Section : Carburettors

Diaphragm or not diaphragm? 

Posted By : Andrew Booth, 09-Apr-2004, 05:16pm

My Vitesse is not running smoothly despite an engine tune-up. It coughs and splutters under heavy acceleration. The problem is helped a little by pulling out the choke.

I've been told that it could be the diaphragm in the Strombergs, so I had a look. Both diaphragms appear to be intact ie no holes or obvious major splits.

Is there anything else that can go wrong with them? Could it be am invisible micro-hole??

• Diaphragm or not diaphragm? 

  Posted By : Jonathan Galling, 10-Apr-2004, 08:42pm

  Andrew.
  
  Just replaced mine after lengthy discussion with father-in-law who was in the trade in the 60-70's. He (at length and in great detail) explained that it's the key component in the carb, and hence might be your problem. I think mine were only a couple of &163;, but what a difference, much smoother and quicker pick-up. I couldn't see any obvious defects but as I've only recently bought the car (January), don't know when this was last done.
  
  He also had a 'fiddle' with the distributor. That was more to do with the 'run on' I had when turning off the ignition. That's stopped now too! Can't hurt changing the diaphragms, even if it's a process of elimination?
  
  Jonathan.

  • Diaphragm or not diaphragm? 

    Posted By : Andrew Booth, 15-May-2004, 03:01pm

    Well, replaced the diaphragms, and so far no change. Have replaced plugs, leads, dizzy cap, rotor arm, condensor, points and coil. No change. Compression test is ok. Pistons in the carbs are no stuck.
    
    Off to a rolling road to see what happens!

    • Diaphragm or not diaphragm? 

      Posted By : Andrew Booth, 07-Jun-2004, 11:39am

      Rolling Road tuneup highly reccomended. I was only getting 20bhp at the weels to start with, now I'm getting 80 at the wheels and she flies like a rocket!
      
      The engineer at Motoscope in Northallerton ( http://www.motoscope.co.uk/ ) advised me that there was a series of little things that were all contributing to the misfire, including: gasket between air box and carb was on upside down (doh!); timing - was advancing 60 degrees when it shouldn't have been; fuel startvation caused by fuel pump full of crud