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Thread: Fuel pump ?

  1. #1

    Default Fuel pump ?

    Does the stock fuel pump have a return?

    i am working on another guys 715 and in an attemp to get it running/stopping.

    i had to order a civvy style single stage fuel pump because the stock one was gone. it has no return port and is creating more pressure than the float can apple to the needle. fuel is just pumping out of the bowl vent. i have a filter with a retun line built in, but see no area on the tank for a return. i am going to plumb it to the vent in the filler neck if all else fails. but the good news is that it runs on gasoline great before it floods itself.
    thanks
    Ryan

  2. #2
    Join Date
    Sep 1998
    Location
    North Central Wisconsin
    Posts
    11,520

    Default

    There is no return line for the stock pump.

    Usually, the needle will be blown off the seat around 5-7 psi...if the civvy pump is made for a carb, it shouldnt be exceeding that psi number...or it wouldnt work on the civvy carb.

    If you do put in a return to the filler neck vent line you should make sure there is nothing in that line before you do. It is often holding a quantity of fluid, like old gas or some other nasty stuff, that has been in there for a long time. This is due to the vent line starting up at the filler neck and ending up at the air cleaner but dropping to the frame in between. The low area of the hose fills and doesnt go anywhere...

    Might be something to avoid using as a return line too as this is the tanks vent line and if you push fuel into it and it sits in the low part, the tank wont vent.

    I bought mne and didnt know tis problem. I was driving, after filling up, for about a hour...truck died like it was out of gas...basically, it was...I finally tried removing the fuel cap after trying everyting under the hood and heard the tank breath in deeply.

    When I got home I took the line off and blew it out...there was ALOT in there...

    NOTE: If you are gonna blow out the line, remove both ends and blow from under the hood...like an idiot, I blew from the tank end...what a wonderful lesson I learned when I looked under the hood........

  3. #3
    Join Date
    Jul 2007
    Location
    Rhoadesville, Virginia (five miles from no place)
    Posts
    5,125

    Default

    Two other things to add to Jon's info above:

    1) Be sure you have a vented gas cap if you do decide to route a return line to the filler neck, otherwise you'll have no way for the tank to vent.

    2) I tried to use the filler neck vent for a return for my fuel injection. The fuel returning and spraying into the filler neck is fine until you decide to remove the cap while the truck is running. It will give you a nice shower of fuel! I made a 90 degree fitting to turn down into the filler neck and direct the fuel downward. With the F.I. there is some considerable volume. With a mechanical pump it is much less but still something to consider.
    "Free advice is worth what you pay for it."™

  4. #4

    Default

    i talked to the guy last night and he was fine with me adding an additional fitting to the steel filler neck, so the tank can vent and still have a return. for now i just want it to run without flooding.
    Ryan

  5. #5
    Join Date
    Jul 2007
    Location
    Rhoadesville, Virginia (five miles from no place)
    Posts
    5,125

    Default

    Have you put a fuel pressure gauge on the pump to see what kind of pressure its putting out? Most mechanical pumps generally aren't capable of more than 2-3 psi. Even the little "ticker" electric pumps are only capable of 3-4 psi max.

    I'd check the needle valve and float in the carb too, before I went to the trouble of stringing a new line all the way to the back of the truck.
    "Free advice is worth what you pay for it."™

  6. #6

    Default

    i rebuilt the carb, new needle valve. and when i found the problem i took the bowl off the carb and made sure the float actually floated. i could get the needle to stop flow of fuel with no real presure, so i am assuming it is functioning
    Ryan

  7. #7

    Default

    After reading this and you're other thread I think you have the float adjusted incorrectly. The fuel pump should put out 4-5 psi. Less than this or more than this the carb won't operate properly. If fuel is coming out the vent then your float level is too high which is again consistent with the leaking fuel in the other thread.

    How did you set your float level? Did you follow the procedure in the manual?

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