The fuel pressure should be 3.0 bar above the inlet manifold pressure. So with the throttle wide open it should be about 45 psi (gauge) and with the throttle closed it should drop to around 35.

If you suspect fuel delivery probelms then first check both pumps are working.

John Millward

1984 633csi atomatic. At 55mph it feels like I have air bubbles in my fuel line. Cruses fine at lower speeds. When I hit the gas it reluctantly takes off. And, of course, its tempermental! It just started with my last fill up of Texaco 92. If the octain in the gas was not quite up to par, would my performance chip cause the above symptoms? (Its an overpriced Dinan chip) What is a good way to check my fuel presure while driving 60? and what should it be at? I have a fuel pressure gauge.