Lotus Elan

leaky carb?

PostPost by: theelanman » Tue May 07, 2013 2:23 pm

having not had the car long I was a little perturbed by the smell of petrol when I got in the car to drive home yesterday......
the carb nearest the bulk head has always appeared to have a small leak (occasional drip)
this was never smelt before...the other is fine
half way home I thought the smell wasnt too good so I stopped and cleaned the petrol off the carb and from under where it had been dripping......there was nothing to write home about from a quantity point of view.....but I could still smell fuel on the rest of the trip.....
I again when I got home lifted the bonnet (hood) to find a few more drips but nothing significant and after about 10mins with the bonnet left open the smell of fuel has gone......

the only thing I can think of that Ive done any different is that I parked the car on a bit of an incline with the rear being the high point......I cant see this making a huge difference as it wasnt that high...but would be keen to hear any ideas...

thanks
G
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PostPost by: m750rider » Tue May 07, 2013 6:31 pm

It could be the fuel pipe that splits to the two carbs that drips down, if it is the original plastic it is known for cracking; or it could be leaking from the float chamber. Try cleaning everything extremely well till it is completely dry, then using your finger tip see if you can find where it is leaking from. You will feel it with your finger before you can see it with your eyes.

Regardless, find it and fix it as a fuel leak here can lead to a fire quite easily. All it takes is a small spark from the coil, distributor, or spark plug wires with partly failed insulation to catch the engine bay on fire. One easy way to check for bad wires is to run the engine in the complete dark and look for "fireflies". If there is bad insulation/wiring you will see small discharges going to whatever ground is nearby.

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PostPost by: MickG » Tue May 07, 2013 9:43 pm

You don't state where exactly the drips are comming from?

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PostPost by: theelanman » Wed May 08, 2013 5:39 am

there are usually a few drip just under the carb....however on this occasion the top of the carb was also 'wet'

I guess I need to run the car stationary and watch......
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PostPost by: MickG » Wed May 08, 2013 8:38 am

I should have also asked in my previous reply but what carbs have you got?
Webber, Stromberg or Dellorto

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PostPost by: theelanman » Wed May 08, 2013 9:21 am

weber....
:-)
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PostPost by: Robbie693 » Wed May 08, 2013 10:22 am

Could be the gaskets on the fuel line banjo's, I quite often have to tweak the bolts up while running the engine after I've had the fuel lines off for any reason. (I have Dellortos but I think the fuel inlets are similar?)

Or maybe the cover gaskets?

Hope this helps

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PostPost by: MickG » Wed May 08, 2013 9:48 pm

Having had a petrol leak after a rebuild I would check the following.
Fuel lines from pump to carbs.
Fuel line banjo's at each carb replace fibre washers if necessary.
The gaskets on the top of the carb under the wing nut and around the top cover should not leak petrol as they are above the fuel level, but check any way.
Main jet and float setting, is this correct and doe's the needle valve shut off when the floats rise.
Now where I did get a fuel leak was from the air box adjacent the the oil breather inlet.
Take off the air box and see if you notice any tell tail streaks on the back plate from the air inlet to the carbs or around the air horn.
If there are signs of leaking petrol from the air inlet then the needle valve and floats need adjusting/renewing.
If leakage is detected from the air horns (a common problem ) the following should solve the problem.
Petrol can leak from the main jet along the auxiliary venturi and out of the air horn where it slide in to the carb body. This fix is documented in the +2 owners manual using blue hylomar put a bead around the air horn flange and leave to set, also put a small blob in the slot that accepts the venturi retaining clip. After about 5 minuets refit the air horn and tighten. You could use RTV but I think you will find most are unsuitable for use with petrol.
I hope that helps, it fixed my leaks :D

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