Hi, I have a Weber DGAV on a 2lt type 4 that is all new and the throttle doesn't quite close 100% which is causing the idle to run too fast. I think the mechanism might have been assembled too tightly as there is slack in the cable and the spring is tight, is that possible? Does anyone have the instructions that would have come with this kit as it was fitted by the PO. Thanks Mark
There is a cold idle adjustment screw behind the choke heater capsule that sits on a stepped cam when it's cold. This screw is linked to the wire coming down to the throttle shaft. It's meant to keep the throttle slightly open on a cold start. Only when the choke has opened up a bit does the throttle drop back onto the end stop screw you can clearly see. So my engine idles at 1600 rpm on cold start but drops back to 800-900rpm within about 30 seconds when you press on the throttle. There is a little bit of metal that you can push gently up on behind the choke capsule that rotates the cam and the cold idle screw will hop off and the throttle will drop back onto the warmed up endstop.. but if the engine is cold it will then try to idle really slowly..
Thanks both, it's not the cold idle as ironically it idles well from cold but when warm the throttle isn't closing fully. It's also not any type of adjustment as if I push on the throttle mechanism it closes that final mm or so and the idle settles to what it should be. I'm well aware of that article and have first hand experience of how bad these carbs are without any heat in winter. I would like to move to dual carbs but that is an expense that has to wait Thanks Mark Sent from my SM-S901B using Tapatalk
You have a T4 so what you need is to put a spring in line with the accelerator cable to help pull it shut. The cold start linkage is sloppy and can get sticky so what you describe can still be due to stickiness in that region - if it closes properly if you disconnect the wire then its somewhere in the cold idle linkage.. The cold idle screw was catching on the hose clip on the vacuum takeoff for the distributor advance on mine. Don't put a spring at an angle to the line of the cable, or it wears the carburettor body which is the bearing (no bushing..it was made cheap for Ford) for the throttle shaft. Then the butterfly catches because the butterfly isn't in the middle of the bore of the carburettor any more. That's what happens on a T1 especially where the spring goes "uphill" from the line of the throttle cable. Also without a Buttys bits linkage your throttle probably doesn't open 100% as the travel from the pedal end (17mm) is less than the travel for wide open (22mm) at the carburettor.
Theres one quite strong spring round the throttle shaft, the fitting kits provide another straight spring. Springs pulling off-line need to be stronger and wear it out faster. Check throttle cable has no kinks as the Kinks don't help the cable returning. Also the spring under the accelerator pedal has a tiny part to play..
I didnt start on whether the carburettor is any good for the T4, as the PO already wants to change: - you can make up hot air feeds for it for a T4 to improve it, but it will always lurch and stutter and waste fuel. And when people flog off progressive carburettors that are little used because their bus runs like rubbish so doesnt get used, I get a 1985 vintage carburettor with a little corrosion but no wear off eBay for £21, to replace one I wore out after 90000 miles on a T1.
Thanks, the choke sticking is something to investigate. I do have a strong spring pulling parallel to the cable but this doesn't seem to be enough. I have already bought a buttys throttle kit as I couldn't believe how terrible the standard one is but not fitted it yet. Once I get these problems solved I will take it to a rolling road as power-wise it pulls really well (I have 1600 EB and its a huge difference) but the exhaust is too sooty and fuel economy shocking. Again it'n destined for the bin at some point but not yet.
They have to go on sideways I suppose to get the fuel to try to go equally down front and rear intakes.. . Or disconnect the linkage on the second barrel and pretend it's a pair of Weber ICT32's with functional chokes... hmm...
Be interesting to look to set up. Ones I saw were actually on downdraft manifolds but I always wondered whether you could use shortened versions of the normal set up with the relevant holes blocked off. Be fun to try!
About time I followed up on this, got a Butty bits accelerator kit on now and I don't seem to be getting the sticky throttle but I don't know what has changed to fix this. I had a rolling road session yesterday, Interestingly she made 65BHP which according to the book should be 70BHP so not too bad. The jets were 130 and 137 and it's now on 120 & 120. It's reduced the real richness when the second butterfly opens but I think it's struggling too much at very low revs and small throttle openings, not driven more than 3 or 4 miles yet but tomorrow I will know more as I have a couple of 30 min journey's to make. The RR operator had a lambda sensor shoved into the exhaust pipe and it was far too rich all over on the previous jets, when the second jet came in there was a puff of black smoke so it was much improved on the changes and he felt it was probably as good as it was going to get but suggested I drive around and see how it feels. I've read plenty about how rubbish these carbs are in this scenario so I'm assuming the cold air this morning is highlighting the problem as well?
Fair point but it's wasting so much money on fuel and the missus who's truck it is doesn't want to fork out several hundred more for at best a set of used carbs that then probably need more money spending and an RR session to be jetted correctly when ultimately it runs fine, just not as smoothly as I would like it.
Got to be one or the other! Throwing good money after bad? I understand what you're saying, I just think the sooner you realise that carb is just not ever going to run nicely without being too rich the less money you'll have wasted finding that out for yourself. I'm no better really, my first bus cost me £3.5K, I then spent another £3.5k on it before I faced the fact that it was always going to be minging and sold it for £700. lol ouch, but I don't regret it despite the huge loss.
I think @Zed speaks the truth. You'll spend the rest of your days trying to get the Weber working properly.
More hot air and manifold heating needed for a centremount carburettor... which isnt there on a T4. And the compensation for that is the wasting fuel. Visible smoke is really wasting fuel, and it will be losing power too.. At the transition, for a while its running on the primary main and secondary idle jet, then the secondary main eventually cuts in, so that secondary idle needs to be treated as a sort of main jet too. Should have bought dual Webers with some of the RR money and paid for it with the additional MPG.. I am just about OK on a T1 with this carburettor but it took a lot of experimentation with a permanent AFR meter and all the stock hot air and manifold heating in place.
