I have never worked on a 5.0, but I assume it is like the 4.5.

First of all, this is K-Jet, not D-Jet, so don't go looking for trigger points.

The car is starting better when it's cold because the cold start valve starts to fire at 15 deg C. So you are getting a shot of gas to get it going, but that only lasts for a second or so at 40 degress F, and then the mix is too lean to stay running. So the good news is that the valve and the relay are probably OK.

There are three things to check. First, the warm-up compensator richens the mix at low temps. Unplug it and put a voltmeter on the contacts on the wire and make sure you are getting 12V to it. Measure the resistance on the unit, and make sure you don't have an open circuit.

Next is the auxiliary air valve. It bolts to the water jacket and allows extra air during warm-up, which raises the idle. As the coolant warms, it slows down and eventually closes and the idle air valve supplies all the air. So if the idle isn't up over 1000 RPM, this may be the problem. You can try some PB Blaster - it may be stuck shut.

Last is the basic mixture. If it is really lean, the engine simply won't run when cold. You might also have crud in the fuel distributor in ijectors, making the mixture lean. Go no more than a 1/4 turn clockwise and see if that helps. If it doesn't, put it back.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe