Club 80-90 Forums

Whilst doing the MOT the tester, old school, showed me the screen on his machine that tests emissions. On the only relevant test (Co2?) the maximum permissible figure was 4.0 something. Our camper was registering 0.2 something. He pointed this out and said it was obviously running lean. I should have paid more attention.

The DG engine and carb are 130k old and original, nothing has been touched for a long while, everything is working as it should and the old thing is as sprightly as ever. I am reluctant to upset anything and the Pierberg is unknown territory for me. I've wiggled the pipework and can see no splits etc.

Shall I leave everything well alone or is there a simple mixture screw on the carb somewhere? if so, please tell me where. 

Hi mate, 

I rebuilt my carb not that long ago, With the rebuild kit its rather simple and theres a good video on youtube to follow I've attached at the bottom, the same guy also does the assembly video else where. 

The mixture screw is rather easy to get to if you know where to put your screw driver as its towards the front on the right hand side as your looking at the engine from the back. The kits come with a replacement O ring for the screw too.



 

A couple of turns on the mixture screw will sort
That , go to the mot station and adjust it
On the machine to 3.5

Thanks all.

Regarding the mixture screw is it 'in' for leaner and 'out' for richer?

Too lean too much air ? Or possibly not running on all cylinders properly .

Running beautifully and no sign of any air leaks that I can find which is why I am reluctant to fiddle.

(If a Pierberg has butterfly spindles I suppose they could be worn after 130k and letting in air?)

Squirt some brake cleaner or WD40 on and around rather vac pipes and inlet manifold , if the revs rise there is a leak

The CO reading is NOT enough to tell the story.

Before doing any work on the fuel system, I advise you to go to a workshop or even the same MOT station and connect the car once more to the emission test.
Register the readings of the CO, CO2, HC, O2 and Lambda once for idling, and then once the engine is 30 second steady at 2,000-2,500 rpm. 
The combination of the readings will tell the whole story, and I will be happy to decode the information for you.

Oren

Many thanks for the suggestions. I will start by going over the pipework etc using the WD 40 trick to be followed by a visit to athe garage with the testing kit.

Three questions about the mixture screw:

Does the screw control air or fuel to adjust the mixture?

Is it 'in' for leaner and 'out' for richer or the other way round. (I have found the internet contradicts itself)

Am I right in thinking that it only affects the mixture at idle?