venturi nozzle

[jonnyshaw49]

i think i have found the fault at the top of the carb in the centre of the venturi is a nozzle which should let fuel out down the venturi under load or on driving, but its dripping on idle, giving engine too much fuel, as markey says 2 things could cause it the needle valve brass seal letting fuel through or the idle jet, so this morning i took both carbs apart and swopped the needle vales to eliminate it, then checked the idle jet, i put carb back together and refitted, car idles alot smoother now but looking down the venturi the nozzle is stil dripping a tiny drip at a time. what could this now be a worn carb?? there is a brass insert pressed into the carb (idle air jet) could this cause it? are they replaceable, i was going to swop carbs oln the car, but on the other carb the end of the mixture screw has snapped off so couldnt swop it. and whoever owned carb has filled it with like tiger seal so can get it out, so gonna have to get a new mixture screw orderd and swop it. has anyone any other ideas that could be causing the nozzle to drip at idle??? thanks

[Ian S]

They tend to do that if the main jet is 1.3mm or above.

Standard main jet is 1.2mm.

But the car goes quite a bit better with a 1.3mm.

[jonnyshaw49]

it has a standard 120 in, ive tried 2 different ones and its still doin it :cry: any thing else likely to cause it

[Sparkie]

try richening up the mixture at idle. there are so many cars doing this at the moment, i think its cos so many people are trying to run them too lean at idle.

[jonnyshaw49]

ok ill try winding mixture scew out a tad, its currently set and 2 and half turns from fully in thanks

[Mart]

Check the enrichment diaphragms (for splits/tears) as well.

[jonnyshaw49]

tried them mate put new ones in out of carb kit, today doubled up washers under needle valve and swopped acc pum nozzle for a different one and new rubber seal, still got same problem, which is the acc pump jet seal???

[Markey Mark (BD)]

tried them mate put new ones in out of carb kit, today doubled up washers under needle valve and swopped acc pum nozzle for a different one and new rubber seal, still got same problem, which is the acc pump jet seal???

The acc pump jet you changed (brass jet that points into the venturi and spring on top) has a seal sat under it, when you pull it out sometimes it comes with the jet or sometimes stays in the body of the carb

[jonnyshaw49]

i thought it was that mate, i swopped it and replaced with a clean one that had a very free balbearing then i used a rubber o ring out of my gasket set and removed the one from under in, still no joy. what is the 1 stage to check im getting confused with all the stages, im not a mechanic lol(wish i was) but a wood butcher lol thanks

[Markey Mark (BD)]

Thats it check the first stage enrichment mate, its the removeable jet in the enrichment body. As mentioned before check the gaskets too just incase.

Also have a play with the mixture screw, it maybe that your car needs to run little richer on idle, not uncommon for them to want that to do that.
Way i set my own up is take it out till it sounds best then take it in alittle just before you hear the revs starting to drop off.

[jonnyshaw49]

nice 1 mate ill check this in the morning, cant wait till its sorted, how does winding mixture screw out cure it?? how many turns max do you recommend? or shall i just go off ear? carbs are weird things lol, how much is efi conversion lol.

[jonnyshaw49]

round 30 lol.

some weird things happend today, took enrichment body off and ran carb cleaner through 1st stage 2nd stage and they all were clear, stretched springs, refitted to car and same again nozzle dripping, then gave mixture screw a go with car at 1000 rpm idle(on standard guage so could be out), winding it out half a turn at a time, nothing happend untill i got to 3 full turns out, so 5 and half overall, the nozzle stopped dripping, but the car still runs slighly lumpy lol. as i was turning the mixture screw out there wasnt much engine note change at all.car still seems to be struggling on idle at 1000 rpm. so what does this mean mixture screw is worn etc??? is it safe to run with 5 and half turns out?? i havnt got a wideband set up yet and car is garaged so cant check afr's , what you guys think???

[Markey Mark (BD)]

Having the mixture screw wound out 5 turns will be fine, won't interfere with how the carb works when its driving mate as thats done by all the other enrichment circuits.

When you rebuilt the carb did you put a new seal on the mixture screw?

[jonnyshaw49]

didnt get a new mixture screw mate its the original as is bunged over with silicone, do you think i should get a new one??? i tried spraying carb cleaner over the top of the mixture screw when it was running on idle and no change in sound so dont think the seal is leaking

[Markey Mark (BD)]

didnt get a new mixture screw mate its the original as is bunged over with silicone, do you think i should get a new one??? i tried spraying carb cleaner over the top of the mixture screw when it was running on idle and no change in sound so dont think the seal is leaking

Maybe worth trying a new one mate as its the only thing you haven;t changed.

Clean out the mixture screw tube too, remove all the silicone and then stick the new one in

[jonnyshaw49]

will do, may aswell as its minor to what else ive checked, thanks for all your advice, ive learnt alot on carbs over the last few weeks. there tricky things to get right, once get a decent turbo and wideband will set it up myself

[Sparkie]

try richening up the mixture at idle. there are so many cars doing this at the moment, i think its cos so many people are trying to run them too lean at idle.

:cooter:

[jonnyshaw49]

smart arse!!!!! lol but why is it still slightly lumpy??? should i try taking idle above 1200 and finding a happy medium between mixture and idle, as rpm gauge might be out

[jonnyshaw49]

hi messed with carb today , left mixture screw at 5 and half turns, lifted idle up to 1200 so didnt sound like its struggling, sat in the car and put my foot on the accelerator and the pick up on revs time was delayed like it hesitates worse, i noticed the more i wound the mixture screw in the better the hesitation problem became , but the idle became lumpier, so im stook between hesitation problem and lumpiness on idle, so going to have to wait untill new mixture screw arrives, now engine is running much better noticed a rattling over the gearbox side like clutch release bearing, so with engine running pressed clutch and the noise stopped and the engine idles slightly smoother as though the release bearing is not fully disengaging and making the engine work harder on idle.i replaced the clutch a few months before i took the car off road and the clutch was fine on the road. will it be just because its been stood a while in the garage? will it free up when i take it back on road or is it a gearbox out job??? i also had flywheel lightened and balanced, could it be this done wrongly and making a noise when engaging with clutch??

[Markey Mark (BD)]

Th rattle sounds like a release bearing, could of gone like that because it has sat around. Take it for a spin and see if it clears up or stays the same.

Best prob waiting for mixture screw and sticking that in before playing with carb, sounds like your almost there with it. Got mine sorted today, campus carb was doing same dribbling fuel down, abit of patience and playing with it got it sorted and its idling just below 1000rpm nicely now

[jonnyshaw49]

yeh ill do that wait for mixture screw and then have a mess, in that carb book i have it says gt turbo should idle between 700and 900 rpm but can see that happenin just by changing a mixture screw, but cud be wrong, i still think there might be something else wrong on carb as its still slightly lumpy but it could just be the mixture screw, thanks again for all ur advice its really helped mate, can get onto my next problem lol

[Markey Mark (BD)]

yeh ill do that wait for mixture screw and then have a mess, in that carb book i have it says gt turbo should idle between 700and 900 rpm but can see that happenin just by changing a mixture screw, but cud be wrong, i still think there might be something else wrong on carb as its still slightly lumpy but it could just be the mixture screw, thanks again for all ur advice its really helped mate, can get onto my next problem lol

If the seal on the mixture screw has worn away it can cause alot of prob's, almost like running a carb without one. If you've ever had one pop out it's impossible for the car to idle

[jonnyshaw49]

nah never had that happen so maybe could be all down to mixture screw so when it comes ill bang it in. i orderd it of ebay for 3.99 with 1.50 postage so 5.50 all together, its cheaper to buy at cgb but his postage is 8.00 on everything, is there anywhere cheaper if i ever need another???

[Markey Mark (BD)]

nah never had that happen so maybe could be all down to mixture screw so when it comes ill bang it in. i orderd it of ebay for 3.99 with 1.50 postage so 5.50 all together, its cheaper to buy at cgb but his postage is 8.00 on everything, is there anywhere cheaper if i ever need another???

Speak to Mike (phase 1 16v turbo), he deals with new and secondhand 5 gt spares he's your best bet, does good price's on parts and postage