How will you tell if the fuel pump or the pressure regulator is faulty?

 

Buy a cheap oil pressure gauge (that you will be using as a fuel pressure gauge) and a metal "T" that you plumb into the fuel line just after the fuel filter - FSM says what your particular engine's fuel pressure must be at idle and certain manifold vacuum values - if fuel pressure conforms to those specs then pump and regulator are probably ok.

In addition - after engine is switched off, the fuel pressure in the line should stay at around 35 to 40psi for a minute or so and should not immediately drop to zero ................... if it drops too fast you may have a funky pump/regulator/injector

 

So it's almost next to impossible to tell the difference of a faulty pump from a regulator??

 

Both can produce the same symptoms when faulty - ie low fuel pressure at certain times/temperatures.

What exactly are your symptoms to make you suspect either?

 

1. My car won't start and the battery is good.
2. It wont start before and I changed the fuel filter. It worked fine for <2 days and now it won't start again.
3. It cranks but doesn't continue.
4. When it was working before, I can hear a higher pitch "clearing throat" like sound before it starts.
5. I'm not sure if a knock sensor can cause this too but I also have a Code 34.

 

You can forget about the KS for now. Sounds like you're on the right track because of the odd sounds you're describing. Otherwise I'd say to check the ignition system. Either check that fuel pressure or simply replace the pump and see if your problems go away.

 

Can I check fuel pressure without a starting engine?

 

Yes - see my first post here - simply turn key so that ignition lights come on and your fuel pressure should be around 35psi+ (see FSM for your particular engine) ............... and if you switch off, the pressure should very slowly decay

 

If there's enough pressure, the fuel pump is probably good right? But if the pressure decays very fast, it's the pressure regulator? Do I need to do a volume test as well?

What kind of ignition test should I conduct?

 

You cannot have pressure without adequate flow - so get the "T", do the plumbing and start talking actual numbers and results of tests - no use talking it to death. Fast decaying fuel pressure can be regulator or pump or injectors as I said in the beginning already.

As for the FSM and what ignition tests to perform:

http://forums.maxima.org/3rd-generat...re-asking.html

Its simply too much to type out here again

 

What does a high pitched "clearing throat" like sound indicate when starting? I'm pretty sure it's the fuel system. fuel pump newly replaced and now I can hear a buzzing sound from the back (which is the pump, right?) but this distinctive sound is bugging me. I've been hearing it with my old pump before it failed. Does it indicate a restriction in my fuel system or new pumps really do that?

 

No clue what the sound is like so no idea what it can be - though pump is probably a good guess.

The "T" ........................... the "T"................... is the answer as I said before - results from running the motor with that in the fuel plumbing can tell anybody way more than a throat clearing sound