Sorry to ask dumb questions, but my CD Rom has seemingly outdated information and non exact part diagrams of the Fuel Pressure Reg.
I have p/n 0 438 161 001, in my '88 300TE. Blowing into the center orfice with my mouth, I get no flow. Blowing or sucking on the opposite, vacuum end , there is also no flow. But, blowing into either of the side orfices, there is a definite, slight air flow.

The diagram, such as it is, seemingly shows that there should be no flow.

Would, or can anyone confirm this?

Assuming that I have a leak between chambers, this would account for the fact that the car won't start for lack of gasoline to the cylinders and that I should replace the regulator. Actually, I'v already replaced everything else between it and the gas tank.

__________________
'76 240D-Sold
'78 240D-Sold
'85 300 SD, 165K-Sold
'88 300 TE, 165K-Sold
'64 Porsche 356C Cabriolet- under restoration
'86 560SL 124K Miles-Sold
'94 320E Wagon, 74K Miles-128K Miles JUNKED
'06 E350 Wagon, 84K Miles
07 SL550, 14K Miles

Ron,

To orient you, and someone please verify, the fitting at the opposite end from the vacuum fitting (actually it's a vent to atmosphere) is the return to tank line. The small side fitting is the return from fuel distributor line. The big side fitting is the fuel pressure line.

It seems to me that fuel pressure is a signal to the regulator. The regulator regulates injector pressure by modulating the flow of excess fuel from the fuel distributor to the fuel tank. It does not look like excess fuel should go from the pressure line to the tank through the regulator as it does with PWM systems.

If you're saying that what you blow into the big side fitting is felt at the small side fitting or end fitting, that sounds like a leaking regulator. The chamber fed by the big fitting should be isolated in all normal circumstances from what I understand in Charles Probst's book on Bosch FI systems. Again, I defer certainty to Steve and comrades.

If you want to try the regulator in my 91 SE, I can be without it this weekend. Contact me off the list. Please tell me it's easy to remove and reinstall

As a check in the absence of a fuel pressure tester, crack a fuel line at any injector while cranking the engine. Is there fuel in the line?

Sixto
tabijan@yahoo.com
91 300SE
87 300SDL
81 300SD

For the record, it is normal for there to be a slight amount of leakage between the two side connections. Blowing in one side will result in a slight amount of air coming out the other side port.

__________________
'76 240D-Sold
'78 240D-Sold
'85 300 SD, 165K-Sold
'88 300 TE, 165K-Sold
'64 Porsche 356C Cabriolet- under restoration
'86 560SL 124K Miles-Sold
'94 320E Wagon, 74K Miles-128K Miles JUNKED
'06 E350 Wagon, 84K Miles
07 SL550, 14K Miles