We have a customer's Toyota 42-6FGU25, frame # 68662 equipped with a 4Y and a duel fuel ("convertible" in Toyota speak) that gives us diagnosis problems. It has approximately 8000 engine hours. When the operator drives across the yard at full speed, pedal to the metal so to speak, the truck will run fine for a short period of time then start to sputter and lose power and sometimes completely stall. If you shut down the machine for a few minutes it will start right up as if nothing was wrong. We know that the machine does this when the operating temperature is normal but we as yet do not know if it does it when the engine is "cold". We have done the obvious stuff, tune up with plugs wires cap and rotor. As well we installed a new regulator. We also have spent a lot of time on "adjustments" particularly on the dual fuel carb. Has anyone else experienced such a situation? I'm looking for advice on what the next thing we should look at. I have also posted the same question in the Mechanical discussion forum.
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A bit late but, had this happen with a 4y on dual fuel before, we had to install a balance pipe from the air cleaner intake pipe (dirty side) to the atmosphere side on the LPG converter. It also sometimes happens when a snorkel is fitted to a LPG 4x4.
I've had that issue when the the ignition system starts to fail. Install a timing light on any plug wire & check if the spark becomes erratic when the machine starts to act up.
4k hours is around the time a build up can occur in the inlet manifold. Eddy also has a point about the valve lifters, they do stick on the 4Y particularily if the engine oil is not changed to shedule, Lots of guys that don't know LPG engines just look at the oil color and say the oil is OK even if it is past its service time. Have you tried a compression test?..... hope that helps Scrid
Hey Bobby I have a 4y in a Toyota with almost 4K hours on it.
It doesn't actually stall but will run crappy mid throttle. Have you seen the manifold cause that issue as well?
i'm with bobby, if it's not that, try replacing the lifters, their cheap and will cause that same problem at high rpm.
I have a 5FG with the same motor and mine is doing the same thing. Some days it runs ok, other days it runs like crap. I rebuilt the regulator and have taken the carb and gov. apart 2-3 times and cleaned it out every way possible. It was pretty clean. Its only got 4xxx hours on it. (1998)
I dont think its the valves, it wasnt a gradual issues, it just happened out of no where.
Take the carb off, if you havn't allready, and check the inlet manifold, when the 4Y has done >4000 hrs it gets a build up of gunge on the hot spot inside the inlet manifold which restricts the flow, giving a lack of power symptom. Bobby
pull the head get a valve job. the seats are recessed into the head.
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