No Spark Gremlins

[MetBlue]

For best part of a year now, I've had the odd occasion where my car just does not want to start. Normally, she starts as soon as the engine turns over.
Until this week, it's always been inconvenient timing and I've just had to use my other car, being unable to investigate.
The following day, probably after a recharge of the battery because I've taken a lot out trying to start, I'll get in and she'll fire up first time and run like a dream.

This routine has maybe happened on 2 or 3 occasions over a year. Fortunately, it's always happened at home.

Last week, I changed the timing belt and fortunately the car started and ran beautifully whilst it warmed up and on a short test drive.
Yesterday I put it on charge, then this morning - No start. Fuel pump ticks away,but no fire up.

For once I was able to investigate. There's good fuel pressure at the carb, but taking a plug out and looking for a spark - Nothing.

Unplugged the rev limiter - Still nothing.

Unplugged the feed to the AB14 from the dizzy and found one very bad connection. Only about 3 wire strands unbroken and very soon the blue wire had parted company from the socket and spade. - Both connections cleaned and remade. - Very hopeful this could have been the issue, but NO. Still no spark.

Next, Air box off and into the dizzy. Immediately noticed one side clip was not clipped over !! and the Vacuum pipe was disconnected and plugged !! Took the cap off and found some dry dusty powder like stuff scattered around inside. Rotor arm off and the inner cap taken out. This is where the dust came from.



No doubt all caused because one side of the cap was not clipped down. Cleaned it all up, blew compressed are around inside dizzy and cap, then rebuilt without the plastic cover, but taking care to ensure both sides of the cap were clipped down. Didn't do anything with the vacuum advance for now though.

She then fired up....But is it the fix, or had the gremlin just decided it was a good time to play the joker !!

For the record, my cars a MY 92 car with electronic ignition. Am I right the pick up is a hall effect sensor or is it optical. If optical, it could explain the issue if the broken bits got in the way, but I suspect it's a proximty type, hence no rational explanation I can see.

I wonder if she'll start tomorrow?

Tony

[Hawaiis0]

Bugger. Well done. Good find I reckon.

I know what i'll be doing next!

Haven't been in there in 8 years. Maybe I should have

[MetBlue]

I left the cover out for now, but in hind sight wondering if I should. Got feeling the cover will also help centre the diz cap? It's clearly meant to do something.
Any thoughts anyone - Or someone with a spare off the car who can compare with and without.
Tony

[bash]

I might be wrong..... Not uncommon, but the plastic thing is probably there to stop electromagnetic interference from the spark jump from rotor arm to cap post. My rover v8 has one too.
Bash

[rbgosling]

The pick-up is magnetic, not optical.

Hopefully it's just the cap not being properly clipped on that has been the cause of your issue.

I seem to recall that there should be some little V-shaped clips that hold the cap clips in their hole in the distributor base. These are not really essential, and are probably usually missing, but I did get some from the Distributor Doctor when I did my engine rebuild - see the second bottom picture in this link.

Sounds so much like the issue I had for nearly a year after my engine rebuild! Maybe 1 in 4 times it wouldn't start. Once running, it always ran fine (except once, on the way home from the Donington Classic festival with all the family in the car). Usually if I removed the distributor cap and put it on again, it would start, but that was a major PITA to do regularly and in random car parks, since the air box and trumpets had to come off to reach the distributor every time. Especially near midnight, in a field in Leicestershire, about to head home from the Download festival, with my two older sons.

Eventually I put some effort into diagnosing the cause. It was one missing tiny washer inside the distributor, without which one part wasn't held firmly to the base and so electrically grounded, so just occasionally it would be floating and not make a connection so no spark. I'd failed to put it back when I stripped and rebuilt the distributor as part of the engine refurb.

[rbgosling]

Only just realised, writing that, that my two worst let-downs both involve coming home from Donington, with family in the car. Wonder if there's some connection...???

[Pete Boole]

If you are missing the little "v-clips" I've got a couple.

Pete

[bash]

After doing a bit of intercrap surfing opinions differ on the plastic shield but it is most commonly called an 'anti flash shield'. Apparently if some oily fumes get into the cap a small explosion can occur ignited by the spark across the rotor arm to distributor cap. Not uncommon on some early v12 jags apparently.
You learn something every day eh.
Bash

[Marten]

For best part of a year now, I've had the odd occasion where my car just does not want to start.

Could be the ignition switch getting tired. When worn it is possible for it to disconnect the power to the ignition when you engage the starter. Symptom is the engine tries to catch when you let go of the key. Check that the coil is powered during cranking with a testlight

[MetBlue]

or had the gremlin just decided it was a good time to play the joker !!

Yep. The joker was being played

8:00 AM Saturday morning, car loaded up and ready for 100 mile trek to Castle Coombe, but car had other ideas. It was a damp morning, with a good amount of dew on the car.
First thought - Somethings damp so played hot air gun gently around the ignition amplifier and coil ( not realistic to do much on Dizzy without removing air box). - No change. Cranks but no fire.

Then remembered I have a spare AB 14 in the parts that came with the car, so easy swap, but still no go.
Swapped back to the original AB 14 ( don't know for sure the spare AB 14 is any good), disconnected rev limiter - Still nothing. Rev limiter plugged back in.
Removed no 3 plug - Definitely damp with fuel, so dried off with the hot air gun, plugged onto the HT lead and rested on the block. Daughter came out and cranked the engine, whilst i watched the plug.

We had about 1 second of definitely no spark, then the engine tried to catch and the plug was sparking like it was Nov 5th.

At this point, I just knew it was going to run, so plug in, fired up and off the Castle Coombe we went. 90 Minutes later than planned - Thanks Gremlin.
Ran perfect for the rest of the day, and again today.

More convinced than ever now that this is something getting damp and breaking down under load when cold / damp. Later in week plan to change the dizzy cap and rotor arm - And put back that plastic divider, cos I don't like the suggestion Bash found that it is to prevent explosions. - There's only 4 places i want explosions in my car, and one of them ain't in a distributor underneath carbs.

Tony

[robertverhey]

I’d replace the cap and rotor. I’d be suspecting that some damage occurred to either/both while it was running partially unclipped.

[MetBlue]

. More convinced than ever now that this is something getting damp and breaking down under load when cold / damp.

Cold / damp . Another theory in the bin. Those on the Ollie run will be aware my car played silly b***ers again this morning - in the middle of one of the hottest periods in the hottest, dryest summers for years. Exactly same symptoms as described earlier in this thread.
Bryan's spare coil swopped in. No start. Changed back.
Dodgy spade connector broke when refitting, but repaired. Still no go.
Then Alan's old dizzy to coil HT lead fitted to coil and offered to block. Cracking spark.
Just knew at this point that plugging the cars HT lead back into coil would have her running, and sure enough, it did. No further trouble all day.
Doesn't really make sense, but reading back on the thread, I'm starting to like the ignition switch possibility.
Tony

[richardw]

Glad you got going again Tony. Was chatting with Alan about his problems and think it would be worth putting together ideas and practical experiences re ignition problems and coming up with an upgrade package that we could recommend to owners so these problems that seem to plague us go away, or at least reduce the possible points of failure, hence simplifying diagnosis. Will kick a new topic off tomorrow and let’s see where it goes.

[Alan_M]

Maybe you could put together a “hot wiring” kit to bypass ignition switch ready to clip on to the coil and starter solenoid and have it ready for its next tantrum

[HC180]

How have you fared Tony?
I had the same symptoms. It was the connector in the middle of the AB14 to distributor wire (under the carbs/airbox). Pushed the bullet through the rubber housing and managed to re-use. It was hanging on by a wire.