2006 mcx apex fuel problems

[925rotax]

2006 apex mcx, running 17 psi. Last weekend during a climb the sled was sputtering at wot until i throttle chopped it. Ran great at 1/4 to 3/4 throttle. I came home and removed seat , tank, heat shroud, etc. Charged the turbo intake to 20 psi and shut off the air compresser and looked/ listened. I found that # 2 injector rubber seal was leaking. Upon removal the seal was damaged . I replaced the seal. Today it ran good at 1/4 and at wot it sputters and wont make power. I had to pull out of a pull that i normal would pull w ease. At 1/2 it sputters under load and runs crappy. I pulled it apart again ,charged 20 psi and see / hear no leaks. I looked at all 4 injecter top seals and there seated. It really seems like a fuel issue.When I ran it on flat I could get 15 pds w sputtering and it definatly was not 15 pds , felt like 10, low on power. Any ideas? Thanks

 

[TURBLUE]

exhaust donuts? the other thing i had problems with is the fuel would boil in my tank from the exhaust...would cut out like your saying...put heat fabric between your tank and tunnel...

Werent you having this issue earlier?

 

[925rotax]

Today I rode it aprox 30 mins on trail 2' powder. I then went uphill pull wot and pulled out of climb , because of sputtering and loss of power. I pressure tested the system again tonight and there are no leaks. Exhaust donuts under the heat shield? , under the tank? cr racing tunnel on it . I dont see the exhaust donuts, are they close to the block and have clamps? because the clamps are tight and no signs of donut material around? thanks turblue. Im new to the rear mounts ,always owned front mounts

 

[TBird]

It seem as your problem is that the secondary injectors don't add any fuel, why is that? check following:
1. Is the cable from the InterCooler hooked up?
2. Is a boostline connected to MCX ECU?

To do a simple test, hook your compressor to the boostline running to the MCX ECU, turn on the sled and let it idle, add pressure to the boostline, a couple of PSI is enough for the injectors to start adding fuel, over 17psi they are fully open and your engine should flood!
Start there.

 

[TURBLUE]

if its a 06 kit it ill have the same box as mine..do the test that tbird explained, mighy only be a map sensor....we had one of these go on us this year on buddies sled.....

 

[TURBLUE]

How many psi of boost are u running when u say good to 3/4 throttle? It will prob start to sputter at 4-6 psi of boost. Like really fall on its face. If that's not the case the mcx ecu should be ok. Mine was doing what u explain last year a bit. And it was the gas getting hot and the external fuel pump would suck air intermittently. They other thing I found at the end of the year my exhaust donuts between the bellows and exhaust pipes. The 4 clamps. Were shot. I would get a set of the copper donuts from thistledoo just to eliminate that problem.

 

[JIM]

If you are doing and air test to the intercooler and dont have an air guage at the rear of the sled too you may not be letting your test by the valves, rotate your motor and put a guage at both ends... Also the older control boxes had a condensation problem and it may need to be dried out and resealed..

 

[925rotax]

First of all thanks for all the info guys, really helps on problem solving. The sled doesnt really fall on its face at 4-6. When I ran it on flat ground at 10 it seemed okay for no sputering, craping out, just seemed low on power. Pin throttle above that it really starts to sputter and the pull isnt there , worse under load climbing. Climbing it really sputters like starving fuel or exhaust leak as turblue suggested. Also no power, but will show 15 pds. I am in my shop w it on the hoist, will start looking at exhaust leaks [ donuts] cracks. It runs like a trx I had with loose header bolts. I will post what I find. I got spanked by a 900 dragon on noss. I cant have this happen, sure you guys know what I mean . Hopefully out next friday to put a show on!lol

 

[925rotax]

Tbird says to start sled at idle, pressurize the mcx ecu line w a few pounds, 17 pds should cause it to flood. If I m understanding this. As the sled is idling , increase the shop air compresser to 17 from 3-4 to check for flooding or not. which will check for a good or fauty ecu.

 

[TURBLUE]

with the sled running if you add pressure to the map sensor or the ecu( depending on which box you have) it will flood due to it adding fuel....if it doesnt your problem is the map sensor or the box.......which mcx box do you have?

 

[925rotax]

Thankyou Turblue, I have generation 1

 

[TURBLUE]

then you will pressure up the map sensor.....should be a small sensor with a vacuum line going to it clamped close to the fuel rail.....5-10 psi and if it starts to die...its not the map sensor.....pull the cover off the box and see if there is water in it....i had problems with that and moved to to here..

 

[kinger]

Did you check the obvious...Fuel filter?

 

[925rotax]

I went over the entire exhaust and no cracks, blown seals etc. No air leaks up to 18 psi on intake side. The electrical connection off the intercooler is good, fuses good. I didnt check the obvious ''fuel filter'' thanks Kinger. I will check that and pressure up the ecu line. Thanks again Turblue. Will also check the secoundary fuel pump for pressure tommorrow as well. Turbo impeller is good and acuater.Injectors are seated properly and connecters.

 

[TBird]

With all info so far my bet is fuelpump or filter, usually if it would have been ECU or sensor your sled would sputter as soon as boost comes on, but if it runs good up to ~10lbs it's usually a restriction in fuelflow due to bad fuelpump or clogged filter.
But anything is possible, could be a clogged injector in IC also, as they fire simultaneously, if one is bad there's not enough fuel for high boost.