No fuel after float bowls? Twin hs4
Turbo Mini Forums

Hello chaps!

I'm trying to get my mini started but I'm getting no fuel through the jets I assume?

Float bowls are both full...

Carbs have been rebuilt,

Any advice?

Doing my nut in haha

Cheers!

Lacking a lot of info.

Fuel will only exit the jet when there is airflow over the bridge to draw that fuel in to the engine.

So do you have fuel flow to the carb, pressure ? you say twins, so does either carb get fuel, is there fuel in the bowls etc etc.

Why were the carbs rebuilt, was this a problem before hand ? was it a competent person rebuilt them ?

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Sorry for being so vague,

Yes I have fuel to the bowls, both are full and pressure is good from there back,

The bowls fill up but fuel goes no further than there?

Rebuilt as a precaution as to unknown source they came from.

Big vacuum leak? Inlet not bolted up quite flush? If nothing is drawing out of the jets there's no vacuum from the engine, might be all sorts of things, like spark plugs loose or valves not sealing/valve clearances non existant.

take the dashpot off and using a silicone hose or similar, see if you can suck a little fuel up the needle, if so its not blocked and if the engine isnt drawing fuel when cranking either theres insufficient vacuum or the float level is a mile out

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

I've emptied the float bowls and blow air back through there with dash pot off and need removed?

Where's a good place to start looking vacuum leaks? Plugs are in tight, manifolds tight, valve clearances are set

Make sure the rubber seals that the jet to float bowl isn't on the piss I did this in a hs4 and it wouldn't draw fuel due to rubber blocking it

Surely this wouldn't allow air to blow through if that little rubber seal was on the piss?

How do you know no fuel is getting through? Its not like you can see it in an SU.

Could be a red herring and its ignition related. I had a problem getting my minor to start after winter this year. Had sparks so thought it was the carbs but turned out to be duff condenser giving 'weak spark'. You couldn't tell any fuel was getting in there at all really. They aint like webers that pile it in from the throttle pump and flood the thing.

Getting full choke?

Well if I use a syringe and squirt abit of fuel straight in, it fires straight up?

Yup getting full choke too

Ok. Maybe you have the jets set too high so you're just not getting enough fuel through rather than none at all?

You should see the needles/pistons bounce a little as you crank. It's a good sign all is well with the vacuum side of things i think.

I shall double check that little bounce,

I set the jets at the recommended 12 flats, even if unscrew them 24 flats it still won't even cough haha

Haven't got the wrong Size jets on it?? Or pull them right down and try starting it?

Edited by stevieturbo on 1st May, 2016.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Have you set the needles correctly so that the dashpots fully drop? (or are they spring loaded?)

Do the dashpots fully drop in any case. If they're sat high you won't get vacuum across the jet.

Oil and springs in the dashpot?

Have you blocked the fuel breather? This would vac-lock the float bowl.

Finally, one of the first post asked if the float heights had been set correctly? Have you checked?

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

Another "old skool" test on carbs to see if float height,jet blockage etc. is restricting fuel so there is not enough for the engine to start is to remove all the filters and gubbins in the way and and mostly block the inlets with your hand(s) and get someone else to try to start it with the throttle held partly or mostly open.
Don't block the inlets totally with your hand(s), just mostly so you feel the vacuum as the other person cranks it and that will suck a lot more fuel out the jet(s) - like adding with a syringe - but from the carb itself.
It's like using the choke on a conventional fixed jet carb, it forces more fuel in.
If it fires and stops when you take your hands away you know there is a restriction on the fuel or the bridge/piston over the jet isn't at the right relative height to create the vacuum itself.

EDIT - bit missed

Edited by Rod S on 2nd May, 2016.

Schrödinger's cat - so which one am I ???

right then,

thank you for the advice everyone,

i double checked everything everyone has said in here, i wasn't overly happy with how fast the dash pots were dropping after lifting, so wiped them down and polished them with some metal polish as per vizards recommendations, glided much better.

im assuming it just wasnt getting enough fuel as per steve rather than none at all, with the jets wound all the way open it would splutter,

i found a pair of new hs4 jets in my spares bin and just thought id swap them over (eliminate all factors) and now it'll start, with the jet nut screwed out 24 flats...

so i think i need different needles in there as a starting point?

thanks again for everyones advice!