Fuel Pre-Filter Plastic Line - PeachParts Mercedes-Benz Forum

pat201 · #1 03-31-2004, 02:37 PM

I just replaced all plastic fuel delivery and return lines (including the fuel pre-filter seal & fuel filter). However after 10-15 cranks there is only air and no fuel in the plastic delivery line which comes to the pre-filter. All other lines (five of them - six in total) show that they have fuel.
How many other cranks should I try before the air is removed by the pump? I am concerned that I may have done something improper.

pat201 · #2 03-31-2004, 02:38 PM

It is a '99 e300td with 115k

TMAllison · #3 03-31-2004, 06:28 PM

Your IP needs to prime the system.

To do so you must crank the starter for 30-40 seconds. If a repeat is needed it is recommended to wait a few minutes so as not to overheat the starter motor.

It may take to or three tries.

When you think it has caught, keep cranking a few seconds longer to be absolutley certain. Not being certain results in 2nd and 3rd attempts and eventually the battery wears down.

Will usually run rough for a second or two and then even out as the IP gets rid of the remaining air in the system.

Should be fine after that.

pat201 · #4 04-02-2004, 09:26 PM

Thnaks for the advice. It worked perfectly (tried 2 more times).
I already driven the car 100 + miles but there is still air visible in the plastic fuel line which leaves the pre-filter. Should I be concerned?

TMAllison · #5 04-03-2004, 03:25 AM

Any fuel leaks anywhere? Where fuel leaks out, air can enter.

Most folks dont replace the line from the inside of the IP (has a banjo bolt, black fuel hose with clear line intersecting), it has o rings where it enters the fuel filter housing that should also be replaced. My dealer parts person said no one had ever ordered that part so I only replaced the o ring on mine.

I had a frothy stream of bubbles at certain RPMs after replacing my lines and difficulty starting and loss of power at times. I had to replace the fuel shut off solenoid (black plastic valve with 3 lines and electrical connection) mounted on the side of the IP.

As I udnerstand, the shut off solenoid should turn on the check engine light if malfunctioning although it may not if only leaking.