The Saga….

…. of my Mercedes’ electrics has gone on since January and might well end with a perfectly good car going to the scrap heap because of an electrical fault that no one seems to be able to pin down. Even the much vaunted Mercedes ‘Star’ diagnostic machine didn’t tell me anything I didn’t already know, in fact it told me to replace the crankshaft position sensor despite the fact that it had already been renewed. At this point the engine was running but not so well that you’d trust it on anything but a local journey. So I borrowed a regular code reader and plugged it in to see what it had to offer. 4 faults came up: Crankshaft position sensor, camshaft position sensor, mass airflow sensor (MAF) and exhaust gas re-circulating thingummy (EGR). I replaced (or had replaced as the crankshaft sensor is all but inaccessible) everything – except the EGR which I cleaned out – and started up. The engine ran for about 2 seconds, stopped and hasn’t run since. It turns over readily enough and although fuel is getting to the injectors, it sounds like the injectors aren’t firing and consequently, no fuel is getting to the cylinders. I gave up at this point; electrics (and rulers) are just not my thing. If anyone has any ideas……

I managed to complete a stone trap – there’s a couple on order – before I was whisked off to Halden in Norway. I’d been there before a couple of years ago but hadn’t had the time to have a look round.

On this visit, my room had a slightly more interesting view than the last time (see April 2015) – every little helps.

The marina was a bit busier and, having a car, I was able to nip up to the castle (on the left of the picture) and get a handle on the layout.

The Nexans Skagerrak cable layer wasn’t due to arrive for a couple of days so we had time to kick our heels and get settled in. A bit like the other parts of Scandinavia I’ve visited, trees, granite and lakes are the staple diet and, unless you’re an outdoorsy, running, jumping, pedalling sort of person, finding something to chew on is not easy.

An interesting building in the market square….

… a charming public park,

and it looks like they’re building some sort of gallows up at the castle so I know I’m not the only one who’s finding things a bit slow.

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19 comments on “The Saga….

  1. Hi,
    About your Merc maybe it is some corroded ground connection somewhere and I would have verified with an ohmmeter that all the grounds are precisely that. One of the wires connected to the battery minus and then seeking with the other for some non zero ohm ground on:
    -engine
    -calculator
    -dashboard
    -etc
    Does my explanation makes sense?

  2. Take all the injector stuff off and go old school with a nice carb. I have no ìďea with these new engines.

  3. Ritchie Wilson says:

    What year and model is the Mercedes?

  4. Ritchie Wilson says:

    More from the edge of the world: Assuming you’ve got no power supply or ground issues with its ECM I’d be mighty suspicious of what the reference voltage for the sensors you are getting codes for is doing. The crank angle sensor itself might be OK but if the rest of the circuit isn’t functioning properly and hence the CAS signal is either going missing it is otherwise implausible then its likely going to shut down the injector operation. Always remember that fault codes are only an indication that a control module has seen a parameter or group of parameters that it thinks is abnormal, not an indication that a particular part needs to be replaced!!! Multiple codes for different components could well mean something common to those systems is malfunctioning.

    Edited by franc123 at 12:59 pm, Sun 16 Jul

    Quote
    franc123 (367 367 positive feedback) 12:56 pm, Sun 16 Jul #2

    and

    my first thoughts is a bad ground on the engine.

    the no start could be because of something you did while replacing a part. (eg clean out egr but now its stuck open)
    thats why i like to do one at a time.

    one other cause can be interference. seen that on other vehicle where a bad relay (i assume burnt contact) was causing inference on the crank sensor. that caused no start as it screwed up the signal and ihid all the rpm pulses, so ecu won’t turn injectors on as it was seeing no rpm.
    test sensor with oscilloscope. the wave forms should be in the service manual.

    Quote
    tweake (29 29 positive feedback) 1:23 pm, Sun 16 Jul #3

    NB franc 123 is an experienced mechanic. tweake sounds plausible IMO too.

    • I couldn’t work out if the butterfly on the EGR should be open or closed when at rest – mine is open. I think the fault being common to the four sensors is a definite possibility. I’ve had ground problems and had to run a new and separate ground from the ECU to the chassis to get the engine to turn over. Then the turbo seal went bang while accelerating (that was easy and cheap to replace) but the stopping and starting problem remained.

  5. Ritchie Wilson says:

    More from The Antipodes: What is the model, variant and age of the car and where was it sold new? It’s not from the era when the wiring loom insulation was failing prematurely?

    Had a E320 that did this and was cured with a replacement fuel filter which had an internal fuel pressure regulator. The crank angle sensor and main HT lead from the coil were replaced as well. The eh voila!…zum zum zum

    Quote
    kiwitrader43 (218 218 positive feedback) 5:18 pm, Sun 16 Jul #7

    • I’ve changed the fuel filter. The model is an ‘Elegance’. I did wonder about the wiring loom breaking down. Whoever signed that mod off needs taking down to the seventh basement to review his decision more comfortably 🙂

  6. Ritchie Wilson says:

    all those sensors would share a common ground and power supply. you could, if you were electrically inclined, pick off each sensor and feed it separately via its own (5 volt?) power supply with a good noise suppression and see where that gets you. it could be that one of the sensors that ISNT reporting a fault is infact putting noise on to the circuit so the others are reporting faults

    crazy as it might sound but an old crappy battery can cause issues also with a raised 0 volt line under load. try it with a known good battery. 6 months of inactivity could kill a battery easily causing low volts and codes when cranking

    fordcrzy (49 49 positive feedback) 6:09 pm, Sun 16 Jul #12

  7. I support all Ritchie’s comments.

  8. Ritchie Wilson says:

    Latest suggestion: Did you do a relearn of the egr when you refitted it? Won’t start if it’s open.
    From…….
    bigfatmat1 (49 49 positive feedback) 7:09 am, Mon 17 Jul #20

  9. Ritchie Wilson says:

    A suggestion from Mr Berg: I so hope it’s not the dreaded “green copper” wiring loom. Have been down the road a few times with these and have ended up replacing the entire loom in one car (trust me, one night in the shop I bloody near burnt the thing).
    check all your earths including baring back the insulation to check the wire to terminal connections. While there check a few of the wires in the loom. Hopefully a quick look won’t find any of the dreaded green corrosion. Best of luck, Berg.

  10. A big thank you to all you guys who’ve suggested stuff – thanks Ritchie for acting as a conduit. I’m stuck in Norway at the moment but I know what I’ll be doing when I get back!

  11. Bob Masterton says:

    I’ve been thinking about your Mercedes’ problem. Perhaps it’s caused by age related corrosion in the wiring between the modules and the PCM. Since three components are involved, perhaps a common ground?
    It seems to me that you’ve eliminated all the other possibilities.
    Cheers,
    Bob

  12. Yes, just what the first comment said!
    Good luck Nigel,
    Renaud

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