viper hard starting unique condition

S

snowbiscuit

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Jan 30, 2004
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This problem has been on my 2002 viper since day one and I have had it in to two different dealerships on three occasions and has yet to be fixed. Yes the fuel pump has been siliconed. I have owned many Yamahas, so it is not like I dont know how to start a sled. I have no problem starting when engine is cold, like sitting over night. And have no trouble running, shutting off for short period of time( 5 min). It is when turning off for period of 30 to 60 min. If I dont choke but just open throttle on first pull it will fire briefly but like it runs out of gas. I believe, but am not sure that the bowls are dry at this point and the only way I can get it started is full choke with throttle open and it is many many pulls. I have tried different starting combos but with no luck. I know there must be others having same problem and any help would be greatly appreciated.
 
only after riding

On cold starts, like in morning, no problem. Only after sled has been warmed up. Let it sit 30-60 min, agony begins.
 
A good service dealer should have tested your fuel pump, and checked the needle valves.

I would create the condition where you experience the problem, and then check things out. Things I would look for include . . .


  • Restriction in fuel lines from the tank
    Debris in fuel pump
    Defect in fuel pump fittings
    Fuel line routing
    Needle valves in carbs

Have you tried setting the starter (often called choke) at the halfway setting and not touching the throttle? Remember that this is not actually a choke, but simply an additional fuel circuit that richens the mixture when engaged.

Personally, I hold my throttle about halfway open, and give one really brisk pull whenever the motor is warm. Very rarely does this not start it on the first pull as long as the engine is warm or slightly warm. If it doesn't start, then usually I have gotten lazy and not done it just right.

I would also check the plugs after one pull where it doesn't start in this condition. This will tell you a lot about what is happening.
 
Don't know why the list didn't work in the previous post, anybody else know?
 
I also have an 02 Viper. When I stop for lunch I have to 1/2 choke to get it started. This is after setting aprox 1 hour. Does not seem to matter how warm or cold the outside temp. is

Works for me.
 
...another possiblility might be "vapour lock" ,

When a hot engine is shut off, the temperature of the engine and everything on it continues to rise for awhile as the engine undergoes a period of "heat soak." This can cause fuel to boil inside the carburetor bowl, fuel lines and fuel filter. When you attempt to restart the engine, "vapor lock" obstructs the flow of fuel and the engine doesn't want to start.

This is much less of a problem on fuel injected engines because the fuel is usually under much higher pressure inside the injectors and fuel line. Even so, a fuel line routed near an exhaust manifold or a fuel rail that's exposed to a lot of heat may still suffer the same kind of problems.

Heat soak problems such as these can sometimes be cured by wrapping insulation around affected fuel lines, and/or installing an insulating spacer or heat shield under the carburetor. Not sure if the Viper carbs are heated but insure that the coolant manifold is turned off in warmer temps.

srx_eh
 
I just wonder if pluggin that fuel pump breather is an issue on really hot days....I wonder if you take the silicone out of that vent in the bottom of the viper fuel pump (Yamaha's Fix) and just space them up on some washers or nuts about 1/4"...hmmm.
 
Mr. Sled

Tried to space the fuel pump, raised it about 3/16 of an inch, and it froze. Siliconed it and it has been fine ever since.
 
hmm. never had them freeze once I spaced them up...water in the gas may make that happen ....well if it works for you great!!!! just thinking out loud.
 
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