About a month or two ago I posted a message asking everyone for their opinions
and help regarding my occassional nonstart issue in my 1993 300E. The car
would crank and not start, and at other times it would be fine. The car would
occassionally die out at an abrupt stop. Well, since that time I've replaced
the OVP, fuel pump relay, and had the alternator, battery, and fuel pump
checked and they are all fine. Well, the problem still very much occurs and
two mechanics are still baffled...one of them being a reputable Mercedes
dealership in Chicago (Loeber Mercedes). In all fairness to them, the car
starts fine whenever in their hands. Anyway, I am starving for information and
desperate for anyone's help. I want to thank everyone for their advice and for
sharing their experiences with me when I first posted this problem.
You've dealt with the usual suspects, now its gets more difficult.
You say that sometimes the engine cranks but won't start.
Is the engine then hot or cold?
How do you then finally get it going?
Also, when it stalls upon a sudden stop (of the car), does the engine
restart immediately or is there a problem to get it running again?
These symptoms occur regardless of the engine being hot or cold. The car gets
going again when it finally starts, which could be in two minutes or two days.
Again, when the engine stop at a sudden stop, it most often then not starts
within a minute.
bet the fuel pump is getting close.
is it one you can hear?
mine in my truck cycles for about
5 seconds when i turn it to on before turning it to start.
it is 10 years old things get tired .
also something in the ignition could be breaking down.
things never go wrong at the shop.
that is why i let them run around in mine for a few days if it is one of
the goofy things.
the case, minus a few cans!
Does the car have spark when it quits and/or refuses to start? My 300TE
had these symptoms on 2 different occasions. Once it turned out to be the
coil and the other time (more difficult to diagnose) it was an intermittent
CPS crankshaft position sensor failure ( CPS is the one at the rear of the
block). The output of the CPS can easily be checked with a voltmeter set at
AC millivolt setting. If the CPS reading is zero or inconsistent, the
engine controller decides to turn itself off - no spark.
The CPS can loosen, get gunked with oil and/or just fail.
As another poster said, here's where it starts to get difficult because
you've ruled out most of the easy stuff.
Now is the time to spend some time with your mechanic and together develop a
strategy that will allow YOU to gather the information HE needs to isolate
the problem. Something like keeping a remote start switch in the car and
temporarily mount a fuel-pressue gauge under the hood to see of you have
fuel pressure or not. When the failure occurs, report that data point back
to your mechanic and then on to the next step. It's a long slow process,
but not nearly as ostly as throwing money at it.
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