2008 WaveRunner troubles

[boudin]

Sorry, I'm not following how the fuel tank check valve could affect anything here. The difference in 'woosh' sounds you are hearing could just be the difference in the amount of fuel in each tank. Besides, when the check valves go bad, it's usually in the other direction.

The fuel pressure regulator will keep the pressure at ~46psi. A clogged fuel pickup intake screen could be affecting pressure or flow. It's attached at the bottom of the fuel pump and requires removal of the sender assembly to check.

-Greg

 

[Midnight2V]

Sorry, I'm not following how the fuel tank check valve could affect anything here. The difference in 'woosh' sounds you are hearing could just be the difference in the amount of fuel in each tank. Besides, when the check valves go bad, it's usually in the other direction.

The fuel pressure regulator will keep the pressure at ~46psi. A clogged fuel pickup intake screen could be affecting pressure or flow. It's attached at the bottom of the fuel pump and requires removal of the sender assembly to check.

-Greg

Not sure what you mean by "each tank". Is there more than one tank on this model? No sarcasm intended, I genuinely don't know.

If the fuel tank were to have a clogged vent (not necessarily the check valve, but possibly the line itself), it could develop a vacuum when the fuel pump displaces fuel from the tank that is then consumed by the engine. If the vent cannot pass air into the tank to fill the void left by the consumed fuel, it could result in too much vacuum on the suction side of the fuel pump, causing insufficient fuel flow. On the flip side, if the tank was building pressure, you are probably right in that the FPR should maintain pressure at the proper level, assuming it is working correctly.

 

[boudin]

He was comparing the 'woosh' sound between his two skis when removing the gas cap. The pressure building up in the tank.

Need to pull the check valve out and and make sure you can blow through the top side (just with your mouth). With it removed, then also blow through the line with an air hose to see if it's clogged.

-Greg

 

[Midnight2V]

Gotcha, thanks.

 

[Pinhacker71]

Looks like a pita to get to check valve. Guess I can take off hood to gain access.

 

[boudin]

As @Midnight2V said, try just running with the fuel cap loose if that's easier for you. Just be careful on the VX as they tend to swamp in the front. You don't want water splashing in your filler hole.

Really, though, it sounds like you have a fuel issue. I would try swapping fuel sending units with your other ski. The hard part is wriggling out the sending unit with tank still in the ski.

I've seen VXs run great with 3-year-old+ fuel. No joke. But, have you tried fresh fuel?

-Greg

 

[Pinhacker71]

Skis ran great when I picked up. Ran great for about an hour one day then for about 30 min on another day. All of a sudden at full throttle just lost power. Went from about 50 to 35 with same decrease in power through throttle. Just feels sluggish.

 

[boudin]

A recap of what you've done:

1. New CR9EB plugs
2. Removed the air filter--was oil soaked?
(this alone fixes many VX issues)

3. Swapped injectors with a known running ski. (eliminates a clogged injector and a loose injector plug)
4. Checked compression... >164psi in each hole?
5. What else?

-Greg

 

[Pinhacker71]

New plugs
Air filter was soaked. Removed some oil and removed air filter. Ski ran good when I discovered the soaked air filter. Didn’t bog down until about 30 min running after I removed it.
Swapped injectors. No difference
Swapped coils. No difference.
Swapped batteries and rectifier. No difference.
Pulled pump, impeller looks good and space between wear ring looks good. Sealed pump just to make sure no gaps. No difference.
All plugs spark when start with grounded to engine.
Compression good in all cylinders.
Tech at Yamaha dealer said it sounds great and can’t hear it missing or any issues.

 

[boudin]

Sanity check: This is a Deluxe right? Are you somehow in SLO/Learner mode? What is your max RPM?

If not, then yes, swap fuel sending units next.

-Greg

 

[Pinhacker71]

Didn’t come with remote. Learner mode is not illuminated and 7000 rpm. My understanding is learning mode is lower rpm than that.