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Topic: Weird carb problem - cold start up (Read 209 times) previous topic - next topic

Weird carb problem - cold start up

Hi All,

I am hoping someone can point me in the right direction please with a fault that I have on my 1990 1.6 Driver with the Pierburg E2E carb.


When starting from cold, it starts immediately, RPM is 2000 for a second or two, then it drops to about 900 and it runs really roughly as if it is choked up. About a minute or two later when it has warmed slightly, it clears itself and runs smoothly again.

The choke plate moves ok.

Any ideas ?

Thanks
Richard
Golf Driver 1991 - 46,000 miles from new

Re: Weird carb problem - cold start up

Reply #1 –
Yeah, I do.  I had exactly this problem.
The choke is controlled by two things, an electrical connection and by coolant.  First thing to do, when the engine is cold is disconnect the wire that goes to the choke from the plug that comes from the thermoswitch (grey one I think), on the plastic housing in front of the head.  Switch the ignition on, you should get 12v.  If not, check the thermoswitch is getting 12v from the fuse box.  If your getting 12v from the fuse box but not after the thermoswitch the thermoswitch is knackered, and needs replaced.
Next check.  Use a multi meter to check continuity between the choke housing and the battery.  The choke housing screws into plastic, and there is a tiny wire to earth it.  If there is no continuity, create a new earth wire via one of the choke housing screws, back to an earth or a battery.  If you dont have a multi meter, remove the air box with the engine cold, put the ignition on but dont start it.  The choke should start to move within a minute.  If not the electrical connection is broken somewhere.  On my driver both the thermoswitch and earth were knackered.

Assuming the electric choke is working correctly, and it still has the problem, loosen the choke screws and back the choke off by rotating it.  I had to turn mine 10mm.  If I don't it runs too rich for about a few minutes.  Another thing I sometimes do is turn the ignition on for say ten seconds before starting it.  This gives the choke a chance to warm up a bit before starting.  As the Pierberg carb gets old it seems to need less choke than the factory setting, probably because the passages get a little worn with age.

Re: Weird carb problem - cold start up

Reply #2 –
Hi all,

Sorry it has taken so long to provide an update but I only managed to work out what the problem was today.

After checking the areas mnetioned by Keekster64 i didn't find anything wrong so I gave up on it for a while.

Today I thought I would have another go at it and eventually figured it must be the pull down unit. I checked the vaccum by disconnecting the top pipe on the unit and sucking on it and I could hear a hissing noise.

Turned out that the pipe going to the green vacuum resevior was split part way along beneath the brading. It was the only bit of pipe I didn't change when I swapped out the rubber vacuum pipes for silicone ones!



Golf Driver 1991 - 46,000 miles from new
 

Re: Weird carb problem - cold start up

Reply #3 –
Quote from: Lambo911 on
Hi all,

Sorry it has taken so long to provide an update but I only managed to work out what the problem was today.

After checking the areas mnetioned by Keekster64 i didn't find anything wrong so I gave up on it for a while.

Today I thought I would have another go at it and eventually figured it must be the pull down unit. I checked the vaccum by disconnecting the top pipe on the unit and sucking on it and I could hear a hissing noise.

Turned out that the pipe going to the green vacuum resevior was split part way along beneath the brading. It was the only bit of pipe I didn't change when I swapped out the rubber vacuum pipes for silicone ones!




Glad you got to the bottom of it.  So many hoses, its easy to miss a split.  The one part of the system I've never quite got my head round is the choke pull down unit, and how it relates to the rest of the system.  Fortunately its never given me a problem.  Thanks for the update.  Always good to hear how someone got on.  Hopefully you've got a better understanding of the carb now.  They look very confusing, but it is possible to get to know them