Questions and Answers
Sentra Fuel Pressure
Q. I own an 1989 Nissan Sentra with a TBI fuel injected engine. Some time back I started having problems with power and the car started surging a bit. I therefore replaced the fuel filter and put some injector cleaner in.
When this didn't work I checked the fuel pressure and found it was to high. Following a repair manuals recommendations I therefore replaced the fuel pressure regulator. The problems continued however. Then, for a short time the car started idling sporadically really high, one time it would idle high, the next it would be normal. Now it is no longer doing this, but it is still surging and has started stalling. What else can cause the fuel pressure to be high? I'm really frustrated with this one.
A. The fuel pressure at idle should be 34 psi. If it isn't, the only thing besides the fuel pressure regulator that can cause an excessively high fuel pressure is the fuel pump. If allowed to run rampant, that fuel pump can put out over 90 psi. So a relief valve is built into the pump that opens at around 50 psi.
However, replacing the fuel pressure regulator should keep the pressure at 34 psi regardless of what the pump is putting out. I would say you installed a bad fuel pressure regulator.
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