Cold Start: Stalls... OVP, Coolant Temp Sensor, CSV

[kwh]

Hello All

'92 190e 2.0

Cold start problem... eventually starts... v.rough idle...
stalls if gassed... seems like cold start valve (CSV) or
coolant temperature sensor (CTS).

Runs better as it warms... fine when hot.

This problem is common and seems difficult to fix without
throwing money at parts (hit 'n' miss) which I cannot do since
I'm too skint to be a cheap-skate, as happens when you own Mercs

I need to get the fan clutch temp sensor (bridge the connector!) as well...
I have tried to measure the 4-pin sensor Resistance (across Pins 2/4
or 1/3 goes from 1800 to infinity in less than a second. Too quick for
CSV, isn't it?

I think that I'm getting far too little voltage at the CSV during cranking
because the voltage is dropping... (ahhh... was that a penny dropping?!)
due to thermo-time switch or resistor in CTS (pairs of pins for each?).

It's late and I still love Mercs. Not this one as much as my 123. Ahhh joy!

Thank you.

kwh
84.107
83.123
92.201
& Yamaha TTR600 (where's the spare wheel?)

 

[Stevie A]

Haynes manual shows correct resistance for coolant temp sensor should be:
6000 ohms at 0 degrees C
1200 ohms at 40 degrees C
325 ohms at 80 degrees C (when fully warmed up)
Measure with meter across pins in X formation if it is a four pin plug.
1800 sounds too much and it should show constant resistance.

I'm sure mines showed 600 ohms at ambient temp of about 15 degrees C.

Just in case also - check distributor - if it is worn can cause hard start and stalls as this happened to me and replaced it and problem was solved.
8)

 

[kwh]

Cold Start: CSV, CTS OVP (over priced relay)

hye Stevie thanks.

rotor & cap are ... er... ok, plus warm idle & run is too smooth
for that to have caused such relatively sudden problems;
but... point taken. pieces ordered, particularily since it is
now (suddenly?!) colder and damper (but not spring-ier ).

could be the fuel pump relay Pin 50 low or no output... funny (huh?) thing is
that the Haynes manual has a typical (ie.not exact) wiring diagram which
i think may be for the earlier models, with a separate thermo-time switch.

is there supposed to be 12v at pin 50 from the fuel pump during start?
is thermo-time built into the 4-pin CTS configuration on the later models?
is there supposed to be 12v across the CTS leads diagonally during start?
is there supposed to be 12v across the CSV supply during start?

hope all is well with the 6 wheels of our mercs!!!

ken higgins