OM603 fuel pressure
 

Hi, i have a question about my S124 Om603, the issue is when leave the standind for overnight the fuel from my prefilter runs out, and when i start the car in the morning it takes longer to start because it has to pump the fuel up, i've cleaned my fuel trainer and changed both of my fuel fiters and bled the system several times and i can't seem to understand what's causing this issue, i've noticed that it gets worse when the weather is cold, anyone has any ideas what could cause this issue ?

Wrong section you need to post this in the diesel section

Most likely an Air leak somewhere in the fuel system. Check all the hoses and clamps. Is the fuel pre heater still there? Does the om603 have one? They’ve been known to leak air in.

The 603 does have a fuel preheater, however it is before the lift pump which has check valves in it, so even if it does leak, it won't cause the prefilter to run dry. If there is excessive air in the system from a major leak it can pool in the filter though.

Check for leaks on your rubber fuel hoses and replace the crappy clamps if they're still OEM, I had nothing but trouble getting mine to give an airtight seal.

Look around the output nut on the lift pump and the banjo bolts on the filter housing and injection pump for signs of weeping.

Check your fuel tank after a trip to see if it has a vacuum on it. If it does, it could easily suck fuel back to the tank after the car is shut off. There's a two-way valve under the car that attaches to a vent tube in the tank. If the valve fails or the tube clogs, you can very easily pull a vacuum on the tank.

Are you parking with the front of the car uphill?