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Matt, Engineer
Category: Mercedes
Satisfied Customers: 22002
Experience:  Mechanical Engineer with 23 years experience in the auto industry, 8 yrs in formula 1 engine testing
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I have a 1993 190E 2.3 that my son drives, it is having a

Customer Question

I have a 1993 190E 2.3 that my son drives, it is having a difficult time starting and idling until its warm, once warm it starts easily - I just replaced the OVP relay and it's still doing it I'm thinking the fuel pump relay may be bad as well - the car had a bad alternator regulator and was pushing 18V through the system
JA: Has your car been stalling?
Customer: no, not to my knowledge
JA: Are you fixing your 190E yourself? What have you tried so far?
Customer: the OPV valve relay
JA: Anything else you want the mechanic to know before I connect you?
Customer: no
Submitted: 1 year ago.
Category: Mercedes
Expert:  Matt replied 1 year ago.


This could be incorrect fuelling due to a faulty water temp sensor. If this is the problem then the ECU will be leaving the car constantly ' on choke' and not reducing the fuelling as the engine warms - so unplug the sensor and clean the contacts on both sides with some switch / electrical cleaner (not WD40) and inspect the wiring for any signs of damage to the insulation especially where it runs over other components and through the bulkhead- if this doesn't help consider replacing the sensor as they're not expensive

Check for exhaust leaks before the O2 sensor as if this has been experiencing an exhaust leak then it will have been running very rich as the sensor will see the extra air pulled in as fresh / lean fuelling and be adding fuel to compensate.

this can lead to catalyst failure as the extra fuel can re-light inside and melt the catalyst

The best way to find an exhaust leak is to run the engine from cold and feel around the exhaust joints with your bare hands - you'll have about 30 seconds before it all gets too hot and you should feel any escaping gas blowing over your fingers

Customer: replied 1 year ago.
Thanks, ***** ***** are clean, I have an extra and will replace it. The alternaltor went bad a while ago and sent 18v through the system, I replaced the OVP relay, could that have damaged the fuel relay too? It acts like it isn't getting enough fuel
Expert:  Matt replied 1 year ago.


if you've had an overvoltage then its possible the main ECU has been damaged, its unlikely to have damaged the fuel pump relay as they are simple devices

I'd suggest it may be wise to remove the engien ECU and send it off for repair