Cold Start Valve - Manual Button

[kampala]

My cold start valve has been acting up once again.  In the past, I have gotten it to work by cleaning the relay and cleaning the contacts on the Thermo Time Switch.   This time I decided to not chase the usual suspects but install a trigger button.

Over the years I have read quite a bit about folks adding a button to manually trigger the cold start valve.  However, my search capabilities must be failing me as I could not find photos of where folks installed the button so that it's hidden and yet accessible.   

I know this may disturb some of our purists (Achim & Hans, you may want to look away) as I drilled into one of the underdash pads to install the hidden button.

I took power from the radio fuse box which is located right next to the cold start valve and it had an unused terminal - so I added a jumper in the fuse box and added a fuse for the button. 

Ran the wires through an existing unused grommet into the right side underdash, next to the wiper motor, removed the underdash foam panels and ran the wires over the steering column, to the underdash pad on the left of the steering (LHD car).

I drilled a 19mm hole in the left underdash pad close to the steering column as there is enough room to fit the switch directly next to the steering column.   Had to cut a little foam on the underside of the dashpad to allow the nut to grab the switch. 

The most difficult part - reinstalling the underdash foam pads and aligning the screws.

Works great.   

(two more photos in next post)

[kampala]

two more photos

[wwheeler]

That is slick! Nice installation! I have installed one and used the radio power take off as well. The CSV system on mine still functions as normal when the engine cranks. The way I wired the new button and use it is in addition to that and before the engine cranks.

You will have to determine through experimentation when is the best time and how long to activate the CSV. I made a chart given the various conditions of ambient temp and engine temp and then documented what worked best.

This was a well known "fix" back in the day. I think the only reason Mercedes never used it is because it is not automatic and therefore flew in the face of their engineering efforts. It is obvious to me given the number of  changes to the cold start systems over the years of production, that there were issues and Mercedes continually tried to find solutions.

Have fun with the CSV button!

[FresnoBob]

I also installed a manual momentary switch for my CSV, but I have never found a combination that makes starting optimal.  The car seems to start well without the use of any manual addition of fuel, but a bit of accelerator during cranking. 

[kampala]

When cold I turn the key so fuel pump is running, a few seconds later I hit the button and about a second later I crank the motor.  Car starts immediately.  I would guess I am holding the button down for total of about 3 or 4 seconds. 

When motor is warm, I do not use the button but only move the accelerator pedal about half-way as per mercedes instructions.  Works just fine.