W202 - Limp Home Mode & Cut-Out Problem

[richip]

I would really appreciate some help as my patience and bank balance are rapidly running-out.

I have a year 2000 C220 CDi Sport that has now done 196K miles. Up till recently it has been a paragon of reliability. I travel all over the UK and the car has been nothing short of excellent.

Unfortunately it has recently developed two problems that I assume are related, although I'm happy to be proved wrong. The first is that the car goes in to the dreaded 'limp home mode.' I have had the mass air sensor, pressure control sensor, high pressure fuel pump and a leaky injector changed but still have the problem. The fault codes seem to change - when you fix one another appears.

The second issue is that the car started to cut-out, usually after slowing down following prolonged high-speed driving. The top of motorway slip-roads was a favourite place, although the outside lane of the M6 was certainly the scariest. The fault has now evolved and the car will stall after being restarted. In both events it takes a number of minutes to restart.

I know similar problems have been referred to on this site, but nobody seems to have had the misfortune to experience them both at the same time.

Any help would be hugely appreciated. I'm a huge Merc fan and also run a 107 500SL but I'm starting to lose the faith.

Richip.

 

[television]

You have to do basic test first that is to make sure that the Over voltage relay is giving 12volts out to the ECU's. Also check that the battery is giving 12v, though our cars will start OK on 10-11volt they will not run well.

Malcolm

 

[richip]

Thanks Television - I'll run that test and come back to you.

 

[Stevie A]

Sounds like OVP relay being faulty, with the symptoms for older Mercs being as you described above. Could be something else as your car is newer but try the OVP first as it affects fuel pump relay, ECU etc causing stalls and hard starting. Check as Malcolm says.

 

[richip]

I've just had the car back from my local Merc specialist who've found a hole in the intercooler. I guess that would explain a number of problems including the inaccurate error messages relating to various sensors. They've not tested the OVR yet, but will do so when fitting the intercooler. I've also suggested they check the exhaust for a blockage.

Thanks again for the suggestions and I'll keep you posted.


Richip.

 

[richip]

Just fitted a replacement intercooler which has transformed the car. The old unit had split down one seam causing a major leak. I still have starting problems so I'll test the OVP relay this weekend.

 

[rajinder_1]

Starting problems also check ignition switch.......

Regards

 

[richip]

Just been informed by my local dealership that late model 202's don't have OVP relays. Apparently cars with the stubby plastic infra-red keys were not fitted with them.

They have suggested low pressure fuel pump or the seal on the fuel filter - anyone have any ideas?

 

[richip]

Problem now solved. I removed the engine cover and then ran the car for ten minutes. When I swithed off the ignition I could see diesel draining back from the fuel filter through the clear fuel pipe. Mixed with the fuel were air bubbles!

I unscrewed the lid of the flask containing the fuel filter, replaced the seal and the draining problem disappeared. I'm guessing the existing seal had either been damaged or not fitted correctly.

 

[Stevie A]

Well done Richard. Good to report back to help others.

 

[davebox]

Very interesting post's. Im having problems with Limp mode also. Waiting for the dealer to have the car in on Wed.
Ive bit through the hard bits at the end of my fingers and am now at the wrist (well almost).