Yamaha F115 2003 fuel pressure

[Hookedonsnook]

Ok so i'm trying to work out my problem with this motor bogging down.... I've been out of town and am now getting back to work on it. It isnt running at full rpms (is now topping out around 4500) if i pump the throttle it will get higher.... So this should be a fuel restriction problem. Either in a filter, injector, or a bad fuel pump right? I want to check my fuel pressure, but what is the best way to do this? What pressure is it supposed to read? and does it read a higher pressure at higher rpms? or is it constant? also if i test it and it reads low that means there isnt enough fuel getting to the injectors, but if it tests normat then that most likely means an injector is clogged. Is that correct? I've also read on here that running injector cleaner through it is bad.... why is this? Sorry for all the questions, but i just want to try to understand how all this work so i can get it fixed and for future reference. Thanks guys!

 

[Hookedonsnook]

Re: Yamaha F115 2003 fuel pressure

Rodblot when you say test the rail pressure at the problem RPM what is my problem rpm? right now the engine tops out around 4500 RPM, but if i ppump the throttle i can get it to around 5000 RPM.... what should i be looking for at that RPM? i've read up about it and should the pressure be around 40-45 psi? Thanks for your help

 

[rodbolt]

Re: Yamaha F115 2003 fuel pressure

dude read some on speed density open loop EFI.
the only thing "pumping" the trhottle does is rapidly move the TPS, as the TPS voltage increases rapidly the ECU opens injector on time and will fire injectors both synchroneously and asychroneously. its an electronic equivalent of a carbs accelerator pump.
rail pressure s CRITICAL and CONSTANT.
only time it spike is at rapid intake vacum loss and then only by about 5PSI and then only momentarily.
works in conjunction with the above TPS thing.
you max RPM with a normal load should be 5800 to 5900 RPM. if not you will post about making oil.
rail pressure testing is ONLY valid AT the problem RPM AND LOAD.