2001 F115 Yamaha fuel injectors not squirting????? stumped

[Moose2500]

I have a 2001 f115 Yamaha that I bought from a mechanic in Rockport. He overhauled the engine and it has low hours (under 300). Well it stopped running for me and I could not fix it even with the service manual and my mechanical knowledge. So I took it back to him to have the yearly service done and to solve the no start issue. In the end he found that the fuel injectors are not getting any signal from the ecu. The lower unit fluid has been changed, spark plugs engine oil, water pump checked, new pulser coil, cleaned vst, fuel pressure checked, ecu swapped from another engine, the fuel injectors have been proffessionally cleaned and tested. The fuel injectors will fire if voltage is applied to them. To no avail can we get the injectors to squirt. Can someone help me out please......we are lost

[fairdeal]

Yamaha applies power - 12V+ - to the injectors at key on
and then the ECU provides a ground to make them fire

do you have power at the injectors?
you've already swapped the ECU....

[pstephens46]

Are you sure you have the correct ecu?

[rodbolt17]

there is a reason real mokaniks are rather busy and charge a lot.
all you need is an alternator.


find a real mokanik.

[boscoe99]

there is a reason real mokaniks are rather busy and charge a lot.
all you need is an alternator.

find a real mokanik.

If the new alternator does not fix the problem, it might be the drive belt. A cogged belt is best.

[Moose2500]

Alternator????

2001 four stroke F115 yamaha
it has a stator not an alternator? is that what you think the problem is?

[boscoe99]

2001 four stroke F115 yamaha
it has a stator not an alternator? is that what you think the problem is?

Nope. This is just rodnut being silly and me following him.

The fuel injectors, the idle speed control valve, the spark plugs and the high pressure fuel pump should all battery voltage to them when the key is on. On the red wire with a yellow tracer. Do you have voltage to those components?

[Moose2500]

YES! voltage to those parts

[rodbolt17]

actually it does have an alternator. it consists of a stator and a rotor.
the pulser coils tell the ECU when to fire the injectors.
if the coils fail,wires fail or the stop lanyard is pulled the injectors quit.
can be tested with a DVM set to hz.

[Moose2500]

thank you I will have my mechanic double check that, since it was replaced possibly it could still be an issue.

[boscoe99]

2001 four stroke F115 yamaha
it has a stator not an alternator? is that what you think the problem is?

It is terminology.

Virtually all mechanical devices that create electricity all have a stator and a rotor. Actual magnets or electro-magnets move by a coil of wire and in so doing create electricity.

What most consider to be an alternator is usually belt driven. Like what you find on most automobiles or trucks. Airplane engines use them but they can be belt driven or gear driven.

Some Mercury outboards and Honda outboards use a belt driven alternator. No Yamaha outboards offered here in the USA use them. Yamaha uses what is known as a PMG for Permanent Magnet Generator. Magnets on the inside of the flywheel move pass coils in the stator and in so doing generate electricity.

Now to make it confusing, Yamaha will sometimes refer to the electrical generation system as an "alternator". Just don't go thinking that it has a belt like your automobile does. Or gears.

[boscoe99]

thank you I will have my mechanic double check that, since it was replaced possibly it could still be an issue.

The electrical generation system won't be at fault. As you have stated, all of the electrical components have electrical power to them. Specifically in this instance, the fuel injectors.

The ECU applies a ground to the injector to make it open. If the ECU does not provide the ground then the injectors won't function. The ECU might have failed internally. Hopefully not. The ECU depends on some components to tell it when to ground the injectors to make them operate. If those components are not doing their job then a perfectly good ECU won't do its job. Junk or no input in means junk or not output out.

If your mekanik needs help why not have him come here instead of having you be his middle man?

[Moose2500]

could the ISC valve make the injectors not fire? or is their any other sensor that could stop the injectors from firing? The ISC valve has been checked and cleaned, but the manual says its not a repairable part only replaceable?

[boscoe99]

No the ISC valve cannot make the injectors fire. Or not fire.

The ECU grounds the injector to make it work. The pulser coils tell the ECU when to make the injector work.

Either the ECU is failed or the pulser coils have failed or the wiring has failed.

The injectors should all fire one time when the key is turned on. Put your hand on an injector. Or each injector. Turn the key on. Does the injector pulse? That will at least tell you that the ECU is sending a ground to the injector and that the injector is receiving the ground.

[Moose2500]

so when the key is first turned on the injectors should all pulse I guess to prime the engine kinda? and then on startup the pulser coil will send signal to the computer to keep the injectors on time. so if the ecu is working properly then the injectors should pulse once when the key is turned on. I will try this.