250 Starts cold fine, restart after warm a problem

[Capt Patton]

Yam 250 2001 (TXRZ)
Starts up fine when cold, after engine is warm (it does its 1000rpm warm up for min or two as normal and is good to go) however, after stopping for a few mins to fish spot, I have trouble getting it started again. When she does start, after about 6-7 trys, it will putter around 400-500 rpm for 10-15 secs (on the adge of cutting out) before gets going and settles at 600 rpm. I have changed all filter, plugs, (02 sensor is clean, but not check with winky blinky), the only one I have not changed in about a year is VST. Any ideas?? Thanks

 

[rodbolt]

Re: 250 Starts cold fine, restart after warm a problem

O2 sensor wont show up on a winky blinky.
if its bad or no signal to the ECU fuel is fixed rich at low speed and lean above 4000 RPM.
check for any codes with a winky blinky, check for leaky injectors with the fuel pressure test guage. when was the last time the low pressure pumps were changed?
but the ECU wont record a dirty or failed O2 sensor, the ECU will create a lean or rich condition based on the signal though.

 

[Capt Patton]

Re: 250 Starts cold fine, restart after warm a problem

Okay 1)check for any codes with "WB" 2) check for leaky injectors with fuel pressure test guage. Got it thank you. I have never changed the low pressrue pumps on this engine, so I will do so (they are do to be changed). Just asking for my own knowledge, why would (or could is better way to put it) poor working low pressure fuel pumps be a problem on warm restarts,,,,VST must have okay level of fuel if it was just running? Thanks again for suggestions.

 

[rodbolt]

Re: 250 Starts cold fine, restart after warm a problem

if you have a pinhole leak in a diphram its possible to have a very rich restart.
cold it should idle about 1200 RPM then drop to about 730 RPM,625 or so in gear in the water.
however that engine is rather hard on lift pumps so we reccomend replacement before they rupture and take out a bearing.
also check the plug caps with an ohm meter.
your describing a rich restart condition. but if the winky blinky says nothing is wrong its time to look at things the ECU does not monitor. saves time chasing ghosts.

 

[Capt Patton]

Re: 250 Starts cold fine, restart after warm a problem

Thanks for explaining. This engine is one of a pair on my boat, and not sure if it has any relation however the Fuel Computer does have this engine using about 10%-15% more fuel than its counter part at most rpms (over 1000). I guess there could be a connection with the rich restart?

 

[rodbolt]

Re: 250 Starts cold fine, restart after warm a problem

most likly a bad lift pump or the ECU is increasing the fuel pulsewidth in an attempt to force it to idle at the ECU mapped RPM for a given TPS and CPS signal in conjunction with an engine temp signal.