Why is my sump filling up with fuel ???

[Michael D]

that's why I use. 98 octane fuel in my classics. as yet there's (allegedly) no ethanol in 98 octane fuel

[Reckless Rat]

There's 5% ethanol in E98...

[Ivor Hawkins]

I think I’m right in saying Esso Supreme doesn’t contain ethanol...I hope it is, I plan my journeys around Esso stations for that reason!

[flywheel1935]

Oooops, forgot to mention, using 98 octane too.

[John Cornforth]

Hi flywheel1935



To answer some of the points raised.

You say the engine was tested by the rebuilder.  Was this with the same Zenith 26VA carb you are using now, or another ?




Fuel spillage on priming suggests a too-high fuel level in the float chamber for some reason.  If so, this must be sorted before anything else. A leaking needle valve or punctured float are two favourites, but other things might be the cause.

Modern A7 replacement pump diaphragms are sold as Ethanol resistant.  I use 98 octane as some brands are reputed to presently have little or no ethanol, though the legal limit is 5% so this situation could always change. I can't see it having any marked effect on starting/running difficulties. The published density of modern fuel (0.72 to 0.78) doesn't seem to be significantly different to that used in the 1930's, so any change in float chamber level will be pretty small.



New 26VA jets are listed by Austin Reproduction Parts (Willie McKenzie) and possibly by others.  Burlen in Salisbury also handle Zenith spares.  However, I doubt if wrong sized jets alone would account for the symptoms you have.

I don't think the higher CR would be enough to weaken or prevent a spark even with standard ignition.  Bear in mind that the throttle is near closed when starting, so you won't be getting as high as the 110 PSI you quoted until the engine is under load. I suggest you don't go wider than the standard plug gap of 20 thou (0.5 mm) unless there is a good reason.

One last thought. Electronic systems and unsuppressed ignition leads make unhappy bedfellows, so I recommend resistive plug caps if you have electronic ignition.

[flywheel1935]

Hi John, funny you should mention the carb, as when I supplied the old original engine the carb fitted had a very worn butterfly spindle, and on the engines return an alternate carb was supplemented. He assured me that the f/pump diaphragm was attended too. So by coincidence I now suspect the carb is overflowing/rich/etc hence the difficulty in starting and the fuel in sump scenario. (again) ???
The 'powerspark system' fitted came as a total kit with, Dizzy, Coil, Carbon leads and plug caps. in one package, and performs as expected, timing with the Hall sensor is by the old way of taking off the coil lead and seeing it spark, will set at 20 degrees BTC as suggested by the "builder" .

[Bob Culver]

re above. I have broken the rule very many times over the decades, as did my father previously, (and experienced mysterious condenser failures) but when drawing sparks a moderate spark gap must be provided. On open circuit or long gap very high potentially damaging volts appear in both pri and sec ccts. Caution esp applicable with electronics (I have been told that many modern lawnmowers are damged by just one open circuit sequence.) To keep volts down a small gap was recommnded fro magnetos (The volts reqd to fire a normal or rich mixture are modest) I time 50s, 60s cars with crank handle by shorting the main ht lead and watching and listening for the break spark at points while hand turning.

[Ruairidh Dunford]

I cannot help with your fuel problem but wanted to make the point that over the last 4 years I have fitted more than 60 electronic distributors to Austin Sevens, all with standard copper unsuppressed HT leads, without issue.

I have found the following very important to the life of the units:

1. they should be fitted with a coil that measures at least 2.4 ohms, any less and the module will start to fail.

2. connections must be very tight, any sparking will immediately fry the unit.

3. if the battery drops to below 6v on starting, the units will not work until the starter switch is released.

[John Cornforth]

Hi again

If you are timing by looking at the spark (preferably use a spare plug) at effectively zero RPM then you should be setting the static timing i.e. at minimum advance. The 20 degrees is at MAXIMUM advance (3500 RPM plus). For static timing a figure more like 4 degrees is appropriate.

Beware of an error in some Austin handbooks which carried over the timing settings for manually adjusted distributors into the automatic advance era.

If you have a strobe and can put some accurate marks on the camshaft pulley, then the advance can be checked out with the engine running.

[Renaud]

Hi Ruairidh,
Which brand or brands of modules are you speaking about please?