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I have an 1986 300e sedan, gas engine with 260,000 miles. Love the car, runs great, but doesn't like to start when the engine is warm (recently shut off, or even a few hours later). Let it sit over night and it start great when fully cold. I've run many tests and checks and can't quite figure out the problem. It appears to be too much air or not enough fuel on a warm start, too lean. I never smell fuel/flooding, the spark plugs are dry and never get any black clouds of exhaust when it starts. It appears to be too lean.

I've replace all the seals around the injectors as some were leaking air into the manifold. I don't seem to notice any other vacumm leaks. When it does start, it runs great. No hestitiation, great acceleration, great idle in all conditions wet or dry so I don't think I have problems with wires, distributer or plugs. Also rebuilt the head 6,000 miles ago (valve job and new headgasket) and have good compression across all 6.

So I start looking into fuel delivery. The fuel distributer has about 78 psi when running on both upper and lower chamber at idle (I converted all bar specs to psi). At 2500rpm's they are still both equal. I don't think this is right and maybe part of the problem. I though the pressures should be diffent at high rpm's. When shut off I did a leak down test and it held at 41psi for about 1 hour and beyond which is well within spec. I then check the injectors' release pressures and found 2 of tof them a little low (41 psi) so replaced them both. Now all 6 injectors release at 50 to 58psi which is within spec. I don't think I have a check valve problem, fuel pump or regulator problem as my running psi is good as well as the holding pressure after shutdown. I also checked the cold start injector and it appear to be ok. It gets 10.2 volts whle cranking, and only when cold. Has anyone ever come across something like this? Is this a common problem? Could there be something with the air flow sensor postion indicator?
 
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