HI...1999 Yamaha ox66 150 h.p. How can I trouble shoot the supply voltage for the fuel pump? Tried swapping key switches and wiring harness from port motor same result. Motor will run on starting fluid? When you try to start the motor the start prime light comes on and stays on. How does the pump know when to come on and off (ie. sensors or something) I omh. out pump motor and it's the same as the port motor that runs fine. Thank You Much Ken
a tad confused on the start prime lamp as its not a Yamaha thing.
did you make sure the stop lanyard is in place,if its not you should get an audible alarm,if they actually work, and no pump voltage.
to properly test the pump voltage with the key on test from the red pump lead to engine ground.
also test thye resistor located just above the throttle body assy, if it fails there is no low speed running.
check the fuel pump fuse in the fuse box.
anytime the key is on the pump should recieve 12V but the ground is controled through the blue wire running to the ECU.
a quick test of the pump is simply use two jumper leads,one between the pump red and the 12V on the starter solinoid terminal and the other from blue to ground.
at key on engine off the ECU runs the pump about 5 seconds then removes the pump ground, the 12V is still at the pump but now there is no circuit path.
do you have the service manual and a digital voltmeter ?
Thank You for the info I will check all that you have said. No I do not have a manual but on monday I'll go get one. Yes I have a multimeter and will check things out. I have one question about the red + 12 volt to the pump, does it go though the ECU or does it go staight to a fuse (where is this fuse) and then to the 12 volt supply. I've located one 30 amp fuse (good and small like a auto fuse) and two large fuse's in the big black rubber block and they are both good. How does the ECU know when to supply the - voltage for the pump when running?. I just got these motors, so the start prime light is new to me, (I had two 1987 200 Yami's loved them BUT they used too much fuel) The light is just to the left and down of the dual keys, it's within the yamaha key plate 6"x6". On the right hand motor that runs good it comes on then you first turn the keys for aroung 5 seconds then goes out. Thank You Sooo much for all the information Ken
actually when the key is turned on the key on yellow closes the main relay and feeds the key on yellow voltage to the ECU,fuel pump and a few other circuits.
the ECU then closes the ground for the fuel pump for approximatly 5 seconds to pressurize the rail. once running and below about 1800 RPM the ECU ground path is through the resistor mounted above the throttle body and is controled by the pulser coil signal,thats what tells the ECU the engine is runing. take away the pulser signal and the ECU will remove the pump ground.
above about 1800 RPM the resistor is taken out of the circuit and the pump speed increases.
remember in a series circuit current flow is limited by a resistor, reduce the avalible current and you reduce avalible voltage and the pump runs slower.
at the pump 9 V running below 1800 is normal.
HI Just wanted to tell you what I did. I checked for 12 volts on the red wire at pump with key on, and there is nothing. What do I check next? I then tried to jump out the pump with 12 volts and a ground and there still is nothing. So I took the injector pump apart and found the pump frozen! so I soaked it in carb cleaner and after many tries it started to work, seems to work just fine now Thank Goodness new one is $435.00. One note to anyone out there that would like to try this, when you have the pump motor out, all by itself look into the intake and with a strong needle try (BE VERY CAREFUL) to move the inpeller (CAREFULLY) I though the black fins were a filter into the pump, turns out to be the impeller of the pump itself, could have save me an hour of my time. O.K. where does the 12 volts come from? do you think the ECU is dead?. Thank You Ken
HI just wanted to tell you what I did today. I tried to run the bad motor with freed up injector pump (jumped out with 12 volts) and no good not even a cough. So I changed out ECU from good motor thinking the injectors aren't firing as well as not turning on pump and still nothing, BUT now the bad pump comes on and off like the good one does! (So now I know I have one bad ECU) So I changed out the injector pumps and the motor is comimg to life BUT will run for 2 seconds then die and the alarm sounds. Dirty injectors maybe? can they be cleaned? and what does the alarm mean? Oil tank full (even changed oil sensors) and motor cold!. Thank You So Much Ken Please can anyone help?
Does anyone want to hear something WILD!!!! I when back the the garage and tried the motor 4 or 5 more times each time she ran a little longer and longer and finally stayed idling (rough very rough) but running! I think the injectors are dirty or maybe clogged (number 2@3 intakes seems to be drier then the other 4) I also change the big resistor from motor to motor with no results. BUT as I was giving up for the day I put the bad ECU (I thought) and unfroze fuel pump (I fixed) on the good engine, hook up the hose and turned the key and to my surprise the pump turned on for 5 seconds and then she fired right up!!!!!!!!!! I just don't get it BUT I love it! Both motors are running and now I can clean them up change water pumps, clean 02 sensors, injectors and fuel filters and run decarb though them and hit the water. Thank You Ken
P.S. The little light on the key switch that says start prime stays lite as both motors where running?? any thoughts? and when the one motor was stalling, when it quit the horn would beep on and off kind of fast what does this mean?