Make sure your belt is not too tight. I had the same problem a day back, just felt like my belt was loose and I tightened it (on 87 260E). The next thing I knew was it had starting problems that I never ever had. I also had put some engine degreaser and some water to clean the engine's front area. So I thought it was water and I can wait a few hours and it will start fine. Infact, it did start couple of times fine the next day (today) but then failed to start again. I figured it had to be the tightened belt. So I loosened it a bit and guess what, the car started just fine, several times. I am not sure what the reason is but a belt which is tighter than needed causes starting problems.

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Saumil S. Patel