One Way

fuel rail and pressure regulator suggestions-78 280Z

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    Progress continues slowly on this resurrection project.  Acquired the car a few years back.  Had not been registered since 1996 and the storage years were not very friendly to this amazingly 100% complete and original car. Being over 40 years old and badly sitting for some 20 years, the fuel system needs a total restoration.  I am cleaning up the fuel rail-bit of surface rust in areas- and will be painting it with hi temp engine spray, primer and top coat.  I am assuming the fuel pressure regulator is bad, and know all the injectors are bad.  Am I better off to just replace the pressure regulator with the OEM factory style, or upgrade to an adjustable unit with a gauge?  This is a budget project with a basically stock engine rebuild in the plans.  This is not a " numbers matching restoration" but trying to build it as a reliable, fun, driver.  Is the adjustable regulator and gauge worth the necessary minor modifications-mounting bracket, plumbing, etc.?  Thanks for all the great input I have received from the great Z car people on this site, John-Lugoff, SC

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    I would stick with OEM regulator. I would buy and install in the engine bay a good fuel pressure gauge. Since you are replacing the injectors, I would probably wait and measure PSI with your current regulator before buying a new one. It is important to really understand what psi readings you should see at idle and under load / rev. See FSM and read forum messages.

    Also, critical to make sure efi electrical connections are solid and clean, no vacuum leaks (follow the tiny vacuum lines that enable hvac controls, boot for afm / throttle body, egr valve, etc), clean fuel, etc.

     

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    Most of the adjustable regulators lost pressure rapidly after shutdown.  It's very annoying, people spend hours diagnosing hard start problems and end up replacing their regulators to one that doesn't leak down.  If you find that you need more fuel to the injectors it's better to add resistance to the coolant temperature sensor circuit.

    Short - a good OEM style regulator will probably work best.

    While you're on it though, replace all of the rubber fuel hose, especially the high pressure side.  Even back at the fuel pump.  They dry up and crack and split longitudinally and will probably leak.  Plus they're not designed for ethanol fuel.

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    And...if you really want to go an extra step for reliability, get an aluminum fuel rail.  These engines typically have heat soak/hot start problems and that is one thing that seems to really help the problem.  Very little worse than getting in to your car after 20 minutes in the store, with people watching and wondering about the cool little sports car, just to sit there for 30 seconds that seem like 30 minutes while the engine coughs and pukes until things cool down.

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    The '78's a lot easier to replace than the previous years.  It only has one inlet and then the return to the fuel tank line.  I bought from rockauto for about $70 IIRC?

    I made myself an aluminum rail and it really helped displace the heat.

    The critical measurements are in post #21 from our good friend @Willoughby Z

    And Zeds dead on about those adjustable FPRs.  The only one I've ever read that held pressure was an Airtech I believe, $250.

    You can make your own gauge for $20 and put it after the fuel filter similar to @EuroDat's.

    FuelPressureTest1.jpg

    Edited by siteunseen
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    Thanks for the great tips.  Every rubber hose is going to be replaced as we tackle this project.  The aluminum fuel rail looks a whole lot simpler and cleaner than the OEM style with all the tubing and fittings.  I will study that out a bit further.  I think the OEM rail has 3 open ends on it for the 78 model?  The aluminum rail seems to just have the 2-one on each end.  I will have to search through some pictures and see how one of those aluminum fuel rails is mounted and secured,  Thanks again, John-Lugoff, SC.

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    Been doing my research on this great website, even though I am an admitted and verifiable computer dummy, was not able to connect to some of the suggested links, the aluminum fuel rail seems to be an improved choice over the complex spaghetti bend tubing of the original.  Drilling and tapping are in my limited machining capabilities and seems like a doable project costing a lot less than the premade aluminum rails. Sounds like a fun challenge.  Just a couple of questions?  How is the new rail attached to the intake?  Are the barbed fittings tapped with NPT sizes or O-ring thread?  Do the threaded end of the fittings need to be flush with the interior base of the rail?  I could not seem to get the link with the measurements required but thought using the original rail as the template could also be a correct procedure.  Thanks for any additional experienced help and advice.  The aluminum fuel rail sure looks nicer, neater, cleaner than the spaghetti bend original fuel rail and sounds like it may also improve driveability and performance.  Thanks again, John, Lugoff, SC.

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    P.S.  Just found the measurement specs on the link.  Should be helpful.  Assuming this was a 3 ft fuel rail?  Some of the measurements were given from the end of the fuel rail , but the most important figures are the distances between each barb.  Thanks again, computer dummy John.

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    The injectors hold mine up nice and firm.  You'll need to get a '78 FPR and I used high heat threadlocker I believe from Permatex.  Tried teflon tape but it leaked.  That stuff dissolves in gas.  Just saw your post above, Slow Hand typer.  You buy it by the foot but it's actually shorter.  I'll measure mine and get the total length asap.  I have some photos on my laptop you need to see.  Run a "T" out the back, one to the FPR and the other side to the CSV.  

    And the threads on the barbs won't reach into the main line of the rail.

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    It's a measure 10 times, check level up and down 6 times, don't get in a hurry job for sure but it's actually easy. I was quite surprised with my results.

    20190824_083809.jpg

    Edited by siteunseen

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    Thanks for the great tips.  Teflon tape is a great sealer for household plumbing projects, but not very valuable when it comes to automotive or industrial applications involving gas or oil.  Sorry for the response delays but work-shorthanded as normal the past several months, church work-love serving my LORD and SAVIOR-and babysitting-always a lot of fun with the grandkids, get in the way of the car project at times.  Still waiting on some additional responses about the BCCD delete option or access to the diaphragms and gaskets needed.  Thanks again, John, Lugoff, SC

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    The picture is worth a thousand words.  Barb fitting appears to be 1/8 NPT ?  Please correct me if I am mistaken.  Also I know the FPR stands for the fuel pressure regulator, but not sure about the CSV designation.  I will certainly need to do some more homework on the plumbing.  The original FPR on the 78 has 3 barbs.  I believe 1 is the vacuum and the others were the in and out lines.  I may have it all wrong in my head.  That happens quite often.  Thanks for any additional clarification and help, John-Lugoff, SC.

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    CSV is the cold start valve, on my rail it is fed from a dedicated port on the fuel rail.  you are correct on the 78 fpr, mine is mounted on the firewall with injector hose from the output of the rail.  The other side goes to the fuel return line.

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    Thanks for the info on CSV.  Should have figured that one out for myself.  My mental image of the CSV is on the other end of the intake.  I guess it really does not matter which end supplies the fuel to the CSV.  Looking forward to this modification project and sourcing the aluminum fuel rail material, good quality barbed fittings, and the challenge of the drilling and tapping.  Suggestions welcomed, John-Lugoff, SC.

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    Just tried to fire my 280 for the fist time. Sitting 12 years plus. Replaced pump OE, injectors, all rubber lines. Pressure gauge. Cleaned and or replaced everything feasible that looked worn and or deteriorated. I had the tank cleaned and lined. Have not installed the tank as of yet. Want to restore the rear suspension first allowing more room to work. I tried to crank the engine using two fuel cans. Supply and return. The results were it fired and quit over and over again but would not run. This is what I found after trying to crank the motor.

    36 psi holding for two or three minutes then dropping down considerably after a few minutes. 

    The return can had a lot of fuel in it. Almost as if it was bypassed directly back to the tank.

    Have decent spark coming from the original coil. Rotor and cap look ok. Could be the original wires.

    Does it sound like the FPR is stuck in the open position. Everything on the vehicle is original. I’ve owed it since 1984.

    any help would be much appreciated 

     

     

     

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    7 minutes ago, Yarb said:

    Just tried to fire my 280 for the fist time.

    What year is it?  Not all 280Z's are the same.

    You might do better to start your own thread instead of piggybacking on old ones.

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    Sorry, new to the site. I can go back and start a new thread. It,s a 78 

    F7E40B10-5883-48EC-967B-1E950E23742E.jpeg

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    Sounds like it's starting on cold start valve gas, but the injectors aren't opening to keep it running.

    Might also be the oil pressure switch or alternator.  Try removing the oil pump sensor connector.  This will cause the fuel pump to run when the key is on so watch your cans.  The pummp will stay on so you'll know if it's a supply problem or something else.

    How long does it run for during each start attempt?

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    Won’t run more than 4 or 5 seconds and it’s not smooth. Are you talking about the oil pressure switch they mention in the FSM?

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    Yes, the switch and sensor are combined in one unit.  Just pop off the plug at the round sensor/switch on the side of the engine block..  Turn the key on and the pump should start running.  It's a good test of the fuel pump control system.

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    During this procedure will the fuel normally bypass the regulator and go to my return tank? On Initial turnover I’m getting 36psi and after it sits for a few minutes it drops down to 10lbs static. Meanwhile I’ve sent a lot of fuel to the return tank.

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    Try clamping the return hose off. Needle nose Vise Grips with rubber hoses on them work for me.

    Don't completely close it off, work up a little at a time.

    Edited by siteunseen

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    1 hour ago, Yarb said:

    During this procedure will the fuel normally bypass the regulator and go to my return tank? On Initial turnover I’m getting 36psi and after it sits for a few minutes it drops down to 10lbs static. Meanwhile I’ve sent a lot of fuel to the return tank.

    Yes, that's how the system works.  Fuel passes through the regulator back to the tank after 36 psi is reached.  The fact that it leaks down after the engine dies might affect starting time but won't affect how it runs once it starts.  You have a running problem not a starting problem.

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