Subject: SUZUKI DF-40 ROUGH IDLE NOW 1 CYLINDER
Engine: 2005 Suzuki DF-40, 4-stroke electronic fuel injection, less than 200 hours. Fuel/water separator changed in 2010, quality gas storage additives used.
Problem Description: The Last year or two engine started to idle rough (700-800rpm) but was OK above about 1200 rpm, and boat performance of 5800 rpm, 26.3 mph ran like new. Before winterizing, pulled plugs and #1 had some black stain/carbon residue on center post ceramic (plugs #2, #3 looked good). Then I ran boat thru one 8 gal tank of gas with strong mix of fuel injector additive. Monthly during winter ran engine on muffs 10-15 minutes, idle still rough. First time out engine started and ran at high idle for about 5 minutes. Within 1 minute of leaving dock engine started missing and quit. Very difficult to restart, sounded as if only one cylinder firing, then with restart, returned to dock.
Troubleshooting on muffs: (summary of numerous actions)
· Cleaned all three plugs (#1 some hard carbon residue, #2,#3 looked OK, grayish ceramic)
· Rough idle at low rpm, better at 1200 rpm but at max idle throttle engine rpm cycled up/dn (surging) between about 2600rpm and 3000 rpm.
· Reduced idle power level and engine “dropped” into running OK mode about 2300 rpm
· Ran engine per above conditions for 1.5 hours, running ok except periodically ( 10 min or so) there was an occasional miss. (NOTE: Last year running at full power there was an occasional miss which I just assumed was some “junk in the gas” going thru.
· Then reduced idle speed and engine idle rough (bit worse than before), and at low idle speed engine stopped. Was very difficult to restart (just like first time this year on the water described above), multiple misfiring and finally with engine running only on one cylinder (#3).
· Fuel injectors look like NEW, plugs mostly like before.
· Outside of engine with plugs connected to ignition circuitry and grounded, all plugs were firing while using engine starter and with battery charger connected. It did seem that the first few rpm firings were brighter than the later rpm firings in this short duration test. Occasionally some “sparks” seemed brighter.
· Focusing on #1 and #2 cylinders, first interchanged injectors #1 and #2, then restored and interchanged #1 and #2 ignition circuits/plugs> No Change/Difference in results. This was when cylinders #2 and #3 were working in early tests.
· When rough idle (only one cylinder missing) it is always #1 and disconnecting electrical feed to ignition coil makes no difference, leading me to conclude that #1 is not combusting at all.
· It appears that #3 cylinder works OK (most all of the time) thru all of this testing.
Would appreciate any help or suggestions, especially troubleshooting to locate actual problem component(s). With the price of parts I can’t afford to randomly buy new parts hoping they will solve the problem.
Engine: 2005 Suzuki DF-40, 4-stroke electronic fuel injection, less than 200 hours. Fuel/water separator changed in 2010, quality gas storage additives used.
Problem Description: The Last year or two engine started to idle rough (700-800rpm) but was OK above about 1200 rpm, and boat performance of 5800 rpm, 26.3 mph ran like new. Before winterizing, pulled plugs and #1 had some black stain/carbon residue on center post ceramic (plugs #2, #3 looked good). Then I ran boat thru one 8 gal tank of gas with strong mix of fuel injector additive. Monthly during winter ran engine on muffs 10-15 minutes, idle still rough. First time out engine started and ran at high idle for about 5 minutes. Within 1 minute of leaving dock engine started missing and quit. Very difficult to restart, sounded as if only one cylinder firing, then with restart, returned to dock.
Troubleshooting on muffs: (summary of numerous actions)
· Cleaned all three plugs (#1 some hard carbon residue, #2,#3 looked OK, grayish ceramic)
· Rough idle at low rpm, better at 1200 rpm but at max idle throttle engine rpm cycled up/dn (surging) between about 2600rpm and 3000 rpm.
· Reduced idle power level and engine “dropped” into running OK mode about 2300 rpm
· Ran engine per above conditions for 1.5 hours, running ok except periodically ( 10 min or so) there was an occasional miss. (NOTE: Last year running at full power there was an occasional miss which I just assumed was some “junk in the gas” going thru.
· Then reduced idle speed and engine idle rough (bit worse than before), and at low idle speed engine stopped. Was very difficult to restart (just like first time this year on the water described above), multiple misfiring and finally with engine running only on one cylinder (#3).
· Fuel injectors look like NEW, plugs mostly like before.
· Outside of engine with plugs connected to ignition circuitry and grounded, all plugs were firing while using engine starter and with battery charger connected. It did seem that the first few rpm firings were brighter than the later rpm firings in this short duration test. Occasionally some “sparks” seemed brighter.
· Focusing on #1 and #2 cylinders, first interchanged injectors #1 and #2, then restored and interchanged #1 and #2 ignition circuits/plugs> No Change/Difference in results. This was when cylinders #2 and #3 were working in early tests.
· When rough idle (only one cylinder missing) it is always #1 and disconnecting electrical feed to ignition coil makes no difference, leading me to conclude that #1 is not combusting at all.
· It appears that #3 cylinder works OK (most all of the time) thru all of this testing.
Would appreciate any help or suggestions, especially troubleshooting to locate actual problem component(s). With the price of parts I can’t afford to randomly buy new parts hoping they will solve the problem.
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