In Reply to: AFM testing aftermath posted by Artem Grigortyev on January 10, 2001 at 10:27:14:
I had to replace my transfer pump when I started getting hesitation when accelerating strongly (at least as much as an auto 528e can). Why you get the exact opposite effect is puzzling.
Here's one idea. Maybe it has to do with the way the pressure regulator acts assuming there's a certain volume of fuel coming in from the pumps. If that volume isn't there then strange things should happen. Since the pumps operate at the same speed continuously I suppose the regulator opens and lets fuel back into the tank at idle and closes in order to maintain pressure at high rpms. If the pumps are faulty and the regulator opens at idle then the pressure drops dramatically thus causing the stalling. At high rpm the regulator closes so whatever available pressure is concentrated on the injectors.
Of course if that's true then hell knows why I had the hesitation in high rpms only. If anybody knows the answer to this riddle let me know.
'88 528e automatic