OM642 Remains cranking after some time has passed

[Geek2232]

Excuse me,

I have a W211 E320 cdi with 108k miles on the om642 V6 diesel engine. Up until a couple of years ago, it was serviced regularly using genuine parts, even by the main dealer.

I've got a problem where when it's left for a couple of days unused it'll take a bit longer to start, it always does start but it's like when you change the fuel filter and theres air in the lines, once it does start it runs perfect and will start again that day and even the next no problem at all, its only when it's 2+ days.

There isn't a glow plug light or engine management light on, and it's hot here right now (more than 30 degrees Celsius), so I doubt they're needed.

Using my rudimentary OBD reader, I have tracked the fuel rail pressure: with ignition on number 2, it ranges from 6.5 bar to 8.7 bar, and when the engine is started, it stays around 300 bar and climbs as the throttle is applied. Bosch made the battery, which is relatively new.

I've checked under the hood and didn't find any major leaks; however, I did notice a tiny mist of oil (or maybe fuel?) on the fuel hoses connecting the high-pressure pump to the fuel filter; however, the mist is so tiny that I am unable to determine its source or whether it would have any impact.

Can you think of anything?

[Geek2232]

http://shop.ebay.co.uk/?_nkw=fuel+filter&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338181132&toolid=10001&customid=2518X1570512Xffa19062902c35627815c3622b12d245&subId2=15

[dave783]

Hello! In the winter, my CLS, which has the same engine, acts similarly. It happens frequently that the engine starts the second time I turn the key without trying to turn it over. Does the fuel drain back have anything to do with it? It functions admirably, just as you said it would.

[Geek2232]

Yes, this is exactly what I'm considering; I believe it has more to do with fuel than glow plugs. At this point, it's just annoying, but it always starts and runs well afterward. Is anything out there that you've tested or looked into?

[alpaco45]

Basic possibilities.
Air leaking in, most likely through the fuel filter.
Too much evaporation.

[Geek2232]

The fuel pipe connections, for example, are allowing air to enter. Is it possible to also have it sucked in by the high-pressure pump? I need to check for injector leak off.

Also, usually this would manifest as a fuel leak, right? I can barely discern any scent of diesel in the slight mist that lingers around a few of the fuel pipes.

[alpaco45]

Fuel may not necessarily escape when air enters.
An 'o' ring seal, located in the fuel filter's center, can serve as the ingress point. I was able to diagnose that using PTFE tape.

It is true that a fuel pump can release air. Repair kits have been utilised on that. Engine that was much older, though.

A leak off kit was rigged for the 646. Some tubing and plastic soda bottles from a dollar store made up the bulk of it. Clear and efficient.

[drummer]

Make sure the injectors aren't leaking by checking the glow plugs.

[keithmerc220]

What happened to my CLS required me to replace the relay and all six glow plugs. Nothin' changed. It appears that one of the fuel pumps is leaking fuel back into the tank, according to further reading. After two ignition cycles, it began immediately.