sx250 wont run btween 1800 - 3000 rpms

[nagrof]

2001 yamaha sx250txrz I have cleaned o2 sensor changed the three fuel pumps cleaned the vst filter the fuel pump filter,I just pulled the fuel injector filters out and cleaned them,they were clean,I replaced the plugs also checked tps voltage and adjusted the butterflys per service manual..It surges around 1800 ,It wont stay at a set rpm between 1800 and around 2800 rpm.set it on around 2100 or so and it zooms up to 3300.... ...any help would be appreciated

 

[garyN]

Re: sx250 wont run btween 1800 - 3000 rpms

nagrof<br /><br />I have the same problem with a small Yamaha four stroke and they are unable to find the cause. My advice to you is, if you have a warranty still, get it into the dealer and park it there until he can the the technial service people to actually look at it. It is likley you have a probnlem with the "electronic choke" circuit, they may be part of the brain and that is what I would try to get replaced by the factory. YOu are not the only one with this problem so have the dealer check the service bulletins.

 

[bigbrownbuku]

Re: sx250 wont run btween 1800 - 3000 rpms

start with a fuel system vacuum test nagrof. start at the tank side of the engine filter under the cowl.

 

[rodbolt]

Re: sx250 wont run btween 1800 - 3000 rpms

hello<br /> now is the tinme you have to find a competent tech that can test it in the water. GaryN has a carb problem. I dont know why they cant find it but its not a yamaha issue I think its a tech issue. on your 250. its just an EFI. its not vodoo. however there are certain things that must be checked while under a load. also remember that as the hull moves forward and gains speed there is a small area that will be difficult to hold a staedy rpm. however there should be no up and down surge. test the o2 sensor while under a load with the test harness and a DVM. also test the high pressure fuel rail at the problem RPM. all tests have to be done under a load . some times it takes a bit to find it. but over all its a simple straight forward system if you understand how all the parts work together.its all suck squeeze bang and blow. to increase rpm you have to increase air and fuel and eventally timing. no other way to make power. a flaky high pressure pump will do funny things.how familiar are you with the reason EFI works at all ?

 

[nagrof]

Re: sx250 wont run btween 1800 - 3000 rpms

thanks for the replys,this is my first stab at efi<br />trying to save a buck or two. The boat runs really good at high rpm,low rpm it surges,runs rough also,I can get it to do it in the driveway,just got my service manual back out and started going through all the sensors tests..The 02 sensor that checked good last time is only measuring 4 ohms where it is supposed to measure 100... ..now to go get a bank loan to buy a new 02 sensor hope that is all of it..Thanks again...Ill let you know...

 

[rodbolt]

Re: sx250 wont run btween 1800 - 3000 rpms

cant ohm an O2 sensor.<br />buy the manual and the test harness first

 

[nagrof]

Re: sx250 wont run btween 1800 - 3000 rpms

I am reading out of manual it says first step <br />measure o2 sensor heater resistance out of spec <br />replace I measured across o2 sensor i measured ohms..supposed 2 be 100 ohms it was4 ohms I checked it wih another meter..3.8 You obviously know a lot more than I do about this the 02 sensor is really expensive ..the next test for it is to heat it up and check out put voltage....I was thinking about doing this step ,I called the dealer 300 bucks I talked to a guy in the service dept. he thought I should replace it he didnt feel any other steps were necessary..but he is puttin his kid through college (like I am)<br />what do you suggest I do next? test harness?Am I lookin for shorts? Thanks

 

[rodbolt]

Re: sx250 wont run btween 1800 - 3000 rpms

the heater circuit is just that. a heater. has nothing to do with is the sensor actually operational. I suggest if you wish to continue repairing your EFI to lean how it works. its not voodoo nor black magic.<br /> its a simple striaght forward EFI system just like almost every car used in the mid 80's to mid 90's only we burn oil.<br /> the test in the manual to heat it with a propane torch is totatal bull sheet. total BULL SHEET I say.<br />the test harness is about 11 dollars. plugs in the output side of the O2 sensor so you can watch what the sensor is doing.<br />this is not voodoo I say<br /> but a lot of things happen very rapidly each rev ov the crank. has any one put the winky blinky test lamp on it?<br /> if no codes are set you either have an in range failure or a mechanical failure.<br />that stupid puter cant tell if the sensors have bogus info or not. just if they have a total failure.

 

[nagrof]

Re: sx250 wont run btween 1800 - 3000 rpms

thanx,i will look for test circuit.

 

[rodbolt]

Re: sx250 wont run btween 1800 - 3000 rpms

hello<br /> if the heater part of the sensor is bad it will require a sensor replacement. the test harness for the sensor will fit both connections. look for 12v on the heater wires. the flame test in the manual is useless. use the test harness and with the enigine running in the water not muffs hook up your DVM to the green wires using the test harness, remove the airbox. with the engine idling you should see a fluctuating voltage between .3 and .6 volts.<br /> place a finger over the top butterfly air hole. you should see the voltage rise. remove the finger and it should fall. but it should never just remain steady.

 

[nagrof]

Re: sx250 wont run btween 1800 - 3000 rpms

Thanx for the advice I finally broke down and took it in...02 sensor checked fine he couldnt get it do anything for him,until he changed he impeller and went to test it and a coil started cuting out ...its going to wind up cheaper than if I would have followed the books advice and changed the 02 sensor..I thank you..