05’ F225 Electrical mishap

[Robert093090]

Good afternoon,

I was wondering I could pick some of your brains about an issue I’m experiencing with my 2005 F225. My ISC/IAC valve is turns on and off constantly (sometimes along with the VST pump but not always) when I turn the battery switch on to the starting battery. Not even when I turn the ignition switch on, when I turn the ignition switch on, nothing really happens. Now, this ISC issue doesn’t always happen, when I turn the battery switch on and off it reverts back to normal. The engine is idling at around 1000rpms.

What’s really throwing me off is that the VST pump also goes crazy along with the ISC and what fixes this is turning the power off and on through the battery switch. The ignition switch honestly is just turning the starter and gauges.

This whole issue came to fruition when during an outing when it was running perfectly fine and while *****ing the engine died and wouldn’t want to turn back on and when it did it would run really rough and not for long.

I changed ALL fuel filters and VST pump screen which was really clogged at all.

[fairdeal]

Hmmm.
Well, although a general guiding principle here
is that ECM problems with Yamaha EFI 4-strokes
are "almost un-heard of"

this sure sounds like an ECM problem...

The ECM has 'always on' power if the battery is connected to the engine.
it normally performs some function - re-setting the IAC valve -
with the keyswitch off.

if the IAC or HP pump are activating with key off -
I can't think of an explanation other than internal failure of the ECM.

[Robert093090]

Hmmm.
Well, although a general guiding principle here
is that ECM problems with Yamaha EFI 4-strokes
are "almost un-heard of"

this sure sounds like an ECM problem...

The ECM has 'always on' power if the battery is connected to the engine.
it normally performs some function - re-setting the IAC valve -
with the keyswitch off.

if the IAC or HP pump are activating with key off -
I can't think of an explanation other than internal failure of the ECM.

And sometimes they don’t activate when the battery switch is on, i find it weird that the ignition switch is off yet there’s power being sent to these two areas with just turning on the battery switch

[boscoe99]

And sometimes they don’t activate when the battery switch is on, i find it weird that the ignition switch is off yet there’s power being sent to these two areas with just turning on the battery switch

Many outboard motors and automobiles/trucks operate in that manner.

[Robert093090]

Many outboard motors and automobiles/trucks operate in that manner.

So that’s not necessarily a fault or a possible problem?

[HarrisonDawgs]

Are you blowing fuses? Went thru similar problems with 225SHO a while back. Virtually everyone was telling me a bad ground somewhere. When pump came on in VST it would blow fuses at times, not at other times. After weeks of tracing wires, sensors, grounds, etc we had no where left to go other than replace ECM. New ECM solved problem. 300 hours later it's still fine. Maybe you could "borrow" an ECM to see if that is the problem. Mechanic suspected internally fried circuitry.

[Robert093090]

*Update* so the electrical issue is solved. There was a cable that use to feed the old analog fuel gauge that was creating a short . Now the fuel pump turns on only when key is on and the IAC works when key is off.

Now on to the other issue...motor is idling rough and I’m noticing that the lift pump sometimes turns on and off while idling how it should but other times it stays on and that’s when the engine runs really rough and when I rev it it sputters and turns off when it comes back down to idle.

im going to isolate the fuel tank as a possible issue due to faulty fuel lines but I’ve read that the fuel check valve if stuck open can cause the lift pump to go crazy?

[fairdeal]

the lift pump sometimes turns on and off while idling how it should but other times it stays on and thats when the engine runs really rough..

Im going to isolate the fuel tank as a possible issue due to faulty fuel lines but I've read that the fuel check valve if stuck open can cause the lift pump to go crazy?

The lift pump runs when it is given a ground (normally, by the driver, itself grounded by the ECM)

How would "faulty fuel lines" - or "a check valve stuck open" - provide an electrical ground to the pump?

*Update* so the electrical issue is solved. There was a cable that use to feed the old analog fuel gauge that was creating a short . Now the fuel pump turns on only when key is on

nor does this make sense

[Robert093090]

So it could be a faulty ECM or Lift pump?

[99yam40]

maybe a wire from the pump getting a ground from some other source than the ECM

[HarrisonDawgs]

I went back and re-read your original post. I think you said pump in VST was erratic. Is it this pump or the pump that supplies fuel to the VST? Have you had the VST apart? Not uncommon for the pump in the VST to get clogged with sludge/water/rust/etc, however usually the problem is that it will not pump at times and needs a "bump" to start it spinning. I think if you feel this pump (vst) is the culprit, you should re-enter VST for inspection. Make sure pump is locked in proper position. Look closely at wires for nicks or shorts. Are they pinched? Bent oddly? If all appears good I would still bench test the pump with a 12v battery and some test leads. I had one once that was giving me trouble and I found that most of the time it needed a whack on the bench top for it to run. Other times it would run without hitting it. I replaced it with new but later found out that sometimes they can be cleaned of gum by soaking in solvent or using an ultrasonic cleaner. Otherwise the only thing I can see that would make it run more than expected is a low fuel pressure condition (sensor) or a bad ECM. I haven't looked at a 4stroke manual in quite some time. Maybe others more familiar will chime in.

[Robert093090]

I went back and re-read your original post. I think you said pump in VST was erratic. Is it this pump or the pump that supplies fuel to the VST? Have you had the VST apart? Not uncommon for the pump in the VST to get clogged with sludge/water/rust/etc, however usually the problem is that it will not pump at times and needs a "bump" to start it spinning. I think if you feel this pump (vst) is the culprit, you should re-enter VST for inspection. Make sure pump is locked in proper position. Look closely at wires for nicks or shorts. Are they pinched? Bent oddly? If all appears good I would still bench test the pump with a 12v battery and some test leads. I had one once that was giving me trouble and I found that most of the time it needed a whack on the bench top for it to run. Other times it would run without hitting it. I replaced it with new but later found out that sometimes they can be cleaned of gum by soaking in solvent or using an ultrasonic cleaner. Otherwise the only thing I can see that would make it run more than expected is a low fuel pressure condition (sensor) or a bad ECM. I haven't looked at a 4stroke manual in quite some time. Maybe others more familiar will chime in.

Well the erratic turning off and on of the VST pump and IAC valve was due to a short that I already found. Now everything works as it should with key switch on and off. What I’m experiencing now is rough idling and I noticed that when the Lift Pump starts doing it’s below 1200rpm idle cycle, the engine settles down and eventually idles fine within maybe 20 seconds or so. But, other times when I start it and the engine doesn’t settle back down to regular idle, I found that the lift pump isn’t doing it’s regular cycle as the other times, it’s like it stays on.

When I try pumping the primer, the primer gets hard and then soft again. I believe because the VST pump is using the fuel in the VST to supply the other components.

[Robert093090]

*Update*

changed the ISC valve and problem is fixed. Motor is idling without any issues. Going to be testing it out soon with a good day out on the water.