PICT 34 - Engine Running Leam

[TakeLifeEasy]

To prevent the engine running too lean and reduce the air flow into a PICT 34 carb, do I just turn the volume screw anti clockwise?  How do I know when I have turned it enough?
Many thanks

 

[Resto-raider]

It's best to use a CO meter so you can tell exactly when it is running ok. It's not guess work.

 

[Trikky2]

To prevent the engine running too lean and reduce the air flow into a PICT 34 carb, do I just turn the volume screw anti clockwise?  How do I know when I have turned it enough?
Many thanks

Throttle butterfly itself should be closed at idle. The big screw is air. The little screw below it is fuel. Both work on the principal out is more, in is less.

Engine warm, ticking over, turn the small screw in until the engine slows. Then turn it out to get highest idle speed. If the idle speed is now too fast, turn the big one inwards to slow it down to the correct idle speed. Repeat the adjustment of the small screw again.

 

[TakeLifeEasy]

Many thanks all for the info, on Friday I will be taking it down to a friend of mine who owns a garage and can test it so will report back.

 

[TakeLifeEasy]

Just to conclude this post. I had the van rigged up to a C02 monitor at the local machanics on Friday and the van was indeed running lean and the carb is now balanced correctly or so we assume. It has been balanced with the C02 sitting between 1-2 on the computers reading Does anyone know if this is correct as I have not seen any reference to this parameter anywhere?

I need to give the van a bit of a blast to make sure all is OK but waiting for the rain to stop!

 

[Happystamps]

He's referring to CO, not CO2. It's measured in percentage, if you're only getting 1-2% CO2 then your engine would be DAMN inefficient!

(CO2 is given off during a complete burn, an incomplete burn gives off CO, O, & Hydrocarbons)

Personally I like to set mine a bit richer, usually just above 3%. You might be OK, but listen out for any rattling noises like loose tin when you're hot & going uphill. Any of that, kill your engine before it kills itself and richen it up a bit (assuming your timing isn't completely ******).

 

[TakeLifeEasy]

Happystamps many thanks for the info. Just taken the van for a run and here are my observations -

1). Engine fired up quickly but a little sluggish on tickover once it started / before it was warm. Engine ticked over lovely once warm.

2). A little hesitate pulling away in first gear and needed a few more revs than I normally use to move the van. Nothing much just a little loss of power.

3). Runs great going through the gears and at cruising speeds.

4) After I got back, I noticed condensation on the pipe the carb sits on, it was cold to touch. I have never looked for this before so maybe it has always been like that? I only ran if for about 15 minutes so maybe this condensation gets burnt off as the whole engine bay warms up. https://drive.google.com/file/d/0B5usV8coTRBAcnlfbTlRWFpkY0k/edit?usp=sharing" onclick="window.open(this.href);return false;

The only thing that was changed on Friday was that the machanic noticed air being sucked from the inlet pipe on the carb at the front yet there was no pipe connected on that (it does now have the vaum pipe connected. https://drive.google.com/file/d/0B5usV8coTRBARXhOTC1PS3dGWnc/edit?usp=sharing" onclick="window.open(this.href);return false;
It didn't before Friday). He also noticed that the vacuum pipe from the distributor was connected to the inlet pipe on the left of the carb (just behind the spring) yet there was no suction coming from that pipe. He has blocked it off but there is no suction coming from it. Once he put the vacuum pipe as shown in the picture the engine immediately changed its idle speed down from racing ahead to a steady idle. Is this connected correctly?

Again, many thanks for everyone's help.

 

[Trikky2]

Vac pipe facing you on the carb is for operating warm/cool air inlet flap on the air cleaner (if you have the model that uses vac) or the Retard part of the twin vac unit on the dissy (if you have that type of twin vac canisters).

If you have neither of these on your bus then this vac port on the carb should be blocked off - eg not used but also not left open.

The vac signal to operate the vac advance on the dissy comes from the tube on the left of the carb - not the one on the rear facing you.

This correct port will Only provide vac at light throttle and None at tickover.

 

[TakeLifeEasy]

Trickky2, thanks for the reply so it was connected properly in the first place with the exception that there was nothing blocking off the one facing me ( warm/cool air inlet flap on the air cleaner). Now, if put it VAC pipe back on the vac signal pipe and block off the one facing me, will I need to setup the carb all over again or are the 2 things not related?

Many thanks for your help, this carb will be the death of me!

 

[Trikky2]

Yes you will need to repeat the setting up of the carb, because if that rear pipe is not blocked off, it will leak air into the carb, which will cause it to tick over faster and leaner than it should.

Hence now, with it blocked off correctly, you will likely find the tickover too slow and too rich.

 

[TakeLifeEasy]

OK thanks. I will pop down the mechanics early this week, put the pipe back on the side of the carb and block off the front inlet and ask him to setup the mixture again. So am I looking for him to set CO to about 2-3% ?

 

[Trikky2]

OK thanks. I will pop down the mechanics early this week, put the pipe back on the side of the carb and block off the front inlet and ask him to setup the mixture again. So am I looking for him to set CO to about 2-3% ?

I set these the way I described in my earlier post :lol:

 

[Resto-raider]

Between 3% and 4% would be good, that's how we do it.

 

[TakeLifeEasy]

Right, got back from work, put the pipe from the distributor back onto the inlet on the left of the carb (vac signal to operate the vac advance) and blocked off the one facing me (operating warm/cool air inlet flap on the air cleaner). Thanks to Trikky2 for putting me back on track ;-) I also noticed the new fan belt I fitted last week had loosened off a bit so I tightened that up. I then checked the points all OK and then the timing which was out. Reset the timing and then gave the van a spin and it seems to be running a lot better. The only thing I am now noticing is that I need to give it a bit more throttle than I used to when starting off in first gear. If I don't, there is a bit of a hesitation. Moving through all the other gears seems fine and it appears to be picking up nicely. Fingers crossed all is now OK however, I will give it a much longer run this weekend to double check everything.

Many thanks for everyone's help on this, it is VERY much appreciated. I am gaining some knowledge but I still have a lot to learn. The good thing about when things go wrong, I learn quickly!!!!