How do I identify the cold start injector, om my Mercedes and is it easy to disconnect!!!! if anyone has a diagram or an easy to understand explanation it would be appreciated. Car is a U.K spec 1988 3 litre

mikemaddison@hotmail.com

Not sure about your UK spec. car, but US models do not have a cold start injector. Cold enrichment is provided through the EHC unit instead.

Thanks John
What/where is the EHC unit, car is starting fine then runs like a bag of spanners with black smoke as soon as the car warms up, not the famous fuse behind the battery I've checked. local dealer reckons that the system that helps for the first few seconds of warm up may not be shutting down so car running way too rich ( explaining the sooty plugs) would like to disconnect this to see if it makes a difference before throwing money at it

The EHC is a small rectangular black box mounted on the rear side of the airflow sensor. You will need to remove the air cleaner to see it. The EHC has a plug with 2 wires that can be unplugged for testing. Do not remove the entire EHC because it contains pressurized fuel.

EHC's can go bad, symptoms are leaking fuel and cold running problems. However, there are many other things that can cause the "bag of spanners" (I love that) problem you describe and I would check other engine control inputs first, such as the coolant temperature sensor.

Good Luck....

> US models do not have a cold start injector

???

I'm pretty sure US-spec M103s have a cold start valve. Follow all the lines from the fuel distributor. One will lead to an injector between the #3 and #4 injectors. This injector will have a 2-pin electrical connector. Pull the pin and the injector won't fire. It will continue to leak if there's a mechanical problem with it.

Sixto
95 S420
87 300SDL

It's not the cold start system (and you do have a cold start valve), it's an oxygen sensor or warm running mixture problem. In closed loop mode you are WAY rich, but this could be a number of problems.

You need to check fuel pressure, the voltage to the EHA (EHC in brit-speak), the duty cycle on pin #3 on the diagnostic connector, and the oxygen sensor.

This will tell you what is wrong -- bad EHA, bad fuel pump, bad pressure regulator (check for fuel in the vac line going to the valve cover from the pressure regulator), plugged return line, toasted engine control box, etc.

You may in fact have a defective fuel distributor -- running way rich with black smoke is a clue. Only cure is replacement. Also not likely if it only does it warm -- defective fuel distributor runs way rich cold too.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!