02 yamaha 250hp ox66 dies at full throttle

[mikep6]

runs good at 50mph but when trying to open up to in the 70s like you turned the switch off i have alreadt put these parts on

High pressure pump
3 low pressure pumps
filter in vsp tank
filter on the side of the engine
filter on the boat
primer pump
fuel pump resistor
when i replaced the high pressure pump run perfect when i took it out 2 times then started again i put a voltage meter on the fuel pump when going down the lake and it cut off the meter went from 3.32v to 0 then back to 12v
oh ya the last time after putting on the resistor it died at 65mph then died 2 times going on plane . please help me again.

 

[rodbolt]

Re: 02 yamaha 250hp ox66 dies at full throttle

chunk more parts at it, your dealership needs the money.
or use a plan of trouble shooting.
sometimes intermittant faults are best checked with an analog voltmeter.
what is the fuel rail pressure when it fails?
why replace the pump resistor for ANY issues above 1200 RPM ?
where are your meter leads when testing pump voltage?

 

[mikep6]

Re: 02 yamaha 250hp ox66 dies at full throttle

the volt meter was on the red wire at the fuel pump the pressure drops to 0 and as the resistor goes i just didn't know any better the dealer said it wasn't losing volts but i did a check myself on the red wire side of the fuel pump and thats the result i got with a craftsman volt meter i ran a pig tail wire from the pump to were i was driving and hooked a ground in the dash when it died thats when i noticed the meter went from 3.32v to 0 then went back to 12. somthing volt in about 4 seconds

 

[rodbolt]

Re: 02 yamaha 250hp ox66 dies at full throttle

with 1 meter lead on the pump red wire and the other to a good ground you have 12V anytime the key is on.
period.
if not then check the yellow key on power and the main relay power.
the resistor is on the ground path from the pump to the ECU, the ECU completes the ground path for pump operating current.
below about 1200 RPM the resistor is in the circuit and drops operating voltage to about 9V. above 1200 and the ECU bypasses the resistor and the pump runs on a full 12V.\
however on the pump red wire, and ANY other yellow/red yu will have 12V+ to ground anytime the key is on.
so your either loosing your ground path when using your meter or the 12V pump supply is missing.

 

[mikep6]

Re: 02 yamaha 250hp ox66 dies at full throttle

i wired a toggle switch and ran a wire to the fuel pump so i knew it would keep 12v coming to the fuel pump and it still stall like you turned the switch off that was at 5000 rpm and around 68mph and thats a red/yellow wire that goes to the fuel pump i said red sorry.the dealer said when it stalled fuel pressure went to o thats when high press fuel pump was installed ran perfect 2 trips to lake then all came back

 

[rodbolt]

Re: 02 yamaha 250hp ox66 dies at full throttle

to make ANY electric device work you have to have 2 things, a power supply source and a return path.
on your 250 the power source is via the main relay and the pump supply circuit, the RETURN path(ground) is completed by the ECU.
so if one meter lead is on the 12v supply source wire and the other on an engine ground and voltage goes to 0V either we lost the engine ground path(return) to the supply source OR we dropped the supply source.

 

[mikep6]

Re: 02 yamaha 250hp ox66 dies at full throttle

were is the main relay and pump supply located and how would i check it

 

[rodbolt]

Re: 02 yamaha 250hp ox66 dies at full throttle

out of memory I cant say with any certainty, they moved it about over the years.
if it loses a ground or the key on yellow power supply it drops off and you lose the ECU,fuel pump and injector voltage.

 

[mikep6]

Re: 02 yamaha 250hp ox66 dies at full throttle

the key switch yellow wire is that what your saying? if so can i run a toggle switch and hook up on the motor 12v from battery to see if thats whats breaking down? 1 other thing on the battery i have 1 big ground and hot wire then i have 1 little ground and hot wire the little ground wire i noteced that it was croded over and replaced

 

[rodbolt]

Re: 02 yamaha 250hp ox66 dies at full throttle

I would not toggle switch anything.

 

[mikep6]

Re: 02 yamaha 250hp ox66 dies at full throttle

i have 2 wires on the battery ground one big wire 1 small wire the smaller of the 2 had crossion in the wire cut it out and replaced end havent tried it out yet but what do i check next thanks mike