Ok i got twin weber 45s on my golf, and i think they are overfueling. The engine idles ok, but when you put your foot down it is really hesitate to rev, so bad its undriveable atm, anyway so you put your foot on the throttle and if your keep going it clears after about 2.5k and revs ok. Also when you rev it from the throttle linkage under the bonnet it behaves the same, but you can observe fuel spraying out the trumpets as you rev and then when it gets past 2.5k this stops as if all the fuel is being sucked in. Ive checked timing etc and everything else is fine, im using a filter king with pressure gauge, is it possible that this is allowing to higher pressure to the carbs? what sort of pressure should the gauge read? Or is this more likely a carb setting up issue? Cheers James
Hi James There could be MANY things, or a combination of things causing the problem your describing. Could be the wrong idles, pumps, fuel pressure etc. First off, list yr engine spec and choke size, plus yr current jetting set up and we can go from there. What is your current fuel pressure ? You need a setting of around 3psi, a little more on a high output competition engine, but 3psi is more than enough for 90% of applications. Have you or anyone had the carbs apart ? the Auxillary vents could be in the wrong way around.
right ok, the engine 9a with kr cams, im afraid i dont know the spec on the carbs atm, i bought them already on the car, which i have receipts for being setup on a rolling road some time ago (therefore i hope the choke and jet sizes to be suitable). Is there anyway, other than dismanteling to discover this data? before i go down that path The car was running ok (still overfueling, but not impossible to drive) before recently, since then they have been fiddled with by myself and a friend, which has lead to the current situation . After your comment with regard to the appropriate fuel pressure, i can advise the pressure reading on the filter king gauge (presuming it is acurate) to be slightly over 12psi. This as i expected, after a comment from my friend, is rather excessive. Would, in your opinion, this cause a situation like what i am experencing? and does the filter king unit perform a function of pressure regulating prior to directing fuel to the carbs? Thanks in advance James
"12 psi".. bloody hell! Well you've found the start of yr problems!... yes, the filterking is also a regulator. Remove the domed nut on the top, that will give access to the adjustment screw. Crack off the locknut and turn the screw to bring the pressure down to 3psi, then lock up the nut. The choke size can be found by looking down the carbs, it's stamped into the bottom of the chokes. Try the above first. I can guide you through finding the jet numbers if you want to see what you have after.
Well i tried adjusting the filter king and it does nothing, so took it apart and its knackered, so new one of those me thinks first. Are they capable of reducing pressure from 12 to 3 psi? Will find out choke sizes and report back edit: chokes read 30 how do i find out the jet sizes? Thanks
yes , they'll actually stop fuel flow if wound back completely! We use one on a bike carbed engine , which needs even less pressure than Webers . The Jet sizes should be stamped onto them , but you may have to take them out to see.
No probs (as stated above) dropping the pressure with a filter king. 12psi is still a lot though, a facet red top competition pump only puts out about 8psi, what pump are you using? 30mm chokes are WAY too small, sure it say's 30 ? And are you sure they're 45's ? unusual to have a choke that small in a 45. It should have at least 34mm chokes with a basic spec 2ltr 16v, with carbs and exhaust. The jets are under the caps with the butterfly nuts on top. Take them out one at a time and make a note of the numbers. The long middle part with lots of holes is the emulsion tube, look for a number like F16, the jet in the top is the air corrector, it'll have something like 175 stamped around the edge, the tapered jet at the bottom of the tube is the main fuel jet, it'll be marked something like 140 on one of the flats sections. The shorter of the jets are the idles. look for a number like 50F8. There are two brass screws towards the butterfly (manifold) end of the carbs. In there you'll find the pump jets, stamped around the shoulder will be a number like 40, 45 or 50. be carefull not to loose the tiny ally washers at the bottom of the shoulder as you take them out, thay can be tight sometimes, try not to burr up the tips with pliers.
Ok so i got the numbers now, and you were completely right, the chokes say 36 not 30, anyway here goes. Weber 45DCOE Choke size = 36 Main jet size = tube F16 = tip 145 Idle jet = 9 6.5 Pump jet = 45 Got the new regulator on, preset at 3 psi im lead to believe. So how do those figures sound? Do they just need setting up or do jet need to be changed etc? Also should i attempt to set them up myself or get someone to do it for me. Oh and came across this page which was useful, expecially for the diagram, for anyone who is interested http://members.aol.com/dvandrews/webers.htm
Ah good. 36mm chokes are still a bit too big for your current spec (but far better than 30's), they would be good for a genuine 170hp, so will cope with a few more mods yet. As long as the jetting is close then they will be ok. I'd start with the following with 36mm chokes... 145 mains 185 air correctors F16 emulsion tubes 40 or 45 pumps 50F8 idle jets ...and work from there. Looking at what you have, it should'nt run too bad if tuned correctly. Have another look at your idle jets & the air correctors (the jet in the top of the emulsion tube) to get the numbers off them, and set up the idle mixture's and idle speed. Start the engine, turn each idle mixture screw (the ones with the little springs under them) fully in (one at a time) until it stops turning (dont force the screw, just use light finger pressure on a screwdriver), then back out 1/2 a turn at a time until the idle sounds at it's best/highest, keep turning until the idle speed drops off then go back to the point of best running. Do this with all four screws then go back over them again, turning 1/4-1/2 turn either side of the best point until you find THE best point again. Obviously you will have to adjust the idle speed as you do this until you have them running the best you can, then set the final idle speed. If the idle screws end up between around 1-2 full turns out, then the idle jet's ar'nt far off. Finer tuning from there comes from experience, but if you can achieve the above then it should be running well and drive ok. DONT presume the regulator is set at 3psi, I believe that is the standard setting but check it with a gauge... presumption is the mother of all f%$k up's !
Right the air correctors say 155 and the idle jets said 9 over 6.5 (i dont know if they are non weber jets, just a guess) but i did have some other jets the previous owner gave me so i put them in 60F9. Should i look to change the air correctors and idle jets to what you have suggested? will they make a noticable difference? Also i have got it all running now, tuned as best i could, as you described. It idles well and revs ok when not under load, but when put under load it dies. If i advance the timing it the throttle response is better but it over runs badly, you can just about drive it under load but not for long. I dont really no what to try now, i have changed the rotor arm and leads with spares i had, which makes no difference. James
Those air's will be a bit small, which will richen the mixture at high rpm. 60F9's are also rich, normally used in 1800-2ltr competition spec engines. 9 over 6.5 arnt Weber jets. Try turning the idle mixture screws right down (closed) and see if the engine speed drops/falters or even rises. If it does, adjust as I previously mentioned, though smaller adjustments, 1/4 turn out at a time and wait a few seconds for the engine to settle. I doubt they'll need to be out by much more than 1/2 a full turn or less on those jets. The engine also drives on the idle jets on light throttle, that's when their richness will show up. You really need to check/eliminate the fuel pressure, if the "new boy" has set up the regulator from the factory it could be miles out from the correct factory settings, remember what presumption is! Your at the stage with the carbs to get them on a good rolling road that KNOWS how to tune Webers. If they are good and do it regularly, they should have some idle jets & air correctors to try to get the set up correct. The first 3 things I'd check are the auxillary vents are the right way around (though if it was running fine before you fiddled you could ignore that for now), fuel pressure, smaller idle jets. Keep us posted.
Still cant get this running right, changed the idle jets and air correctors to the ones suggested, adjusted the fuel pressure to a true 3psi, but yet no joy. Even had a guy round the look at it and he left without fixing it and had no idea what was wrong. Advance the timing to get a nice idle, then rev it and the revs stick at that point, then climb, and wont return to idle until the ignition is switched off and on again. The throttle cable isnt sticking the carbs appear to be shutting off ok, the inlet cam is timed correctly, i have no idea what to try next. Its as if the carbs are sticking open, but as far as i can see (with them on the car) they shut off when tension is released from the throttle cable as they should.
Have you checked the float hights,needles and the needle rubbers , if they are set too high or are damaged and sunk the engine will over fuel and give the symptoms that you describe
No havent looked at them yet, and previously they had been running under high fuel pressure (12psi) i will have a look at this today. Edit: What needle valves and float spec should i have? Cheers James
Is it not overfueling anymore now then ? It now sounds like a classic case of poor throttle linkage. If the linkage is worn, the throttles will return to a different place each time, the non genuine linkages are favorite for this, the type with either a steel or cast base bracket, and steel or cast piviot arms. I've cured the above problem before by fitting genuine Weber throttle linkages which are much more positive in opperation and dont suffer with the sidways movement that the cheaper type do, even when not very old. The Weber linkages are around 90 quid (which is why many fit the cheaper type to begin with) but are adjustable, and fit/work superbly. If it's still overfuelling then check the floats/needle valves as suggested. The needle valve tip must be unworn, i.e no ridges on the tip, and need to be sized at 2.00 for your engine (stamped on the shoulder of the valve assembly). If you have the round brass floats, the gap between the float and the carb lid WITH the gasket fitted (so your measuring between float and gasket) should be 7.5mm when the tang of the float is JUST touching the needle valve.. hold the lid upright so the float swings to achieve this. With the float in full droop, the gap should be 15mm... carefully bend the floats and/tang to achieve this. If it's the later type square black plastic floats, the gap wit hte float tang just touching needs to be 12mm, again, with the gasket in place on the lid, and full droop needs to be 26mm measured at the far edge of the float (furtherist awat from the needle valve). What did you fiddle with if it was running well before... idle adjustments, linkage ?
Right ok so i have had (all be it limited) success today woohoo! So i messed about with the floats which were out a fair bit, and checked the needle valves which were fine. So the break through was achieved by dropping the throttle screw as low as possible without it stalling, idling about 500/600 rpm, then opening the idle screws suitably, then it seems to drive ok. Still feels as though its getting too much fuel between idle and low throttle (as it splutters and generally doesnt pull smooth), then once past that it revs freely. I have to admit the throttle linkage on there currently is seriously pony, and i will definately be saving up for a nice weber twin cable one soon, but im not convined this is entirely to blame. Any further suggestions? Thanks for the help from everyone so far, if it hadnt been for your help i think i may have pushed it into a field and thrown a match to it some time ago Cheers James
The throttle linkage can make a BIG difference, been there, done that. Glad to hear progress has been made.
Whats the difference between top mounted and bottom mounted linkages (other than visually)? and also i presume twin cable is better, is this correct? is there much difference that will be noticed (other than the price)? Also the linkage i have at the moment is single cable, is it difficult to change this to twin cable if this is the option i choose? Cheers
