W124 -Warm Start problem - experience
Like many other posts in the past, I too have suffered with my car (1990 W124 200TE), occasionally refusing to start after a short run.......I thought it might help others to share my experiences........
Symptons: Car starts fine from cold with no running problems. Pull up and switch off after (say) 10 minutes running - return to car after 10 minutes - it starts but stops as soon as I let go of the key - no amount of throttle pumping makes any difference. Car may not start for up between 5 and 45 minutes. problem is sporadic but VERY irritating when it happens.
Interestingly, car WILL run if ignition key is held 'on' - (which is a very bad thing to do to the starter dog and ring gear!). Does however indicate to me that problem is electrical.
Occasionally, turning off all auxilliary power drains does sometimes help to get it started - but not always. A lowish battery definitely aggravates the condition and its always worse in cold weather.
1) Removed OVP relay ( behind flexible plastic shield behind battery), its the smallest one under its own small plastic cover and has a flip top with a (10a) fuse. With CARE the can can be opened (remove its fuse first) and prise open flange with a small blade & remove board from the bottom -carefully!
There isn't much in there but check for grey /powdery solder joints and re-wet & solder for good measure. There is a small IN4000 series diode, which, if it fails will not allow the relay to open due to back emf effects. Easy to source and replace - get it the right way round if you do - (polarity band at one end).
Re-assemble - self amalgamating (rubber)tape is good for ensuring a seal.
Results? - in this case nothing - car still had the problem ..... :-(
Next.....remove fuel pump relay ( same location, at the rear and in this case labelled 'Kickdown' ??). Its a black box about 8cm by 3 cm by 8cm. Easily seperated and contains a much more populated circuit board., many of the components are very common, cheap and available IF someone wanted to get into this at component level!
However, in this case I again just re-soldered ALL the joints using a fine PCB iron and very fine self-flux solder (a solder pump or de-solder braid is useful to have around if you accidentally bridge connections). The whole thing takes about 30 minutes to do carefully - don't attempt if you can't use a fine iron effectively! It is important to 're-wet' joints with a dash of new solder as old solder may melt but not actually re-flow onto the component pins.
Re-assemble - put back in the car.
So far (1 week), no sign whatsoever of the problem and I really have tried to replicate it /aggravate it.
I know this is not a cure-all but if it helps someone else out there then this typing was worthwhile!
Regards to all MB owners,