fuel problems maybe?

Post by **bmcecosse** » Fri Dec 04, 2009 9:00 pm

I TOLD YOU that on November the 12th!!

Post by **rayofleamington** » Fri Dec 04, 2009 10:36 pm

glad you've fixed it - it couldn't have been anything other than fuel related from the description.

Post by **cadetchris** » Sat Dec 05, 2009 4:20 pm

maybe it wasnt the carb sticking, its been doing it again today, pain in the manifold really.
when i undo the dash pot and then start the engine, it starts perfectly, could it just be the dashpot plunger thingy thats u/s and not the actual carb?

Post by **PSL184** » Sat Dec 05, 2009 4:24 pm

Very strange - usually they won't run with the carb damper unscrewed. Still sounds like its fuel related though - Maybe a bent needle or the damper is still sticking ??

Post by **MarkyB** » Sat Dec 05, 2009 4:34 pm

Can you lift the carb piston when the damper rod is fitted?

The brass bit on the end should be able to move around a bit.
If the rod is bent at all it will bind.

Post by **cadetchris** » Sat Dec 05, 2009 4:39 pm

the needle is as straight as a ruler, so i have no idea

Post by **bmcecosse** » Sat Dec 05, 2009 4:40 pm

Asked before - DOES THE PISTON RISE AND FALL EASILY ? Try it with your finger - yes - with the damper IN. It must rise to the top (against the oil obviously) and then fall back to the bridge.

Post by **cadetchris** » Sat Dec 05, 2009 6:09 pm

will try tomorrow during daylight time. it should do, but we will see

Post by **dalebrignall** » Sun Dec 06, 2009 9:29 am

put some light oil in the dash pot 3in 1 is fine .

Post by **cadetchris** » Sun Dec 06, 2009 3:18 pm

tried the carb today, the piston lifts with a little resistance (from the oil in the dash pot presumably) and then drops back down.
i have checked the needle and its nice and straight, though i have realised that when the engine is off, the carb float is flat down against the jet, and when the car is started, is still remains flat down against the jet, HOWEVER when i undo the damper pot cover, the whole pison raises slightly and the car starts.
any particular reason why this is causing the car not to start with the dashpot cover screwed in?

Post by **MarkyB** » Sun Dec 06, 2009 4:29 pm

Only a little air can get in when the piston is down.
As the engine sucks more air in it should lift the piston.
It sounds like yours is sticking for some reason.

Post by **cadetchris** » Sun Dec 06, 2009 4:52 pm

thats the problem, i have no idea why its sticking. i have had the whole thing in bits today, changed all the seals, cleaned the whole thing in lovely clean petrol, reassembled and gone for a drive, went into the shop, came out and it did exactly the same thing, which was solved by undoing the dash pot cap and it started fine.

Post by **MarkyB** » Sun Dec 06, 2009 5:26 pm

How about some pictures?
The piston, the inside of the dash pot cover and the brass bit on the damper rod come to mind.

If you have had it all apart, did you recentre the jet?
Does the piston make an audible clonk when it falls? It should.

Post by **cadetchris** » Sun Dec 06, 2009 5:28 pm

it dosent make a clunk when it falls, just a nice smooth action.
how does one recentre the jet?

Post by **MarkyB** » Mon Dec 07, 2009 9:06 am

It should clonk.
The "nice smooth action" is the needle binding in the jet.
I think you loosen the jet holder a bit, tap the carb then tighten it up again.
Have a look at these:http://www.sucarb.co.uk/TechnicalDetail.aspx?id=35

http://www.youtube.com/watch?v=sxVFCY_1 ... re=related

You DON'T need to dismantle the carb, just do the centring bit.

Post by **Kevin** » Mon Dec 07, 2009 11:32 am

Excellent Marky that youtube link shows it in detail including the clonk, and Chris should be able to sort it now,

Post by **bmcecosse** » Mon Dec 07, 2009 12:22 pm

Just check the little damper on the rod end. It should have some 'free lift' - in fact I believe there used to be a range of different dampers with different free lift. BMC certainly specified particular free lift (usually 90 thou) on the Works Minis - but of course they may have made that by slightly modifying standard units. The point is - this free lift allows the main piston to rise slightly before the damping effects come into action. So just check that little piston on the end of the rod is free to move up and down slightly.

Post by **cadetchris** » Mon Dec 07, 2009 2:30 pm

i have fiddled witht the jet and their is now a satisfying clunk as the piston hits the bottom. as for the damper on the rod end, it has free lift, i replaced the whole rod and damper initially as i thought it was this which was knackered, but its still doing the same thing.

its got me stumped really, as the carb is clean, jet centred, no blockages and everything is nice and clean and set up right, plus the carb its self is about 3 years old, so it couldnt of broken completly in that amount of time

Post by **bmcecosse** » Mon Dec 07, 2009 3:00 pm

So - it's still not starting even though the piston now 'clunks' ? But if you release the damper - it starts just fine ??

Post by **cadetchris** » Mon Dec 07, 2009 6:14 pm

yep, thats exactly whats it doing