One for the Yamaha 4 Stroke/Fuel System Gurus

[jbsman099]

2003 Seafarer 228, 92 gal main tank, no aux tank, and 2003 Yamaha FXTR 225.

First time out, after doing some work on the boat/engine (which I'll describe below), the following occurred: After idling along for a period of time as in trolling, the engine loses power and stalls upon throttle up to get back on plane. Restart only gets a brief run at about 500 rpm, drops to zero. Will not restart after that. I checked the fuel squeeze bulb and it was very soft. I pumped the bulb, which took about 10 pumps to firm, and the engine started. I was close to the dock so tried it again - idle along 10-15 minutes, power up, fuel starvation, bulb soft.
Once I do get it started and on plane, it will run as long as I want it to. It is only after running at or below 1400 rpm or so that the bulb goes soft and eventual fuel starvation. I did notice that before the engine idled at 600 rpm, now 500 rpm.

No hint of a fuel leak anywhere in the engine cowl, battery box area, or bilge. Not the slightest fuel odor anywhere.

The work I did prior to this included: Changed engine mounted fuel filter, changed hull mounted water separator, replace the old squeeze bulb as the old one was hard and cracked.

Here's the kicker though - after doing all that, I was having trouble getting fuel to the engine with the squeeze bulb. Every time I quit pumping the fuel ran back down into the tank. After some research it seemed the culprit to that might be the anti-siphon valve on top the fuel pickup tube. Took a look at it and it was gunked and I could not get all that out, so obtained a new anti-siphon valve from the local Grady/Yamaha dealer.
Noted the new anti-siphon valve spring was much stronger and it took more force (suction) to open it.

Prior to this "work", the engine always ran strong, never stalled or cut out. It could be something totally different, like maybe a fuel pump, but the coincidence would be awfully strong.
I did notice that before the engine idled at 600 rpm, now 500 rpm.


That said, would a weak fuel pump show up now, with a new and much tighter anti-siphon valve installed?
Could I possibly have bought an anti-siphon valve that is for a much larger engine or twins?
What else could it possibly be?
Hope to put it on a trailer this weekend and try to figure it out. (I think I threw away the old anti-siphon valve)

Any suggestions appreciated

 

[Andrew93]

I would check the low pressure fuel pumps, maybe the extra work required on them caused the diaphragms to crack. They are common to fail, normally not a bad idea to change every few years. You might just have 1 bad and thats why is running at higher rpms? Just a guess

Unbolt them from block and squeeze primer, if they leak they are bad

 

[jbsman099]

That's a very good idea. I'll include that in my troubleshooting. Thanks

 

[seasick]

Note that if you have an air leak in the fuel delivery plumbing, you won't see any fuel leaks and probably won't smell gas. I suspect that either the separator filter or the on engine gas filter has a leak and most likely that is due to a poor sealing on the filter or cartridge resulting in sucking air and loosing prime. I would look first at the on motor fuel filter if it is the clear bowl type. Undo the bowl, check the gaskets and reinstall making sure the flange is seated squarely

 

[jbsman099]

Thanks I will check those as well. Would the prime be more likely to be lost at idle vs 4800 rpm. Engine seems at any rate, to lose the prime while idling around.

 

[seasick]

Thanks I will check those as well. Would the prime be more likely to be lost at idle vs 4800 rpm. Engine seems at any rate, to lose the prime while idling around.

If you have a small air leak, the engine will get a reduced fuel flow. As the fuel burn rate increases ( at speed and/or load), it will reach a point where the flow is less than the demand. Eventually the motor will starve for fuel. As demand goes down, the gas flow will resume at low loads.

I forgot to also mention that sometimes when the separator filter is changed, all or some of the old rubber gasket gets left on the underside of the mounting flange. That can result in the new filter not sealing correctly.

 

[jbsman099]

That makes good sense to me. I won't get a chance to troubleshoot until the upcoming mid-week. Will post what I find at that time.

 

[seasick]

Let us know what you find and good luck.

 

[Chessie246G]

swap one of the fuel lines (low pressure to vst) with a clear hose temporally to check for air bubbles. Should be zero air. If air present keep swapping fuel lines back to the tank until you find solid fuel in the clear hose.

Im going to also ask the obvious.... fuel bulb is installed correctly??? they are directional.

 

[seasick]

Im going to also ask the obvious.... fuel bulb is installed correctly??? they are directional.

Good point.
Did the primer bulb ever get firm when squeezing?

 

[vocz]

Agree, check the directional, if all fail, I would put the old squeeze bulb back and see if it run better. You may have the defective bulb right out of the box.

 

[seasick]

The thing that doesn't support this theory is that the motor started and ran for a while.

 

[family affair]

My bet is on the clear fuel filter bowl. If it is anything like the f150's, it has all of the fabulous design qualities to make it leak air. My port engine did the same this year after changing the filter. To get it properly seated, I removed the assembly from the engine and compressed it with my hands. There was a gap. 30 hours later, not even a hiccup.
As for the primer bulb, that is another design gem. They are very fickle about orientation while squeezing to draw fuel. Ive read countless stories of bad bulbs out of the box. I thought I had one too till I disconnected the output side and squeezed at a different angle until fuel flowed out into a container. Once the valve in the bulb was wet and the air out of the intake side, I was good to go. The manufacturers could probably cut their returns in half if they bothered to provide that detail with the part.

 

[DennisG01]

Could also have a restriction in the vent line/fitting. It may not be strong enough to cause a problem when the engine is running at higher RPM, but possible at lower RPM (less suction by LP pump). At idle-ish speeds, the engine will run until the VST tank is emptied. Inability to (easily) draw fuel via the fuel bulb also supports this possibility.

Try running with your fuel cap off.

Make sure the fuel bulb is angled slightly high towards the engine side. Sometimes it doesn't matter... sometimes it does.

 

[jbsman099]

Well, 99.99% sure I've found the problem, and dumb on me. Given that the boat ran great until I changed the engine mounted filter, primer bulb, water separator filter, and anti-siphon valve, I concentrated on those areas, working back from engine mounted filter. No problems there, except a line clamp (cable tie) was slightly loose at the engine filter. The actual problem was at the spin on water sep canister. Now I recall that I took the bracket off to relocate it slightly, and with the new canister on, dropped the dang thing from the boat to the driveway. Checked it out, but certainly not well enough. On inspection today, I found that the fall to concrete bent the canister slightly so it "wobbled" as it threads up into the bracket. When fully seated and very tight on one side, the rubber gasket has enough space on the other side to allow some air in at high power. Probably haven't seen that in this forum before!!
I'll replace it of course, and also take the opportunity to improve clamps, tighten/double clamp a couple of fuel line fittings and should be good to go.
Lot of good suggestions above, which I'll hang on to in case this is not the problem, but really, it has to be the deformed canister top.
JBS

 

[seasick]

Makes 100% sense. Glad it turned out to be something simple.

 

[jbsman099]

Well, the saga continues - perhaps.

Let me go back to the beginning for a moment. The reason I changed the anti-siphon valve was because after changing the water sep and engine fuel filter, I could not get any fuel pumped up into the new water sep canister and the engine using the original primer bulb. I tried two additional primer bulbs with no success, so decided on the anti-siphon valve. Changed that. Still couldn't get fuel up to the bulb, so resorted to a handheld vacuum pump, which worked.

Fast forward, while underway, the engine loses prime at speed over time, stalls. Pump bulb a few times, prime restored, wash rinse repeat.
Found warped water sep canister that could not physically seat well. Changed that with a new one.

So now, I am back to the original problem that I cannot get a primer bulb to pull fuel from tank to water sep and on to engine. Tried 3 different bulbs. That is the same condition I was in before I did anything at all I've tried pumping both with engine filter hose connected and with hose disconnected.

(All hoses in good condition. All clamps on and tight. Primer bulbs oriented in the correct direction. Water sep filter seated correctly. Loosened tank fill cap just in case.)

I can get fuel up to the engine with the manual vacuum pump again, but my question now is - Is it somewhat normal that a primer bulb will not draw fuel in a completely empty fuel line/canister, or is there still a problem that I would be covering up by using the vacuum pump? Reluctant at this point to use vacuum pump and launch again until I know a bit more.
Thanks to all who reply.
JBS

 

[family affair]

See post 13.

 

[jbsman099]

Agree the engine filter bowl does need a good shove to get the o-ring up and to seat. That is done. I was thinking perhaps I should 'pre-fill' the water sep with a fuel, so the primer could get a bit wet. That, and orienting it upward, as you suggested, may do it.

 

[Don Davis]

I have Suzuki’s now but ran Yamaha‘s for over 20 years, I always fill the new fuel/water separator filter and clear bowl with fresh fuel before I install it back on the plate/bracket. That way I can check for leaks right away.