Lotus Elan

Weber start device

PostPost by: englishmaninwales » Wed Oct 30, 2019 7:19 pm

I seem to have a small chronic fuel leak from the start devices on both carbs. Small amounts of fuel seems to come from around the rear air intake channels on the device and runs down onto the throttle spindle cover plate area and under the carb body, as the car is running. Over time eg this summer?s motoring, this has become an oily mess.
Whilst I?m uncertain of the cause and I never use the start device, I wondered about fitting the start device elimination kits that I?ve seen available.
Anyone have any thoughts on the cause of the leak (? worn / leaky starter valves) and advisability / experience on fitting this kit?
Thanks
Malcolm
1966 Elan S3 Coupe
1994 Caterham 7
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PostPost by: Concrete-crusher » Wed Oct 30, 2019 10:21 pm

Having replaced my starter devices this year , I find that although you don't need them to start in cold weather they are great for increasing the revs while cold until the engine has warmed up, so maybe keep them with new gaskets

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PostPost by: elanner » Thu Oct 31, 2019 11:06 am

There are lots of posts in the forum on this problem so have a search around.

As far as I can tell not only is it possible to have (1) the leak you describe through the starter device air intake but also (2) a vacuum to build up in the accelerator pump chamber, pulling fuel into it (past the throttle spindle?), which can then dribble out past the cover when the vacuum decays, typically when the engine is switched off.

I'm confident that I suffered from both. The cure to (2) is to drill a hole in the accelerator pump chamber cover - as Weber did for later carbs.

The cure to (1) vexed me for years but this past spring, after reading a note (by Rohan?) about float chamber needle valve settings with modern replacement valves not being as cut-n-dried as they used to be, I decided to simply ignore the float setting in the manual and set it to about 9.5mm (the manual calls for 8.5 mm). To my astonishment this instantly fixed the problem. Of course, it has also lowered the fuel level in the jets but I didn't notice any difference in running so I never got around to measuring it accurately. I guess the level must have always been slightly too high. It's very nice to not have a fuel damp area around the distributor & HT leads.... :-)

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PostPost by: englishmaninwales » Thu Oct 31, 2019 9:23 pm

Thanks for the very helpful information.
Malcolm
1966 Elan S3 Coupe
1994 Caterham 7
englishmaninwales
Fourth Gear
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Posts: 521
Joined: 26 Jul 2013
Location: Ruthin North Wales

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