Hello MBZ experts. Our 1995 C280 has a serious, intermittant, no-start issue! We bought the car three years ago with 60k and it now has 110k on it. Over this period the car has failed to start aproximately 100 times!!!!! I would say it is most often a hot-start problem and when it fails to start if you wait ~30mins it will usually start up, sputter and then run fine. We have taken the car to the MBZ dealer and three independant shops who have all failed to cure the problem

The car is in excellent condition and we have done a whole bunch of work to keep it in top condition, including...new battery, OVP relay, head gasket, H2O pump, and lots more.

Can anyone suggest some possible solutions to the no-start problem? One very strange thing we have noticed is that sometimes when opening the door locks with the remote key fob the rear doors don't unlock and when this happens the car won't start. If you lock and unlock the doors again it will start. Is this just a fluke or do these cars have factory immobilizers?

Any advice would be greatly appreciated

Do you have a No Start condition or a No Crank condition??
Different diagnosis.

My mistake. "No start", it will crank for hours

Thanks

May want to have someone look at the Crank Position Sensor...

Archieves -- "Wire Harness"

Hello Arthur,

Thank you for the information. Is the crank position sensor a known problem on this engine? Would a faulty one not cause other running issues? This car runs flawlessly once it is started.

When I first had this no-start problem two years ago I did look over the archives and found the harness issues, however I think mine is okay. How can I tell? If it was the harness I would think the problem would have become more frequent or worse over the past 50k miles.

How many hours should I be charged to change the crank position sensor?

0.5 ?

__________________
2007 C 230 Sport.

Sounds easy I will go ahead and replace the CPS to see if it helps the problem.

Since this is mostly a "hot start" problem, could it be something like the old cars suffer from like vapor lock, possibly from leaky injectors?

It really baffles me that this no-start problem has remained consistent for over two years, not getting any better or worse. Usually a faulty part will deteriorate and the problem will occur more often, making it easier to diagnose.....not this one

Here are some of the possible faulty parts I've come up with that might be the cause of my problem.

-Fuel injectors (leaking and flooding the cylinders)
-Fuel pressure regulator (not holding pressure)
-Relay for factory immobilizer (does this car even have one?)
-Engine wiring harness (doubt it since the cars runs perfectly)
-OVP (already replaced a year ago....no improvement)
-Neutral switch (would it be semi-faulty for two years?)
-Ignition swtich (can this cause a crank but no-start situation?)

If I replace ALL these parts it will cost more than the car is worth so I really need to narrow it down a bit more. I am usually quite good at diagnosing problems but this one has got me fooled!

Thanks

<<
-Fuel injectors (leaking and flooding the cylinders)
-Fuel pressure regulator (not holding pressure)
Fuel pressure test

-Relay for factory immobilizer (does this car even have one?)
Car would nor crank

-Engine wiring harness (doubt it since the cars runs perfectly)
Very probable

-OVP (already replaced a year ago....no improvement)
Tap it when condition exist
-Neutral switch (would it be semi-faulty for two years?)
Car would not crank
-Ignition swtich (can this cause a crank but no-start situation?)
Possible , but doubt it.
>>
Crank sensor heat soak possible.

Arthur,

It is great to have a guru helping out with the diagnosis I will add a couple more comments/questions below:

Can this test be done by an independent mechanic with common tools or would only an authorized MBZ dealer be able to do it? Would you say this is a common issue with these fuel injection systems?


Ouch! Are there some common areas of the harness I can inspect to see if it a bad one?


I didn't know this was possible. So the crank sensor can get too hot and malfunction?

Thanks again for the advice

There is enough info on fuel pressure, wire harness , and crank sensor in the Archieves to fill a NY City phone book..
You just have to look..

CPS replacement

__________________
-- raymond~
47º 34'N 122º 18'W