F225 Yamaha issues

[Krjohns16]

So happy I found this forum!! I have been reading about the F225 Yamaha fuel issues because...I too am having issues that seem to be fuel related. My 2004 F225 has been having issues with the old owner who sold it to me as is. The engine, after sitting 24+ hours I have been able to start it and idle beautifully. After two or three minutes approximately, it will stall and be extremely difficult to start or not start at all. If I did get it started, it will only run at 1400 rpm or higher, anything less will back fire, miss, or stall. Fuel pump asm. has been replaced within the past 3 months or less than 20 hours ago. (Note: only stated on the invoice fuel pump asm. $330.) I have used a separate fuel can to eliminate the fuel tank and lines to the fuel ball. Same issue. I can hear the low pressure pump run for the 10 seconds then stop as per the manual. Leaning toward removing and cleaning/testing the VST . Just for full disclosure, I have disconnected the shift cutout switch and the neutral switch with the same results (reconnected.)

Any ideas before I dive in???

[marchmadness]

ok there's a lot going on. First you don't say what pump has been replaced. Also when the motor stalls is the vst empty? Did you check or replace the pressure relief valve? Did you check the fuel lines , fuel filters etc. I would start and see if the vst is running empty that will lead you in a direction.

[Krjohns16]

Thank you for responding.

Previous owners receipt states that the fuel pump assembly was replaced to the tune of $350. I don't know which one at this point. The "relief valve" was replaced in 2016 for other issues at the time. I eliminated the fuel lines , fuel tank , and water separator by running an external fuel line at the bulb. The engine fuel filter is clean, no water. The ones I don't know about is the "F" filter on the low pressure pump or the foot filter on the high pressure pump.

How do I tell if the VST is empty???

[marchmadness]

The best way to know is when the motor shuts down there is a brass screw on the bottom of the vst, open it, also there is a black plug towards the top, pull that out and there is a schradder valve that releases the pressure. vst should hold around 8 oz. you can also squeeze the primer ball and see if the vst fills.

[Krjohns16]

Cool, I am going out to check today. If it is low or empty, does that point to the low pressure pump??

[Krjohns16]

Big day at the dock.
1. Verified low pressure pump is pumping by removing the output line and pumping into a glass jar.
2. Checked that the VST was not empty when it stalled, approximately 8 oz. of fuel from the drain screw.
3. Removed VST and checked the F filter, high pressure foot filter, float, float valve and that the high pressure pump works. All good and clean.
4. Removed ISC and found it had what seemed like a carbon substance on it. Cleaned by blowing it out with air and reinstalled.
5. After reassembling and checking engine filter, attached external gas tank to the inlet of the previously new fuel bulb.
6. SAME ISSUE...no idle and eventually stalls after 3-5 minutes. Then hard start, only runs at higher RPM, approx. 1400 rpm or higher.

UGH!

[99yam40]

can you hear the ISC rattle when you turn the key off(resetting to 100%) for the next start?
if the ISC is stuck and the ECU keeps trying to move it, it is possible to overheat and Hurt the ECU

[marchmadness]

ok a couple of things. How did you check the high pressure pump? I believe it should be putting out around 40 psi. I think if you hook the motor to the diagnostics you can check the isc for operation.

[Krjohns16]

I may not be close enough to hear it but no, I don't hear it rattle. I will hook up the diagnostics next. I didn't realize I could test it with the engine off, of course can't check with the engine on if it wont idle. I checked the high pressure pump by hooking it up to power, all looks new and clean.

I do appreciate the comments, I think i'm getting somewhere.

[TownsendsFJR1300]

I may not be close enough to hear it but no, I don't hear it rattle. I will hook up the diagnostics next. I didn't realize I could test it with the engine off, of course can't check with the engine on if it wont idle. I checked the high pressure pump by hooking it up to power, all looks new and clean.

I do appreciate the comments, I think i'm getting somewhere.

With the cowl off, have someone turn off the running engine.

Once the engine stops (higher RPM's or not), you WILL hear the rattle, if it's working correctly. About 2 seconds of rattling..

[Krjohns16]

I will be employing my wife to assist me, if she doesn't throw me off the boat due to a "docked" boat, I will get back to you. When I had the ISC, out I noted the center "plunger" only moved about 1/32nd of an inch in and out. Is that normal?

[fairdeal]

I noted the center "plunger" only moved about 1/32nd of an inch in and out. Is that normal?

I have not actually measured - but would estimate its closer to 1/8

you can decide:

https://vimeo.com/264625510

[Krjohns16]

Well, I didn't hear the ISC, BUT... I did unplug it and the engine runs like a charm. The diagnostics show it at 30% and goes up and down with the RPM's???? IT'S UNPLUGGED! What on earth is it for or does it do if unplugging it solves the issue?

[99yam40]

the 30% may be what the ECU is requesting, but the ECU has no idea if the ICS is at 30% or any other %
if you do not hear it rattle then it sounds like it is not moving as it should

[TownsendsFJR1300]

Well, I didn't hear the ISC, BUT... I did unplug it and the engine runs like a charm. The diagnostics show it at 30% and goes up and down with the RPM's???? IT'S UNPLUGGED! What on earth is it for or does it do if unplugging it solves the issue?

The ECU sends signals to it. It's SUPPOSED TO open and close (as in the video) adjusting the idle to spec. ("Idle Speed Control" , I believe).

If it's not rattling (and should upon shut down) and I believe I've read it should show around 60% (I may be wrong the exact #), 30% sounds too low.

They do fail.

.