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Thread: Not Sure Where to Start

  1. #1

    Array
    Status
    Offline
    Join Date
    06-20-2017
    Posts
    9
    Location

    Roan Mountain, TN
    Vehicle

    1996 Mitsubishi Mighty Max
    Engine

    4G64

    Not Sure Where to Start

    So, I recently purchased a couple pickups to rebuild and use in my fleet. I'm having issues with my 88 ram 50. To start, I had to replace the radiator and intake from the grill to carb. Tried to start, but only turns over. A little fuel or starter spray and it will start.
    However, here's where my first major issues arise. It won't idle on its own as I have to keep some pressure on the pedal to keep it going. As I'm forcing idle, it's a little rough and won't hold a consistent rpm.
    Also, pedal to the floor, the engine doesn't sound like it could be turning faster than maybe 3,500 rpm. Can't swear on that number as I don't have a tach, but it's definitely not reaching anywhere close to red line before it stops rising in speed.

    And my last issue (so far) is that it won't run long enough to do much diagnostic work. I can give it a bit of gas, keep it running and all that, but after a bit of time, it will die no matter what I do. When it does this, it acts like the battery is almost dead. It will crank 3 times a bit slowly then bog down on the 4th.
    All that seems to help is letting it sit. I can come back later, and repeat this process, but it's getting old as I've made no progress whatsoever.

    Now, clues I have are these; there are a couple valves for vaccuum lines I've found with nothing connected. I can't figure out where they go and plugging them seems to make no difference.
    There is some type of sensor in the bottom of the breather boxes neck (Not sure what the proper name is, but it's what contains the air filter.) There are two wires that have been cut that I can't find the other pieces or where they went.
    And lastly, I am getting a good oil pressure and oil is getting to the heads, so I don't think anything is moving dry.

    So, where should I start? I'm thinking the vaccuum lines or egr valve may be at play. I'm not sure where the lines would go, but we can figure that out. I've also been told that timing could cause this.

  2. #2

    Array
    Status
    Offline
    Join Date
    07-27-2020
    Posts
    5
    Location

    Philadelphia, PA
    Vehicle

    1988 Dodge Power Ram 50
    Engine

    G54B
    Is it still on the stock carb? Mine is the same year, had similar issues, I ended up upgrading to a weber outlaw 38 DGES and the difference is night & day. Not to mention, my engine bay is now super spacious without all of those ridiculous vacuum lines!

  3. #3

    Array
    Status
    Offline
    Join Date
    06-15-2014
    Posts
    6,059
    Location

    Adelaide, South Australia
    Vehicle

    1985 Mitsubishi L200
    Engine

    G63B
    The majority of the vacuum lines are ancillary control lines for emissions etc. Here is a manual diagram for the vacuum line routing. Seeming your truck is running all these lines and you've mentioned carbie woes, your engine isn't a 4G64 (the 2.4 is EFI, so you most likely have a G63B 2.0). Not going to make a difference in diagnosing the fault. There could be a number of issues with it not running - wrong fuel line orientation (the 2 fuel lines coming out of the pump have been crossed over, resulting in insufficient fuel delivery to the fuel bowl), a bad fuel filter (clogged), fuel pump is toast (not enough pressure), ignition timing screwed up (too much advance/retard), a bad coil, carb is dead (needs strip down and rebuild - this is not a job for carb noobs as the Mikuni is a biatch to work on...) The Mikuni itself has common faults from age/wear and tear that will straight up nerf performance - main culprits are accelerator enrichment pump (symptom is a flat spot on opening the throttle) and secondary vac actuator (no power from mid throttle upwards). Some of the parts are either difficult or to source or are NLA (choke wax pellet is absurdly hard to find and even harder to install)
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