2004 f225 LP fuel pump

[bravajo2]

Issue recurred

Rodbolt,

The issue recurred. I started the boat, idled for a 10 minues, took off on a 20 mile ride and everything was fine. I watched the fuel flow gauge very closely the whole time and it seemed to draw fuel periodically below 1200 rpm and continuously much above that engine speed.

Fished for a couple hours both drifting and idling and everything was fine. Fired up the engine and took the 20 mile ride back to the dock. Once I dropped down to 1200rpm in the no wake zone before the dock the fuel flow gauge hardly ever drew fuel over a 5 minute period. I docked the boat and within a minute or two the engine stalled due to fuel starvation.

I sat my son at the helm, pumped the primer bulb and cranked the engine back on. I asked him to watch the fuel flow gauge at idle for any indication of flow. The engine ran for 5 minutes with no flow registering on the gauge until it stuttered and stalled again.

Both times this problem happened it was after a 40 minute run in hotter than usual weather (88+ f degrees).

Not sure if this sounds like a problem with the check valve you mentioned or vapor lock? The problem seems to happen on a warm engine.

Any diagnostic tips appreciated.

Thanks,
Joe.

PS I don't think the primer bulb is faulty as it pumps fuel up to the motor just fine and doesn't have a problem when running, only idle.

I am tempted to change the racor and the filter under the cowling just to rule that out although I'd think that would show up at 4000 rpms as a bigger problem than idle.

[rodbolt17]

why not simply let it idle about 3 min, then clamp off the hose between the relief outlet and the pump inlet T.
its really really that simple.
its not hard to test.
forget about vapor lock, it aint happening.

[bravajo2]

Pinching the hose

Rodbolt,

Question about diagnosing the problem:

If I don't see flow on the flow gauge and I pinch the hose like you describe should I expect to see the fuel flow gauge register flow again?

Is the idea that the relief valve opens at some pressure level and allows excess pressure to vent back into the inlet of the pump?

Joe.

[rodbolt17]

eggzachary.

the ONLY reason that valve is there is to maintain about 10 PSI at the VST inlet.
once the VST is full and the needle shuts off flow to the VST the relief valve opens fully and routes all fuel back to the pump intake.

now picture this, and remember the pump CYLCES on and off.

valve leaks a tad when the pump cycles off, a bit of fuel drains past it. now we have a little air bubble.
now it turns on, takes 5 of the 10 seconds to fill the vst. now that air bubble is foaming and when the pump shuts off it gets an even larger airbubble.
after about 5 min of idle the lift pump is basically air bound and cannot pump fuel due to the bubbles.

that's why after about 3 min of idle time I clamp the line with needle nose pliers and see what happens.

[bravajo2]

Got it.

Thanks for the description.

I'll wait for a few mins at idle, clamp it off and see what happens.

Joe.

[boscoe99]

Gasoline flow is sensed well upstream from the motor if and when a conventional inline fuel flow transmitter is used to drive a fuel flow gauge.

If the lift pump pressure relief valve (aka check valve) is stuck open then gasoline will simply loop around the lift pump instead of flowing to the VST. The gasoline will take the path of least resistance. The VST will run dry since it is not being resupplied with gasoline.

The relief valve is designed to be normally closed. So that gasoline flow will be from the lift pump outlet to the VST. However, when the inlet to the VST is closed (VST is full of fuel) then there is no fuel flow and pressure will build up at the outlet to the lift pump. That increased pressure will open the pressure relief valve so that fuel continues to flow through the lift pump. Fuel pressure is lowered and fuel keeps flowing through the lift pump to lubricate and cool it.

If you pinch the fuel hose as Rodbolt suggests you are simulating a closed pressure relief valve which will force fuel to flow to the VST instead of looping around the lift pump.

See fuel flow path below:

[bravajo2]

Conventional fuel flow sensor

Thanks for the additional explanation boscoe99.

The fuel flow tandsucer in my system is upstream of the entry point of fuel at the bottom of your diagram...between the racor and the under cowling filter.

As you said, if the relief valve opens prematurely, gasoline will flow in a loop around the lift pump and never draw fresh fuel across the traditional flow sensor thus the dash gauge will show a lack of flow.

I didn't realize the float in the vst closed a valve at the entry point to the vst and prevented the flow of new fuel.

Interesting design.

Let's see how it goes in testing the relief valve. I hope that is the problem!

[Ljs3@mindapring.com]

Have similar issue. Brand New LP pump, check valve, filters, cleaned VST. Motor starts and runs fine but stalls at any RPM. Same issue on remote tank.
Have 12v at LP pump with fuse removed but LP pump doesn't seem to cycle when motor is running. Checked connections. Do the pump drivers go bad? Even the Yamaha mechanic gave up. Any ideas?

[boscoe99]

Have similar issue. Brand New LP pump, check valve, filters, cleaned VST. Motor starts and runs fine but stalls at any RPM. Same issue on remote tank.
Have 12v at LP pump with fuse removed but LP pump doesn't seem to cycle when motor is running. Checked connections. Do the pump drivers go bad? Even the Yamaha mechanic gave up. Any ideas?

Start a new post and explain what is happening and when it is happening.

You and the OP can have the same symptoms but completely different problems. One guy's leg is broken because he got hit with a baseball bat. The other guy has a broken leg because of leukemia and brittle bones. Both have the same symptoms but each has to be treated differently.

Give us the complete model of your motor.

And you say that it stalls. All of the time? How can a motor be stalling but "runs fine"?

[Ljs3@mindapring.com]

2002 225 TXRA. Motor starts fine, runs fine for 2-4 minutes then stalls. Squeeze the primer bulb (new) and it keeps running. Same symptoms on remote tank. I can hear the new LP pump cycling on and off. F filter going into VST is new and hoses are clear. Clamps are tight. Stalls at 700 rpm or 2000 rpm, no difference. Have replaced check relief valve and cleaned VST. Something is keeping fuel from filling VST I think as manual pump keeps it going. VST pump was replaced two years ago. VST filter is clean. Have had no boat since 7/4. Unhappy wife and kids...tnx!

[Ljs3@mindapring.com]

Yamaha f225 fuel pump issue. Has stumped Yahama mechanic.

Yamaha 2002 225 TXRA. Motor starts fine, runs fine for 2-4 minutes then stalls. Squeeze the primer bulb (new) and it keeps running. Same symptoms on remote tank. I can hear the new LP pump cycling on and off. F filter going into VST is new and hoses are clear. Clamps are tight. Stalls at 700 rpm or 2000 rpm, no difference. Have replaced check relief valve and cleaned VST. Something is keeping fuel from filling VST I think as manual pump keeps it going. VST pump was replaced two years ago. VST filter is clean. VST input valve and float appeared okay when I cleaned it but not sure. Is there anything in the pump driver or ECU that could be causing it? Here is odd thing, motor starts and runs with same symptoms with fuse. removed. Does that mean anything?
Have not replaced air vent check valve I cleaned it, but would that keep VST from filling?
Have had no boat since 7/4. Unhappy wife and kids...tnx!

[bravajo2]

More diagnosis

Boscoe99, rodbolt,

I have performed more diagnosis and it is leading me down a different path.

This past weekend I ran the engine at idle and listened for the LP pump and watched the fuel filter housing as well as the fuel flow gauge.

I allowed it to run for 30 mins at idle and the pump cycled properly (10s on / 20s off) and fuel flow was visible both on the gauge and in the filter.

I raised the rpms to 1300-1500 and the LP pump ran continuously with a fuel flow registering constantly from .6 -1.2 gph. It ran for 20 mins.

I reduced the speed back to idle and after about 5 mins an issue occurred. The LP pump was making the sound of running like normal but no fuel flowed on the gauge or visible in the filter. This seemed to be the problem I had experienced before. Throughout the next set of "on" pump cycles sometimes it drew fresh fuel and sometimes it didn't. It never ran out of fuel and stalled but there were definitely periods where new fuel was not being pulled from the tank.

When the problem occurred I tried clamping off the relief valve return line and it didn't seem the have an impact.

I took the boat out later and after 5 mins of idling it stalled again....hmmm. I pumped the bulb and everything was back to normal. I ran the boat around for 2 hours in a combo of being on plane and lengthy periods idling around. During that time the boat stalled twice, both at idle, both times after a prolonged period of not showing flow on the fuel flow gauge. After each stall a bulb prime and restart fixed the problem.

My gut is that there is either a vacuum leak between the tank and the LP pump or that the check valve in the bulb has an issue as someone mentioned above.

I think my first step is to swap out those components and see where it leaves me.

Thoughts?

Thanks again,
Joe.

[Ljs3@mindapring.com]

I have exact same issue. Replaced primer bulb, no difference. Replaced fuel loop check valve,for $110, no difference. As I understand it, the primer bulb is only crucial if it totally fails and the fuel filter with the plastic bowl drains. Mine stays full and motor still stalls. I suppose it's possible that I have a faulty F filter but it appears clear and only is a year old. There is something in the VST that is causing it to not stay full.. I have not replaced the little vent lines but they appear good. Have also not replaced the inline air vent check valve. Have you?

[bravajo2]

Ljs3


Problem sounds slightly different. Mine can run for hours and properly draw fuel from the tank and keep the engine running and then for some unknown reason, miss a few 10s cycles (pump runs but doesn't draw fresh fuel as witnessed on the fuel flow gauge) and then it stalls.

Periodically it will miss two or three idle pump cycles but it won't stall. Other times it'll miss 10 or 15 cycles and engine will stall.

Problem has never happened while pump is continuously pumping (above 1200 rpm)

Joe.

[Ljs3@mindapring.com]

Yes that is different. Mine consistently stalls regardless of rpm. Yours may be a simple matter of replacing the fuel loop check valve if you have already replaced the LP pump. I put a stethoscope on mine and it cycles perfectly.