2.5 260 Fueling Issue

I have a PP 260 that has been rebuilt (2 hours on motor) and I'm having a fuel delivery issue of some sort. Initially the motor would run great anywhere from idle to 6,000rpm, once you would reach 6,000rpm the motor would hit a wall and the more throttle you would give it the worse it would run.
The problem has gotten worse since testing. Motor will only run under load (in gear) if you hold the enrichment button down on the key, otherwise it will stall. Motor runs perfect in neutral.

Fuel pressure is correct
Injectors have been flowed and cleaned
Swapped ECU's
Drained & cleaned the tank, hoses, filter & fresh gas (no debris found)
Map sensor & Air horn barb are clean and free of blockage.
Compression is good
Reeds are good
No obvious indication of a bad stator/trigger or rectifier, however I have not tested them with a meter.

Thanks in advance for any input. -T2

the push tha key enrichment should not function on tha 260.. enrichment should only work with start circuit.... unless someone has changed it..

I have 2 1996 260s and BOTH keys enrich on key push!

Carter Powell

they have ta be fixed ta do it.. factory buries tha push key circuit (yellow/black) in tha harness... ya gotta dig it out and hook it up.... i had ta do it with every efi, laser and/or horn motor i had over tha years.. its not an uncommon thing ta do... think there were a few dealers back in tha day that would do it when they rigged junk.....

does ya pressure vary any at all past 6 grand???.. check tha orifice in tha "T" at tha return... probably nothin' but worth checkin' in between butt scratches.....

anti siphon vale or partially plugged vent? I would try a remote fuel tank with working vent.

Rock

was anything done to tha block when it was rebuilt?

Ok guys, I'm back at it again. I took the injectors off again and sent them to brucato and had them clean and adjust which they definitely needed. When I put them back on the boat ran perfect. Fast forward 3 weeks to when I took the boat out again and I'm having the same issues. Motor will slowly lose rpm until it shuts off under load, idle & revs are perfect in neutral. Once again the enrichment circuit which is wired to key push will make the motor run perfect under load. Can someone explain how the enrichment circuit works for me? Does it pulse the injectors once per push? Does it add voltage to the ignition system? If I HOLD the push key enrichment down the motor will run perfect, 2 seconds after I let off the key push enrichment the motor will lose RPM until it shuts off. I have gone through the majority of the fuel system (pump, injectors, tank vent, hoses, inline fuel filter, orifice @ return, etc..) I have not changed the gold regulator.

thx for your input.

Maybe ethanol in the fuel? Soaking up water when you’re not using it for a while? Sometimes fuel varnish green goo can happen quick in certain situations maybe it’s gumming up the injector screens?? Cheap to check, a bit of work to dig that stuff out. Just some guess here hope this might help

What ECU(s) have you run?

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Originally Posted by 25two.stroke

What ECU(s) have you run?

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Brucato ACU w/ a stock 260 curve & the CDI ecu that came with the motor.

All good suggestions. I think you are on the right track and have a good clue with the enrichment circuit helping the problem. I would call Brucato and ask how the enrichment works and where he thinks the issue is.

Also be careful in your testing! If it it going lean at WOT you can kill a piston pretty easy...don't ask me how I know...

Disconnect the air temp sender and go run it. See if it goes. Should make it run rich about 10%.

Seemed to run a bit worse with the air temp disconnected.

https://www.youtube.com/shorts/LQZAPk-ATTE

Did you eat a reed? Compare all plugs to each other see if any hole/s read different