Lotus Elan

Pertronix Ignitor failure.....

PostPost by: elanner » Sun May 16, 2021 1:19 pm

(Following on from pharriso's ignition fun, here's what I ran into over the past couple of weeks.)

I'm sure many of us are running Pertronix ignition systems and find them an utterly reliable alternative to points. Mine has been in the car for about 15 years, 10 in my ownership without ever being touched.

However, when my Elan started running very poorly a few weeks ago I decided to check the static timing and found a ten degree difference between #1 and #4 (respectively, 8 degrees BTDC, which is a bit late, and 2 degrees ATDC, which is very late). So I pulled the distributor to see what was going on.

The Pertronix ignitor uses a magnetic sensor in place of the points and a plastic sleeve with four embedded magnets that fits over the rotor shaft. The sensor detects the magnets as they spin past. On removing the sleeve I found that the magnets had detached from it and were sitting on the rotor itself. The glue that held the magnets into the sleeve had presumably failed. Due to the 2:1 crank:distributor rotation ratio a 1 degree movement in a magnet translates to a 2 degree change at the crank.

I could have tried to glue the astonishingly strong little magnets back in place but decided to replace the entire thing. The sleeve for the new unit has been updated so that the magnets are fully embedded into the plastic and cannot fall out.

So, a cautionary tale for anybody with an old Pertronix ignitor with glued-in magnets: take the sleeve off once in a while to check that they are secure. (Gluing them back in would be a fun exercise because they are powerful enough to leap together when placed in the sleeve, and you have to maintain the correct North-South polarity if the sensor is to work properly!)

Other notes:
- For a standard Lucas 23D4 distributor the correct Pertronix ignitor is a LU-148.
- For a Pertronix distributor of the type that R.D. Enterprises sells for the Twin Cam the correct Pertronix ignitor is a LU-143A. (I've not actually examined the distributor that Ray is selling today, but I'm confident that my 15 year old distributor is one of his - from the website picture it's identical.)

Nick

Elan-Pertronix-magnet-sleeve annotated.jpg and
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PostPost by: elans3 » Sun May 16, 2021 7:42 pm

Exactly the same thing happened to my 18 year old Aldon Ignitor a few weeks after buying the car back last August. I fitted the Aldon version (exactly the same as the Pertronix), in 2002 when I first bought the car. I presume it had been faultless in the interim, but a week or so after buying it back last year, it started to misfire. I first thought it was a blocked carb jet, Went out in it and it misfired worse. managed to get it home on 2 cylinders, and removed the distributor cap & sleeve, and found two of the magnets had attached themselves to the distributor shaft. Glued them back in and it was back to top performance again. Bought a new sleeve from Aldon which is in the glove box.........
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