115 four stroke problem

[baygoat64]

2007 f115tlr

Cannot get #4 cylinder to function. This is what I've done:

Compression tested.... all cylinders equal
New Plugs
new vst filter
cleaned injectors
Checked for spark at plugs....spark at all four
swapped injectors....problem stayed at #4

There seems to be no pulse at the injector
Traced both wires; red/yellow back to common connector; purple/green back to ECM.....no breaks in wires
Put test light on #4 injector connector........nothing.

With injector connector disconnected, using flash light battery, momentarily touché injector contacts and cylinder fired briefly and would fire each time power was given to injector.

I'm down to the ECM but I don't want to spend about $1,000 unless I'm pretty sure it's the problem.

I don't have the Yamaha software so I can't check for any thrown codes. Is there any condition that could cause one cylinder to be shut down.

Sorry about the long post. Any help greatly appreciated.

Baygoat64

[boscoe99]

If the red/yellow wire has 12 volts on it at all times, and the Pu/G wire has continuity all the way to the ECU, but the ECU is not applying a ground to the Pu/G wire, then what else can it be but the ECU?

If it were my motor I would disconnect the connector at the injector and verify there is 12 volts on the R/Y wire when the key is on. Re connect the connector at the injector. Then disconnect the connector at the ECU. With the key on, momentarily ground and then unground the Pu/G wire. See if the injector fires. It should. This will confirm that the wiring is in good condition.

You might want the injectors removed so that fuel can be observed spraying, or not spraying, when the injector is energized. Just be careful not to let any spraying fuel get ignited.

[baygoat64]

Thanks for the quick reply. I'll try grounding the purple/green wire at the ECM connector but I'm not quite sure how this could be done with the injector removed??

[rodbolt17]

don't need to, use a paper clip inserted at the backside of the ECM connector,
from there you can either use a DVM with a frequency(Hz) function or a jumper wire to momentarily ground it.

[boscoe99]

Thanks for the quick reply. I'll try grounding the purple/green wire at the ECM connector but I'm not quite sure how this could be done with the injector removed??

You remove the injector rail, with the fuel hose and the injectors attached, from the motor. Reattach the electrical connectors to the injectors and then temporarily tie the injector rail to the motor to support it.

With the key on, the pump should pressurize the injector rail with fuel. Fuel should not be leaking from the injectors. If and when you ground the Pu/G wire, and if the wiring to the injector and the injector itself is good, you will pulse the injector and fuel should spray out.

[Nautical]

Very ingenious idea Boscoe..Can get a quick look at the spray pattern too.Just should be careful with any sparks or flames that may ignite, but a quick burst should not be of concern ..hopefully!

[baygoat64]

Thanks for the responses. I did the test and the injector worked when the purple wire was grounded. Sooooooo, I've ordered a new ECM from you guys. Thanks again for the help and for providing this forum. It's great to have access to people who know what they are talking about.

John

[rodbolt17]

who says we know what we are talking about.
it is the internet.
gotta be true if its on the net.

[boscoe99]

who says we know what we are talking about.
it is the internet.
gotta be true if its on the net.

Where in the hell did you read that?

Oh, on the inner web.

Must be true then.

Hell, I don't even believe my own crap when I read it on the inner web.

[rodbolt17]

how much I believe is directly related to how many refreshing beverages I have had.

how much I type sometimes depends on the quality of the ethanol .

[99yam40]

how much I believe is directly related to how many refreshing beverages I have had.

how much I type sometimes depends on the quality of the ethanol .

quality of the ethanol or quantity

[baygoat64]

Ok guys,

Replaced the ecm with a new one. No change. Number 4 cylinder still does not fire. Swapped coils........no change. Where do I go from here? Help!

[TownsendsFJR1300]

You posted earlier the injector wasn't working;

I did the test and the injector worked when the purple wire was grounded.

Sounds like a bad ground / ground wire for that injector as it works when you manually ground it.


The above post (post #4) sounds like there's NO spark on #4. Can you please verify? No spark on #4 or the injector not working..

[baygoat64]

plenty of spark; plug wire will arc 1/2 to 3/4 of an inch. It's the injector that won't fire. Thanks for the reply.

[TownsendsFJR1300]

plenty of spark; plug wire will arc 1/2 to 3/4 of an inch. It's the injector that won't fire. Thanks for the reply.

Tks for the clarification.

As posted previously;

Sounds like a bad ground / ground wire for that injector as it works when you manually ground it.

I'd be checking the harness (possible internally broken wire) / connector ends, etc, starting at the injector and working back.. Find out where your loosing your ground.