1981 380SE hard starting

When cold (left over the night) my 380SE is very hard to start. It takes a lot of cranking and when it fires it does so only very poorly (requiring full trottle) for the first half minute or so.
When warm (that is, have been standing for an hour or so) it starts with the slightest touch of the starter and runs smoothly (I love that sound :-).
I'm guessing that the warm-up regulator may be at fault. Am I on the right track? Both the voltage to the regulator and the coil resistance within are within specs, though. Any other things I can check the warm-up regulator for?
Other probable casues of the hard starting? I've verified that there is sparks; there is gas spraying out the injectors; there is compression; and the cold-start valve is working for the specified couple of seconds at the current temperature (approx. +5C).
This problem appeared suddenly (would not start one cold February morning but ran fine the day before). The car has 450' km below the belt.
Other likely causes?
Thanks, pej
--
Per Erik Jorde

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It is most likely the warm up regulator. The bimetallic pin inside it will get out of whack over time. You can 'bend' it to the right position to correct the problem. It won't be accurate but enough to get started. Since at hot temperature, the warm up regulator simply shuts off.
If you open the bottom of the regulator, inside you will see a pin... you need some sort of reference so you know how much you bent... You only need to bend 1mm at a time... so from that reference mark you can calculate if it actually moved 1mm.
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Thanks for the suggestions. Greatly appreciated.
pej
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Per Erik Jorde

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