and its still going strong.

Bruce.