Questions and Answers
Sentra Fuel Pressure Regulator
Q. Some time back I wrote you about the fuel pressure on my 1989 Nissan Sentra TBI running too high. You thought I probably got a bad pressure regulator. Well, since then I replaced the fuel regulator again and the fuel pressure is still running about 45 psi. In looking through my repair manual this time I noticed that it said to confirm that when the vacuum hose at the bottom of the regulator is detached the fuel pressure rises considerably.
This made me think that maybe the vacuum hose was plugged so that the pressure was always running high. I therefore went to check the vacuum hose it talked about, and didn't see one. The bottom of the pressure regulator has the fuel return line and the top has a vent hose that returns to the TBI, I'm pretty sure that hose is not supposed to have vacuum on it.
The question I have is if there's some way I could find out where this vacuum hose is or see if this is valid for my model. I have a Haynes manual for 1982-1994 Nissan Sentras and this information was under the TBI section so I believe there should be a vacuum hose to the regulator, but I'm not finding it.
A. Your car definitely should have a vacuum line to the fuel pressure regulator. It maintains the fuel pressure at 34 psi at idle and disconnected it should go to about 45 psi. Below is a picture of the fuel pressure regulator from a 1989 Nissan Sentra.
1989 Nissan Sentra L4-1597cc 1.6L SOHC (GA16i)
Additional Information provided courtesy of ALLDATA
