Mercedes W208 rescued from China

[valhalla]

I had a very nice looking W208 dropped-off on a trailer last week, barely able to start, let alone run. Initially it was a case of whipping the battery off and giving it a good reconditioning charge, just to get a level playing field. Oh, and some fuel, just to rule that out.

I finally got a look at it this afternoon, last "little" job before closing the doors on the workshop. It just about managed to roll into the front of the shop... It seems every garage and his dog has bounced this one round; nothing has been left undisturbed, every little thing left undone. The guy that wanted me to fix it has been given it for free, because it "cannot be fixed". This was the "last chance saloon" before it departed (minus some nice spares) onto a packing container destined to the Far East.

Having looked at it for 75minutes, ruling out everything that had been disturbed (i.e. tightening it all up again and measuring it properly, including a full fuel rail and regulator pressure test), I then concluded that all it had was a lean misfire off idle, which screams "MAF meter" to anyone with a inkling of diagnostics. Having got a good secondhand Bosch MAF insert from another W208 on the shelf, a grand total of 10minutes and 5p worth of grease had it in place, the car started and purring, ready to spin its wheels up the road for a 5minute test-drive.

I phoned the guy up, explained that the labour was a bit more than the parts, but if he could run to 5p for the grease, he now has a very nice, not rusty, low mileage, clean, MoT'd W208 230CLK to smoke around in for the next few months. The contentment down the phone line was worth all the aggravation earlier in the week on the rest of the fleet......it almost makes this business worthwhile!

[mayfly]

Well done. It annoys me how many mechanics out there condem an older car if it's got a problem that their diagnostic tool dosnt tell them exactly what's wrong. They won't go to the bother of checking it out properly and even on here how many times when you ask for help on an older car do you get, off to China with it.

[Noberator]

I do like a happy ending. I bet the new owners well chuffed with the outcome. Nice one Valhalla.

[chippie]

Apr 16, 2015 9:23:19 GMT 1 mayfly said:

Well done. It annoys me how many mechanics out there condem an older car if it's got a problem that their diagnostic tool dosnt tell them exactly what's wrong.

Back to basics,spark,fuel,compression......
Had a similar experience with a T plate Corsa ....had it to two garages,first said lambda probe......after hooking up his box of trix,second garage said,ah needs a top end recon....yeah ok,I can sort that....

I sat with the car idling, just listened to the engine as I throttled it up and down.....it was reminiscent of spitting back thru a carb when the mixture was too weak....that was when I cottoned on to it being MAF ........new unit fitted, engine ran like a sewing machine after that...how satisfying..

[valhalla]

Apr 16, 2015 11:00:08 GMT 1 chippie said:

Back to basics,spark,fuel,compression......
Had a similar experience with a T plate Corsa ....had it to two garages,first said lambda probe......after hooking up his box of trix,second garage said,ah needs a top end recon....yeah ok,I can sort that....

I sat with the car idling, just listened to the engine as I throttled it up and down.....it was reminiscent of spitting back thru a carb when the mixture was too weak....that was when I cottoned on to it being MAF ........new unit fitted, engine ran like a sewing machine after that...how satisfying..

I can understand why a garage might leap on the Lambda probe diagnosis, but in this day and age, a decent PC-based oscilloscope really is very little money for the quality of information that it provides. The Merc is a bit rubbish by any standard, as it falls neatly between being "simple" and then "OBD" compliant. The AutoCom CDP+ does not have much in the way of trim-values to study (nor the MaxiSys908), so a 'scope of the sensor heater currents and output voltages is all you have to go on. In this case, I had a good steady+hot heater current of 1Amp, and the sensor was swinging nicely at a a good old frequency around idle, then clamped flat lean at circa 0.2v as soon as you lifted the engine off idle. Pretty conclusive when added alongside a series of measurments off the fuel rail Schraeder that showed the regulator matching manifold depression (2 "hits" in one measure; regulator works, and there isn't a manifold leak at idle to throw the trims out) and able to control fuel pressure under snap acceleration (well, a lethargic coughing and wheezing off idle......), as well as reasonable fuel pressure before and after running (no massive leak-down).

Now, if I can find that spare brake pedal switch that always goes on these and throws the BAS lamp on the cluster, then he will have an MoT candidate as well!