Engine hesitates after startup

[Laurence243]

This started happening a few months ago - when I start my FZ6 and rev the engine within the first minute or so it hesitates to rev up. The idle is smooth but in neutral or under power it is almost like it is low on fuel. My mileage has been consistent at 42mpg, I started using yamahas recommended fuel additive to no avail. I notice sometimes when I turn my ignition on the whir from the fuel pump almost sounds choked - it is high pitched almost like a squeal. It only has 9k miles but I know the po let it sit in the winter.

Any ideas? Should I replace my fuel pump? It runs fine after the first minute or so of riding.

Will post video of it later

 

[TownsendsFJR1300]

Does the pump squeel continuously or just for a moment or ?

If the pump is definitly squeeling now, I'd pull the pump and and first inspect the tank for rust.

You'll likely find rust there, there's several different ways to deal with it.


Pulling the pump takes some finesse... The below pic with the arrows show how to disconect the fuel GAUGE from the pump. This make it considerably easier to remove.

Once out, you can access the filter which is pretty much NON servicable. You can get some crap off it but the filter itself is NOT replaceable.

This will give you an idea of the condition of the pump.

From the description, it doesn't sound good. The pump( & pump filter), if plugged up, would certainly slow the amount of fuel that should be pumped.

It sounds like it failing and just a matter of time before it quits altogether.

There's bikes getting parted out all the time here and a used pump (if needed) is much cheaper than a new one..

 

[Laurence243]

Bah. Those pumps are expensive.

Here is the video, it doesn't really do it until the third rev
https://docs.google.com/file/d/0B2-VbUcK-W_EQS16SEFiZTBtU2c/edit?usp=docslist_api

 

[elus1ve]

If you always go to the same gas station, try to switch for a couple of times. Mine had the same symptoms and it turned out to be the gas i was feeding it. Something you might want to try before taking things apart.

 

[Laurence243]

I had been running chevron premium, then switched to 87 about a month ago. Been getting it mostly at fred meyers, but it would do the same thing with premium as well

 

[TownsendsFJR1300]

I didn't hear any pump whine, perhaps outside(not in the garage with the fuel cap open) it might be heard..

In that video, when you started it up, was it in the "start from dead cold mode"? Or was it already to temp?


*Does the engine, after overnight, at initial start up(just pushing the start button, NO THROTTLE) have an approx 200, maybe 300 HIGHER RPM while cold and eventually settle down?

 

[Laurence243]

That was a cold start, it doesn't do it from a warm start, and doesn't happen when it is warm.

 

[TownsendsFJR1300]

Do you have the higher idle when its cold(no throttle help) and it settles down?

 

[Laurence243]

By 100 rpm or so, if that. Btw does this bike have an OBD II connector?

 

[TownsendsFJR1300]

I'm in Florida and can start the bike cold in the 80's(F) and I get roughly 2-300 rise in cold RPM's, so 100 isn't much(I'd have to say below normal)

Of course, when cold, the engine needs more fuel. If your engine (ECU) isn't richening it up enough, you could get that hesitation. (IMO, I wouldn't be revving it like that for the first couple of minutes, but just my 2ct's)

While this happens when its cold only backs this.

There is no OBD port like a car to plug in to.

This is the unit, for adjusting throttle sync, cold idle, etc;



It may very well need cleaning. I think you can adjust the cold idle RPM.

Member FinalImpact knows more about the unit than I do and can point you in the right direction about cleaning/adjusting it.

I've heard of some members with a whinning fuel pump(mine isn't) and would suspect its failing. May fail soon, may go years. IMO, I would still pull it apart and inspect, especially the filter, for rust. I just wouldn't want it failing at an inopertune time..

[MENTION=15974]FinalImpact[/MENTION]

 

[Zealot]

Going to throw it out there, my bike revs seem kind of sluggish like you describe right up until about the Lo text goes away and turns to a number reading. Revs prior to being warmed up make it sound like it's drowning, but once it's at least 40 degrees and above, not a problem. Always figured it was a combination of sub optimal temperatures for combustion and oil still being thick and cold. Not a single problem once I'm going.

 

[TownsendsFJR1300]

Going to throw it out there, my bike revs seem kind of sluggish like you describe right up until about the Lo text goes away and turns to a number reading. Revs prior to being warmed up make it sound like it's drowning, but once it's at least 40 degrees and above, not a problem. Always figured it was a combination of sub optimal temperatures for combustion and oil still being thick and cold. Not a single problem once I'm going.

Mine does the "drowning" sound, extra fuel on the cold start up. I start the bike up, let it idle as I gear up, helmet/gloves and usually have a temp # before I pull out of the driveway.

Where I'm at, I can keep the RPM's under 4k until the engine gets to temp(which is what I do, even longer actually, till the engine oil heats up a bit)

 

[FinalImpact]

Does it have a fuel controller on it or is it stock? More important; does it do it under load while taking off or just static rev's? In stock from that are all sluggish compared to what they can be, but the 3rd rev is notable.

Does the temp gauge appear to report the correct engine and air temps?

Mine when below temp "Lo" if held at say 2K from cold start, when it hits 104°F it suddenly jumps to 2500 RPM.... So, I suspect it changes the fueling crossover providing LESS fuel / Leaner and that jumps up the RPM based on engine temp.

Like above, I don't cold rev anything until its up to temp.

 

[Laurence243]

I don't rev my engines cold normally either but it does happen while under load as well and that's the easiest way to illustrate it [emoji14]

I was wrong, it does idle at about 1400-1500 when cold, then goes to about 1000.

My buddy is thinking it is a dirty injector, because once warm the injector would be working better. Going to pull them and take a look this weekend.

Slightly on topic, what am I looking at cost wise for a power commander 5 and a dyno tune? Any places in Idaho to go to or should I go to 2wheeldynoworks? Not looking for tons of power but I'll need a new fuel map when I get my slip-on. Any other, cheaper options?

 

[thisisbenji]

Jeeeze...... my bike has done this since it was new. I always thought it was just a ****ty FI warming up. My carbed bike did the same thing, except it was manually controlled by the choke lever.

Should I be concerned?

 

[FinalImpact]

And at 12k in 2nd or 3rd, a faulty injector would show itself with a real nice vibration. A leaking one would cause idle issues. I really doubt its an injector. It does rev clean to 13.5k warm, yes? If no, Test the fuel pressure.

Also look at plug gaps being excessive. Too rich, with too much fuel and it hesitates as it just can't burn it.

Lastly, Verify TPS low and high numbers and if yours is lower, peak at the CO values... These things may have a relationship.

 

[TownsendsFJR1300]

Jeeeze...... my bike has done this since it was new. I always thought it was just a ****ty FI warming up. My carbed bike did the same thing, except it was manually controlled by the choke lever.

Should I be concerned?

Not in particular.

As noted, let it warm up some (just common sense), wait for both the coolant temp and oil temp raise up a bit before revving the snot out of it...

I don't think mine does it but I've NEVER revved it to 4K while cold. Absolutly NO hesitation while starting out BUT I keep the rev's low until wamed up some..