Engine cuts out (or tries to) when clutch pedal depressed

pip007 · Post by **pip007** » Thu May 19, 2011 10:09 pm

When slowing for corners and lights etc. (i.e., low revs), depressing the clutch pedal causes engine to cut out or try to cut out. Note: Just had major tune up, electronic ignition, valve clearances set, carbs (2 x Strombergs) sorted, the works. It is starting and running great except for this issue. Also note that car did this before the tune up. Any thoughts on the cause of this? Can I rectify it just by increasing idle speed?

ChrisC · Post by **ChrisC** » Fri May 20, 2011 7:09 am

there are a few things that can cause this and the more educated amongst us will I am sure correct me or come up with other ideas.

Given the work you have had carried out - I doubt it is an electrical ignition problem so personally I would first look for a vacuum leak which would be in the form of a loose or perished hose on any of the vacuum pipes - especially the one that connects to the inlet manifold. This causes the mixture to be overly weak at idle but I would have thought the tuner would have picked this up...

What I dont know is how you test for a tight vacuum seal other than your symptoms going away.

daverawle · Post by **daverawle** » Fri May 20, 2011 8:36 am

ChrisC wrote: What I dont know is how you test for a tight vacuum seal other than your symptoms going away.

Use a propane torch (unlit) in the area of the suspected leak.

Dave

ChrisC · Post by **ChrisC** » Fri May 20, 2011 8:50 am

Interesting idea... what is the concept behind doing that? Oh and thanks for the parcel Dave :)

daverawle · Post by **daverawle** » Fri May 20, 2011 9:01 am

If there is a leak the engine speed should increase when it 'sniffs' the propane.

Dave

chuffer · Post by **chuffer** » Fri May 20, 2011 10:54 am

Might this not be a mechanical issue? Pressing the clutch pedal down tries to drive the flywheel and crank assembly forward.

If a crank thrust washer is kaput, might the whole thing move forward and give these symptoms?

I've no experience of this, so hoping someone might confirm if this is a feasible theory.

Ray

Post by **Heuer** » Fri May 20, 2011 11:10 am

I had a similar problem which was down to spindle wear in the SU's. It was difficult to set the idle speed correctly as what worked while the car was static was undone when it was on the road because of vibration and movement. You say you have had the Stromberg's 'tuned up' but have they been professionally rebuilt?

pip007 · Post by **pip007** » Fri May 20, 2011 10:59 pm

Thanks guys. Carburetors were not fully rebuilt, but had gaskets, diaphragms replaced. However, there is does appear to be vacuum leak in one carburetor as idle speed increases when I spray ether towards the throttle valve spindle. I've increased the idle speed for the time being and that prevents it trying to stall, but will have my mechanic take another look at the carburetor. I'm trying not to invest too much in these Strombergs (have sunk at least $500 into them already) as I plan to fit triple carbs next year. Hopefully these will get me though the rest of this driving season.

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Engine cuts out (or tries to) when clutch pedal depressed

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