Crashguy2016
New Member
Brief Background: 3 years ago had 2 BRP Short Blocks put in. 4 x new Nikumi Cards installed, synced and tuned about 2 months after engines. Has run pretty good the last few seasons. 787 engines.
Changed the Bilge pump a few weekends back. Not related I am sure, but this started right after!
Running at full throttle, about 7000 RPM on plane, the left engine would just “die”. It would quit completely. Usually it would re-start, run again for a brief moment, then die. Some times it would stutter like it was running on one cylinder. Worked on it some, had spark. Checked fuel pump. The fuel side was fine, the vacuum side was sloppy and a bit punky. Why change one! I changed BOTH fuel pumps. Started up best its ever (or so it felt). Ran it flat out - Left engine DIES like before.
I have eliminated fuel as the cause - see below.
Hmmmmm. Maybe Coil?? Bought a new-to-me coil. Really clean looks great. Swapped it in. Better. It kind of runs. At least it starts every time and one cylinder runs all the time. I can swap coil wires and the firing cylinder fires no matter which coil wire is attached (expected - single coil, two cylinders).
New Spark Plugs in both engines too.
The WIERD ISSUE: When monkeying around it will run on one cylinder. Let’s say, the rear cylinder. Shut it off, check plug, yup rear is warm, front is cold. Wait, re-start a few times, now the BACK is running and warm and the front is cold. Again, makes NO difference which plug wire is on the spark plug or which plug is in (I have moved those from left to right as well to make certain it wasn’t a bum new plug).
Not fuel. Can spray fuel / ether /Brake cleaner into non-running cylinder and it wont fire. New carbs and swapped fuel source between engines. Just can’t be carb or fuel related IMO.
MPEM? Maybe, I suppose. But I have regular, reliable spark on the left side at both plugs. It just swaps back and forth between cylinders in some random order.
Rectifier? I don’t think so. I can unplug either or both plugs and no difference.
Rave valve stuck? I pull of the caps and they both move. Again, with random front/back firing I doubt this as the cause. I have not pulled the valves to check their condition.
Twisted Crank? Putting at TDC and a rod in both, the other is at BDC and pressing on the rod in the BDC when the other is at TDC creates NO movement. Best I can visually tell its not a bent crank. Also, if a bent crank, wouldn’t one ALWAYS not fire?
Compression: One is about 148PSI the other >135 PSI. Again, since random front/back I doubt this is the issue.
Whichever plug isn’t firing is a bit oil-wet as you’d expect (I think) since it is pumping oil and not burning.
Starting: I did note that it went “CHUNK” when I went to start it Saturday. A few tries later and it turned over fine. Pulled the plugs to make sure it hadn’t hydraulic locked for some reason. It has occasionally now, with the issue I am having ”struggled” to turn over randomly. That may be wear and tear on that poor starter with all the back and forth testing.
I am STUMPED. ANY suggestions / ideas are welcome.
The RIGHT engine runs GREAT.
Today I pulled it and dropped off at SeaDoo dealer for them to look at it. More WEIRDNESS: running it over to the boat launch it ran up to about 4000 RPM on the left / 1 cyclinder but OCCASIONALLY the seconds cylinder would kick in for a bit, on and off, and I’d get about 5000 RPM out of it.
I don’t think the coil or pumps were a waste as it will reliably start, idle and run on one cylinder. Before changing the coil it wouldn’t idle on the one cylinder worth a crap. Always needed a bit of throttle.
Thanks,
Brad
Changed the Bilge pump a few weekends back. Not related I am sure, but this started right after!
Running at full throttle, about 7000 RPM on plane, the left engine would just “die”. It would quit completely. Usually it would re-start, run again for a brief moment, then die. Some times it would stutter like it was running on one cylinder. Worked on it some, had spark. Checked fuel pump. The fuel side was fine, the vacuum side was sloppy and a bit punky. Why change one! I changed BOTH fuel pumps. Started up best its ever (or so it felt). Ran it flat out - Left engine DIES like before.
I have eliminated fuel as the cause - see below.
Hmmmmm. Maybe Coil?? Bought a new-to-me coil. Really clean looks great. Swapped it in. Better. It kind of runs. At least it starts every time and one cylinder runs all the time. I can swap coil wires and the firing cylinder fires no matter which coil wire is attached (expected - single coil, two cylinders).
New Spark Plugs in both engines too.
The WIERD ISSUE: When monkeying around it will run on one cylinder. Let’s say, the rear cylinder. Shut it off, check plug, yup rear is warm, front is cold. Wait, re-start a few times, now the BACK is running and warm and the front is cold. Again, makes NO difference which plug wire is on the spark plug or which plug is in (I have moved those from left to right as well to make certain it wasn’t a bum new plug).
Not fuel. Can spray fuel / ether /Brake cleaner into non-running cylinder and it wont fire. New carbs and swapped fuel source between engines. Just can’t be carb or fuel related IMO.
MPEM? Maybe, I suppose. But I have regular, reliable spark on the left side at both plugs. It just swaps back and forth between cylinders in some random order.
Rectifier? I don’t think so. I can unplug either or both plugs and no difference.
Rave valve stuck? I pull of the caps and they both move. Again, with random front/back firing I doubt this as the cause. I have not pulled the valves to check their condition.
Twisted Crank? Putting at TDC and a rod in both, the other is at BDC and pressing on the rod in the BDC when the other is at TDC creates NO movement. Best I can visually tell its not a bent crank. Also, if a bent crank, wouldn’t one ALWAYS not fire?
Compression: One is about 148PSI the other >135 PSI. Again, since random front/back I doubt this is the issue.
Whichever plug isn’t firing is a bit oil-wet as you’d expect (I think) since it is pumping oil and not burning.
Starting: I did note that it went “CHUNK” when I went to start it Saturday. A few tries later and it turned over fine. Pulled the plugs to make sure it hadn’t hydraulic locked for some reason. It has occasionally now, with the issue I am having ”struggled” to turn over randomly. That may be wear and tear on that poor starter with all the back and forth testing.
I am STUMPED. ANY suggestions / ideas are welcome.
The RIGHT engine runs GREAT.
Today I pulled it and dropped off at SeaDoo dealer for them to look at it. More WEIRDNESS: running it over to the boat launch it ran up to about 4000 RPM on the left / 1 cyclinder but OCCASIONALLY the seconds cylinder would kick in for a bit, on and off, and I’d get about 5000 RPM out of it.
I don’t think the coil or pumps were a waste as it will reliably start, idle and run on one cylinder. Before changing the coil it wouldn’t idle on the one cylinder worth a crap. Always needed a bit of throttle.
Thanks,
Brad
