choke problem with Pierburg carb

[begemoth]

Hi,

I know there are quite a few threads about the Pierburg carb but I haven't found one which corresponds to the problem I have. Apologies if I missed something.

My camper is a 2.0 petrol with a Pierburg 2E carburetor. I've had the same issue on and off for a while now despite several visits to the garage. Here's what happens : if I drive the van for some time, especially in hot weather, stop for more than a few minutes then try to turn engine on again and it stalls as soon as I've driven it for more than a few meters. It starts again a couple of times until it simply won't fire at all. I have to wait the following day to get it started again. It doesn't do it if I stop for a shorter period of time.

From what I understand there is a flap activated by a coil. The coil is supposed to expand when the cooling liquid is hot but obviously the flap does not open as expected when the engine is hot. The only other thing I noticed is that the cooling level drops over time - I checked when I had the problem again on Sunday : the expansion tank was empty but the main one was only an inch to the top. As I mentioned the choke and its components have been checked by at least 3 garages, the plastic pipes connected to it have been changed.

Question #1 : can the cooling liquid situation explain the problem? It's not like the main reservoir is empty or anything

Question #2 : when we had the same problem on holiday, a garage in France attached the flap in open position. I had to rev the engine a bit to begin but it worked fine without the choke. Is it advisable not to use it in the long run?

Question #2 bis : how can I do so that the flap is always on or at least never completely closed?

Question #3: how can I troubleshoot the problem? Any steps I can follow to eliminate potential causes?

Thanks

[kevtherev]

Are we to assume you have actually looked at the choke flap while the engine warms up?

[kevtherev]

Q..1 no
Q..2 the bi metal spring that moves the flap is adjustable.
Q..3 firstly observe the flap during warm up.

In the warmer months the flap will not be fully closed on a stone cold engine. (maybe about 3/4)
It should take less than 6 mins to open fully.
Does the flap flop about or does it spring to the same place when cold

[begemoth]

Thanks Kev,

Here's how it looks when starting from cold

20160712_163225.jpg

and 6 minutes later

20160712_163809.jpg

no great difference as you can see.

It does not flap about and springs back to its position as far as I can tell.

Am I right in thinking that there such a thing as fast-idling? I think it does that even after 6 mins

[marlinowner]

When mine was playing up I just took the butterfly (flap) off with the two screws - don't drop them in though! Still started right through winter with a bit of throttle nursing. I also had it held open with a bent paperclip for a while.

[kevtherev]

OK
Let's do the simple stuff first
There's a choke heater, from the top of the auto choke housing, a black wire with a white connector, is this connected to a yellow connector?

[kevtherev]

And you can see here where it is
also the adjustment range

[kevtherev]

When the engine is running and cold this heater should be powered up, put a meter on the yellow connector it should have 12V

[kevtherev]

Removal of the housing (three screws) will show the dog that fits in the spring.
this mechanism should be free to move

[begemoth]

Thanks Kev and marlinowner. I will check the voltage tomorrow.

this mechanism should be free to move

are you suggesting that I remove the housing completely or just undo the screws and check that it rotates ok?

BTW Any reason not to do what marlinowner suggested and simply remove the flap?

[kevtherev]

You can do both.

[begemoth]

a black wire with a white connector, is this connected to a yellow connector?

a white one actually, see below

20160713_114838.jpg

I measured the voltage later on, not sure how to do it but I connected one lead of the meter to the inside of the connector and the other lead to the large metal structure that goes across underneath - the one you can see on the picture above with the number 025 129 713 A. It gave me all sorts of readings between 1 and 13 e.g 5, 7 etc.. in random order until it went to 0. I then checked the position of the butterfly and it was wide open. The whole thing took 2 mins max.

Does that sound normal - or rather - is it supposed to switch off after a while?

[kevtherev]

The inlet manifold is not the ideal earth just to the housing body would be better
The current should switch off at 67 deg.

.....I then checked the position of the butterfly and it was wide open.

So it is working now?
it didn't open in your last post

have you tried to remove the housing yet to see if everything is ok?
Leave the hoses in place, just undo the three screws and pull it away from the carb, make a note of the housing position for reassembly

[begemoth]

Thanks again for your help Kev, much appreciated.

So, I've just tried measuring the voltage again, this time connecting to the choke housing. From cold, turned the key to connect the battery but did not start the engine. Reading gave me 11 something briefly then I think I heard some sort of noise (coincidence perhaps) then 0. Tried again with engine on, this time it never left 0.

The flap was open as I described in my previous post but when I started the engine and pressed the pedal a couple of times it went back to its original position. I then let the engine run for a bit and the flap did not move at all.

I then managed to overcome my fears of doing something wrong and opened the choke housing. The coil looked nice and healthy and the cog on the receiving end was fine too. I moved it and could see the butterfly opening and shutting accordingly. All good.

Probably the overexcitment of having discovered something new but I then did something I perhaps should not have and pressed some sort of lever - see picture below.

20160714_180733.jpg

The flap was then wide open and I could not close it by moving the cog. I managed to put the choke housing back, Started the engine again, reved a bit and the flap went back to closed.

I think it was open last time because I had pushed that lever. I haven't seen the flap open up by itself at all when the engine was running.

Spoke to the mechanic who had fixed (or not) twice and he's adamant that he got it to work. Fact is that this problem's been bugging us for a year and keeps coming back. He also advised again removing the butterfly, I quote :

If you remove the choke flap completely, you stand a very good chance of it not starting at all from cold, or cranking of so long it kills the battery. Also, to stand any chance of starting, I will have to make the fuel mixture unreasonably rich. This will lead to dire fuel economy, polar bear slaughtering emissions and probably soot up your plugs and cylinder heads. I strongly advise against removing the choke flap or wedging it open.

Any thoughts? Thanks!

[begemoth]

Update : took the can to the garage and the mechanic could not find anything wrong with it ?!?! He suggested that maybe I had been accelerating too much on idle - and that's what flooded it. He also said that the flap should open only when we start pressing on the accelerator and not when idling.

I mentioned the dodgy voltage measurements - which he had not checked - and he thought that this could have something to do with the cut off valve. Does that sound plausible? Why would it not stall every time I'm idling then and not only when starting with a hot engine.

@kevtherev : what do you think?