E320 Starting Problem

I have intermittent starting problems on my 96 E320. I've replaced about everything that I can think of, from the coils, plugs, computer, fuel filter, sensors, etc..
Does anyone think this could be fuel injectors? I turn the key, and sometimes it starts fine, other times (same day), it takes a while, I hear a "chunk", then it starts.
How about the starter? Can the starter be causing this? I have always known the symptoms of a starter was that the engine wouldn't turn over at all.
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If it cranks and starts easily when the motor is cold vs. after 5 miles of driving the starter or an injector is suspect. My '97 E320 had a delayed hot start from a leaking injector - but it always started - and started perfectly when cold.
If it refuses to crank at all then the starter is the prime suspect.
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First of all... stop spending needless money. Explain in more detail of what kind of problem you are having.... especially if engine is hot or cold... first thing in the morining or not... when things happens...
I am thinking either of the two things... but I need to know more...
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The reason I am just sort of guessing is because no one I have discussed this with (mechanics) can help me out. It usually starts when cold, but not all the time. It will eventually start, but could take 5 to 10 tries. It always cranks. Sometimes it has left me stranded, and I would tow it to a shop, and it starts everytime. The fact that it is so intermittent is the toughest problem to diagnose. The symptom I hear is a clunk sound when it cranks, then right after that sound it starts.
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A clunk sound when the starter is cranking suggests the starter or its solenoid are prime suspects. But since it always cranks I suggest you first check something else ... this really happened to my '97 E320.
I bought a new battery and installed it. About nine months later the engine cranked fine but failed to start. First time in ten years that it didn't start. Turned out that the new battery had leaked acid into the + terminal post to such a degree that the bolt that clamped the electric fuel pump wire had been totally corroded away and the fuel pump's power wire(s) had fallen off the + battery terminal! No fuel pump = no fuel.
I replaced the leaking battery, bought a new 6mm bolt & nut and all was fine again.
P.S. The battery is under the back bench seat, on the right side.
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I would agree with TG... battery is primary suspect. If it is old, replace it. Save some money and buy Autozone battery... great price with great and easy warranty. If you are positive that battery is good, by doing a free battery test at Autozone... then go to second paragraph.
If the issue is still there, then I would say crank position sensor is bad. This would cause non-starting condition and is baffling... sometime it works and sometime it doesn't plus it test out okay physically until you replace it with a new one.
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Was the 96 still plagued with the electric Harness and OVP problems?
I just rebuilt most of the harness for my 1994 E320 and it made a huge difference.
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I am not sure... but I don't think they are plagued with those "green" wire insulation that rapidly deteriorates..
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Anyway, things to look for are: - fuel pressure - listen if fuel pumps spin just after turning the key - ignition - see if you have a clear spark - intake manifold vacuum - look for leaks, try to disconnect vacuum lines from manifold one by one and block the "hole" - temperature and other sensors - see if all are connected correctly
If still no result from these simple tests, have a diagnostics readout to direct you to the fault, before you start looking towards injectors etc.
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The car has 205k miles, and it has been acting up this way for about 40k miles. That's how intermittent it has been. Looking back at my records, I replaced the crankshaft positioning sensor at 170k, new battery and alternator at 200k. Nothing comes up on a diagnostic readout. I'll check the + terminal on the battery, but I do hear the fuel pump everytime I go to start it. New plugs about 2 months ago.
Thanks for all the responses.
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wild guess (because you've provide sparse description of ailment and symptoms) is that the crankcase position sensor (search CPS) is the cause. this is one of the oft described problems with the w210s. try going to the various MB forums e.g. benzworld.org, mbworld.org, and mercedesshop.com and search under w210 forum, or tech forums. see if the unpredictability of the no-start resembles your observation.
next time, be more clear, specific, and factual about the conditions leading to the problem.
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" crankcase position sensor (search CPS) "
correction: make that CRANKSHAFT position sensor.
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