Idling & starting problem F225

[seafishingindia]

Hi Guys...First post here and we need some help. We are based in Port Blair Indian Andaman & Nicobar Islands. It's a pretty remote place and we need to be self sufficient. We normally cope well with engine sevicing and breakdowns, but this ones got us stumped. Below is a brief background the engine it is a 2003/4 F225 Yamaha

About one month ago we were not getting the full rpm out of the engine it was maxing out at 4300 rpm whereas prior to this max rpm was 5400 rpm

Also when starting the engine it would high idle around 1200 rpm this would then slowly reduce to 600-700 rpm.

On shifting into gear the rpms would drop and the engine would miss and almost stall unless the throttle was increased, once increased the engine would run normally through the rev range but not go beyond 4300 rpm.

About 4 days ago it stalled and would not start, our local mechanic has done the following:

· Adjusted the throttle sync screws

· Adjusted the tps voltage

. Checked Thermostats

· We have replaced plugs, there was carbon fouling but acceptable, one plug had some oil on it

· We have checked the fuel lines

The engine will not start unless it is given some throttle and if it does start it is missing and idling high, there was also some backfiring on trying to start the engine at times.

More adjustment has been done to the above and as of now

· It does not self start

· If helped then it is idling at 2500 rpm

· It is not missing at 2500 rpm

Attached yds data sheets and comparison (to follow cannot upload exel) with the other engine which is in running condition.

Any help you can give us will be of much help as we are quite stuck here with no special tools at hand.

Thanks and looking forward to your responses
( Having a challenge loading the exel diagnostic sheets will post PDF shortly)

[rodbolt17]

classic signs of fuel contamination.
test rail pressure,test compression,test spark.
could have also clogged an injector.

[seafishingindia]

YDS Data added...What do you think guys?

[seafishingindia]

Thanks Rodbolt...we will check today. Appreciate you taking time out to help!

[rodbolt17]

me thinks untrained stick skinners have been handling this engine.
that or you have serious issues.
its very abnormal to have recorded 4 sensor codes in the past 15 min of operation.
shows signs that some one for some reason was randomly unplugging things.
thats what we call splatter gunning.
splatter gunning ALWAYS leads to extra parts,steps and time.
fastest way to trouble shoot that engine is first test spark and compression,I prefer leakdown testing.
then check the rail pressure and look at the YDS or winky blinky for stored codes.
rather than unplugging things,find out what and why the switches exist.
most switchs when unplugged are read by the ECU as OFF.
you MUST know what on and off means to the ECU and what its looking for and why.
same with sensors,typically the ECU is looking for a feed back in a range.
unplug it and the ECU will run in a default map and continue on.
may be degraded but it will run with any sensor unplugged.

[rodbolt17]

dunno about one of the best.
I have been a master tech for Yamaha since I passed the master tech exam in 2006.
its a stupidly simple speed density open loop fuel injected motor.
ECU failures are incredibly rare and usually caused by the ISC valve sticking.
easily tested with a laptop.
Typically backfires in the intake are an indication of lean A/F mixture in the intake manifold.

whats an intake air setting?

[rodbolt17]

there are not but 6 injectors.
40n hours is about 39 hours to long.
its a dirt simple system.
run without the airbox,watch which intake is blowing flame and smoke,clean/replace that injector.

each injector has a filter basket, sometimes you can spray them out with carb cleaner.
as the fuel pumps are blow through types brush dust from the armature can clog the filters.

gasoline actually flows over the motor windings and through the brushs and out the outlet to the injector rails.

[rodbolt17]

I can clean the VST and change 6 injectors in 2 1/2 hours all day long.
in fact if I open up the VST and its very dirty I automatically replace the injectors.
VST has to be removed to access the port side injector.
I guess you could remove the intake but that's a hassle I don't want.

stbd side you release the quick connect on the rotor cover and simply remove the rail.

we keep spare known good reworked injectors at the shop for the F200-225 just for this.