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NA 1990 300zx, no fuel pressure after new pressure regulator


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Theron21
User

Aug 30, 2016, 8:08 AM

Post #1 of 21 (1507 views)
NA 1990 300zx, no fuel pressure after new pressure regulator Sign In

 have a NA 1990 300zx that doesn't seem to be getting fuel past the fuel pressure regulator. I just bought a new pressure regulator and installed it in hopes that would fix the problem but it still doesn't have any pressure past the regulator. When I got the car just about all the rubber in the engine bay was dry rotted so I have replaced all the vaccum, fuel and water lines. I also did aiv, prvr and egr delete to simplify the engine. I have the vacuum line that goes to the FPR going to the plenum as instructed in multiple forums I have read for doing the aiv and prvr solenoid delete. Only thing I can think is that the plenum isn't creating enough vacuum to open the diaphram in the FPR but i dont know how to fix that. I can spray starter fluid in the plenum and the car will start up till it burns off the starter fluid...


kev2
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Aug 30, 2016, 8:26 AM

Post #2 of 21 (1500 views)
Re: NA 1990 300zx, no fuel pressure after new pressure regulator Sign In

This a track only vehicle, off road?
Did you check fuel pump - start with fuse and relay as well as wiring to pump?


(This post was edited by kev2 on Aug 30, 2016, 8:35 AM)


Theron21
User

Aug 30, 2016, 8:37 AM

Post #3 of 21 (1497 views)
Re: NA 1990 300zx, no fuel pressure after new pressure regulator Sign In

Yes sir.. I have pressure all the way up to the regulator then nothing after the regulator. That's why I bought a new regulator thinking it would probably fix the problem but still no pressure to the fuel rail.


Theron21
User

Aug 30, 2016, 8:39 AM

Post #4 of 21 (1496 views)
Re: NA 1990 300zx, no fuel pressure after new pressure regulator Sign In

Sorry I didn't see u asked if it was a track car. No its gonna be a daily driver if I can get it running


Theron21
User

Aug 30, 2016, 8:51 AM

Post #5 of 21 (1486 views)
Re: NA 1990 300zx, no fuel pressure after new pressure regulator Sign In

Could it be that my plenum has a small leak or the throttle body is adjusted just a hair to high and it isn't creating enough vacuum inside the plenum to open the diaphram in the FPR?


kev2
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Aug 30, 2016, 9:01 AM

Post #6 of 21 (1475 views)
Re: NA 1990 300zx, no fuel pressure after new pressure regulator Sign In

how much fuel pressure ?
did you change filter ?
remove the vac line to FPR that would be full pressure ie WOT.


Keep the emission devices they will be needed for registered vehicles.


Theron21
User

Aug 30, 2016, 9:14 AM

Post #7 of 21 (1474 views)
Re: NA 1990 300zx, no fuel pressure after new pressure regulator Sign In

I don't have emission regulations where I live but idk exactly how much pressure. I didn't think it had pressure at all till I took the lines off and the 1 that goes from the filter to the regulator had alot of pressure in it as gas blew out everywhere when I disconnected the line but when I took the regulator off the line that goes from FPR to fuel rail was bone dry.


Tom Greenleaf
Ultimate Carjunky / Moderator
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Aug 30, 2016, 9:26 AM

Post #8 of 21 (1470 views)
Re: NA 1990 300zx, no fuel pressure after new pressure regulator Sign In

Just comments in general for this: Kev2 said it just now - leave it alone if for legal road use. These cars at the age and older had harsher emissions requirements designed then for the Japanese limits were much earlier than other places.


Car/engine was very well made to tolerate what they designed with not alterations. I can't guess what altered might prevent fuel deliver at all is you really mean ZERO - none with ZERO pressure.


They also design in to shut fuel flow off this or that way in case of an accident - guessing how as I can't know. If it sees no vacuum at something you altered it might think engine isn't running so don't deliver fuel.


Get pressures if you hear pump working. Think hard about putting it all back the way it was designed as none of the controls harmed it's power or performance TMK at all so no benefit to by-pass anything on this,


T



Theron21
User

Aug 30, 2016, 9:27 AM

Post #9 of 21 (1469 views)
Re: NA 1990 300zx, no fuel pressure after new pressure regulator Sign In

I just tried to start it with the vacuum line disconnected... didn't change a thing. I can feel the pressure in the lines going to the FPR then I can feel the one on the bottom side of the FPR and it feels like it has no pressure in it.


Tom Greenleaf
Ultimate Carjunky / Moderator
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Aug 30, 2016, 9:42 AM

Post #10 of 21 (1465 views)
Re: NA 1990 300zx, no fuel pressure after new pressure regulator Sign In

You really need real pressure observations not just "feels like" stuff.
General again: Vehicles since forever almost need to stop fuel delivery on purpose. By 1990 and long before even there would be "grace" periods for start up as there would be no vacuum. If none seen would be a way to shut it off to prevent a wild fire.
If they sold a car that could pump fuel over a hot engine and know accidents happen and could it would be sold or recalled.
You can't know every design the car would work for. Around 1990 models you'd have some or all of Japan's requirements which usually covered California without alterations was ahead of limits than other states or countries.


In short - pressure? Is there any that just meets specs? Then think about why it doesn't pass the regulator vacuum controlled or electrically watched also? I just can't know that for this just that you messed with it,


T



Theron21
User

Aug 30, 2016, 9:44 AM

Post #11 of 21 (1465 views)
Re: NA 1990 300zx, no fuel pressure after new pressure regulator Sign In

If the car was telling itself not to put fuel to the engine it wouldnt stop it at the regulator... the regulator has no hook up to the computer its mechanical not electrical. I did remove the Pressure Regulator Vacuum Relief. PRVR Solenoid raises the fuel pressure under certain conditions. It is believed that it was implemented to prevent "vapor lock", a condition that plagued early 240Zs, but is practically unheard of on modern fuel injected cars. Everything I have read on doing the delete on this solenoid said it would be fine to do away with it and re run the vacuum line to the plenum which is what I did.


kev2
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Aug 30, 2016, 9:59 AM

Post #12 of 21 (1460 views)
Re: NA 1990 300zx, no fuel pressure after new pressure regulator Sign In

fuel pressure 35PSI and 43psi vac line off...
AS pump only runs @2seconds might want to jump relay to 'prime' system, seeing this is second FPR - correct part?- I am guessing the issue is pressure -


FYI: You cannot remove or render inoperative emissions devices, doesn't matter what state - AND being old these parts will get harder to find and more expensive.. keep it all - stock is best.


Theron21
User

Aug 30, 2016, 10:04 AM

Post #13 of 21 (1459 views)
Re: NA 1990 300zx, no fuel pressure after new pressure regulator Sign In

How do I jump the relay to prime the system? Which relay exactly?


Tom Greenleaf
Ultimate Carjunky / Moderator
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Aug 30, 2016, 10:14 AM

Post #14 of 21 (1456 views)
Re: NA 1990 300zx, no fuel pressure after new pressure regulator Sign In

OK - Can't be at this one thread forever. You've added vacuum (so you think) that it would have had for that one item would suggest it's effectively ready to work. Just because you found a spot to tap vacuum doesn't mean it's the "manifold" vacuum it could be air speed or venture effect vacuum.


My real point is Japan was early and made designs per order. This was probably available for use with leaded fuel and adapted to that as well. Lower octane than another place had and so on. Aggressive engineering to market cars to as many places as possible.


It's just primary rules or not to disallow fuel to flow under certain circumstances is all I'm saying. How each maker does what for absolute sure at this age is going to be difficult to know and was on the list of reasons why it doesn't seem to get fuel.


Could use some real pressure and vacuum readings so you can see that thing at least get what assorted items should expect,


T



kev2
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Aug 30, 2016, 10:43 AM

Post #15 of 21 (1447 views)
Re: NA 1990 300zx, no fuel pressure after new pressure regulator Sign In

on the top @ center of page is a window "MESSAGES" send me a message with your email and I will to send you some info...
I am wondering if the information you were getting was helpful or not.


a project car is a good hobby and the learning was invaluable - I remember but I digress.


Theron21
User

Aug 30, 2016, 11:12 AM

Post #16 of 21 (1441 views)
Re: NA 1990 300zx, no fuel pressure after new pressure regulator Sign In

Is there any way u can send me your email in a message? I tried to send you mine but it wouldnt load to send it. It just sat there for the past 10 minutes trying to send but it wouldn't go through.


Discretesignals
Ultimate Carjunky / Moderator
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Aug 30, 2016, 11:53 AM

Post #17 of 21 (1435 views)
Re: NA 1990 300zx, no fuel pressure after new pressure regulator Sign In


Quote
I just bought a new pressure regulator and installed it in hopes that would fix the problem but it still doesn't have any pressure past the regulator.


You're not going to have any pressure after the regulator because that line goes back to the fuel tank. The pressure line from the pump goes into the fuel rail after going through the fuel pressure damper. You need to T in a fuel pressure gauge at the line that goes into the rail or damper. It should be at or near the specs that Kevin provided. If you have pressure at that point, you need to find out if you have injector pulse.







Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Aug 30, 2016, 12:02 PM)


Theron21
User

Aug 30, 2016, 12:04 PM

Post #18 of 21 (1430 views)
Re: NA 1990 300zx, no fuel pressure after new pressure regulator Sign In

I don't exactly mean pressure. Just fuel in general. It's not going past the regulator. I just went and got a vacuum pressure tester and my intake has almost no vacuum while I'm trying to crank it. The needle hardly even moved.. could that keep the regulator from working?


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Aug 30, 2016, 2:30 PM

Post #19 of 21 (1408 views)
Re: NA 1990 300zx, no fuel pressure after new pressure regulator Sign In

I'm glad DS jumped in here because you were making no sense at all. I don't know why you are the least bit concerned with what is after the regulator. You need to test your fuel pressure BEFORE the regulator and then determine if there is any issue at all.

Forget about the return line. It tells you nothing.



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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.



kev2
Veteran
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Aug 31, 2016, 10:05 AM

Post #20 of 21 (1378 views)
Re: NA 1990 300zx, no fuel pressure after new pressure regulator Sign In

        
Theron21 did you get the information I sent?


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Aug 31, 2016, 12:21 PM

Post #21 of 21 (1370 views)
Re: NA 1990 300zx, no fuel pressure after new pressure regulator Sign In

Lets try to keep as much information as possible in the thread so all can see it.



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

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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