Sport Jet 120 dies at idle, will not re-start

[dmeals]

Work and/or troubleshooting that has been done:<br /><br />· Carbs disassembled, cleaned & adjusted <br />· Stale gas drained from tank, replaced w/fresh <br />· Rev limiter replaced (engine had no fire initially) <br />· Wire harness, connections & key switch all checked & appear to be OK <br />· Stator DVA checked – 260V <br />· CDM modules replaced (suspected hot CDM caused start failure) <br />· Enrichener replaced (burnt leads going to top of old enrichener) <br />· Voltage regulator leads not burnt, tachometer functions correctly <br />· Spark plugs are correct heat range and condition is good <br />· Fuel filter is new <br /><br />Parameters:<br /><br />· Engine starts, runs well for 15-20 mins, dies at idle & will not re-start until allowing to cool down <br />· Engine runs strong throughout power band before dying, WOT is approx 5,600 RPM <br />· Warmest temp recorded is 136 degrees – block, head, exhaust <br />· Cranking DVA after engine dies is 260V <br />· Unplugging rev limiter does not affect start failure <br />· Unplugging fuel enrichener does not affect start failure <br />· Compression for #1 cylinder is 145 pounds w/warm engine <br />· There is spark after engine dies <br /><br />Feedback / suggestions appreciated. <br /><br />Dan

 

[eurolarva]

Re: Sport Jet 120 dies at idle, will not re-start

Sounds to me like you are overheating. Replace impeller and run for a day without a thermostat and see what happens.

 

[eurolarva]

Re: Sport Jet 120 dies at idle, will not re-start

Sorry double post.

 

[funpilot]

Re: Sport Jet 120 dies at idle, will not re-start

Sorry eurolarva, the Sport Jet 120 does not have an impeller (water pump) it gets its cooling by bypassing some of the water from the jet drive into the engine.<br /><br />How is your timing? Should be 32 degrees BTDC at cranking speed at WOT, spark plugs out. The big screw on the bottom of the tower shaft is low idle timing screw (not an idle speed screw) it needs to be set at eight degrees BTDC at idle (about 1100 rpm). The throttle plates are completely closed for idle on this engine. Next time it won't start, disconnect the throttle input and assure that the throttle plates are closed, and try starting.<br /><br />I doubt that loaded (jet pump fully loaded with water) that you have 5600 rpm. The water tends to limit the revs to about 4700-4900 rpm depending on who you talk to. The only time you should see higher rpms is coming out of the hole, or jumping a big wake, before the rev limiter kicks in. That should be about 5300 rpm. Your tach might be in error, or I'm not understanding something.<br /><br />How is compression in all cylinders, and by proper plug, are you using the QL76V surface gap plug?<br /><br />good luck,<br />fp

 

[jdana29]

Re: Sport Jet 120 dies at idle, will not re-start

Originally posted by dmeals:<br /> Work and/or troubleshooting that has been done:<br /><br />· Carbs disassembled, cleaned & adjusted <br />· Stale gas drained from tank, replaced w/fresh <br />· Rev limiter replaced (engine had no fire initially) <br />· Wire harness, connections & key switch all checked & appear to be OK <br />· Stator DVA checked – 260V <br />· CDM modules replaced (suspected hot CDM caused start failure) <br />· Enrichener replaced (burnt leads going to top of old enrichener) <br />· Voltage regulator leads not burnt, tachometer functions correctly <br />· Spark plugs are correct heat range and condition is good <br />· Fuel filter is new <br /><br />Parameters:<br /><br />· Engine starts, runs well for 15-20 mins, dies at idle & will not re-start until allowing to cool down <br />· Engine runs strong throughout power band before dying, WOT is approx 5,600 RPM <br />· Warmest temp recorded is 136 degrees – block, head, exhaust <br />· Cranking DVA after engine dies is 260V <br />· Unplugging rev limiter does not affect start failure <br />· Unplugging fuel enrichener does not affect start failure <br />· Compression for #1 cylinder is 145 pounds w/warm engine <br />· There is spark after engine dies <br /><br />Feedback / suggestions appreciated. <br /><br />Dan

 

[jdana29]

Re: Sport Jet 120 dies at idle, will not re-start

I'm having the same problem. What was your outcome??? Jon