MCX Apex Vapor locked?

[TURBLUE]

Had a strange thing happen over the weekend....riding all day turned the sled off for a few minutes and started it drove a few feet and it dies....so try to start it and it starts idles rough and dies out.....tried several time with and with out throttle and same thing...starts runs rough and dies out....so started looking at things...tried running it with the MCX injectors unplugged nothing worked....then as I was cycling the key I noticed that the secondary fuel pump I have installed for the 310 mcx kit sounded like it was running out of fuel....there was a half a tank, but did notice there was a lot of venting comming out the vent line of the tank....So I pushed it to the bottom of the hill to level it a bit and it started right away....weird tooked it back to town and through it in a heated shop for the night...never missed a beat the next day....Think there was vapor in the suction going to the pump?

Its a apex MCX 310 kit 2006....

 

[millstreet]

OOPS

 

[millstreet]

http://www.ty4stroke.com/viewtopic.php?t=83980

 

[TBird]

I haven't any fuel lines nowhere near any hot stuff, where do you have the secondary fuel pump?
And you say "secondary", does that mean you have oem still inside the tank?
I only have the external, never missed a beat, third season.

 

[thamax]

sounds like the fuel boiled on you cause it won't start till it cools down either the fuel line got to hot or the fuel rail pretty common on the nytros

 

[Agman 57]

I'll add my 2 cents, I have a Nytro with a MPI stage 1, but with the stage 2 fuel pump(external pump) and I have had it seem to vapor lock 3 times in the last 1100 miles. Seems ok if you start it fairly quickly or let it set for say 10 -12 minutes. But if you try it after about 3-4 minutes it seems to have no fuel. I pull the hood and side panel off and it will re-start much quicker. I even put a second hose over the incoming fuel line to try and insulate it and it has still happened once more to me. Maybe the fuel rail theory is what is happening? My stock Nytro has never had this issue.

 

[TURBLUE]

I never had this happen in 3200 miles 5 seasons.....kinda weird....

 

[TURBLUE]

Has anyone had problems with the fuel boiling on there MCX apexs.... was out on the weekend and it seems to hesitate under acceleration sometimes goes lean on the AF...Thinking its vapor locking once in a while... how much fuel pressure is suspose to be for the apex with the extrenal pump?

 

[TBird]

Don't know if you still have the OEM fuelpump in the tank (see my earlier post) but if you do, remove it!

Heard of several (including me) noticing that it runs a little rich in low rpm off boost after the external fuelpump is installed, and my theory is that this is because there's some restriction in oem fuelpressure regulator and is not able to bypass enough fuel on idle and low rpm.
And with the OEM fuelpump still installed i noticed that the external fuelpump sometimes cavitated when idling.
After i removed oem fuelpump i never noticed that again.
I never experienced any vapor lock.

 

[mbarryracing]

Jan,

When removing the intank OEM fuel pump, what do you use for a fuel pickup in the tank?

 

[TBird]

MCX Nytro style pickup, also CR Racing have similar.

 

[TURBLUE]

stupid question but where the installs typical done with leaving the stock fuel pump in? Also on the apex come there is no fuel pressure regulator?

 

[TBird]

Apex oem fuelpressure regulator is on the end of the fuelrail on right side.

 

[rxrider]

The new Apex MCX290 kits comes with a new aluminum fuel picup where you reuse the internal fuel filter from the stock plastic fuel picup. Good idea to keep fuel lines away from any heat source and insulate them well.