Fuel pumps have three types: the rotor cells; the gerotors, which are similar to some oil pumps as they squeeze liquid through the use of a star-shaped rotor; and the turbine type, the latest trend in original equipment (OE) manufacturing. Pump inadequacies can cause drivability problems such as momentary cutting out, hesitation, low power, and stalling at inopportune moments. Here are the things you should look into when diagnosing your Nissan Sentra fuel pump assembly's problems and their causes.
Spark, compression, and fuel are the legs of the tripod that support an engine's ability to run; so for a car's engine to give a good performance, you have to make sure that aside from the fuel, the spark and compression should also be working at an optimum level. Do a spark check and make sure the camshaft is still connected to the crankshaft, and if these two elements are okay, you might want to start checking the gasoline for problems.
If you don't hear the pump running for a few seconds after turning the key on, you might want to check the fuse to know whether it's blown or not. Fix it if it is; repair is also necessary if pump electrical draw, or the amps it's being forced to carry, is too high.
Amperage testing can be done by hooking up the meter in series with the load, or with an inductive pickup you clamp around the wire. You need to connect one of the ammeter's leads to the positive battery post and the other to the pump's hot wire.
If you see anything over 5 amps with a low- to mid-pressure system (13 to 45 pounds per square inch), or 7 amps with a high-pressure version (60 psi), you've got a problem. Too low psi is also not good. Causes of too few psi to start your Nissan Sentra can be clogged fuel filter, a blocked pick-up sock in the tank, a crimped line, and of course, a weak pump.
Violent or fast needle swings between dead-head and running pressures in your Nissan Sentra's gauge means everything is okay. A slow rise means trouble for the engine's workability; pulling the pressure regulator's vacuum hose should help you see an increase in the swinging.