Weird carb problem - cold start up

October 13, 2024, 01:33:34 PM

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

Re: Weird carb problem - cold start up

Reply #1 – November 04, 2024, 05:58:20 PM

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.