Snowmobile Fanatics banner

1 - 20 of 27 Posts

·
Registered
Joined
·
16 Posts
Discussion Starter · #1 ·
Hello everybody,

I have this 1991 Arctic cat Lynx 339cc that has had this same problem for years. It is my putter sled so I just have never taken the time to fix this issue.
Here is what it does:

1)After running for a while it will not let me leave it idling, it will slowly decrease in rpms at idle until it finally stalls.

2)When I open the hood there is air in the line all the way to the tank. To start it I have to hold the gas wide open and sucks the gas back down to the carb

What I have done to try to fix this:

1) Replaced ALL hoses (inside tank and out)
2) Changed fuel filters

Symptoms of sled: (just obvious observations
spark plugs are always nice and brown
always fresh fuel
always starts wonderful every morning, 100% power until the sled it all warmed up, then loses prime at idle and stalls.

My theory...
bad fuel pump?? Sled only gives me trouble after it has been running a while.. air temp does not affect this one way or another (whether it it -30 or +30 all is the same)

If you need anything cleared up let me know. Thanks!
 

·
Registered
Joined
·
8,108 Posts
yeah, sounds like a fuel pump thing. but i would think it would be hard to get it to start in the morning. It could also be the needles or seats, but unlikely.
 

·
Registered
Joined
·
16 Posts
Discussion Starter · #4 ·
Yeah it seems to be a problem after it is warmed up and been running a while. When I go to start it in the morning, it start first or second pull. However if I have been running it for a while and I shut it off, I have to hold the throttle wide open to get it going again. If I shut it off, walk away for an hour, come back, it starts right up.

Like I said before, I saw air in the line, so I went with the obvious and changed filters, fuel lines, etc. The air must be getting in somewhere else, and the fuel pump is losing prime when the sled is warmed up.
Thankyou for any ideas!
 

·
Registered
Joined
·
8,108 Posts
are you SURE that it isn't flooding, and the seats are leaking? When you have a flooded motor, the only way to get it to start is holding the throttle wide open. When it won't run, pull a plug and pull it over (with the ignition OFF). If any fuel shoots out, it's probably flooded.

now-adays snowmobiles also use enricheners, NOT chokes, so cranking at WOT is counter-productive to drawing more fuel to the motor. Leave the throttle closed or slightly open if you think it needs more fuel to start.

-Dean
 

·
Registered
Joined
·
16 Posts
Discussion Starter · #6 ·
No I know that it is not flooded, the plugs are always brown and DRY. I know the trick of pulling out the plugs and cranking it over to shoot the fuel out. I am 100% sure it is a lack of fuel problem, when I go to start it after it is warm I can see that there fuel lines have no fuel, by holding the throttle wide open I can see the fuel getting sucked back down the line faster than if I don't touch the throttle. Once the fuel gets sucked down to the carb, off we go good as new!
I have tried running the sled with the gas cap loose (thinking I had a vacuum in the tank) and the same problem persists.
Do you think that I can be leaking air in the fuel pump? It has to be from the fuel pump down, because everything before the fuel pump is new. Thanks for the help!
 

·
Registered
Joined
·
16 Posts
Discussion Starter · #7 ·
hey ripper,

What about the impulse line that goes to the fuel pump from the engine... I never touched that and perhaps when the engine gets warm, it expands and I get an air leak... just an idea, what do you think?? would that not allow it to idle because the suction from the carbs would be too low to overcome the leak, but then at anything above idle the suction would be enough to keep it going?
 

·
Registered
Joined
·
8,108 Posts
Originally posted by joslow420
[br]hey ripper,

What about the impulse line that goes to the fuel pump from the engine... I never touched that and perhaps when the engine gets warm, it expands and I get an air leak... just an idea, what do you think?? would that not allow it to idle because the suction from the carbs would be too low to overcome the leak, but then at anything above idle the suction would be enough to keep it going?
Yeah, that sounds like reasonable thinking... I don't think rebuilding fuel pumps is too expensive, and it may be worthwhile anyway.

AFAIK though, when a fuel pump goes, the suction in the crankcase ends up sucking the fuel into the crankcase, not pumping air into the lines...

-Dean
 

·
Registered
Joined
·
16 Posts
Discussion Starter · #10 ·
Dean,

I might just go with either rebuilding the fuel pump or checking out the impulse line. Since the problem is intermitent I am not sure that it would be a bad, or going bad fuel pump because it would seem that the sled would be hard to start all the time. I never thought of checking out the impulse line from the crankcase, I would assume that possibly when the sled gets warm that line gets loose and I lose my vacuum from the crankcase. Might be worth tinkering with.
 

·
Registered
Joined
·
16 Posts
Discussion Starter · #12 ·
It does not neccesarily go away on its own, rather after an hour or maybe less I can crank the sled over and the air will get sucked down w/ fuel behind it. Once the air is sucked down and fuel hits the carb it takes off and goes. But if I ride a while and let it idle, the sled's rpms will get lower and lower (because starving gor fuel) and it will stall, and then the line is full of air again. And then the cycle starts again as I decribed before (either it will start again immediately by holding throttle wide open and giving anywhere 5-10 pulls, or I can wait an hour, not touch the throttle at all and starts with one pull. It is all a matter of keeping fuel in the line and air out
 

·
Registered
Joined
·
1,932 Posts
I had trouble with my impulse line on my Tcat when it was new. It got kinked when I changed jets once. And the symptoms were a little different. It would run great and then die. No fuel in the line, like you said but it was a major pain to get running again. It may be that since your not buringing as large a quantity of fuel that this is the problem just sound like slightly different symptoms.
 

·
Registered
Joined
·
16 Posts
Discussion Starter · #14 ·
I'm hoping that it is something that simple, I'm at college right now so I have to go home (3 hour drive) to take a look and see what the condition of the line is. I'm almost hoping that it will be a simple fix like a bad impulse line. I'm just thinking now.. (duh why ddin't I think of that before?!) Thanks for all info, I can learn a lot from people with similar problems.
 

·
Registered
Joined
·
4,322 Posts
it does sound like a problem with the impulse line to me as well. i have seen this before. it happened on my 78 jag that i had but it happened because it needed rings and after it was warmed up it would force more air into the impulse line and pretty much shut the fuel pump down.
 

·
Registered
Joined
·
2,273 Posts
Originally posted by bigwilly
[br]
Originally posted by jag340 1990
[br]hi i have teh same problem with my jag
Maybe try some of the things that were already suggested...
Big Willy! I think your onto something! ^^^^
 
1 - 20 of 27 Posts
Top