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Technical fuel pressure too high

Discussion in 'The Hokey Ass Message Board' started by ohenry, Jul 6, 2018.

  1. ohenry
    Joined: Jun 25, 2012
    Posts: 53

    ohenry
    Member

    I've got a problem with too high fuel pressure on my 57 wagon....I have 11 lbs pressure at idle and 16 lbs at a fast idle (1500-2000 rpms).I've replace the mechanical pump twice and put the third pressure regulator on it. I can set the pressure at 4.5-6 lbs. and it will hold there for a day or so then back to the high pressure.. The pump is for a '69 chevy 350, which is the engine in the car...The pressure gets so high that gas will come out of the vent on carb and pour into engine. Before the regulator goes bad it will start leaking...Any ideas from anyone ??????
     
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  2. I would say you need a higher quality regulator or need to adjust the float level on the carburetor accordingly
    I had a Stromberg rebuild kit that the float stop actually did not allow the needle to seat and close off so it would flood out all the time before I modified the float stopper


    Sent from my iPhone using The H.A.M.B. mobile app
     
    RonaldR likes this.
  3. flynstone
    Joined: Aug 14, 2005
    Posts: 1,717

    flynstone
    Member

    cheap ass fuel pumps 2 in a row at 10 lbs, had to add a regulator, to lazy to try a 3rd...never had this problem before....delco's to boot
     
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  4. ohenry
    Joined: Jun 25, 2012
    Posts: 53

    ohenry
    Member

    I've rebuilt the carb and float which didn't help...I'm using Holley regulators..I just today changed from stock cast iron intake and 2 barrel Rochester to eldebrock aluminium intake and 600 carb ...I know this wouldn't fix high pressure but wondered if eldebrock carb would handle it better....it didn't. My biggest question is why would a stock fuel pump put out that much pressure and how to correct it....
     

  5. Truck64
    Joined: Oct 18, 2015
    Posts: 4,833

    Truck64
    Member
    from Ioway

    I've read this is a problem with offshored parts.
    Measure it. If it's bad, take it back. If it takes 10 pumps to find a good one... If everybody sent them a labor charge bill @ $100 an hour for R&R of defective, shitty parts this wouldn't happen.

    One thing you can try is add an extra gasket or two. Probably won't bring it diwn from 10psi to 4.5psi but maybe some. This was a tip somebody brought up here at the H.A.M.B, it moves the pump arm farther out from the eccentric on the camshaft.
     
    Unkl Ian likes this.
  6. Is the pump on your engine for a positive displacement fuel system that requires a fuel return line?
     
  7. ohenry
    Joined: Jun 25, 2012
    Posts: 53

    ohenry
    Member

    No , the pump has no return line....the problem just started overnite...car was running fine one day and the next it was flooding .....that's why I changed the fuel pump thinking that was problem..2nd pump did same thing so on to 3rd thinking I got bad one ...same thing....why would a stock replacement pump put out so much pressure?
     
  8. Truck64
    Joined: Oct 18, 2015
    Posts: 4,833

    Truck64
    Member
    from Ioway

    Because the 2nd grade got laid off that week.
     
  9. Try buying a different brand of pump. I had this happen with a pump I bought at NAPA, 16 psi. retuned it, 2nd was 13 psi. Got one from the Zone, works fine.
    Quality control at some china factories isn't so great I guess...
     
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  10. Engine man
    Joined: Jan 30, 2011
    Posts: 3,476

    Engine man
    Member
    from Wisconsin

    You need a regulator with a return line to the tank.
     
  11. ohenry
    Joined: Jun 25, 2012
    Posts: 53

    ohenry
    Member

    All 3 pumps came from Advance auto....I did notice that all 3 had really stiff springs on the arm ..could that cause pressure spike ?
     
  12. dirty old man
    Joined: Feb 2, 2008
    Posts: 8,912

    dirty old man
    ALLIANCE MEMBER

    Agree 100%, and also agree with trying another brand pump. You say you got it at Advance, but what brand is it? Maybe try a Holley pump or another name brand.
     
  13. 302GMC
    Joined: Dec 15, 2005
    Posts: 6,923

    302GMC
    Member
    from Idaho

    The cure used to be an AC pump. They would give a uniform 5-6 lbs. every time. This may or may not hold true today.
    I learned this lesson w/ an Airtex good for 18 1/2 lbs.
     
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  14. Terrible80
    Joined: Oct 1, 2010
    Posts: 783

    Terrible80
    Member

    I wonder if you put a filter with a return and plumbed it to a tee before the pump would it work the same as a return to the tank?

    Sent from my LG-TP450 using The H.A.M.B. mobile app
     
  15. Engine man
    Joined: Jan 30, 2011
    Posts: 3,476

    Engine man
    Member
    from Wisconsin

    I suspect the regulator failed. A regulator with a return to tank is less likely to fail as it is only subject to the pressure it is set to. Returning fuel to the tank also keeps it cooler as it has a constant flow. The spring in the pump determines the pressure unless the pump has a bypass.
     
  16. Johnny Gee
    Joined: Dec 3, 2009
    Posts: 9,383

    Johnny Gee
    Member
    from Downey, Ca

    Very entertaining to read all the add on's required for a devise that didn't need add on's ever before.
     
  17. seb fontana
    Joined: Sep 1, 2005
    Posts: 7,073

    seb fontana
    Member
    from ct

    Chinese times.
     
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  18. Beanscoot
    Joined: May 14, 2008
    Posts: 2,077

    Beanscoot
    Member

    How the heck can a mechanical fuel pump deliver too much pressure?
    Is your gauge calibrated?
    Considering that you have tried several fuel pumps, and regulators, maybe the fault is not in the pumps.
    The amount of pressure that a mechanical fuel pump can deliver is determined by the diaphragm spring. So a manufacturer would have to install the wrong spring, i.e. one that is twice as stiff as the correct one, to cause the problem you have.
    I would have thought this almost impossible, but maybe in China heavy springs are cheaper than light springs.

    How about getting an early, rebuildable fuel pump and a current manufacture rebuild kit for it. That way the pressure will be what it was when that pump was made.
     
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  19. RmK57
    Joined: Dec 31, 2008
    Posts: 1,824

    RmK57
    Member

    I've always had good luck with Carter mechanical fuel pumps. Some of the higher end pumps are rebuildable also.
     
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  20. Truck64
    Joined: Oct 18, 2015
    Posts: 4,833

    Truck64
    Member
    from Ioway

    That auction site has a pretty wide selection of complete rebuild kits to include Viton diaphragm, for period fuel pumps, that are supposed to be Ethanol tolerant. They cost about twice what a new fuel pump costs though. If you don't need all the springs & gee-gaws maybe Viton sheet can be made to work.

    Fuel pump pressure (and volume) is an important specification, because every further adjustment or setting downstream of the fuel pump on a carburetor is based on the assumption that the fuel pressure is within limits, not too high, not too low.

    Replaced the pump on the ole' Y-Block with an Airtex FE style pump that has the integral filter, and really had to crank the float down quite a bit to get the wet fuel height in the carb bowl right. I bet if I checked the pressure, it's too high.
     
  21. What kind of regulator are you using ?
    Don't say "Chinese".
     
  22. ohenry
    Joined: Jun 25, 2012
    Posts: 53

    ohenry
    Member

    the regulators are Holley and the pumps are Carquest from Advance Auto. Changing fuel pump is a pain as there is no room to work . I've checked all the local parts stores and there are no AC Delco pumps on the shelf...all have to order..
     
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  23. dan31
    Joined: Jul 3, 2011
    Posts: 1,081

    dan31
    Member

    That new Edelbrock won't like the higher fuel pressure either, it will push fuel right past the needles.
     
  24. Johnny Gee
    Joined: Dec 3, 2009
    Posts: 9,383

    Johnny Gee
    Member
    from Downey, Ca

    Laugh all you want but a ball valve tee'd off the pressure line onto a return line to the tank has proven it's cheap cost over high dollar regulators greatly. Not advised for street use so don't do it.
     
  25. flynstone
    Joined: Aug 14, 2005
    Posts: 1,717

    flynstone
    Member

    both of mine were ac delco……..its just no more q/c I guess, never had that problem before, and I have changed out many
     
  26. Beanscoot
    Joined: May 14, 2008
    Posts: 2,077

    Beanscoot
    Member

    "Laugh all you want but a ball valve tee'd off the pressure line onto a return line to the tank has proven it's cheap cost over high dollar regulators greatly. Not advised for street use so don't do it."

    Lots of vehicles had a return system with a carburetor. It would have a restrictor in it, about 1/32" or 1/16".
     
    Johnny Gee likes this.
  27. clem
    Joined: Dec 20, 2006
    Posts: 3,431

    clem
    Member

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