I'm having trouble starting 88 300E. When it does it dies, sometimes restarts sometimes doesn't, wont stay running. I've replaced plugs , rotor.Any ideas ? Car was running til recently-how to troubleshoot possible probs. fuel,sensors, elec. Thoughts apprieciated Thanx MP

Coil could be bad, OVP is a good bet and then O2 sensor then adjust duty cycle.

o2 sensor has nothing whatsoever to do with starting.
Gilly

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Did you replace the distributor cap while you did the rotor? Its time to start troubleshooting...make sure that the wires are all in good condition, that there is no arcing ANYwhere (coil too). How long will it run until it dies? Few seconds? Whole trip? It could be a lot of things...sounds electrical if it is that intermittent (fuel pump relay perhaps?).

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TC
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Also, get out your ohm meter and check the crank position sensor. [coax connection on the EZL box near the coil. Pull it off and check the resistance between the outer ring and the center contact.]

The normal range is about 700 to 1600 ohms.

Mine failed, and the resistance was 30 ohms.

On that car, the resistance spec for the CPS is 680-1200 Ohms. Along with the fuel pump relay, OVP and ignition wires, that would be a good place to start some troubleshooting, and it couldn't be an easier DIY project. Can be done in less than 15 minutes.

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Past Mercedes-Benz:
1986 190E Baby Benz
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I vote the OVP as a starting point.

This will cause hard cold starts. Low cold idles, and possibly bogging / missing when cold.

It can also cause a high idle - 1200 rpm when hot.

Try giving the OVP a wack and see if it makes a difference - the only real way to see is to swap it. Very common.