Issues that would cause an EFI motor to go lean?

[Carter Powell]

I just had a rod go thru the block on my 2.5 260 and all the plugs were white! Last week they were normal tan. What are some of the things that would cause an instant change in fuel delivery. Fuel pump pressure, blocked fuel flow, all injectors lean out. I need to find some possible answers before another motor.

Thanks a lot, Carter Powell

[LakeFever]

I hear ya. Once the motors fragged it’s hard to diagnose everything but once you freshen the power head you need to verify everything. Check fuel pressure first. Timing next. Ethanol laced fuel is bad news for two strokes. Old fuel maybe not enough octane. Is the oil injection deleted? If not do so. Cooling system working as it should be? Injectors cleaned and flowed.

[Jim Speros]

I am always suspicious fuel. Especially with ethanol. Did you dump a filter into a clear container to see if it was cloudy?

[Carter Powell]

It is ALWAYS non ethanol, fresh fuel. All the plugs were white, two weeks ago they were a nice tan. The connecting rod pulled the wrist pin clean out of the piston. Wow!

Carter

[LakeFever]

Fuel pump crapped out or regulator took a dump. If it’s all pistons it’s unlikely injector related. You’re going to want to get your ecu checked for health too. Maybe it messed with the fueling. There’s also the tps if that thing fails your in all sorts of fueling trouble

[Carter Powell]

It has a new Brucato ACU which has worked perfectly since March. So there is no TPS on this motor.

Carter

[LakeFever]

Brucato does away with throttle position sensor? How does the ecu determine when to enrichen?

[Carter Powell]

Not sure, but it has worked better than any ECU I have ever tried on anything before.

Carter

[LakeFever]

I just looked it up there is a TPS on horn motors ( figured there had to be ) you should have a map and a tps and that’s what feeds the acu information to Calibrate your engine properly. There are test harnesses available to set and test your tps which I would surely be doing before bolting any of that fuel system on a fresh power head. I don’t know if you can test a map sensor or not.

[OnPad]

https://brucatopower.com/technical-resources/
No tps with Brucato.

Don't know much about stuff that nice, but after a little research,.. sounds like map sensor and rpm signal control fuel curve. The temp sensor probably has a little influence also. Unlikely on all cylinders, but a air leak could cause a lean condition also. I would definitely check the fuel pressure.

[LakeFever]

cool must me map only

[tlwjkw]

external tps's went away when tha ecu's went digital.... think tha "digital" 11350 was tha first..

[H2Okie]

something you could check is the 4 pin injection connector plug at the bottom of the plenum . The injector pairs all share a "common" Battery Positive with the injector "pulse" signal coming as a negative signal from the ECU to the individual paired injectors . A bad connection of that common battery positive to the injectors would affect operation of all of the injectors at the same time . I have heard of people having trouble with the injector wiring getting pinched inside the plenum and shorting out and if this happened to the positive wire reducing the voltage the injectors received same thing .

This just dawned on me don't the injectors on a 260 mount thru the right side of the plenum on that motor or am I thinking about something else ?

[David - WI]

This just dawned on me don't the injectors on a 260 mount thru the right side of the plenum on that motor or am I thinking about something else ?

Into the side of the "front half" of the block, I think?

534716

[H2Okie]

I suppose as OP suggested possible fuel pump issue but looking at the picture if the pressure regulator on the fuel rail went bad and was dumping rail fuel pressure = less fuel to engine coming out of out of all six injectors

[Carter Powell]

OK guys, help me think this thru. I THINK I found the issue. I pulled the motor apart and got all of the good parts out. But what I did notice was that all of the other pistons and rings looked great, except for #6 which is the bottom most piston. It was just melted to hell and there was water in that cylinder crank area. When I pulled the bottom cap that holds the seal the seal did not have much friction on that end of the crank. If water can get in so can air. I am thinking that it was able to suck in a lot of air along with some water and that caused the lean seizure on # 6. You could also see a lot of agitated oil mixed with water all around the top of the are where the drive shaft comes up thru the the exhaust plate, this area should be dry, why then all of the oil mixed with water. If oil and fuel can blow out then air can be sucked in also! Give me some feedback on this please.
Thanks a bunch, Carter

[LakeFever]

Crank seal. Been there done that, a couple times. On sleds the belts blow up and often can harm the seal and you eat that cylinder beside the clutch up. Newer sleds this isn’t much issue they have better designs but those old rockets and crappy belt tech it was fairly common

[PanRonnie]

Powerhead coming loose from the midplate?
Engine sucking in water through the exhaust
I used to install a sierra gasket which would always burn through the center exhaust dam
After i orded original mercury gaskets and noticed the metal grid reinforcement it has i never used anything else and always check the nuts after a couple of times being out to see if they are loose