2000 MB C280 Crank but won't start, crankshaft issue?

Maintenance/Repairs
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It was on a very warm day back in April that I drove my 2000 MB C280, it ran smooth and well (it has around 116,000 miles and well-maintained). After a few errands I stop to shop at a store for about 1/2 hour, after I came out it won’t start. Just crank but won’t start. Had it tow to my local mechanic, by the time he look at it, it started with no issue, and there was no error code when he plugged in the computer scanner. Mechanic told me it’s either the crankshaft sensor or fuel pump.

The car ran fine since. Then on 6/29, another hot day, it won’t start again after I have driven it for a while and stopped at library for about 15 minutes. Same thing, crank but won’t start. I kept trying every minutes or so, after about 10 minutes it started again.

Both times happened on very warm/hot day. I have spent so much on getting it up and running after 2 years of not driving it (2012 to 2014), not feeling like playing guessing game to replace one thing and turned out to be another. Is it fuel pump or crankshaft sensor?

Thanks.

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Anytime I hear a crank but no start condition on any vehicle, the first thing I suspect is a faulty crankshaft position sensor.

https://www.rockauto.com/en/catalog/mercedes-benz,2000,c280,2.8l+v6,1363801,ignition,crankshaft+position+sensor,7196

Tester

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If the fuel pump is on its last legs, when the car refuses to start, listen for a slight hum from the rear of the car when you turn the key to the “run” position but turning the key to “crank” . If you don’t hear the hum, the fuel pump is likely failing. A light tap with a hammer or the “bump” caused when towing the car can sometimes get it running again.

Either way, if it were my car, I’d replace both. At 116K miles, the fuel pump likely doesn’t have much life left nor has the crankshaft position sensor and either will cause a no-start and a tow.

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Based on my professional experience . . . including as a former Benz dealer mechanic . . . it’s far more likely the crankshaft position sensor

Replace it and be done with it

For what it’s worth, probably 1/2 of the faulty crankshaft position sensors I’ve replaced never generated any kind of fault codes

Once you’ve replaced the sensor, you can measure the resistance of the old one. I wouldn’t be surprised if it in fact has several mega ohms of resistance. The spec is 700 - 1400 ohms, by the way.

And crankshaft position sensors that are on the way out, so to speak, often really act up on hot days.

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It’s definitely possible to test each one, independent of the other. But doing that may take quite a few diagnostic hours, and may require removing them, with the associated hourly labor fee. A compromise play that might be more gentle on your wallet – if the problem can’t be repeated at the shop – might be to do a basic fuel pressure test, and if that passes replace the crank position sensor. If the problem can be repeated at the shop, first thing to do is a spark test.

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Thanks. Had a panic for a day, the mechanic was given a wrong part (something about my car year was a split year), told me crankshaft sensor was changed and didn’t help. Then he called me the next morning said it was the crankshaft sensor just that he was provided with the wrong one.

Bottom line, it worked and car is running beautifully again. But now I have another issue, someone broke my rearview mirror.

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Yup . . . for that engine, there are 2 different crankshaft position sensors, depending on the production date

You have to verify which version you have before buying the new part

The wrong one will bolt up to the engine, but the electrical connector won’t plug in, as your mechanic probably found out

As far as the mirror goes . . . exterior mirror, I presume . . . they are VERY expensive. Insanely expensive, actually.

Is it just the plastic cover that’s broken, or is it the actual mechanism.

On this model, you buy the plastic cover separately from the mirror assembly.

You have to remove the plastic before you can unbolt the mirror from the door.

Please post a picture

It might be worth it to buy used, depending on what’s broken, but even the used mirrors are often damaged.

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Thank you. It’s the mirror piece, not the housing/ cover.
Since it does not bend, no springs, someone pushed hard and broke the connecting plastic connector from mirror to the base. So far, I can’t find used, only eBay from $449 to $505 (if I have the right part number, still trying to verify). Dealer quoted me $650 3 years ago (it was broken by someone 3 years ago as well).

left%20mirror
left mirror.JPG420×538 22.1 KB
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Yup, they’re insanely expensive, aren’t they?

Any chance of finding a used mirror at a “pick a part” type of junkyard?

I seem to remember that some E-class sedans also used the same mirror . . . perhaps 1996 - 1999

I read your other post, as well

Fwiw, I wouldn’t necessarily be so quick to get rid of the car

If it’s structurally sound and has been well maintained, it might be worth hanging onto

We have a 1999 C280 ourselves. The clearcoat is all but gone, but the car is in good mechanical shape and I’ve maintained it well over the years. I drive it every other week. It always passes smog with flying colors, and I have no intention of getting rid of it anytime soon. I’ve invested several hundred dollars in maintenance and/or repairs the last few years, to ensure its suitability for everyday use.

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Any chance of just repairing it?

Some JB Weld perhaps, or a piece of sheet metal screwed to the pieces.

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They are, after few hours of searching found $330-$350 to be the cheapest.

Car is well maintained inside out. detail 2x a year. Most people can not believe the car is a 2000 year model. I did spent $10K+ since 2010 for repairs/replacement here and there LOL, it’s a very fine engineered, real German made vehicle. :sunglasses:

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