Lean idle cause?

[Coastiejoe]

"considering...". The reason for stating that is so that you will not lead me down lines of troubleshooting I have already been. Thanks.
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I did not read it that way, I read it as though you were CONSIDERING CLEANING THE fuel system.. Not Considering you had already done it...

I'm out...

 

[JJinSC]

A few suggestions:

* Replace original Tempo fuel lines, which corrode/disintegrate and contaminate your carburetors internally.
* Remove, disassemble and thoroughly clean the carburetors internally, they have Tempo Trash and years of fuel gum inside of them plugging the internal passages.
* Confirm the pop-off is repeatable and occurs at the pressure as per the shop manual specifications for your model year engine.
* While apart, confirm the high and low sped jets are the correct orifice size.
* I would recommend any carburetor rebuild should include a replacement needle and seat, these parts (specifically the needle tip) will be worn out over a period of 15~20 seasons use.
* Probably a good idea to replace the fuel selector valve, the o-rings are probably dry-rotted and unreliable, may allow air to leak inward as the fuel pump draws fuel from the tank.

It's entirely possible your green check valve in the a-pump circuit must be there yet is undocumented, especially if this was one of the early models when the a-pump was first introduced. You may recalibrate the original carbs to the earlier spec that didn't use the a-pump by installing a larger low speed pilot jet, etc. if you choose to eliminate the a-pump for some reason, such as if the internal diaphragm is damaged or other a-pump parts are broken and no longer available.

To test the a-pump you can remove the air box and watch inside the carb bore while actuating the throttle, it should squirt fuel into both of the carburetor throttle bores (not a small drizzle-drip but a healthy squirt).

This has all already been done. I guess I should stated, but thought my very first line of post would have clarified.

1) all original OEM gray temp fuel lines we're replace 4 years ago.
2) carbs cleaned
3) selector valve cleaned
4) fuel baffle checked, cleaned and repaired for fuse issue.
4) vents and pressure relief valves replaced.
5) engine rebuilt with carbs being rebuilt with OEM kit.
6) settings set to factory settings.


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[JJinSC]

=Coastiejoe;421616]I did not read it that way, I read it as though you were CONSIDERING CLEANING THE fuel system.. Not Considering you had already done it...

I'm out...

Apologies for not being clear. I have added additional info now to clarify my lapse of info. Again, sorry for not being clear.



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[Sportster-2001-951C-Stock]

I want to add since you are confident the carburetors are not dirty internally, you should check the accelerator pump carefully to make sure it's operating as intended, also perform a low pressure test of the fuel lines to make sure there are no air leaks (air in fuel is no bueno), and the fuel tank check valves that allow makeup air to enter the tank, and excess pressure to leave the tank, are both functioning reliably.

 

[Sportster-2001-951C-Stock]

This has all already been done. I guess I should stated, but thought my very first line of post would have clarified.

1) all original OEM gray temp fuel lines we're replace 4 years ago.
2) carbs cleaned
3) selector valve cleaned
4) fuel baffle checked, cleaned and repaired for fuse issue.
4) vents and pressure relief valves replaced.
5) engine rebuilt with carbs being rebuilt with OEM kit.
6) settings set to factory settings.


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Okay there you go, so you've been able to knock quite a few items off the list.

I'd like to know more about the accelerator pump, you were able to confirm a healthy shot of fuel in both carbs when the throttle is actuated?

Based on our conversation I believe your off-idle operation is too lean and causing lean hesitation, your a-pump is supposed to compensate for the lean transition. The earlier ski that didn't have an a-pump had a larger jet but Seadoo was able to switch to a smaller jet once they installed an a-pump, so the a-pump must work correctly or the off idle transition with the smaller jet will cause a lean spot off idle.

That's seems most likely to me.

 

[Sportster-2001-951C-Stock]

If all of this still doesn't resolve the lean hesitation then it's possible you may have to increase the pilot jet size, but this is uncommon in most instances. Of course if you knew the jet was the wrong one it would be obvious.

My 951 had an identical lean hesitation after confirming the entire fuel system was operating properly, so I installed a larger pilot jet to eliminate the lean spot.

 

[JJinSC]

Ok, I have checked the functioning of the a-pump in the past and it did seem to have an issue of which I thought I had resolved. I will take her off the dock tomorrow (if the weather is bad like predicted) and check the a-pump function again. I have had suspicions about it and that undocumented check valve all along.

Question if it is an a-pump mal-function, that would mean only lean when I try to come off of idle and not lean while idling, correct?

Also, the a-pump function can only be checked with engine running, correct?


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[Sportster-2001-951C-Stock]

Now you've got me wondering about that green check valve, I wonder if it's restricting a-pump shot volume somehow? Is the check valve on the inlet or outlet of the a-pump?

I have this feeling the a-pump isn't giving a full shot, this is consistent with a lean off-idle transition.

 

[Sportster-2001-951C-Stock]

Question if it is an a-pump mal-function, that would mean only lean when I try to come off of idle and not lean while idling, correct?

Also, the a-pump function can only be checked with engine running, correct?


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You should check it with engine off, use a mirror or safety glasses and peak into both carb bores while actuating the throttle. You have about two full shots before it runs out of fuel when the engine isn't running.

And yes, the a-pump only adds fuel when you squeeze the throttle, this is necessary b/c when the throttle butterfly is first opened a shot of fuel is necessary to keep a lean condition from occurring as the low speed pilot transition ports begin flowing fuel.

This a-pump strategy allowed Seadoo to install a smaller low speed jet thus improving hydrocarbon emissions performance.

 

[Sportster-2001-951C-Stock]

I want to point out that any small restriction in the low speed transition ports in the carbs bore will also cause a lean off idle operation as well. In case whoever cleaned them didn't make absolutely certain to remove all of the debris and they were completely unclogged. These holes are only the diameter of a small sewing pin, so it's easy to miss if you're not aware they may be plugged with fuel varnish.

But if the ski has always had this hesitation since new and the accelerator is conformed giving a strong shot of fuel, the next size larger jet will certainly fatten it up. Only do this if you're certain there's not something else going on and the carb checks out in every aspect, b/c it's not good practice to cover up problems by rejetting.

 

[Sportster-2001-951C-Stock]

While you're in the bilge, make sure the idle mixture screws are set at least to 1 and 3/4 turns from lightly closed position, you can open them slightly more (such as 2 turns) to keep a little extra fuel in the crankcase during idle as long as idle RPM's don't trend downward while idling. This can also work to your advantage as a sort of fuel source available for when the air velocity first increases through the throttle bores.

I see the '97 787 a-pump is only connected to shoot fuel into the PTO carb, it's not plumbed to the MAG carb. and factory jets were MAIN-(MAG - #142.5 PTO - 147.5) PILOT- #65

http://www.seadoosource.com/carbreference.html

 

[JJinSC]

Is the check valve on the inlet or outlet of the a-pump?

I have this feeling the a-pump isn't giving a full shot, this is consistent with a lean off-idle transition.

It is on the outlet about 1" from the pump itself inline to the carb A-pump nozzles. What puzzles me is why it is there when all I read states that there are check valves in the square elbow which contains the nipples of each carb that the lines attach to.

 

[JJinSC]

You should check it with engine off, use a mirror or safety glasses and peak into both carb bores while actuating the throttle. You have about two full shots before it runs out of fuel when the engine isn't running.

And yes, the a-pump only adds fuel when you squeeze the throttle, this is necessary b/c when the throttle butterfly is first opened a shot of fuel is necessary to keep a lean condition from occurring as the low speed pilot transition ports begin flowing fuel.

This a-pump strategy allowed Seadoo to install a smaller low speed jet thus improving hydrocarbon emissions performance.

The last time I checked, I did it this way and one nozzle (Mag carb) was not shooting. I cleaned it and got it spraying, but like you say, you only get about 1 1/2 to 2 squires with the engine off.

 

[JJinSC]

I want to point out that any small restriction in the low speed transition ports in the carbs bore will also cause a lean off idle operation as well. In case whoever cleaned them didn't make absolutely certain to remove all of the debris and they were completely unclogged. These holes are only the diameter of a small sewing pin, so it's easy to miss if you're not aware they may be plugged with fuel varnish.

But if the ski has always had this hesitation since new and the accelerator is conformed giving a strong shot of fuel, the next size larger jet will certainly fatten it up. Only do this if you're certain there's not something else going on and the carb checks out in every aspect, b/c it's not good practice to cover up problems by rejetting.

I cleaned them the first time when I replaced the fuel lines and I am 100% sure of the job I did (I pay close attention to cleaning and sanitization as I use to home brew). However, a former certified dealer mechanic that is now working on his own did the rebuild of the engine and carbs and I am pretty confident in him. He is pretty sharp. However, before rejecting it may be worth re-confirming myself. I want to think since that check valve is there from the factory, there was something the factory was trying to address. Otherwise, How could this exact same issue make it through so much focused fuel delivery troubleshooting?

 

[JJinSC]

While you're in the bilge, make sure the idle mixture screws are set at least to 1 and 3/4 turns from lightly closed position, you can open them slightly more (such as 2 turns) to keep a little extra fuel in the crankcase during idle as long as idle RPM's don't trend downward while idling. This can also work to your advantage as a sort of fuel source available for when the air velocity first increases through the throttle bores.

I see the '97 787 a-pump is only connected to shoot fuel into the PTO carb, it's not plumbed to the MAG carb. and factory jets were MAIN-(MAG - #142.5 PTO - 147.5) PILOT- #65

http://www.seadoosource.com/carbreference.html

Incorrect, my 97 787 (XP) has a line going to both carbs from the a-pump with nozzles in both carbs. That green check valve is before the T. I will definitely check the idle mixture screws while checking the a-pump.

 

[Sportster-2001-951C-Stock]

I cleaned them the first time when I replaced the fuel lines and I am 100% sure of the job I did (I pay close attention to cleaning and sanitization as I use to home brew). However, a former certified dealer mechanic that is now working on his own did the rebuild of the engine and carbs and I am pretty confident in him. He is pretty sharp. However, before rejecting it may be worth re-confirming myself. I want to think since that check valve is there from the factory, there was something the factory was trying to address. Otherwise, How could this exact same issue make it through so much focused fuel delivery troubleshooting?

Yeah, I went through all of this same stuff with my 951 too, when looking for the cause of my lean hesitation. I made triple sure those transition ports were whistle clean, confirmed everything triple times yet still it hesitated and would quit running just as you describe, my final solution was a larger low speed jet and now it runs/starts like a champ.

This is why, based on my experience, I wonder why nobody else seems to run into this same issue, where the off idle and low speed operation are calibrated too lean.

I used to have an old XP, loved that ski.

 

[Sportster-2001-951C-Stock]

Incorrect, my 97 787 (XP) has a line going to both carbs from the a-pump with nozzles in both carbs. That green check valve is before the T. I will definitely check the idle mixture screws while checking the a-pump.

The guy who compiled that info is pretty thorough so I assume his numbers are correct but you might want to confirm with the service manual to make sure.

Not sure why he noted only the PTO carb is a-pump sprayed, perhaps they came in two flavors.

Speaking of flavors, my preferred ones are the dark brews.

 

[Sportster-2001-951C-Stock]

It is on the outlet about 1" from the pump itself inline to the carb A-pump nozzles. What puzzles me is why it is there when all I read states that there are check valves in the square elbow which contains the nipples of each carb that the lines attach to.

Maybe your carbs don't have check valves in the accelerator nozzles but if they do then you shouldn't need the green check valve. If the nozzles don't have check valves then you're gonna need that green one for sure.

 

[Strizzo]

Sounds fat off idle to me. Are you adding more throttle and the motor stays the same speed progressively running worse with more throttle if you add it too fast? If it's lean it'll sound like a dirt bike off idle, throttle- pause- go.

 

[Sportster-2001-951C-Stock]

Sounds fat off idle to me. Are you adding more throttle and the motor stays the same speed progressively running worse with more throttle if you add it too fast? If it's lean it'll sound like a dirt bike off idle, throttle- pause- go.

Are you saying this based on the video the OP posted, I was unable to download that thing.

 

[JJinSC]

The guy who compiled that info is pretty thorough so I assume his numbers are correct but you might want to confirm with the service manual to make sure.

Not sure why he noted only the PTO carb is a-pump sprayed, perhaps they came in two flavors.

Speaking of flavors, my preferred ones are the dark brews.

Yeah, everything including my shop manual shows the a-pump going to both carbs. the diagrams do, however try to consolidate most of the carb parts in one diagram,but have another diagram with the extra parts of the other carbs. I like the dark brews too, but my favorite is the hoppy brews IPA.

 

[JJinSC]

Maybe your carbs don't have check valves in the accelerator nozzles but if they do then you shouldn't need the green check valve. If the nozzles don't have check valves then you're gonna need that green one for sure.

Well it shouldn't hurt anything as long as it is working, huh? I did check the function of it when I did the cleaning job and I could blow through it in one direction but not the other. The only thing is, since the parts diagram doesn't contain it, I don't know how to reorder a new one to replace it just in case.

 

[JJinSC]

Are you saying this based on the video the OP posted, I was unable to download that thing.

Try the video again, for some reason it was marked as private when I first uploaded it to youtube. I went back and marked it public. Here is the direct link. http://youtu.be/VMOfJsQ42cM

 

[Strizzo]

My 97 xp has two check valves in the accel pump lines. The pump itself doesn't have any check valve so there should be one ahead and one behind.

Verify your pop off and low speed needle settings.

 

[Sportster-2001-951C-Stock]

Well it shouldn't hurt anything as long as it is working, huh? I did check the function of it when I did the cleaning job and I could blow through it in one direction but not the other. The only thing is, since the parts diagram doesn't contain it, I don't know how to reorder a new one to replace it just in case.

Exactly right. There has to be a check valve function on both the inlet and outlet of the a-pump else it's not going to be able to force fuel through the nozzles. All of these have to be oriented in the direction of flow, which of course is towards the nozzle.

Youtube is firewalled on my 'puter, no videos in or out.