mercedes w126 420sec cold start problem

[balge]

measured the resistance of temperature sensor,

cold 0.365kΩ
hot 1.112kΩ

it seems to me that is not working properly.

Don't know if it's the same sensor but I had to replace one on my 230TE and the values for that are

2.2 - 2.8 kOhms @ 20C
290 - 370 kOhms @ 80C

Are there two coolant temp sensors on the head?

Bosch D Jetronic and K Jetronic Troubleshooting - Mercedes-Benz Forum

Might be of use

 

[Firepants78]

New temperature sensor, ordered, hope that resolve problem...
Many thanks again for help.

 

[Firepants78]

new sender coolant temperature sensor changed and....
..NOTHING...

on Saturday I'll connected it to starter motor, I don't have a choice...
..Any idea please share..
Thanks from advance

 

[neilrr]

So, how much £££ are we up to so far?

 

[Firepants78]

new battery -90
new fuel pump relay -£200
new ignition coil -£62
new coolant temperature sensor -£20
--------------
£372

 

[grober]

Right back to the original problem.Correct me if I have got this wrong.
You have a problem with cold starting.
When you tested the cold start valve on a cold cranking engine it failed to spray fuel.
When you tested the valve off the car across 12v it worked.
You replaced the FPR which supplies the COLD SATRT VALVE and that failed to cure it.
You replaced the engine temperature sensor for the injection system [ not the temperature read out sensor for the instruments of course]
The next step logically would be test the wiring continuity and whether that FPR is getting the appropriate signals--- this is really the point to hand over to a pro familiar with the electrics of these cars---- need not be a Mercedes specialist which would obviously be best but someone experienced with Bosch CIS injection systems would be a good second best.

Don't be too downhearted about the money you have spent ---in so far as you have renewed several vital components to the car's running which will enhance its reliability for several years's to come so the money's not " LOST"

Keep that old FPR as a spare as it may be OK as a backup in the future. Be sure to tell the injection guy you go to all the components you have replaced already.

 

[Firepants78]

Yesterday I plugged cold start valve to the contact of "50", and according to my way of thinking, if I had to cranking without valve 2 -3 times for 5 seconds, with the valve (additional amount of fuel) will fire up for the first time after 3 seconds.
To my surprise the car did not want to fire up at all !!!, Without the valve fire up much better but still with some problems, it looks like the valve, now flooding the engine and is difficult to firing.
How is this possible?? any ideas?