New fuel pump, now won't start

[Olazz]

Hi guys,

I've replaced the old "long style" fuel pump with a new short bosch pump.
Used the correct parts and adapter and have connected all up.

No kinks in fuel line and 4/4 tank of new fuel.
Power getting to pump as its whirring and I can feel it spinning. Car struggled to start initially, but started when I used the gas pedal. Ran roughly for a couple of minutes but as soon as I lifted off gas it died. Motor spins and car wants to start but, will just not start.

Do I need to bleed the system, or does the injector pump need resetting with a new pump on now?

Can anyone offer help?

[al_lieffring]

The polarity of the wires could be reversed and the pump is turning backwards. The polarity doesn't matter on the old pump but it does on the new one.
The red (+) terminal on the pump should be connected to the black wire, This wire usually has braided fiber insulation.
The black (-) terminal on the pump should be connected to the brown wire, the color on the vinyl insulation is usually faded to where it could look orange or tan.

Another possibility is that you will need to remove the screw from the third port in the new pump and run a hose from there to a T fitting installed in the fuel return hose at the tank. This third port is there to bleed air blocks out of the system. Even if this isn't what is keeping your car from statring, you should make this modification and it will make for quicker starting.

[280SE Guy]

Here is a picture of the tee (from a W108) that Al is referring to (your fuel pump protective housing will look different):



The "Tee" is available from your local Mercedes Benz dealership along with a couple of clamps.

Regards,

280SE Guy

[Olazz]

The polarity of the wires could be reversed and the pump is turning backwards. The polarity doesn't matter on the old pump but it does on the new one

AL,  you were spot on buddy!
Feel a bit of a dim wit making such a school boy error.
Swapped wires and she fired first turn.... Thanks buddy great help indeed!!

280, Not sure if I still need/should have the T piece you referred to so I will investigate further.

Lazz

[George Des]

Lazz,

Check on the Forum for this. Joe Alexander has a number of posts that address the tee issue. Whether or not you need the tee is determined by the model fuel injector your car has. The early FIs such as those on the 230SLs and 250SLs do not need to use this setup as far as I know.
 
Let me know if you are still having problems rebuilding that long style pump we corresponded about earlier. Perhaps we can figure that out so you have a spare on hand. I still think the issue is with the small armature oring and the re-installation of the bellows.

George

[Olazz]

George,

Sent you a PM