F150 loss of power up top

[sutor623]

Hey guys, long time no see.
I am working on a 2010 Yamah F150TJR. Motor has been kept up with filter changes etc. Only run ethanol free gas from the marina. It is on a 24' tri-toon.

It just started "starving" for fuel at upper rpms. Under that it seems ok at first. When you run it at 3000 rpms for a while it seems ok. Then we give her the gun and she is good to go a 5000rpms for about 10-15 seconds, then it really starts to lose power, then comes back just a bit, but will never catch back up, then loses more power again "surging". If you throttle down to 2300/3000 rpms the issue goes back away.

I put my fuel pressure gauge on the high pressure side and I am reading 45psi at key on, and just under 40psi with the motor idling. (I havent hung off the back of the boat with a test gauge at WOT)

I put a test tank with a clear hose up to the motor. Motor is drawing fuel fine. I even put a low pressure electric fuel pump (5psi) in the line and hooked it up while running just to see if it was a low pressure issue and it still acts up. So by doing that I hope to have eliminated the boat fuel tank as well as low pressure fuel pumps.

Dumped and checked all filters. No debris, no water. Pulled VST and filter doesnt look gummed up. VST tank is clean as a whistle.

So I am puzzled. Is there a resistance reading that I should have for the high pressure pump? Do they ever fail intermittently like this? Should I put it back together and send the fuel injectors off?

Thanks guys, Im pretty crafty with all this stuff and always take the path of least resistance until I find the culprit.

 

[rejesterd]

Lots of things to check for..

1. air leak in the intake manifold or fuel rail (o-rings for the injectors might be bad)
2. clogged injectors
3. throttle position sensor or ISC problem
4. bent throttle valve(s)
5. low compression
6. bad pressure regulator
7. damaged/bent VST needle valve

 

[GaYamaha]

Regarding path of least resistance, did you ever try pumping the primer ball when the issue occurs? Obviously would require another person.

 

[99yam40]

OP did you monitor the fuel pressure on the rail while the problem is happening?
that would tell you if the high pressure pump is running out of fuel and cannot furnish enough fuel at high RPMs.

 

[TownsendsFJR1300]

Probably not your issue but worth addressing.

The only high speed I had with mine ('06 F150) was a drop in RPMs, about 80% of the time. It felt like a fuel issue and turned out to be a bad spark plug (looked new with about 200 hours on the engine).

The marina said the plugs definitly needed replacement, figured it was much easier than digging into the fuel system. Put them in, ran like a top to 6K. No more issues...

Cheap enough insurance in any event..

 

[GaYamaha]

OP did you monitor the fuel pressure on the rail while the problem is happening?
that would tell you if the high pressure pump is running out of fuel and cannot furnish enough fuel at high RPMs.

Yam....can you see my PM????

 

[99yam40]

yes , I answered you too

 

[GaYamaha]

Where is the OP?

 

[TownsendsFJR1300]

Where is the OP?

Stranded??

 

[sutor623]

Guys!! Sorry I fled the scene and didn't return!!

I ended up checking/changing all of the fuel filters. They all looked fine. I also had the injectors flow tested and cleaned. The prognosis on the injectors was good. After that I decided that the only issue at this point was the high pressure fuel pump, even though I saw no signs of failure.

Sure enough, got her all back together and she's running great again!!