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Yamaha 150 4 Stroke Idle Problem


fragmeister

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Hi Raiders,

I am taking this back to the dealer to get fixed but I was curious what other people think is the issue.

Had my motor serviced after the first 100 hours.

The motor is about 12 months old and I always use 98 Fuel.

First trip out after the service was a very cold morning and while the motor kicked over no worries it cut out after idling for about 1 minute.

It was reluctant to start again so I gave the primer a few squeezes ( which I never have to do normally) and she fired up but cut our again after a minute or so.
Repeated the procedure, slipped it into gear and took off. No Issues for the rest of the day even though I stopped many times during the day.

Thought it might be fuel issues so I pretty much drained the half a tank that day and filled her back up in the afternoon.

Last Thursday I went out again an the same thing happened but it was much worse. Even when the engine was warm it would not idle for more than a few minutes before it cut out and wouldn't restart

unless I pumped the primer. When it started again it was fine and it ran fine at speed. Later in the day it cut out under the spit bridge after motoring up at around 4 knots for about 5 minutes as you do in the no wash zone.

I did notice a smell of fuel from the motor after idling for long period that I do not normally notice.

I took the engine cowling off and there is no sign of a fuel leak around the injectors or any where else for that matter.

I figure its probably not a fuel blockage or restriction because it runs fine at speed.

I figure its not a loose fuel line connection sucking air for the same reason.

The smell of fuel at idle, the cutting out and the requirement to pump the primer to restart suggest to me that it is running way too rich at idle and the

fuel pump at idle just can't keep the fuel up to the injectors.

Now I am pretty sure that the motor has an electric fuel pump so that makes it a little unlikely that fuel delivery is a problem at idle even if the engine is running way too rich.

I am thinking that the idle speed settings are screwed up.

As I said its going back to the dealer but I was interested to know whether my fellow raiders could diagnose this one.

I will let you know what it ends up being and Kudos and Respect to the one who gets it right!

Cheers

Jim

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What's your idle RPM?

Could be a few things, first check would be fuel filters and the VST filter.

A sensor could be playing up, they will need to plug it into a computer and that will show up the faulty sensor.

You may need to do a throttle body synchronisation.

With around 100 hrs on it, it should be a pretty simple solution.

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Also could be what's called a "hot soak vapour lock" they'll need to check the fuel cooler for a blockage. There is a canister kit available for your engine. I am pretty sure Yamaha has addressed this problem though and there is a technical bulletin about the issue. Yours being around 12 months old I doubt it could be this issue.

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Also could be what's called a "hot soak vapour lock" they'll need to check the fuel cooler for a blockage. There is a canister kit available for your engine. I am pretty sure Yamaha has addressed this problem though and there is a technical bulletin about the issue. Yours being around 12 months old I doubt it could be this issue.

Thanks.

All sounds quite likely

Idle speed is within range... when it will idle that is.

Fuel filter is new.

Good suggestions though.

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Hi Raiders,

I am taking this back to the dealer to get fixed but I was curious what other people think is the issue.

Hi Jim. Based on your descriptions I'm going to call it for a fuel blockage or restriction and I would say it's connected to something they worked on or changed. For example, fuel filter fitted incorrectly.

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Hi Jim. Based on your descriptions I'm going to call it for a fuel blockage or restriction and I would say it's connected to something they worked on or changed. For example, fuel filter fitted incorrectly.

Yes , this has been on my mind.

I guess I initially ruled this out because blockages generally cause problems at high speed when the fuel demand is higher. Like the common complaint in a car where the engine starts missing at high speed because of a blocked fuel filter.

I guess it could be part of the fuel system leaking air as I have seen this before with a loose rubber fuel line which sucks air but deals up when the suction increases as the pump works harder.

Anyway... we will find out soon.

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  • 2 weeks later...

Hi Raiders,

Ended up being a little split in one of the fuel pump o'rings.

The service manager suggested that it may have happened during the services they performed at the first 100 hours

On idle it sucked enough air to run out of fuel but at higher revs it was not problem.

Fixed but a little disappointing that unreliability was introduced during a preventative maintenance service.

Cheers

Jim

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