2002 SX150TXRA Yamaha can't get it running

[Nietzsche]

This EFI motor set for 2 years without running, with gas in the engine all that time. I emptied out all of the old gas and cleaned out all of the fuel lines. The high pressure fuel pump was frozen so I replaced it. The fuel pressure is now good. I changed all the fuel filters and the spark plugs. Now, when I start the engine, it idles really rough and stalls out when I try to raise the RPM's above idle. No warning buzzer or warning lights. However, if I disconnect the "emergency" (yellow/white) wire from the ECU the engine runs great at all speeds. Any ideas will be greatly appreciated. Also, does anyone know how to read the diagnostic codes without the Yamaha light? Thanks.

 

[rodbolt]

Re: 2002 SX150TXRA Yamaha can't get it running

test all the battery cables and connections. when you unplug the emergency wire it goes to a fixed timing and fuel curve map. all the sensors on that engine can be tested with a DVA meter, ohm meter and standard volt meter. test all the orange sensor wires for a 5 volt reference.. a service manual will be a must as will be some basic test equipment. a stevens CD-77 or equvalent will shorten the time to test

 

[Nietzsche]

Re: 2002 SX150TXRA Yamaha can't get it running

Thanks rodbolt. I took your advice and got a service manual for this engine. I checked all the battery connections and grounds that I could find on both the battery and the engine. I couldn't see anything wrong with any of them but I disconnected and cleaned them all anyway. I checked the throttle position, engine temperature, oxygen density, air pressure and air temperature sensors and they all test good. I also checked the overheat switches and the oil level switches which also test good.<br /><br />I cannot test the ignition system without a peak voltage meter, so I had to order an adapter for my Fluke meter in order to read the peak volts. I will test the ignition system when the adapter comes in.<br /><br />One thing I did find strange is that all of the voltage readings which I am reading while testing the sensors is negative voltage. The manual doesn't specify the polarity, which I assume they would if they expected it to be negative voltage. I tried 3 different meters (1 digital and 2 analog)and they all read the same. I triple checked the orientation of the meter leads and I have them connected right. Does anyone know if this is correct or represent a problem? Can anyone think of anything else I could be checking while waiting for my peak adapter to come in? Thanks.

 

[rodbolt]

Re: 2002 SX150TXRA Yamaha can't get it running

test from the start solinoid positice battery cable to the block. place the red lead on the positive and the black lead on the block. it should give a positive 12V reading. if it does not look for crossed battery cables. there is a way to observe fuel spray pattern but we will wait on that one.