Lack of power - despite adjusting fuel mix

[Rhodierider]

I recently took apart and cleaned / fitted new gaskets my twin solex 34-PDSIT-2/3 carbs on a type 4 engine. Power was never good previously, but since refitting them, I've got very little power (can't get over 45mph on the flat). I've taken the van to a garage to adjust the carbs, but despite the owner saying he'd worked on van carbs before - he said no adjusting he did seemed to have much effect. I've tried different mixes from clearly way too lean out to too rich, but nothing seems to improve it vastly. I know enough fuel is getting to the carbs through the regulator and I've blown compressed air through all of the nozzles/pipes internally. The fuel and idle cut off valves are all tested and working fine too. The garage also fitted new points for me. Timing hasn't been checked, but hasn't been adjusted since prior to stripping the carbs.
The symptons are very little acceleration and a real struggle to get any revs up in 4th. Strangely though when I come to a stop (eg at a give way), acceleration away from the stop seems to be fine which leaves me thinking there's nothing wrong with engine itself.

I'm sure the answer is get it to a VW experienced garage on a rolling road, but if anyone's got any likely suggestions, I'd appreciate it. Also if anyone know's of a decent garage in the Biggin Hill, Kent area, I'd also appreciate it!!

Cheers in advance!

 

[Clarkson46]

The only adjustment for mixture is at idle only and will have no effect at higher revs. If you are lacking power and assuming that the carbs are clean and have no leaks on the manifolds, I would start by checking ignition, points condensor, then reset the timing, the tappets, and check the compression in that order.

 

[Dave105]

just a thought but did you check the accelerator pump delevery volume? cant quite remember what it should be but you adjust it by moving the pin(or adjusting the screw, depends which year) to get the correct volume.
What dizzy have you got and have you had any problems in setting the idle speed using the central idle thingy?

did you do the whole bently/ratwell balancing thing with an airflow meter? they really need to be balanced first otherwise they will end up fighting each other!

had mine rebuilt then had to get a new dizzy and now im learning loads about theses little blighters let me know how you get on might be useful
Dave

 

[Rhodierider]

Thanks guys, I've checked the compression and adjusted all tappets for clearannce. The dizzy's a 009 - but I'm still confused as to why I'm getting far less power than prior to stripping the carbs. When they were stripped I didn't adjust anything to do with the balancing so hopefully they're still roughly there. I think I'm going to have to get it in to a garage to be balanced and set properly!

 

[stagger lee]

if the carbs are significantly off-balance, they won't rev clean from idle. one side'll get fuel momentarily before the other, so it'll be lumpy revving untill the other side catches up. and negligable unbalance, will be just that, negligable.

sounds like, but offcourse may not be a 'baggy' accelerator cable? not been mentioned and maybe obvious, but is the accelerator cable adjusted correctly?

the carbs not opening fully will be fine in low gears, where you don't need as much throttle to get going. but in higher gears it'll be really noticable. driven numerous vans with this issue and your synptoms are identical?

also only firing on three cylinders can do pretty much the same. depending on which cylinder is not firing the engine can start, idles and revs quite freely. like it's normal, but it simply lacks power, but through all the gears.

anyway, food for thought?

good luck with it all.

 

[matt-me]

I agree with stagger lee, check the accelerator cable. I had similar issues, did all the normal checks first, would double check your timing, as mine seemed to somehow get affetected even though i hadn't really touched it.

What i did find; got my son to put his foot on the accelerator full on (engine not on) and still had about a quarter of travel to go at the carb linkage. I have twin ICT's. The arm the cable connects to happens to have three positions, my cable was connected to the outermost point, so i moved it to the middle, inner point. The result being the same push on the accelerator now moves the arm more (cos its a smaller radius) and it opens the carbs up almost the full way. Massive difference, as SL says, more petrol especially needed at higher revs.

A specialist told me something like the way my carbs work, 50% of power comes in the last 25% opening, something like that anyway. Hope that makes sense, am not a mechanic.

 

[Nic B-C]

The only adjustment for mixture is at idle only and will have no effect at higher revs. If you are lacking power and assuming that the carbs are clean and have no leaks on the manifolds, I would start by checking ignition, points condensor, then reset the timing, the tappets, and check the compression in that order.

I would check compression first, then work your way back through electrics.

If none of this seems to be at fault then adjust rockers and thenset carbs at base settings then you are ready to do timing, no point in doing timing till everything else is set as you will simply have to do it all again

 

[Clarkson46]

I usually get all sorts of comments, but I would ditch the 009 and return to a stock svda dissy and then see if you have any problems.

 

[Nic B-C]

No point ditching it if advancing fine which you can check with a gun.

Only trouble you may have with a 009 is a dead spot but shouldnt notice it on twin carbs

 

[Dave105]

009's dont work with twin PDSIT set up. The central idle system will struggle to controll the idle speed and you will have a lot more than a "flat spot". But saying all that I dont see how it can be your dizzy if it was working before your carb overhaul it should still be working now.
Twin carbs dont really need a lot of setting up, balance them at idle and at 3000rpm. do the soloanoid on off trick and adjust mixture screws untill both carbs idle at about 500 to 800 rpm (idle solanoid off) then reconnect idle system and fiddle with mixture and airscrews untill you get 800 to 1000 rpm (which you might be struggling with a 009, I know i was)

one other thing make sure that bothe carbs are opening at the same time i.e. balanced throttle linkage.

have you checked fuel flow/pressure to both carbs? are your filters clogged?

good luck

 

[Rhodierider]

Thanks all for the replies and sorry for not replying sooner. I've been tied up with work and haven't had any time on the van, but when I get a chance I'll take on board everyone's suggestions.