2010 Yamaha f115tlr motor knock

[B3njammin89]

TownsendsFJR1300 i tried swapping the plugs and saw no difference. Is there a way for me to actually have the spark plug installed in the boot to see if the plug itself is sparking?

[TownsendsFJR1300]

TownsendsFJR1300 i tried swapping the plugs and saw no difference. Is there a way for me to actually have the spark plug installed in the boot to see if the plug itself is sparking?

Either put another new spark plug in the hole, then plug the old one into the wire, ground (to block), and crank it over(you need a helper to turn the key while you watch for spark).

It just needs to crank a couple of cycles to confirm it IS sparking steady.. As it was coming out wet, it's likely fouled. I know you swapped plugs around but just confirm the basics.....

You can also pull that plug, attach to a lawn mower spark plug wire lead, ground out and crank it over (same thing, just on a mower, weed eater, etc). I had a Yamaha golf cart not want to start. It had spark at the wire, but still wouldn't fire off. Eventually found the internal main center core had failed / loose-intermediate spark at the plug).

[pstephens46]

Thing thread is starting to twist and turn.

[B3njammin89]

pstephens46 I apologize, it is still knocking. I was just thinking the knocking could partially be caused by spark knock maybe since that low pressure pump is close to cylinder 3 and 4 on the valve cover. I’m not quite sure how those knocks are supposed to sound.

[B3njammin89]

TownsendsFJR1300 i will try that once I get a helper. I noticed my number 4 plug wire looks like it’s turning a brownish burnt color on the end that slides into the boot.

[pstephens46]

pstephens46 I apologize, it is still knocking. I was just thinking the knocking could partially be caused by spark knock maybe since that low pressure pump is close to cylinder 3 and 4 on the valve cover. I’m not quite sure how those knocks are supposed to sound.

Did you ever post something we could listen to? Go create a YouTube account and post a link. Nice long video, not 5 seconds. There is a good bit of knowledge here that may help.

[B3njammin89]

pstephens46 I’m not sure if it’s a good idea for me to start the boat again until I pull the cylinder head off. So come to find out cylinder 4 has 0 compression. I didn’t get this misfire/knocking issue until after I replaced the low pressure mechanical fuel pump and high pressure pump.

The new low pressure pump has a round plunger head while the original has a flat surface plunger. The Yamaha parts dealer confirmed that the part I received is what Yamaha calls for. Is there a possibility the new low pressure pump could have damaged something inside under the camshaft lobe that pushes the fuel pump plunger in and out? Maybe possibly bent a valve or spring somehow? I can’t think of why else all of a sudden the motor just wanted to knock and loose compression. The knock was definitely noticeable when I put on a stethoscope and touched the low pressure pump. My motor has 460 hrs. Can it just all of a sudden just develop a knock out of nowhere?

The original pump I have on my 2010 Yamaha 115tlr is 63P-24410-00-00 and the new pump Yamaha calls out for is 68V-24410-00-00