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Fuel Pump ?

Discussion in 'Mitsubishi Minicab' started by BC1, Nov 26, 2009.

  1. BC1

    BC1 New Member

    Hi All,
    I have 1994 Mitsu 3 cyl . I need to know everything about the fuel delivery system. The truck runs for a little while and stalls out, it restarts and dies again as if there is no fuel etc. I have cleaned the carb several times and got some white stuff out of it.

    There is an item along the frame that looks like a fuel pump, it has an electrical connection etc. Is it the pump?
    I purchased a 12 volt fuel pump, I plan on bypassing the entire system, is this ok.
    Feel free to email me with advice.

  2. 3banger

    3banger Member

    I've got an '89 carbed mitz van. My fuel pump is on the right side under the frame rail near the rear wheel. It's not only got electrical connections, but there should be a fuel filter and lines with hose clamps going into it if it truly is the pump.

    I've swapped mine out with a generic (low gallons per hour) pump. If you've got a fuel injected motor there could be two pumps... one for taking out of the tank and another one that steps up the pressure to somewhere near 75psi for the injection system.

    Take the old pump out and bring it with you when you buy the new one. You should try to keep the PSI and Gallons per hour/minute ratings close.

    You can also get your buddy to turn the key on and off while you have your head in that area under the vehicle. You should hear the pump or just put your hand on it to feel if it shakes at all.
  3. BC1

    BC1 New Member

    Hi 3Banger,
    Thanks for the reply.

    Yes my Mitsu is a carb type no injection. I'm really wondering why all the lines coming out of the fuel tank? Two filters on the tank, one is white plastic the other is a regular see thru type. How much of those lines can I eliminate? I had already purchased a marine type fuel pump, I hope it works.

    Any clue whats fouling my carb wit the white stuff? I think I'll remove the gas tank and flush all the lines and start from scratch.

  4. 3banger

    3banger Member

    Minicab Fuel Lines

    There could be a supply and return line. That would explain seeing a bunch of lines at least.

    If you're willing to take the tank out you're definitely going to clear out whatever might be fouling the carb.

    There should be a drain plug in the bottom of the tank, too. So if you chicken out on the tank removal you can drain it, put some gas back in, take the line off the carb and blow whatever might be in the lines through.

    I had my mitz pump die twice! I couldn't believe a fairly new pump could quit so I went on a carb problem witch hunt.... It was the pump. I'm using a cheap Carter pump from Napa now.
  5. Wribrinurname

    Wribrinurname New Member

    Fuel Pump

    Well im having problems with my blazer not running too well and the fuel pump in it is from a salvage yard when i first got it. The fuel gauge only works half way, when its full its all the way up and when its empty it looks like a half tank when it really isnt, would that be the sending unit or is there another problem it could be?
  6. BC_MMC

    BC_MMC Member

    Well I wonder if that's my problem?
    The truck just stalled one day about 6 weeks ago and would not restart. I looked at the gizmo on the frame rail behind the driver's door and assumed the hoses were for fuel and I whacked it and squeezed the tubes and it started again right away and ran fine.
    When the cold hit here, it started sputtering and running like crap. I assumed bad fuel, added gasline anti-freeze and ended up taking it to a garage.
    The mechanic said the filter (replaced it) wasn't filling up so he blew out the pipes and it ran fine. Halfway home... and started sputtering again.
    Went away for Christmas and my cheap landlord unplugged me... when I tried to start it wouldn't. Couldn't smell gas at all at the carb, and it usually reeks until it warms. Plugged he in for a couple hours, still no start. A couple hours later my friend was here and I pointed out that the thing on the frame rail must be the pump, so I whacked it with a screwdriver and it started as soon as I turned the key.
    And ran for 15 minutes until it sputtered again....
  7. TetsuKuma

    TetsuKuma Member

    Almost sounds as if your fuel level in the carb (float valve) is stuck causing starved flow after initial starting and running. Worth checking at least.

    Also, try disconnecting the fuel line from the pump and drop it in a can, try starting see what the flow is.
  8. fupabox

    fupabox Well-Known Member

    if it will run a while after whacking it the pump is definately gone..the motor brushes are prob. so carbon tracked it takes a whack to get momentary contact..or the rotor shaft bearings are gone needing an initial jolt to move,then the shaft heats up and seizes again..if the pump is serviceable meaning you can take it apart (more than likely not) cleaning the brushes/lubing the rotor shaft bearings, would get some more time from it but not much..try to find an electric fuel pump from a suzuki swift or geo metro to swap in,if you can't get a mitsu one...the problem with an electric fuel pump on a minitruck is cooling.In tank pumps get cooled by sitting in the fuel...larger engined vehicles get a lot of fuel flowing through them ,and susequently cool off better. Mini trucks with the low fuel flow rate are not getting enough cool fuel through them to keep the pump cooled..if the pump is anywhere close to an exhaust component the problem would be magnified and pump failure more common,as would a lot of idling in warm weather.......:)
    Last edited: Jan 2, 2010
  9. BC1

    BC1 New Member

    Fuel Pump

    Hi All,
    I finally took the gas tank out and flushed it all out. I let it dry most of the winter, it's clean now! I put an electric fuel pump on it too. I cleaned the carb out and now comes a new problem! The carb is leaking in a couple of spots, almost went on fire as gas was shooting right on the alternator. I guess I need new gaskets! Where do I get them???
  10. 3banger

    3banger Member

    3g82 Fuel Pump

    I bought ANOTHER pump from Napa the other day. These things are driving me nutz! I smell like fuel 24/7 these days.

    30gph 5 - 8 psi if you're interested.

    Glad to hear you cleaned your tank.. I just did mine and I feel way better about things now that I know the tank is clean, have a new filter and pump.

    I think you might have to check Dan's links to the russian repair manual. It might have an exploded view of the carb and a part # listed. The Mits dealer or maybe even Napa can sort you out once yo have the number.

    I can't remember if silicone resists fuel.. but if there's a product like that that does.. I'd be sure to use it while I waited for my gaskets.

    You might even want to try ebay from time to time...

  11. renchjeep

    renchjeep Member

    Silicone will not resist fuel, unfortunately. You will need to find out where the fuel is leaking out of the carb, and get the proper gasket or o-ring. So far, I have been lucky with my carb. I was able to take it apart, clean all the crap out, re-use the old gaskets, and my Mitsu runs like a champ now! Maybe someone (Dan?) has a line on a rebuild kit, or at least a gasket set. With a lot of patience, maybe you can make new gaskets?

    Good luck--Chris
    Bill_G likes this.
  12. renchjeep

    renchjeep Member

    Almost forgot--I have a parts catalog for the Mighty Mits, probably the same as your rig. 3G81 engine. It has all the part numbers for the carb bits. Let me know what you need, and I can supply a part number to make your search a bit easier. PM me with what info you need.

  13. renchjeep

    renchjeep Member

    What kind of pressure is your pump putting out? If it's too high, it may blow fuel out of the carb. You probably only need 5-7 psi.

  14. Dan

    Dan Member

    I have a few of the carb gasket/oring kits.
  15. greg0187

    greg0187 Moderator Staff Member

    I'm thinking more like 1-2 psi.
  16. BC1

    BC1 New Member

    Fuel pump psi

    I don't really know, I threw away the packaging but I'll check it at the parts store. I'm sure it's way to high as they use them on boats..
    What about a Harley Carb, I read something about using one of those.
  17. renchjeep

    renchjeep Member

    I can't seem to find a fuel psi spec in my repair manual. Anyone know for sure what it should be?
  18. bobnalleweg

    bobnalleweg Member

    I replaced my fuel pump with an aftermarket product rated at 5 to 7 psi and it works fine. I also cut the old one in half to see what made it tick and discovered that there are no brushes just a solenoid with an electronic circuit the reverses the polarity to facilitate the pumping action.
  19. RHM

    RHM New Member

    1991 Mitsubishi Minicab U42T
    I have just confirmed the Fuel pump pressure on another thread re. injectors.. Also I have a James Danko Manual 1990 - 1998, that says 2,8kg/cm2 which converts to 39.8 psi at idle 3.3 - 3.5 @ 2000rpm = 46.9psi
    And was introduced to the web site below.


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