Cold start device testing
 

Hi All,
I'm trying to test the cold start device on my 71 911E. It has MFi and just the last couple of days it's been difficult to start. I pulled the pipe between the air filter and the cold start pump that sits atop the fuel filter to see if there was a squirt of fuel when it's cranked, nothing. I put a multimeter on the power supply expecting to see a momentary feed of power when the engine is cranked and nothing. I checked the fuses, but there's no mention of this device and all fuses appear to be OK. Anyone know how I can test it?

Thanks in advance

I think the throttle needs to be off the idle micro-switch to make the cold start injector work. Do you have power up to that micro-switch?

Check your thermotime switch.
Situated right side top of engine casing under air filter housing.

The micro switch does not really have any effect if you have the lever to the left of handbrake operated (which you should for a cold start) as it ops the throttle linkages.

Check the diag, but from memory it's 12v yellow that starts the op of the switch, it sends a ground. If you get the 12v...pull off the yellow you should get a 75 ohm ground on that pin of the switch.

You are pulling up the throttle lever, right?

Hi Guys, thanks for the replies. I actually found the problem, it was the other end of the wire that feeds the little pump that squirts fuel in thru the air cleaner. At the 16 pin plug just below the cdi box it wasn't making a good connection and therefore not sqirting. Cleaned it up and it now works fine.

Thanks for the help.

Something else, strangely, I don't have the microswitch fitted to my throttle linkage. Is this unusual or did the setup change for the 71 year models?

All MFI cars should have the microswitch. It is an intergral part of the fuel delivery system. Main function is to activate a soleniod on the MFI via a RPM transducer which senses dropping RPMs above 1300 RPM and shuts off the fuel. This prevents the car from getting fuel when it doesn't need it, on de-acceleration thus avoiding the brubely back fire when you are off the throttle and the car is slowing down or shifting. Hope this helps, Allan