Fuel in vacuum advance unit

Post by **JULIAN** » Thu Nov 13, 2008 2:19 pm

I have had a number of issues with the timing/pinking on my 1969 Tavellerwhich has required removing retiming the distributor on a number of occasions and fitting electronic ignition. All is now well, but during this process each time I removed the distributor there was petrol in the vacuum unit of the advance mechanism. I am not comfortable with this for obvious reasons. Is there something else wrong that I may have missed? The car has the plastic type vacuum tube is fitted with an aftermarket brake servo which has its take off on the inlet manifold. Would this effect it?

My 1956 Saloon has the metal type vac pipe with a built in fire trap and dose not show the same problems.

Post by **bmcecosse** » Thu Nov 13, 2008 2:28 pm

Welcome to the Forum - many new members these days for some reason!
Strange you would need to fit electronic ignition - the A series engines run perfectly well on the standard points system. If petrol is gathering in the vacuum advance unit I suspect it may be punctured. Have you tested the diaphragm for leaks? And have you tested the vacuum advance to see if it actually moves the base-plate inside the dizzy ?

Post by **mike.perry** » Thu Nov 13, 2008 2:43 pm

If you have fuel in the vacuum advance unit - beware.
I had the same problem on a Minor that I had on loan. I had just moved away from the lights when there was a bang as though I had driven over a tin can, and the car stopped. I looked under the bonnet and the distributor was in pieces. Apparently fuel had got into the dizzy and was ignited when the points sparked. The cause was a broken diaphram in the vacuum unit.

Post by **JULIAN** » Thu Nov 13, 2008 2:53 pm

Just checked the vac unit by sucking the end of the pipe. It works fine. Fitted electronic ignition to save time when servicing as my wife uses the car every day.

Post by **PSL184** » Thu Nov 13, 2008 2:54 pm

There should also be a fuel trap in the vac line from dizzy to carb which should be mounted verticle with the carb outlet to the bottom.....

Post by **JULIAN** » Thu Nov 13, 2008 3:40 pm

I've only seen fire traps fitted to the early dissys with metal vac advance pipes as on my 1956 948cc. Wher can I get one for the plastic pipe variety. I've tried all my usual suppliers but they dont seam to exist!!!!

Post by **PSL184** » Thu Nov 13, 2008 3:52 pm

Sorry, I wasn't aware of the later type with plastic pipe. My '69 has the metal pipe with fuel trap the same as my '62, '63 & '65...

Post by **bmcecosse** » Thu Nov 13, 2008 3:59 pm

For many many years the Mini didn't have a 'fuel trap' -so really no need. If the diaphragm is not leaking - then nothing to worry about!

Post by **mike.perry** » Thu Nov 13, 2008 4:06 pm

I suppose you could get an old metal pipe, cut the fuel trap off and attach it to the plastic pipe. Cheaper than a new dizzy, although exploding dizzys are quite rare.

Post by **simmitc** » Thu Nov 13, 2008 4:50 pm

It shouldn't do any harm (with electronic ignition you won't have a spark from the points) but check the float height in the carb, and make sure that the needle and choke are operating correctly. Too much petrol in the carb could get sucked / pushed into the pipe.

Post by **JULIAN** » Thu Nov 13, 2008 9:09 pm

Thanks for the help & advice.

Post by **bmcecosse** » Thu Nov 13, 2008 9:30 pm

Are you sure it's not just condensation - that smells of petrol ??
I have no idea if I have petrol in the advance on my car - it's not something I have ever checked! I do know it works - and doesn't taste too good when I suck it !

Post by **Kevin** » Fri Nov 14, 2008 4:12 pm

there was petrol in the vacuum unit of the advance mechanism.

Just checked the vac unit by sucking the end of the pipe. It works fine.

Hmm strange as that sort of contradicts itself.

Post by **bmcecosse** » Fri Nov 14, 2008 4:37 pm

That's what I was thinking!

linearaudio · Post by **linearaudio** » Fri Nov 14, 2008 8:44 pm

bmcecosse wrote:For many many years the Mini didn't have a 'fuel trap' -so really no need. If the diaphragm is not leaking - then nothing to worry about!

Mine isn't split, but I also get fuel in the vac unit!!

Post by **bmcecosse** » Fri Nov 14, 2008 8:46 pm

How do you tell - do you take it off every week and empty it out ? Just leave it be !

linearaudio · Post by **linearaudio** » Sat Nov 15, 2008 9:06 pm

Discovered when the points gap closed up. Took distributor off to get a good purchase on rounded slot adjuster screw, that in turn twisted the advance mech, hey presto a squirt of stale smelling petrol down the leg of my trousers. Oh-no...

Post by **bmcecosse** » Sun Nov 16, 2008 11:16 am

Grrrroooo

Post by **Leo** » Sat Jan 02, 2010 12:16 pm

I know this post is over a year old, but are there any more thoughts on finding petrol in the vacuum unit. I have exactly the same problem with my 1969 1098cc Traveller. I found the vacuum unit was full of petrol when I removed the distributor
The Vacuum unit is not very old and the rubber diaphragm is not split.

Post by **bmcecosse** » Sat Jan 02, 2010 5:48 pm

I think it must be leaking - otherwise the petrol could not get to it....... Whn running on the engine there shopuld be a suction - that would pull any easily vapourised substance (ie petrol!) into the inlet manifold.