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2002 Nissan Sentra fueling issues


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tractorboy
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Jul 28, 2020, 7:32 PM

Post #1 of 9 (256 views)
2002 Nissan Sentra fueling issues Sign In

no CEL runs great on the road at speed. its mostly idling/starting. sometimes will start great sometimes sounds like its only on 2 cylinders then the other 2 kick in. Since there are no codes.....yet, i thought the computer does not know what is happening. so i hooked up my fuel pressure gauge . supposed to be around 50psi, it was around 39 psi. i disconnected the vacuum line from the FI regulator, plugged the manifold connection and applied a vacuum to the regulator..the PSI did not drop. turned off and on again was at a different PSI , I think 20psi. i pinched off the return fuel line and the gauge went to slightly over what it is supposed to read. i released the return and it stayed. I had about 1/4 of a tank of gas ….so what do you think?


(This post was edited by tractorboy on Jul 28, 2020, 7:33 PM)


Tom Greenleaf
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Jul 28, 2020, 9:04 PM

Post #2 of 9 (246 views)
Re: 2002 Nissan Sentra fueling issues Sign In

I'm tired, forgive me please!
Just because it's a bit all over the place with your observations try checking for battery voltage when a lower RPM because you said lower RPM (idle) and start up was going bad on you. That's also when voltage could be below par to pump fuel properly and the rest of everything.


Why? Might be belt is quietly slipping (tensioner at limit?) or battery just losing it.


Other why for a reason: Change of seasons now (for me) the insane heat brings out things that don't do well in it. Power from a battery for anything, a fuel pump and or other electric motors really doesn't like it car/truck/other equipment, household - anything I'm going nuts with stupid crap screwing up!


Tom



Hammer Time
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Jul 29, 2020, 4:24 AM

Post #3 of 9 (236 views)
Re: 2002 Nissan Sentra fueling issues Sign In

I don't know where you got you spec from but here is the factory spec for fuel pressure.

With Regulator Vacuum Hose Connected 235 kPa (34 psi)
With Regulator Vacuum Hose Disconnected 294 kPa (43 psi)

What's more important here is how long does it take to reach spec when started cold. (during the problem)



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



tractorboy
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Jul 29, 2020, 5:01 AM

Post #4 of 9 (225 views)
Re: 2002 Nissan Sentra fueling issues Sign In


Quote
I don't know where you got you spec from but here is the factory spec for fuel pressure.

from Nissans service manual i downloaded from https://www.nicoclub.com/nissan-service-manuals


Quote
What's more important here is how long does it take to reach spec when started cold.

you mean by spec ..the correct fuel pressure? thats just it the fuel pressures are random, i restarted and it was 20 psi stayed like that after the fan came on. another time it was 39psi, undoing the vacuum line has no affect as does applying a vacuum to the fuel regulator.


(This post was edited by tractorboy on Jul 29, 2020, 5:05 AM)


Hammer Time
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Jul 29, 2020, 5:19 AM

Post #5 of 9 (219 views)
Re: 2002 Nissan Sentra fueling issues Sign In

That is a misrepresentation of those manuals. They gave it the name of factory manuals but they actually are not.

Quoite from their page...............Mistakes: Occasionally, you may run across a mistake or misprint in the FSM. While this is rare, we certainly like to know about it. Feel free to email us at webmaster@nicoclub.com if you find something you think might be inaccurate.

My info came from Alldata which does get the info from OEM service manuals and is a paid subscription so mine if the correct one.

If you are only seeing 20PSI at any time, then you have a fuel problem that you need to get to the bottom of. If pinching off the return immediately brings it up over spec, then it would be reasonable to suspect the regulator but make sure that is actually the case.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



(This post was edited by Hammer Time on Jul 29, 2020, 5:20 AM)


tractorboy
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Jul 29, 2020, 10:10 AM

Post #6 of 9 (197 views)
Re: 2002 Nissan Sentra fueling issues Sign In

I was wondering about those manuals, they are a bit sparse considering that the factory manual from Helm for my 2003 Impala is 3 thick volums. And my 2006 Malibu manual I think is 4 volums.


tractorboy
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Aug 2, 2020, 8:09 PM

Post #7 of 9 (146 views)
Re: 2002 Nissan Sentra fueling issues Sign In





something Tom Greenleaf said that indirectly i have been trying to find out and that is belt tension for the sentra. Nissan has a belt tension tool. would it be safe to say that on the longest span of the belt 1/2" deflection in the center pushing down with a finger.


(This post was edited by tractorboy on Aug 2, 2020, 8:12 PM)


Tom Greenleaf
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Aug 2, 2020, 9:11 PM

Post #8 of 9 (139 views)
Re: 2002 Nissan Sentra fueling issues Sign In

Just the note on operating voltage and belt tension:
It's best when even at idle voltage (the pushing force of electrical power) is 13.5 or so not 12ish matters. If alternator slips it wont keep up fuel pump is a motor uses some power that comes from alternator once running.


All toys in things want the correct range or go nuts so all bets off unless right.


Belt is measurable by the "deflection" you mentioned is by longest part between pulleys should be listed is a feel or try turning something not too loose not too tight or hard on all items.
You can watch it via volts at battery or a power port change with assorted things operating at idle should never drop too low if raising idle with gas pedal solves it maybe belt is why tension part of the show,


Tom



Hammer Time
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Aug 3, 2020, 3:38 AM

Post #9 of 9 (133 views)
Re: 2002 Nissan Sentra fueling issues Sign In

Were those pressure reading taken at the same time the problem was present?

That's the only time it will matter. Once the symptoms have passed, there's no point in taking the readings.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.







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