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Erratic rpm ,Trailblazer 250 G

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  • ShieldArc
    replied
    Originally posted by 1997CST View Post
    If you are having trouble idling it's most likely the low speed jets in the carburetor. Your machine was manufactured in 1986. You can try cleaning trhe carb but my suggestion is if it runs and welds in high, just leave it there. Low idle is just a fuel saver. If you're not planning on using this 8 hours a day you won't notice the fuel consumption. Carbs for this unit (most parts are being obsoleted on this engine) are north of $300.
    I thought that too at first but then I remembered that machine idles 2400 rpm which is not a low idle.

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  • Plasma1
    replied
    Originally posted by 1997CST View Post
    If you are having trouble idling it's most likely the low speed jets in the carburetor. Your machine was manufactured in 1986. You can try cleaning trhe carb but my suggestion is if it runs and welds in high, just leave it there. Low idle is just a fuel saver. If you're not planning on using this 8 hours a day you won't notice the fuel consumption. Carbs for this unit (most parts are being obsoleted on this engine) are north of $300.
    Problem was just in the carb to throttle solenoid linkage and idle adjustment screw. I did clean the carb beforehand and did not solve the problem, but once I adjusted everything accordingt to the manual it worked fine. Thanks.

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  • 1997CST
    replied
    If you are having trouble idling it's most likely the low speed jets in the carburetor. Your machine was manufactured in 1986. You can try cleaning trhe carb but my suggestion is if it runs and welds in high, just leave it there. Low idle is just a fuel saver. If you're not planning on using this 8 hours a day you won't notice the fuel consumption. Carbs for this unit (most parts are being obsoleted on this engine) are north of $300.

    Leave a comment:


  • Plasma1
    replied
    Thank u so much for that tip, although I did not mess with the high rpm just the idle, I would imagine it should be checked. The tech manual did not mention that, at least the section I read. I'll look to see if it states the frequency somewhere. Thanks.

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  • MMW
    replied
    When setting rpm in the "weld" position you should measure hz and let the rpms fail where they may. It is more important to have the hz set about 62ish with no load than have the rpm at 3600.

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  • Plasma1
    replied
    Click image for larger version

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  • Plasma1
    replied
    The fuel pump I had just replaced and is working perfectly. So it's not fuel related. I called tech support got the info I needed for the electronics and wiring. The tech sent me the complete tech manual. Tech support also gave me instruction on adjustment for the governor linkage, the link arm to the carb and throttle solenoid. Through my troubleshooting I found that the throttle solenoid only gets voltage when the auto/fast rpm switch is in the auto position. At this point the throttle solenoid is suppose to pull the throttle in the idle position and hold it there until u strike an arch. There's a relay that gets voltage/energized from the electronics with this same switch in auto. When the relay is energized it's set of points closes and furnishes voltage from the battery to the throttle solenoid. I found the problem at this point between the linkage, carb idle adjustment and the throttle solenoid adjustment. So glad it's wasn't in the electronics or the relay, as I disconnected the throttle solenoid and connected the two wires straight to the battery, it tried to pull in to the idle position but could not hold it there. So I adjusted everything according to the tech manual, that fixed the erratic idling problem. Was just adjustments with the carb and the throttle solenoid. Also had to readjust the idle rpm to what the manual said it should be 2200 rpm, it was 1800 rpm.
    Last edited by Plasma1; 01-30-2019, 05:13 PM.

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  • MAC702
    replied
    Originally posted by snoeproe View Post
    Fuel pump maybe?
    My only experience is that these engines have a lousy fuel pump. My dad bypassed his and used an aftermarket inline automotive one and solved most of his issues on a Bobcat 225.

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  • Plasma1
    replied
    Did more troubleshooting. I disconnect the throttle solenoid (only two wires) and the engine rpm increases to weld output and stays there until I reconnect the wires. I also disconnected the wires again and applied 12 volt DC to the throttle solenoid, it tried to pull in to idle the engine but could not hold the throttle there, could it be that the throttle solenoid could be weak, I checked ohm reading on it, shows to have 13 ohms. Checked the intake manifold for cracks, sprayed starting fluid around it, no changes. I am thinking now the problem is the throttle solenoid or the electronics, I’ll test that today. Thanks in advance, Jeff.
    Last edited by Plasma1; 01-30-2019, 05:08 PM.

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  • Plasma1
    replied
    When I first got the unit it would crank over but had no fuel to the carb. I did change the fuel pump and OH the carb. Cleaned the tank checked all the fuel lines. Just finished reinstalling the carburetor and has the same erratic rpm problem. So I have eliminated the fuel as being a problem. Engine runs really good with the switch at high rpm lock position, (so I would not think it to be an ignition problem) but erratic at low rpm with the switch at the automatic position. Visibly checked the electronic boards for burned components or signs of shorts, none were seen. I get 14 volts to the throttle solenoid with the switch at the auto position, I can disconnect one of the throttle solenoid wies and the engine goes into high rpm mode, and there’s no voltage to the throttle solenoid when the switch is at the high rpm lock position. If the throttle solenoid is not energized at high rpm what forces are involved to increase engine rpm for welding rpm, I don’t get it, something has to physically open the throttle, is it the govenor linkage? This would make sense if the throttle solenoid is energized only at low or idle rpm. If that’s the case the problem is either in the throttle solenoid itself, govener, or the carb linkage arm. Also if the electronics is only feeding voltage to the throttle solenoid at idle rpm I will need to check to see if the voltage is intermittent or dropping off somehow. Anyone had this experience?
    Last edited by Plasma1; 01-30-2019, 05:06 PM.

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  • snoeproe
    replied
    Fuel pump maybe?

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  • Plasma1
    started a topic Erratic rpm ,Trailblazer 250 G

    Erratic rpm ,Trailblazer 250 G

    Hello, I’ve got a Trailblazer 250G, two cylinder engine, is an Onan. At idle, switch set on auto, engine runs erratically, rpm goes up and down. I set the idle switch to fast rpm the engine rpm evens out and runs at the increased rpm. Could this be carberation or something to do with the electronics, throttle solenoid ? Also could someone steer me to a tech manual for this unit. Thanks in advance, Jeff.Click image for larger version

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