Ignition Distributor Drive Concerns

[Mike Allfrey]

G'dday From The Sunny South,

Thought it could be of some benefit to pass on recent experiences in the ignition department.

As may be known, my Jupiter is fitted with electronic ignition system and for some time it has worked extremely well. As we approached Armidale last year, the instantaneous starting had slipped away. The engine later became sluggish and was difficult to keep running after starting from cold. It even required some choke to coax it into life when hot. Finally, when working hard, the exhaust note became extremely harsh.

Years ago, I had similar symptoms with a 1960 VW Beetle, and this turned out to be a problematic sealing washer in the main/reserve fuel tap. the washer swelled on hot days and restricted the fuel flow to the carburettor.

Thus, I put this experience to use when diagnosing our Jupiter's erratic running concern. Silly Me!

First the petrol filler cap vent was checked. Blockage here is not really possible with a Jupiter. Next, the inlet filter at the SU pump was checked and found to have some dark brown fibrous looking gunge trapped by the gauze - but nowhere near enough to cause any restriction to petrol flow. The main petrol filter (a diesel fuel filter/water-trap with huge capacity) was treated to a new element and petrol flow from the SU pump was checked. It would have probably kept a Rolls Royce Merlin running sweetly. Good flow was the result. This test was conducted at the pipe that enters a fuel pressure regulator valve that holds the pressure down to 2 psi. The valve was removed and found to have a significantly swollen diaphragm. Aha!

The pressure regulating valve was removed and the pipes connected. The Solexes managed to hold back the SU's prodiguous pressure and the engine was started. No Change. Next consideration was a tank of stale petrol - why does this thought train commence when the tank is nearly full?

It had been filled, through necessity at a non-BP service station and some discussion with others in the know, set the reasoning towards stale petrol, who knows where these obscure brands come from? The tank was drained into clean 20 litre drums and 10 litres of fresh BP Ultimate poured in. Another try, no improvement at all!

I have always treated an engine like a cigarette lighter - the problem can only be fuel or ignition. The car was booked in at Wilson Carburettor Service for a month later, due to staff holidays. My thoughts were now about the accelerator pump diaphragms, after seeing the one in the pressure regulating valve, well, why not? Four more weeks to investigate.

I then started considering the electronic ignition system. A new ignition module (igniter) was tried - $125.00 later, no difference at all. Then it was decided to remove the electronic system and revert to the good old Joe Lucas DM-2 distributor and Joe's sports coil. As Keith Clements and Bill Lock know, I am getting good at the changover! Bingo! All was well in the engine department. At last.

I was not going to let a Japanese distributor beat me and having spent large amounts getting it professionally overhauled, I took it back to Performance Ignition Services for a check over. They listened to my description of the symptoms and came to the conclusion that the pick-up field coil (or whatever it is inside the body) could be the cause, and said they would run it on their test bench. Not long after, they rang to say there was nothing wrong with the entire system. They were still conscious of the engine running well om Joe's DM-2, and they said they would give it some further running next morning and report further.

They rang mid-morning to report that the problem had been found and rectified. What was it?

Probably, as always, it was the cheapest component in the entire system. The distributor drive dog securing pin had fractured adjacent to the shaft on one side only. This allowed the drive dog to pivot on the sound portion of the pin. The poor engine had been suffering from constantly variable ignition timing!

A new, stronger, pin was installed and the work was gratefully paid for. The engine now starts instantly and idles peacefully at an indicated 500 rpm.

My thanks to Ray Hoey, Richard Homersham and David Kennedy for their support.

It is wise to check ignition matters even if the symptoms suggest otherwise.

Regards to all.

Mike Allfrey.

[Keith Andrews]

You think that chassing around!!
I have a issue that is current on the Camaro...a knock, after a $8000 engine rebuild...
http://www.camaros.net/forums/showthread.php?t=95821
then current thread here
http://www.camaros.net/forums/showthread.php?t=102145

Steps

[Mike Allfrey]

Dear Keith A,

What a carry-on! In the Rover Car Club we had a 3.5 P5B that had just been meticuluously overhauled and it had an intermittent knock. To me, familia with such things, ist sounded just like a Jowett camshaft end-float knock - but a fair bit quieter!

I don't think he has found it yet.

Regards,

Mike Allfrey - Pretty Chuffed Jupiter Owner, again!