250 yami stalls and sneezing

[never-satisfied]

99 yamaha 250 os66 fuel injected.stalls at idle,wont stay running,hiccups.3 weeks ago was bogging and shutting off at 4500-5000 rpms.cleaned o2 sensor,replaced 3 low pressure pumps,replaced vst & other fuel filters.ran great for 2 weeks(still does at high rpms,but won't idle.barely runs at idle.ok if you throttle up to 2000 in neutral.please help.

 

[JB]

Re: new to site,help

Re: new to site,help

http://forums.iboats.com/showthread.php?t=250876

 

[triumph190]

Re: new to site,help

Re: new to site,help

It sounds like a fuel resctriction issue. At 2000rpm and greater the fuel pump is sucking hard enough to force fuel past whatever may be blocking it.

Do you have a good flow of gas from the tank to the motor? Take the fuel hose off of the motor, and take the quick connect out of the hose. Try pumping fuel into a bucket using the primer bulb. As you pump look for debris that could be stopping up the fuel line.

If you have a anti-siphon valve, get rid of it! Chances are it is the original, and over time dirt and debris will get sucked up into it creating a blockage for fuel. They are good to have on inboard motors, but 99.9% of all outboards sit higher than the gas tank, and gravity only allows liquid to flow down hill.

 

[never-satisfied]

Re: 250 yami stalls and sneezing

i'm pretty sure(not 100%)there is no anti-siphoning valve.where would it be???the fuel filter on the side of the motor stays full all the time.i went out 50 miles total started the boat to move 10-15 times and it was fine all day until i returned(motor was hot)have not been able to check again,boat is 2 hours away.will that show up on a fuel pressure test?????

 

[rodbolt]

Re: 250 yami stalls and sneezing

OX66 uses a two speed VST pump. you may have to go in and clean the VST filter again,sometimes 1 hiccup (crankcase backfire) is all it takes to take out a lift pump diaphram.
test fuel rail pressure,it must maintan 35 PSI at all rpms, test O2 sensor output voltage according to the tech bullitens disregaurding the flame test one.
that one is useless.
test the lift pump output,test the rail pressure. yes its possible to have a tank restriction thats where the fuel system vacum test comes in.
Have you recently switched to the E-10 fuels ?
and is this a VX250 or an SX 250 ?
have you done the basics of testing compression and spark?
and now not yesterday.
remember all the VST is is a mini gas tank, fuel restrictions will take several minutes of idle to show up so if the idle is nasty at all times I would hunt for other issues as well.
all the lift pumps do is insure an adequate supply of vapor free fuel at all RPM's
as far as the anti-siphon valve, it can be legally removed ,IF and ONLY IF, NO part of the fuel system drops below the level of the tank top.
thats why I have an electric pump,flow meter and a throttling valve to test for adequte fuel supply and excessive fuel system vacum without running the engine.

 

[triumph190]

Re: 250 yami stalls and sneezing

If you have an anti-siphion valve it would be at the top of the gas tank where the fuel hose attaches to the pickup line.

The filter on the side of the motor should always have gas in it no matter what because of the cup or bowl shape design.

A fuel pressure test never hurts.

 

[never-satisfied]

Re: 250 yami stalls and sneezing

OX66 uses a two speed VST pump. you may have to go in and clean the VST filter again,sometimes 1 hiccup (crankcase backfire) is all it takes to take out a lift pump diaphram.
test fuel rail pressure,it must maintan 35 PSI at all rpms, test O2 sensor output voltage according to the tech bullitens disregaurding the flame test one.
that one is useless.
test the lift pump output,test the rail pressure. yes its possible to have a tank restriction thats where the fuel system vacum test comes in.
Have you recently switched to the E-10 fuels ?
and is this a VX250 or an SX 250 ?
have you done the basics of testing compression and spark?
and now not yesterday.
remember all the VST is is a mini gas tank, fuel restrictions will take several minutes of idle to show up so if the idle is nasty at all times I would hunt for other issues as well.
all the lift pumps do is insure an adequate supply of vapor free fuel at all RPM's
as far as the anti-siphon valve, it can be legally removed ,IF and ONLY IF, NO part of the fuel system drops below the level of the tank top.
thats why I have an electric pump,flow meter and a throttling valve to test for adequte fuel supply and excessive fuel system vacum without running the engine.

it is a s250turx.i did replace the vst filter with a new one.the old one was not dirty at all.this idle problem happens all of the time.(just started doing this)
no matter what it won't idle,good at 2000 and above in nuetral.could a bad plug wire cause this???i have not checked them,and they are original.i also plan on testing the tps.

 

[never-satisfied]

Re: 250 yami stalls and sneezing

If you have an anti-siphion valve it would be at the top of the gas tank where the fuel hose attaches to the pickup line.

The filter on the side of the motor should always have gas in it no matter what because of the cup or bowl shape design.

A fuel pressure test never hurts.

does not have a anti-siphoning valve.had that apart 3 weeks ago to check fuel quality.tapped a pump into that hose to pull fuel and check.

 

[triumph190]

Re: 250 yami stalls and sneezing

Could be a fouled plug....when was the last time you change them? You may want to do so. A way to check for a fouled plug is to pull the plug wires off the spark plugs one at a time while the engine is running(idle). The engine should drop the same on all cylinders. If you have one that dosen't cause the engine to drop as much as the rest you could have a fouled plug or...maybe...a bad wire...

 

[rodbolt]

Re: 250 yami stalls and sneezing

and now a post about #5 not firing, again.
that motor uses CCS, between 800 and 2000 #2 does not fire, from 600 rpm to 2000 #5 does not fire rendering the spark plug wire pulling absolutly useless. if you suspect ign,and I dont, simply do a spark test or buy a Kv tester and check it but remember unless its a VX model it has CCS.
the hiccup indicates it running lean, you can use the diagnostic test lamp to check for any codes but almost any failure will lock the timing at 7* BTDC and idle speed will increase to about 1100.
the hiccup indicates we cant get fuel into a cylinder for some reason.
gotta find out why.
could be a fuel injector filter,VST filter, defective lift pump or a bad fuel rail pressure regulator, a bad plug wire cap,a bad plug the list simply goes on but its not hard just takes time and a service manual.

 

[never-satisfied]

Re: 250 yami stalls and sneezing

and now a post about #5 not firing, again.
that motor uses CCS, between 800 and 2000 #2 does not fire, from 600 rpm to 2000 #5 does not fire rendering the spark plug wire pulling absolutly useless. if you suspect ign,and I dont, simply do a spark test or buy a Kv tester and check it but remember unless its a VX model it has CCS.
the hiccup indicates it running lean, you can use the diagnostic test lamp to check for any codes but almost any failure will lock the timing at 7* BTDC and idle speed will increase to about 1100.
the hiccup indicates we cant get fuel into a cylinder for some reason.
gotta find out why.
could be a fuel injector filter,VST filter, defective lift pump or a bad fuel rail pressure regulator, a bad plug wire cap,a bad plug the list simply goes on but its not hard just takes time and a service manual.

unfortunately i don't have a manual yet(it's coming)i appreciate the info and i will be doing some test this weekend.plug caps are original(hope thats the problem)may try to borrow a manual from local dealer!!!

 

[never-satisfied]

Re: 250 yami stalls and sneezing

update!!!!!!!!i bad "new" low pressure fuel pump helped my problem,but not 100% still sneezing at idle and stalling sometimes.removed injectors,pulled the filters out of the injectors & cleaned then the boat ran awesome.thanks for the input!!!!!!!!!clogged injectors=lean condition!!!!!!!

 

[never-satisfied]

Re: 250 yami stalls and sneezing

update:boat is fixed2 clogged injectors.cleaned the screens,re-installed,runs great.thanks for the replies