Turned the key and sounded like a balloon popping. I got under the hood immediately and saw a tiny trail of smoke coming out of the small hole located on top of the air cleaner. Checked the plugs, they're good.
Trying to start it up now, it won't run but chugs and coughs a little bit.
Any ideas anybody? I'd love to find out it's a relay or fuel pump etc. Doesn't everyone's fuel pump whine occasionally, or was it a hint when I heard mine a couple of weeks ago?

The small hole on the airbox is where the air/fuel mix is set/adjusted.

Sounds kinda nasty to have smoke rising out of there....

Mike.

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1990 Euro 190e 2.0l Petrol Now Sold Maybe a w116 280se next

Do you know if the air/fuel mixture has it's own relay? I'm hoping for something as simple as replacing a relay here. The car has experienced electrical situations in the past. Thanks Mike65.

POP was backfire up the intake, you probaly have a serious ignition timing issue, likely a badly corroded cap and rotor or broken rotor. Pop the cap of and take a look.

If everything is fine there, you will need to check ignition timing and fuel pressures, etc.

It's possible you have a bad OVP, but that shouldn't allow just chugging and coughing.

You may also have a jumped timing chain -- this is bad news, and I believe a jumped chain on this engine will result in bent valves and the exact syptoms you describe.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Thanks psfred. Great information. Fortunately, I don't believe the timing chain is the issue...(yet). I checked under the hood immediately thinking a plug detonated. All were covered in carbon deposits. Opened the oil cap to look at the chain, (from what little you can see), the chain was tight and seemed ok.
Several times this past year, I'd hear a tiny pop while starting. The car ran fine after each occurrence. This last one was a little louder and now refuses to start up and run.
A different fuel issue: When the fuel registers less than a quarter tank, the car hesitates and sputters rounding a quick turn.
I want to think these symptoms are all closely related. I'm trying not to assume anything, so what's your opinion now?
Thanks again.
MC

Carbon fouled plugs means you are running too rich and will need to determine the cause after replacing the plugs. Bosch plugs rarely recover from carbon fouling unless properly cleaned, for some reason.

Worst case you have a bad fuel distributor, but you need to check idle mixture and O2 sensor before jumping on that.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Thanks psfred. I had the car towed to the number one guy around here yesterday. There's about 30 Mercedes and Audis parked over there. You think he charges $100 an hour to park too?

This turned out to be a vacuum failure in the fuel/air delivery web of entangled hoses and tubes located under the air cleaner. The O2 sensor was shot too.
Thanks for the troubleshooting guys.
I owe PSFRED a beer for providing a description that got right to the point with my mechanic. I might have rambled on for 20 minutes describing the symptoms in idiotic detail.
Thanks again.