Engine gone pop!

[Ben Nichols 1979]

Hi All

Me again..........

So, was taking the car to have the carbs set up this morning, got about a mile and a half and it stopped. Started popping and then one final pop/fart noise and it died.

The AA came and found no spark. He thought the distributor had failed - removed it and it seemed fine. Then he thought maybe the distributor drive gear - we removed that and it seems fine, the gears are good, it seats properly. We did get a spark but not a reliable one.

He thinks it could be the drive gear on the crankshaft that has failed and the lack of drive is causing the problem to the drive gear and on to the distributor........

My questions I guess are:

1. Is this likely/possible? Would it just fail with no warning?
2. How is it possible to check, or isn't it?
3. It sounds like a full strip down again.......tell me its not although I am pretty sure it is
4. Any other explanation for the fault.........?

Any help appreciated - I was planning on taking the car to Le Mans in 3 weeks which looks unlikely......

Thanks

Ben

[KS]

If the gear's no good then the rotor arm won't turn when you spin the engine over. An unlikely failure to be honest. First thing, is/was the distributor seated all the way down correctly, so the two tangs on the bottom of the distributor drive are engaging with the slot in the distributor drive shaft? If they weren't then it is possible for the distributor lose drive momentarily and the engine will stop as you described. If the AA man has then pulled the distributor drive shaft out of the crankcase to take a look at the gears, and then pushed it back in randomly, then there is every possibility that he's refitted it incorrectly so the timing will be miles out. It will spark but not at the right time. It can fit any manner of ways, but only one right way...

This is a pic of the two slots in the top of the distributor drive in a Beetle engine, but it's the same deal with the Type 4/914 motor.

[Ben Nichols 1979]

Thanks for the message.

Its is seated properly and at the correct 12 degrees from the centre of the hole - we managed to find TDC through the inspection hole in the fan shroud.

I will try turning it over and see if the rotor spins, im pretty sure he could spin it when it was all connected, should that be possible?

Thanks

[KS]

Do you mean he could turn the rotor by itself? If so then the pin holding the drive on the bottom of the distributor has sheered. Or am I misunderstanding your comment?

I'm guessing you've checked the points to make sure they haven't fallen apart, or closed right up. If all good, try replacing the condensor and the coil.

It is possible the drive gear on the crank has failed (unlikely, but...) as some of the new aftermarket ones are terrible quality, which is why I always scavenged parts bins for old original brass ones.

[Bruce M]

Weird... strange diagnosis approach.

If there is no spark, it’s an electrical issue. If you turn the engine over by hand or using the starter the rotor arm should turn. If it doesn’t then yes, there is a problem with the mechanical drive but it far more likely to be electrical.

[KS]

I think we can assume (hope) the AA man carried out basic electrical checks before hitting on the distributor drive. Or maybe not!

[jwhillracer]

I think we can assume (hope) the AA man carried out basic electrical checks before hitting on the distributor drive. Or maybe not!

Rare to find an AA man (or Main dealer "technician") who understands distributors, points and carbs these days...…….

JW

[Ashley James]

Is it a short in the rotor arm?

[Ben Nichols 1979]

I have sent the car to Beetlelink in Aldershot to hopefully sort it out.

The more I think of it the more I think its fuel related, I think I may have linked the fuel pipe when I put the tank back in but as the timing is now shot I needed someone to sort that too......

Fingers crossed they can fix it quick......

[Ben Nichols 1979]

So, an update.

It seems it has a flat cam.....the engine is at GAC in Aylsbury for a full rebuild with new cam etc etc. Should be back in about 6 weeks....fingers crossed.

[gridgway]

Hope it gets sorted ok. But I was wondering what a flat cam is?
Graham

[KS]

Hope it gets sorted ok. But I was wondering what a flat cam is?
Graham

When a cam lobe wears down – there was a spate a few years ago of aftermarket VW cams going flat, largely due to poor quality castings. It is vital to break in a new cam and its followers by running a freshly rebuilt engine at a constant 3000rpm, or so, for about 20 minutes. Failure to do so can or will lead to premature wear of cam lobes and followers.

[gridgway]

Would that have caused the sudden engine failure?
Graham

[neilbardsley]

Condenser failure? Loose ignition wire?

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