78 280z Severe Driving Problems

[Captain Obvious]

@Zed Head cut an FPR open some time ago and took a pic. Surprised he hasn't mentioned it by now, but it looks like this inside:

Some other details in this thread:
https://www.classiczcars.com/forums/topic/47764-inside-an-fpr-the-valve/

[Zed Head]

It does look like a bad FPR.  My FPR bypass suggestion was just to make it more clear for Kinser since he commented on it.  His early videos showed that pressure would drop below 42 psi.

It's just hydraulic pressure on one side and spring force on the other.  Tried to find a view of the offending part in the previous videos but couldn't.

To Kinser - if you decide to get a new FPR beware the adjustable aluminum jobbies.  They leak down rapidly on pump shutoff.  Seems like they'd repressurize quickly but most people are annoyed when their FPR leaks down.  It's a pain and causes starting problems.

[kinser86]

Plan is to replace with an OEM replacement Bosch 64018.

[kinser86]

Alright so it has been a few weeks, funds were allocated and other projects were tended too. We swapped in a new Bosch 64018 Fuel Pressure Regulator and the pressure on the rail stays rock solid at 40-PSI. Before it would steadily climb to 42/44-PSI if you raced the engine a bit. At this point, we are going to drive the car on the street/highway a bit and check the plugs. I've banged my head around other possibilities.. maybe the voltage supply is high at the fuel pump and the stock regulator still can't keep up even though this is a 'stock' replacement. One way to check is to see what the pump pressurizes the system with the oil pressure sensor unplugged and the car turned off. The car does have the alternator swapped for a 60A ZX alternator. I have reached out to Delphi for a map of their pump for reference. Has anyone else run the Delphi pump with factory rails and measured fuel pressure? It almost seems inevitable that a palnet rail and adjustable fpr is needed in this application in order to bring the pressure down. The engine is the most responsive I've ever experienced and initial issues seem to be gone but I wouldn't be surprised to see fouled plugs in the near/distant future to recreate some of those issues. As always, I appreciate everyone's help and the car has improved leaps and bounds prior to the start of this thread.

[Dave WM]

pump output should not matter unless it was way high, so high the FPR can not keep up with it. could just be the new FPR is not the same pressure rating as the OE one. I cant recall if you ever did the return line directly into a bucket (not using the line back to the tank) to make sure it was not blocked or stuffy as Nissan likes to say. The tank can also be an issue even if the line is ok. I have heard of people having issues after pouring sealers into a tank to line it, and not making sure the return is clear inside the tank. I would try process of elimination, you have the new FPR, next would be the return line bucket, and lastly an OE pump. I replaced mine with the expensive OE pump. It had one of those smaller cheaper higher PSI pumps, I just did not like the way I had to wrap a bunch of rubber around it to use the OE mount.

[Zed Head]

1 hour ago, kinser86 said:

It almost seems inevitable that a palnet rail and adjustable fpr is needed in this application in order to bring the pressure down.

Hard to say why you're having such a problem with this.  You are having waaaaaayyy more difficulty  with getting fuel pressure down to about 37 psi than almost anybody in the history of the forum.  Kind of exaggerating but need to be clear that you should not be experiencing this problem at all.  Because it's so unusual it wouldn't be a surprise if you had similar problems with an adjustable FPR.  Even though it's adjustable.  Can't emphasize enough that the FPR is just a spring-controlled check valve, in essence, when the vacuum source is removed.  It's super simple.

It might be that somehow you're adding complexity somewhere, or somebody else did before you got the car.  Have you examined the fuel system return lines all the way back the tank?  I had considered adding a second FPR to my car for a short while because I had a pressure leak-down problem and didn't have the correct FPR to fix it right.  I never did, it was just a thought, but maybe somebody has inserted a second regulator or even a spring-loaded check valve, to hold pressure.  You might actually be fighting a PO's previous "fix".  If so, you'll have the same problem with any regulator.

[Dave WM]

I just re looked at my video  38psi , not exactly 36psi. I am at sea level. I have not confirmed the calibration of the gauge I am using. My setup runs a tad lean at idle, plugs always look fine, almost lean. look at 1:07 to catch it at engine off, pump on. Gas mileage about 22-24 on the highway at 80mph with a 5 speed (3k for 80). I have NO drivability problems (backfire/after fire/hesitation) completely stock setup with orig injectors/FPR and the OE Nissan pump. I take that back it prob had the aftermarket pump I am going to see if I have another video after the OE pump replacement.

 

Edited October 23, 2018 by Dave WM

[Dave WM]

ok well is seems I don't have a clear pick of a static pressure reading (engine off pump on) with the new pump, I will get a new video of that later just to see if there is a difference from the prior video. There are other variables of course, but at least will have a more current reading of pressures.

[Zed Head]

Should have mentioned also that it might be that today's new aftermarket regulators are just calibrated to 40 psi, or have a wide spec. range.  Quality control in the aftermarket is poor.  Bosch does not mean what it used to either.

If it runs well at 40 psi, passes emission, doesn't foul plugs, etc. consider just using it like that.

Edited October 24, 2018 by Zed Head
Said gauges meant regulators

[Dave WM]

I was thinking the same thing about the BOSCH being different from 40 yrs ago.

[Dave WM]

uploading a video now, it will have a test of a BOSCH FPR (says made in germany have no idea of its age, its in a orig box but I could not find any date of manufacture on it).

The test was to connect one side to a fuel pressure gauge (the one I have used in the prior videos), one side to a pressure regulated compressed air supply, and then slowly increase the pressure until it begins to bleed off. I was right on the nose at 36 where it began to open. I know this is not a apples to apples test but perhaps if the OP wants to duplicate it as a comparison it may shed some light on at least the function of the FPR.

[Dave WM]

here it is, the test setup is to eliminate all other variable (fuel rail, pump, lines) and just test the action of the static pressure test. I don't know for sure but I like the idea of the OE style pump have the built in regulation to not go too high, IIRC its 42psi, I doubt its super accurate but still better IMHO than some of the after markets that state they put out 90psi, that is a lot to bleed back. Perhaps the FPR is ok with that, but why chance it? anyway like I said its just my opinion I have no actual long term test to say aftermarket pumps are a problem.

 

 

Edited October 24, 2018 by Dave WM