Fuel Filter not Full?

[Les MacDougall]

2000 Yamaha 250H.P. OX66 Saltwater Seris.
Engine cuts out when running hard or up and down a wave.

Should the Clear Fuel bowl on the side of the Engine be full of gas?
There is about 1" of air that remains at the top of the filter,even when running.
It seems the Fuel is barely high enough to penetrate the Filter media.

History:
The Filter is new.
The Screen in the VST is clean.
The Hi Press Fuel is new.
The (3) Low press Fuel pumps are new.
The Bulb in the Gas line is new.
The gas Fill-up caps were removed, No suction problem there.
The bulb and short piece of Fuel line was put in a Portable Gas Tank.

It seems to be Fuel related.
The Engine will run longer (full Throttle) when the Bulb is pumped.

Thanks,
Les

 

[cousinabe]

Re: Fuel Filter not Full?

Sounds like a fuel restriction between the primer ball and the tank.
1) anti-siphon valve clogged.
2) pickup/draw tube in the tank clogged
3) tank vent clogged. You already verified with cap off, so probably not the issue.
4) bad fuel line.

what were the results when using an external fuel tank? did you still have to pump the ball?

To verify some things, you can also T into the fuel line between the engine filter and lower fuel pump. Hook a vacum gauge to see if you have between 1 and 3 hg, more indicates a fuel restriction.

 

[Les MacDougall]

Re: Fuel Filter not Full?

Should the Bowl be full?

Les

 

[crw1957]

Re: Fuel Filter not Full?

Great question Les. I have sorta studied this idea. Mine is never full on my 225 Ocean Runner, even while running. I also checked the fuel filter on my EZ Go gas powered golf cart and it is never full, even while running. Based on my findings the fuel filter does not have to be full to operate properly. This is me talking. Seems to me it should be full.

 

[crw1957]

Re: Fuel Filter not Full?

Sorry Les. You asked about the bowl. Not sure about the bowl.

 

[mthieme]

Re: Fuel Filter not Full?

Mine are never full eother.
When she wants to cut out, try pumping the primer bulb a couple times.
See if it stays runnging.

 

[rodbolt]

Re: Fuel Filter not Full?

to answer your question,no.
the bowl cannot stay full as its on the suction side of the fuel pumps.
attach a fuel pressure guage to the VST output,attach a vacum guage t'd into the syatem at the lower lift pump intake.
at wot fuel system vacum must remain less than 6"Hg and fuel pressure must remain at 35 PSI.
any deviation and ya gotta find the issue.
lift pump output pressure should remain between 4 and 6"Hg at wot.
a loose or defective knock sensor will mimic a fuel issue.
while your doing your fuel system tests also use the diagnostic test lamp and check for codes.
remember the ECU on that motor will NOT store codes.
they will only be displayed when the code is active and then from lowest to highest one at a time.

 

[PBJohn]

Re: Fuel Filter not Full?

I had a similar problem but mine would just misfire. I found the shift interupt switch was engaging causing a mis-fire. Once unplugged it in ran fine. Also don't rule out ignition. Check the spark plugs and boot caps.

 

[Les MacDougall]

Re: Fuel Filter not Full?

Thanks for checking,
I'll do some more troubleshooting with gauges Turkey Day.

Les

 

[Les MacDougall]

Re: Fuel Filter not Full?

Well, Fuel pressure is 40-50 psi and 2-3in. of vacuum.

Begining to wonder if it's really a fuel problem..

Les

 

[rodbolt]

Re: Fuel Filter not Full?

40-50 psi? OX66?
something is wrong
Z250 runs 50 PSI out of the VST, sx and s 250 OX66 should be 35 PSI.
fuel vacum looks ok though.
now its time to test at the problem RPM with the diagnostic test lamp.
if you want to buy one they are about 70 dollars.
anytime the test lamp is installed automatic oil transfer WILL NOT occur but all alarms and manual transfer will.