My 1983 300 SD has been idling rough and was very noisy. I posted a topic and several people recommended that I use the hand pump to get any air that may be in the fuel lines purged. I have a Bosch hand pump that is black with a large white knob.

I was wondering what was the best way to use the pump to purge the system. I do not have an owner’s manual (it was gone from the car when I bought it).

Should I pump when the engine is cold or hot?

Should I pump with the engine running or off?

Any help would be appreciated.

Thanks……

Good question and I don't know the answer... I did mine when the car was turned off. Not sure if this is the proper procedure. I just kept pumping until I stopped seeing new air coming out of the intake line (doesn't take long). There is still a large air bubble in the prefilter... but I just figured I was not going to rid of that. The car runs fine though... I think the important thing is just to pump.

I just changed my injectors so my mechanic gave me this sequence of events. Take the plug out of the short hose on the last injector (the one near the firewall) and pump the bosch pump till there fuel flows cleanly from it and re-cap it. That should get the air out of the return lines. Use a 17 mm wrench and loosen the nuts where the fuel lines go into the injectors a turn. Crank the engine until fuel seeps from the top of that nut. That should get the air out of the injector feed lines.
Good luck.

yarsetra,

Thanks a lot I will try tis on the weekend.

Much appriciated.........

Be careful with the plug on the last injector. If it's old, it may crumble when you pull it off. Good idea to carry a spare in the glovebox. Also be careful about loosening the injector junctions, fuel is under a lot of pressure there. Don't take a chance on it spraying in your eyes.

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Palangi

2004 C240 Wagon 203.261 Baby Benz
2008 ML320 CDI Highway Cruiser
2006 Toyota Prius, Saving the Planet @ 48 mpg
2000 F-150, Destroying the Planet @ 20 mpg



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