I venture to suggest that as changing the cold start thingy you mean the control pressure regulator often referred to as the warm up regulator that bolts to the inlet manifold. The cold start injector only runs for between 5 and fifteen seconds depending on the vagaries of the thrmo time switch so you could just do a simple continuity check to rule it out. Put a voltmeter acorss the two terminals in the plug for the 5th injector and turn the ignition on; you should get a reading of nominally 12v that will go to zero volts after a few seconds. That would indicate the the thermo time switch is timing out and interrupting the EARTH RETURN. It is failry important to note that the injector is permanently fed with 12v when the ign is on and the ciruit is broken when the timeswitch goes open circuit. If you establish that the thermo time switch is working properly then the only other enrichment device is via the control pressure regulator, where in a bi-metalic strip opens or occludes the two ports inside it and allows the control pressure from the top centre of the metering unit to be bled back to the fuel tank thus aallowing the metering plate to deflect further for a given flow of air thus richening the mixture. It is fairly easy to dismantle it and have a look inside its just a rubber seal on a plate that bends away from the sealing position when cold and fuel flows in through one port and out of the other. As igntion current warms the heating element around the bi-metalic strip, the strip straightens and the pports are sealed allowing the control pressure to rise and allow the metering plate or more correctly force the metering plate to operate within its normal range. The problem you have is that if the unit has gone defective and defaulted to the rich setting during the warmer months, someone may have meddled with the mixture via the adjusting screw in the metering unit in order to get reasonable fule economy, but this is more ooccam's razor the simplest solution iss usually the most common so rule out the thermotime switch dig deeper, and that's enough to be getting on with. come back to me if you get stuck I am the 924 tecchnical advisor.
