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won't idle

Discussion in 'Daihatsu Hi jet' started by J Bike Mike, Jun 1, 2020.

  1. J Bike Mike

    J Bike Mike New Member

    I have owned my truck for about 2 weeks now, way high mileage at almost 20000 kilometers, but always ran wnderfully until one day. It was pretty hot outside, and all of a sudden I had to start it and give it gas pedal every time I stopped. I threw a bottle of fuel injector cleaner in her with a full fill up afterwards and seemed to be good since, also I was checking the vacuum lines that day to see if any were cracked or loose, and I pilled the one off from the throtte body that has something that looks like a plastic inline fuel filter on it. As soon as I pulled it off it, it was sucking air for a few seconds, not running the engine, just off. then when I tried to blow into the hose way from the throttle body that it was connected to, it is blocked. is it supposed to be blocked? Is it like an atmospheric pressure can at the end or something or should I clear it out. I didn't dig too deep as I was on the side of the road with simple tools, and no access to an English service manual.
     
  2. ttc

    ttc Active Member

    They are vacuum check valves.
     
    J Bike Mike likes this.
  3. Jigs-n-fixtures

    Jigs-n-fixtures Well-Known Member

    They depending on the colors are vacuum check valves or vacuum delay valves. They have free flow in one direction, and then a restricted or delayed flow in the other direction. They have gotten hard to replace, because as vehicles went to fuel injection, and more computerized engine controls, the computer, and solenoid valves replaced, or eliminated them.

    If you have computer controlled timing, utilizing a crank position sensor: vacuum advance/retard, and the distributor itself have disappeared. With direct port fuel injection: The vacuum controls for the carburetor, such as choke pull off, have disappeared.
     
    J Bike Mike likes this.
  4. J Bike Mike

    J Bike Mike New Member

    I re read this and realized my thoughts were all over the place,
    So thank you guys for the info, Now I know what those things are, but here are my questions.
    1) Would the large amount of built up vacuum pressure in that line going to the throttle body cause the truck to die instead of idle?
    2) Does anyone have a diagram or any links to shop manuals?

    Everything has been fine since, but I want to change my fuel filter and check all the lines, but I cannot find any info or schematics online like I usually find with most my vehicles.
     
  5. JMM

    JMM Member

    J Bike Mike, my truck is much older than yours ('91), but check under the passenger seat for a vacuum reservoir. There should be a reserve of vacuum available to the engine by design.
     
  6. Jigs-n-fixtures

    Jigs-n-fixtures Well-Known Member

    A build up of vacuum in the fuel tank, would decrease the effective fuel pressure, because the fuel pump generates a maximum pressure above what the pressure is Where it is drawing from. If the pump normally generates 60-psi, and it is trying to pull from a tank at -10-psi, it will only produce 50-psi.

    It is more of a problem on carbureted engine, because the fuel pump is only developing 2.5 to 3.5-psi, so if the pump is trying to overcome three psi of vacuum, it is effectively delivering 0-psi.
     
    Limestone likes this.

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