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Thread: Fuel Pouring out of front Carb

  1. #1
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    Default Fuel Pouring out of front Carb

    So i just got a 240z last week, always loved them now finally a chance to own one. i have been doing very well fixing her up but one thing has me stumped. When the car is running the carbs both appear to work fine, but once the engine is shut off, the front carb begins to pour out fuel from the opening where the air filter would normally go, this continues for a good 15 to 30 seconds after the engine is shut off. any ideas???

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    Registered User olzed's Avatar
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    Im assuming origional carbs and engine.
    What type of fuel pump.Does it still have the fuel return line which leaks excess fuel back to the tank? Might be a leaky float valve in the carb or float level set wrong.
    Last edited by olzed; 09-29-2010 at 10:04 PM.

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    Registered User Travel'n Man's Avatar
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    I'm betting money on the incorrect float setting - just a warning - before you start with the float adjustment - read and research - also go ahead a purchase a min of 4 float bowl gaskets from your local Nissan dealer or Z Therapy - trust me, you'll need them!
    Life's a journey; enjoy the ride!

    Mitchell
    L28 - N42 Block w/Flat tops - N42 Rebello Head & Cam - Triple 40 PHH Mikuni's - Headers - Recaro Seats -
    R180 3.9 Diff - Close Ratio 5 Speed - Toyota Vented Brake Upgrade w/ Porterfield High Performance Pads & Shoes

    1972 Datsun 240z
    HLS30-75040


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    Furthur GreenZZZ's Avatar
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    I had a float bowl needle valve stick open and it leaked while the car was running. I was lucky it didn't burn the car up.
    Lee - 2/72 240Z

    Thinking ahead is NO EXCUSE for thinking!

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    Registered User Gary in NJ's Avatar
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    My money is on a stuck float valve.
    Gary
    Guardian of HLS30-91415
    Previous Owner of a 10/70 240Z ('83-'85)

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    240zdave 240zdave's Avatar
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    Sometimes you can unstick the float valve by tapping the float bowl with something like a screwdriver handle. If that gives no results, then you probably need to get into the float bowl, remove the valve and make sure it's clean and working (blow compressed air through it). And while you're in there, you might as well make sure the float is set properly.

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    Man, that's a stumper. Hard to imagine that with only 3+psi fuel pressure that there would be enough residual pressure, after shut off, to overfill the floatbowl enough to run out the mouth of the carb.

    You are new to the car, right? First thing I'd do is to look into what's there in the way of fuel pump/s. Assuming it's a 240 there should be a mechanical pump on the side of the head and there may be an electric pump back by the tank. Sum total output should not exceed like 3+ psi.

    Let us know what you find. And do not assume the previous owner/s played by the rules.
    Bruce Palmer
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    Registered User mlc240z's Avatar
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    Yes, listen to Bruce.
    I've heard he knows a 'little' bit about carbs.

    Sounds like both a stuck valve AND something causing overpressure like an over-pressured electric fuel pump or clogged return line or boiling fuel.
    Fuel 'pouring' out for 15-30 seconds seems a little extreme.
    Bart

    5/71 240z, HLS30-31306, mostly stock, ZTherapy SU's, Pertronix, Eibach ProKit, KYB, Poly bushings, 60 amp alternator w/Dave's plug bypass, headlight and parking light harness upgrades.

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    Registered User esmit208's Avatar
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    Checking the float valve is something you should do if you decide to open her up. But also the float itself has a seam around it and eventually that seam begins to take on fuel and no adjustment will cure the problem. Get a rebuild kit from Z-Therapy or any other supplier and also look into getting some replaacement GROSE JETS. If you are going to open it up you might as well set your mind at ease with a complete service. The kit should come with a guage to porperly set the float height as well. Also look at an exploded view of the carbs.

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    Registered User Gary in NJ's Avatar
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    Shouldn't the grose jets (float valves) be changed in pairs? I suggest looking at both carbs. Once you see how easy it is to set the front, you'll see that it's worth the effort to check the rear.
    Gary
    Guardian of HLS30-91415
    Previous Owner of a 10/70 240Z ('83-'85)

  11. #11
    AZ Z Fan duffman's Avatar
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    I thought they quit making the Grose jets for a number of years, did they just start making them again? I am excited they are available again and will order some immediately!
    January 1970 240Z
    HLS3001399

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    We have not been able to get Grose Jets for about 8 years.
    Bruce Palmer
    Salem Or
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    AZ Z Fan duffman's Avatar
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    Hey, Bruce, are these the right size of Grose jet for the Z SUs?

    http://www.minimania.com/web/Item/AU.../InvDetail.cfm
    January 1970 240Z
    HLS3001399

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    AZ Z Fan duffman's Avatar
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    Also, how does MSA get the Grose jets for their remanufacuted SUs?

    http://www.thezstore.com/page/TZS/PROD/11-3001
    January 1970 240Z
    HLS3001399

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    Registered User Powderkeg's Avatar
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    Duffman,

    The orifice size and threading are different on the HS Model Su's and will not fit the Z SU's.

    I don't know why MSA keeps advertising Grose jets in their rebuild section. At one time I called MSA and they said they no longer can get Grose Jets.
    Also, I believe that Z therapy is the company that rebuilds the carbs for MSA...so Bruce would know.


    Here's some of the information I have been able to dig up over the years about Grose jets:

    The Grose Jets were made by D & G Valve:
    8 Mt Vernon St.
    Stoneham, MA 2180
    (781) 438-1789.

    However no one answers the phone or returns inquiries by mail (As of 2008)

    I did read a 510 newsletter that stated BTR Engineering in Australia has acquired the patents to the SU's and is producing the carburetors and parts. Unless things have changed since I emailed them (2008) they handled all the SU's EXCEPT for the Z Cars.

    Also, some have had problems with Grose jets sticking too and went back to using the stock parts.

    Hope this helps.

    Dave Ruiz


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    AZ Z Fan duffman's Avatar
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    Thanks,. Dave, I thought Z Therapy did the remanufactured MSA carbs. Sad to hear that they are not available, would like to try them out!
    January 1970 240Z
    HLS3001399

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    MSA is about as poficient at getting out of date info off their web site as we are and I say that only if they still reference Grose Jets. I haven't looked at their web site in a long time..... hell, I haven't looked at our web site in a long time.....

    I would be really surprised if any patents are still in place that would preclude anyone from producing and selling an on/off valve of the Grose Jet variety. They first came out in the 50's. Anyone here proficient in patent law?
    Bruce Palmer
    Salem Or
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    Registered User Powderkeg's Avatar
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    I looked up BTR Engineering and they no longer list a web site.

    What little I do know about patents is BTR can buy the rights. They would also have to pay the yearly maintenance fees. Both of which are not inexpensive.

    If you're really dying to find out, there is a patent attorney who is also a Z enthusiast by the name of Gary Baker at either zhome.com or AtlanticZcarclub who I'm sure would know.

    Maybe the Chinese will manufacture them. . . they really abide by patent law! Sorry...I digress.

    Another question is: who makes the Grose jets that are currently being sold for the mini's and MG's ?


    Duffman
    If it makes you feel any better, yes, the Grose jets are a neat item but the stock jets work just fine. So if you can get past the outdated website at ZTherapy , give Bruce a call.

    Dave Ruiz

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    Registered User olzed's Avatar
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    So, Did the man cure his leaky carb?

  20. #20
    Furthur GreenZZZ's Avatar
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    Quote Originally Posted by Powderkeg View Post
    Also, some have had problems with Grose jets sticking too and went back to using the stock parts.
    My stuck valve was a Grose jet. It happened after the car was sitting for a year so I cleaned it and still run the Grose jet. That was about 10 years ago and no other incidents.
    Lee - 2/72 240Z

    Thinking ahead is NO EXCUSE for thinking!

  21. #21
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    Just to get this thread back onto the ORIGINAL question, when you take the top off the carby, look for any tiny black bits in the bottom of the bowl. If the rubber fuel lines are as old as the car, the inside of the hoses could be breaking down.

    Happened to me with the rear carby. New fuel lines fixed the problem.

    Rick.
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    I adjusted the float, and everything seems to be running fine so far, i have not been able to really work on it the past few days thanks for all the help!

    on a side note, would bad/ torn gaskets be the cause of my 3000rpm idle when mix is lean and idle is set to full low?


    Tim

  23. #23
    Registered User Gary in NJ's Avatar
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    Quote Originally Posted by Captainhaak View Post
    on a side note, would bad/ torn gaskets be the cause of my 3000rpm idle when mix is lean and idle is set to full low?
    No. Is your fast idle screw out at all? That should be fully retracted after the fast balance is set.
    Gary
    Guardian of HLS30-91415
    Previous Owner of a 10/70 240Z ('83-'85)

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    Default Gentlemen, i had the same problem car shutting off

    Gentlemen, i had the same problem car shutting off what i first diid was take the gas tank out and notice it was rusted and sending particles to the fuel pump. so i dumped the old gas tank and replaced it whith a refurbish one problem solved.

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