C220D intermittent surge
 

Symptoms, with hot engine, is a sudden loss of power that restores after a few seconds. This occurs perhaps once or twice on a daily 170 mile roundtrip commute.
I've recently changed the Thermostat, as the high (for UK anyway) summer temperatures, spooked me into a Cooling system paranoia.

Engine now runs at 88C except when climbing at full power, only rises to 95C after topping a 3 mile long 1000 ft hill at 80-85 mph.

So far, I've replaced the fuel filter, and there's no obvious leaks, anywhere on the fuel system - but the problem remains.

I would not expect fuel contamination to have occurred, I'm the only refueller, and I use the same 2 Fuel stations 95% of the time.

The fuel tank is always run down to warning light before refill, that's been my lifelong practice, I'd rather not spark off another round of the "Keep it full vs. keep it empty" discussion, which is already covered in other threads!

This has been going on now for the last 2weeks, 1300 miles.

Personal experience with other marques would suggest either:
1 Air leak into suction side of fuel supply.... any ideas of "Likely culprits"?
2 Tank strainer blockage... the fuel tank on this car is a nightmare to remove, I would very much like to hear if this is likely to be an issue with this model?

Any further suggestions will be most helpful.
Thanks all replies Simon

LOOK for the air leaks first
 

get out your handy little screwdriver and check ALL of the fuel line clamps.
(and if you've attended the church/temple/etc. of your choice faithfully)
it will be the clamps.
NOTE: keeping the diesel tank filled as much as possible allows less air space
which allows less chance for condensation [diesel algae/bacteria/etc. live in
the interface between the diesel and the H2O]
Lastly investigate the possibility of draining the tank,pulling the fuel screen
from underneath.I would only take the tank out to replace it.

We are not worthy enough on this side of the pond to get the "C" class D

Have you changed both of your fuel filters?

Anyone up to some eDFI troubleshooting?
 

After some careful eyeballing, and the recent aquisition of the "WIS" it transpires that there's no pre-filter on this model.
Although there's apparently a service mod since 1999 for fitment of a different Fuel filter that incorporates a water separator/trap. I'll leave that for the time being, as I don't think I'm looking for fuel quality/blockage problems IMHO.

Let me repeat the symptoms, there's always been a slight falter in power after about 2-3 minutes, say 1.5 miles on a cold(cool) engine. This probably equates to about the distance when the heater will start to produce comforting warm air on a frosty day. I've noticed this for the last 5 years, 200,000 miles, so I suspect this is not relevant, merely a step in the DFI fulel supply mapping.

More recently, and specifically during the recent ?Heatwave? we had here, OAT of 90 and above, the engine has occasionally faltered after about 15 minutes, at about the engine temperature which I could describe as stabilising into cruising spped (80-85 mph); around 85-88degC say on the gauge. This is becoming a regular event, but disappears after a further few miles, possibly by the time "everything under the hood" has attained full operating temperature.

From a brief reading of the fault finding chart for the Type 904 DFI system, it looks as if there is a chance that the coolant temp sensor could be a good candidate for replacement.

However, I fear that unless some kind person can add some further insight, there's a trip to the MB Dealer looming here, for diagnostic testing, and inevitably big money to be spent, unless I can come up with some self-help.

My apologies for the long post, thanks for reading this far!

try contacting a member named"TonyFromWestOz"
 

Simon,

He's very knowledgeable.
(I am hoping the "Gnomes of Sindelfingen" exported the C220D model to
Australia)