My 742B with a Mitsubishi engine starts and rins great for aboit 20 or 30 minutes then sputters and dies like its out of gas. If I let it xool down it starts back up but then dies after 20 minutes of running. It has plenty of gas in it. Coolant is full and engine oil level is good. Temp guage shows within safe operating temp. Where do I start to diagnose the problem?
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brdgbldr
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Could be a short in the electrical or a bad ignition switch or a bad fuel shutoff or a bad anti-dieseling solenoid.
My 742B had an anti-dieseling solenoid that never worked when I got the machine. It was disconnected and the tubes that went to it blocked off. It only dieseled once in a while. You could disconnect yours and see if you have the same problem or not.
Your fuel shutoff closes when it doesn't have power. The machine will keep running for about 2 minutes when this happens since there is still fuel in the carb. However, this normally makes it hard to restart the machine since the carb fuel bowl is empty. This could be a bad shutoff, a short or a bad ignition switch causing this.
You could replace the fuel shutoff and see what happens. When mine failed it was actually stuck open which caused fuel to flood the engine and go into the oil since the fuel in the tank is above the carb. There are several posts on here about where to get a new shutoff.
I had to replace the ignition switches in several 742's. They are pretty cheap and easy to replace. They seem to go bad pretty often. I would probably start with this.
Sorry I couldn't be more specific but that's how long distance diagnoses go.
My 742B had an anti-dieseling solenoid that never worked when I got the machine. It was disconnected and the tubes that went to it blocked off. It only dieseled once in a while. You could disconnect yours and see if you have the same problem or not.
Your fuel shutoff closes when it doesn't have power. The machine will keep running for about 2 minutes when this happens since there is still fuel in the carb. However, this normally makes it hard to restart the machine since the carb fuel bowl is empty. This could be a bad shutoff, a short or a bad ignition switch causing this.
You could replace the fuel shutoff and see what happens. When mine failed it was actually stuck open which caused fuel to flood the engine and go into the oil since the fuel in the tank is above the carb. There are several posts on here about where to get a new shutoff.
I had to replace the ignition switches in several 742's. They are pretty cheap and easy to replace. They seem to go bad pretty often. I would probably start with this.
Sorry I couldn't be more specific but that's how long distance diagnoses go.
If it sputters, it probably is a fuel problem. Once it dies I would 1st check it for spark to rule that out. If spark is ok, take the fuel line off at carburetor and have somebody it crank while you catch the fuel in a clean container. There should be a consistent pumping of fuel there. If the fuel flow is good at carb, the problem is at the carb, if fuel flow is non existent at carb follow fuel line back to tank. The fuel hose in mine was in awful condition and had a clogged in line fuel filter when I 1st got it. I would also consider checking the line from the tank to the fuel pump for good flow by taking it off at the pump and letting it drain for a minute into a clean container just to be sure there is consistent, uninterrupted flow. You may have to pull a little vacuum to get the fuel moving, keep the hose low below the level of the fuel in the tank while you observe this. HTH.
Jerry01314
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Jerry01314
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TO bobCAT 742
I had a 742 Ford engine when fuel pump would get hot it would start to sputter after 20M. I bought an electric pump on EBAY or AMAZON for $12. I left the old pump in. I also had trouble with rubber tube that goes in to gas tank in a later date. That can be a head ache.
I had a 742 Ford engine when fuel pump would get hot it would start to sputter after 20M. I bought an electric pump on EBAY or AMAZON for $12. I left the old pump in. I also had trouble with rubber tube that goes in to gas tank in a later date. That can be a head ache.
Tango-Charlie
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I will echo J's comment on the fuel tube in the fuel tank. I had probably the original in my tank and would make the machine sputter at times so I replaced it along with the screen on the bottom. I found the old one to be brittle to the touch and all it takes is a pin hole to make it act up. It may be worth checking. The other thing I did with mine thinking I may have had an intermittent coil that was acting up when it got warm was to replace the points with electronic ignition and replaced coil at same time. Both were Pertronix. My problem was cured.
Try running it with the fuel cap loose, or run it until it dies then loosen the cap and listen for air going into the tank then try to start and see if it runs. Your tank vent might be restricted.
Cary E Sip Sr
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There's a lot of good advice here , I didn't know I had a fuel shut off solenoid , I'm guessing that's the part hanging on the old gas line - ha ! Shouldn't the needle and seat keep the gas from siphoning through the carb if it's good ? I've worked on 2 of those plastic suction tubes and screens . Throw it in the garbage and replace it with a steel brake line and no screen. Wash the tank out first if necessary . Mine had a thin plastic thread plugging screen every 20 - 30 minutes , caused starving for gas., just like you mentioned . I think it was manufacture molding letting go inside the tank , it's only 30 + year old plastic. Let the fuel filter catch the crap , not inside the tank.
