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Anyone ever modify a mechanical fuel pump

Discussion in 'The Hokey Ass Message Board' started by 3onthetree, Jan 9, 2010.

  1. 3onthetree
    Joined: Feb 25, 2008
    Posts: 161

    3onthetree
    Member

    I'm thinking of a way to modify a mechanical fuel pump so as to attach a priming lever. I've seen a few diesel motors that have this feature to pressurize the system and bleed the air from the system after changing the filters etc. This would be a good thing to have on a older car that isn't run every day so you don't have to crank the engine for so long before starting. Just pump the lever a few strokes then hit the switch. Has anyone ever done this or know how to modify a pump in such a manner? Or know of any pumps that would fit Chevys / Fords that already have this feature? Thanks.
     
  2. HemiRambler
    Joined: Aug 26, 2005
    Posts: 4,208

    HemiRambler
    Member

    Never seen it - sounds kinda cool. Another method would be to run an electric pump in parallel - hit the switch just to prime the carb and then run it off the mech pump as normal.
     
  3. Hyway Hauler
    Joined: Aug 31, 2009
    Posts: 670

    Hyway Hauler
    Member

    This is what the accelerator pump on the carb is for...pump the pedal a few times befor starting. Are you new to carburators?
     
  4. 3onthetree
    Joined: Feb 25, 2008
    Posts: 161

    3onthetree
    Member

    No I'm not new to carbs. I've rebuilt and tuned quite a few, and I've only owned a fuel injected vehicle for 2 years, all the rest are carbed.

    My 63 is very cold natured and as a result I don't drive it every day in the winter. I put an electric pump on it, which lasted 200 miles. I'm on my second electric pump and am wondering how long that one is going to last.
    The 51 Chevy my grandmother gave me has always had to be cranked for quite a while to prime the system before it would start as it's not driven daily either. I can remember my father having to pump the snot out of it to get it to start when I was a kid. I rebuilt the fuel pump just a few years ago and the fuel lines and hoses are fine. Just the nature of the beast when they sit for a while.
    I just hate cranking the motors for so long without oil pressure, and I hate the hassle of pouring a bit of gas down the carb. If you drive them everyday they fire right up.
     

  5. pdc
    Joined: Nov 25, 2008
    Posts: 346

    pdc
    Member

    As long as the engines turning, there's oil pressure. Same thing with a mechanical fuel pump, usually its ran off the lope of the cam.
     
  6. Dave Downs
    Joined: Oct 25, 2005
    Posts: 894

    Dave Downs
    Member
    from S.E. Penna

    The problem is that some of the older carbs, especially Rochester B's leak down when sitting and after a week or two you've got empty carbs - you can pump the accellerator pedal all you want but there's no gas in carb so nothing is going to happen. You have to turn the engine long enough with the starter to re-fill the carb(s), and that seems to take forever.

    I've got the problem on my tri-carbed 235, if it's been sitting more than a week I manually prime all three prior to starting, this usally allows the engine to run long enough for the mech pump to fill the carb bowls up.

    I know I've seen mech pumps (gasoline) with priming levers but I can't remember what engines they were on. Electric is really the way to go, flip the switch, wait till the bowls fill (or if you have a guage, it shows normal pressure) and then hit the starter. I have given thought to a mechanical priming pump similar to that found on aircraft, but electric is probably simpler and cheaper.
     
  7. RodStRace
    Joined: Dec 7, 2007
    Posts: 2,647

    RodStRace
    Member

    I agree, electric. Sounds like you need to rethink your install if they only last that long...
     
  8. harpo1313
    Joined: Jan 4, 2008
    Posts: 2,281

    harpo1313
    Member
    from wareham,ma

    seem like someone should come up with a backflow valve that is compatable with gasoline,put it between pump and carb. with an elec fuel pump and mecanical ,wouldnt the elec pump stop flow to the mec when the elec pump is turned off ? or is a bypass line required?
     
  9. carbking
    Joined: Dec 20, 2008
    Posts: 3,109

    carbking
    Member

    Actually, many carburetors "leak up" rather than "leaking down" or 'leaking back". Modern fuel is so volatile, it simply evaporates through the bowl vent.

    The only carb that comes to mind that "leaks down" is the infamous Holley 94 with the direct passage from the economiser valve to the intake. Blow a valve, and fuel enters the intake directly from the bowl.

    MANY military fuel pumps and some marine pumps had priming levers.

    Since many pumps are of the same type, but differ only in clock position and arm, it should be possible to find one that could be modified for most applications.

    Jon
     
  10. RodStRace
    Joined: Dec 7, 2007
    Posts: 2,647

    RodStRace
    Member

    Another leak down is a Q-jet with the seals on the bottom of the mid-section. JB weld 'em!
     
  11. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,087

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL



    I use electric auxiliary pumps on a few of my cars for exactly the reason the OP asks about. However, after several years I have never had a electric pump failure to date. As for 'blocking' the flow for the mechanical pump, no it does not. The mech pump just pulls the fuel right through the electric one even when it is shut off.

    For best results, the electric booster pump should be mounted very near the fuel tank as they work best pushing rather than pulling the fuel.

    Ray
     
    Last edited: Jan 10, 2010
  12. Von Rigg Fink
    Joined: Jun 11, 2007
    Posts: 13,426

    Von Rigg Fink
    Member
    from Garage

    i cheat..i just squirt a little fuel into the throat of my primary carb, and crank it up..works everytime.
    usually after the car has been sitting a few weeks, about a shot glass

    but i like your idea, I have a few older diesels at work that have the little prime lever you speak of, works great
     
  13. the answer is: an electric pump in the fuel line back by the fuel tank. switch it so you can turn it off/on
     
  14. I think it is doable,,,, my old jeep has a primer lever on the fuel pump...
     

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  15. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,087

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    The tricky part, as I see it, is that the position of the camshaft lobe that operates the fuel pump has to be in the 'relaxed' position (not pulling on the diaphragm stem) in order for and aux lever to move the diaphragm stem and pump fuel manually. If the cam is on the high part of the lobe the diaphragm will be in the extended position and held in place by the pump arm. It would necessitate cranking the engine a bit to get to the low point of the lobe, releasing the pump arm/diphragm. The only advantage I can see for the aux mechanical arm is that it would work without battery power.......but, if not batt power, no starter either.

    Ray
     
  16. 3onthetree
    Joined: Feb 25, 2008
    Posts: 161

    3onthetree
    Member

    That's pretty much what I'm thinking of. That looks like a rebuildable type pump, as is the one I had on my 63. I'm wondering if the upper half of that pump would bolt to the bottom half of my 63 pump, then if it would bolt to the chevy??

    "The tricky part, as I see it, is that the position of the camshaft lobe that operates the fuel pump has to be in the 'relaxed' position (not pulling on the diaphragm stem) in order for and aux lever to move the diaphragm stem and pump fuel manually. If the cam is on the high part of the lobe the diaphragm will be in the extended position and held in place by the pump arm. It would necessitate cranking the engine a bit to get to the low point of the lobe, releasing the pump arm/diphragm."

    I can see what you are saying and that's a good point, but I think the priming lever works against the diaphram independently of the rocker that rides on the cam. I've always been able to work the one on Dad's Massey Ferguson regardless of the position of the engine.
     
  17. 3onthetree
    Joined: Feb 25, 2008
    Posts: 161

    3onthetree
    Member

    1935Ron, do you have a part number of that pump? Or year , model and engine size of the Jeep it fits? I'd like to research a little further to see if that would work or not. Thanks.
     

  18. When I get home from work I will look it up and e-mail you
     
  19. Bruce Lancaster
    Joined: Oct 9, 2001
    Posts: 21,682

    Bruce Lancaster
    Member Emeritus

    Many or most British cars of the '50's and '60's had the levers. Flathead Ford ones exist, probably from British built engines or Canadian ones built to British military specs during WWII.
     
  20. ventilo
    Joined: Aug 25, 2009
    Posts: 247

    ventilo
    Member

    "French Flatheads" (military) have a primer lever as well
     
  21. They are both right about the Mil spec pumps

    this is where I get some of my parts for my WWII Jeep

    Part number WO-A-2383 it is a older cat but if you call Im sure he might be able to help

    http://www.debellajeepparts.com/mbpremier.htm
     
  22. rotorwrench
    Joined: Apr 21, 2006
    Posts: 633

    rotorwrench
    Member

    My old 47 Triumph 1800 roadster has the external pump actuator lever and it works great when I let the dam thing set too long.

    The other option is to use a squirt can to pump fuel back into the float bowl on carbs that have an open vent hole or tube. Might be easier to do than installing an electric.
     
  23. Domino
    Joined: Jul 2, 2009
    Posts: 523

    Domino
    Member

    I have seen primers like that on inboard boat engine fuel pumps. I know some boats had small block Chevy's in them. It might be worth a look. There might be one like you are trying to make out there in a boat application.
     
  24. I've had several vehicles that would not start until pump delivered more fuel. Maybe the heat from the engine caused the gas to evaporate after shutdown. I go with the electric pump auxiliary because it also gives you piece of mind when driving out in the boonies. A cautionary note re. that last statement. Fuel pumps fail one of two ways. Either a valve (in the pump) sticks open or the diaphram developes a hole. A hole in the diaphram can cause fuel to blow into the crankcase if an electric pump is pushing from the tank. If the aux. pump is inserted between the carb and the mechanical pump that won't happen but it probably won't pump fuel either if the diaphram is split. This is actually a good thing. But if the failure is a valve, it should be able to pull enough fuel to keep the car running. Be sure to wire the the pump so it won't run unless the ign is on, for safety.
     
  25. silversink
    Joined: May 3, 2008
    Posts: 917

    silversink
    Member

    I have an old carter on a 48 International that if I want to start it after sitting for a while I take the top off the carb and fill the float reservoir before cranking. Works every time.
     

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