Alternative fuel rail. | The Z Club of Great Britain
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Alternative fuel rail.

Discussion in 'S30 (240Z,260Z,280Z) Engine' started by johnymd, Jan 5, 2019.

  1. johnymd

    johnymd
    Z Club Member

    I'm in the process of putting my ratlook 240z back to su's and have a question regarding the fuel rail. I would like to tidy up the engine bay a bit and am considering not using the factory rail/return arrangement. I'm running a red top electric fuel pump at the back and was intending to feed both carbs directly and have a restricted return off the last carb. So in effect it will be pump to engine bay then T off to one carb, T off to second carb, then restictor in the line going back to the tank. Does this sound correct? should I fit a regulator or will the carbs hold back the pressure from the pump. What size restrict will I need?

    all help or advice appreciated.
     
  2. jonbills

    jonbills
    ZClub Administrator
    Staff Member Moderator

    That's basically the same setup as the standard rail, but without the rail isn't it?
     
  3. johnymd

    johnymd
    Z Club Member

    I guess so Jon. It’s just how critical the resrictor size is.
     
  4. jonbills

    jonbills
    ZClub Administrator
    Staff Member Moderator

    I wouldn't think it too critical.
    I have a vague recollection of running something similar on mine a few years ago. I had a short length of metal tube I had as a union between the last hose on the carbs and the return line. I progressively kinked/crushed it until the pressure was what I wanted.
     
  5. toopy

    toopy
    Z Club Member

    From recent memory of renewing some of my bay hoses, the return restrictor hole is only about 1mm or 2mm diameter, i guess because there isn't a huge amount of pressure in the feed line to begin with.
     
  6. johnymd

    johnymd
    Z Club Member

    Thanks for the input.

    I’ve removed all the injection and fitted some su’s now. As a test I’ve put a simple pressure regulator in the supply line and with the pressure set for 2psi the floats hold back the fuel without passing. I’ll run it like this until I get another T piece then put a bleed off restrictor in the return.
     

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  7. toopy

    toopy
    Z Club Member

    I had the very same fuel regulator as in your picture for several years, because from reading other articles, it seemed the right thing to do when changing to electric pumps, however i took it off to renew part of the hose and forgot to reinstate it!

    I still haven't but the car runs as before and that's with a silver top pump in the engine bay which runs at, IIRC, approx 4psi.
     
  8. yellowz

    yellowz
    Z Club Member

    Does anyone use an inertia cut off with electric fuel pump?
     
  9. Jimbo

    Jimbo 1978 260z in yellow

    yes i do
    bought it off ebay for a rover of some description.
    wasnt a lot of money but it works and is a good way to imobilise the car if you hit it on purpose;)
     
    toopy likes this.
  10. Jimbo

    Jimbo 1978 260z in yellow

  11. johnymd

    johnymd
    Z Club Member

    The fascet pumps come in various pressures. The one I bought is 7psi as I didn't realise you could specify a lower pressure when ordering it.
     
  12. toopy

    toopy
    Z Club Member

    As above, wired between the relay and pump..... and the hidden isolator!
     
  13. SeanDezart

    SeanDezart
    Z Club Member
    Official Trader

    John - that's a whole bunch of cabling/tubing running in front of the head very near the fan !
     
  14. johnymd

    johnymd
    Z Club Member

    Yes Sean. Keeps things neat and tucked out of the way.

    The SU's clear your Race/Sport manifold as can be seen.
     
  15. SeanDezart

    SeanDezart
    Z Club Member
    Official Trader

    Nice - can you do possibly do me a profile shot please from front of engine to rear ?

    I'll be fitting up that other header with SUs soon this week - will let you know soonest.
     
  16. SeanDezart

    SeanDezart
    Z Club Member
    Official Trader

    Nice - can you do possibly do me a profile shot please from front of engine to rear ?

    I'll be fitting up that other header with SUs soon this week - will let you know soonest.
     
  17. Rob Gaskin

    Rob Gaskin Treasurer Staff Member Moderator

    John, 2.5 psi is what I use with SUs/Hitachi. If you are running 7 psi you will need your needle valves and floats to be 'spot-on'. I have had problems with flooding which would have been worse at your pressure.

    You don't really need a return (but nice to have) unless you suffer from hot-fuel, many people don't use one.
     
    slaphead and Paul_S like this.
  18. Paul_S

    Paul_S
    Z Club Member

    Thanks for that info Rob. I was about to say my car doesn't have a return (but it does have a regulator set to 2.5 psi).
     
  19. toopy

    toopy
    Z Club Member

    Ive read that Su's and i guess the Hitachi's can be quite forgiving with regards higher than standard fuel pressure, assuming all is in good order as Rob say's

    Weber's on the other hand can be a royal pain in the ar*e
     
  20. slaphead

    slaphead
    Z Club Member

    They can be until you get a tiny bit of muck in the system, and the needle no longer seats properly, you then have the fire hose effect of fuel coming out of the overflow hose at an embarrassingly high rate, not to mention the risk of needing the fire brigade in attendance.
     

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