Again, the fuel-cooler is ONLY in operation when the A/C is turned-on, its function is to reduce the formation of vapor bubbles on the RETURN/EXCESS fuel from the fuel-distributor as it returns to the tank.
Note- it's for USA cars because of the extreme heat in our SouthWestern states (e.g., DeathValley, CA; Arizona, Nevada, etc.)
This was taken from the M104 and M103 Engine Service Manual from Merceds-Benz.
:-) neil
1988 360TE AMG
1993 500E