MCX 240 hp - troubleshooting injectors

TurboCobra · Dec 11, 2010

My MC Express 240 hp kit backfires around 9psi and won't go over. Sounds like the secondary injectors are not coming on. Anyone know how to check this (other than pulling the plenum off)? Sounds like a fuel problem to me (lean), and have looked at the couplers on the carbs - looks okay - but man - it is tight in there! Does anyone know if you can check the red/black wires going to the secondary injector to see if they are firing? Checked out the MC Express chip (at the dealer) and they said it is good. They told me to use a pump and put 5 psi to the chip and the idle should pick up - my sled doesn't do this.... Stared at it for about an hour this afternoon and think I may have to disassemble the complete kit to troubleshoot further... any suggestions would be appreciated :face-icon-small-dis

franklin · Dec 11, 2010

Are the secondary injectors the same type as stock?

Linc · Dec 11, 2010

What's it revving at, if it over revs it will back fire and it won't see full boost.

NM · Dec 12, 2010

TurboCobra said:
My MC Express 240 hp kit backfires around 9psi and won't go over. Sounds like the secondary injectors are not coming on. Anyone know how to check this (other than pulling the plenum off)? Sounds like a fuel problem to me (lean), and have looked at the couplers on the carbs - looks okay - but man - it is tight in there! Does anyone know if you can check the red/black wires going to the secondary injector to see if they are firing? Checked out the MC Express chip (at the dealer) and they said it is good. They told me to use a pump and put 5 psi to the chip and the idle should pick up - my sled doesn't do this.... Stared at it for about an hour this afternoon and think I may have to disassemble the complete kit to troubleshoot further... any suggestions would be appreciated :face-icon-small-dis

How did the dealer test the fuel control box? I would say check all of the connections first. There is key power, ground, signal wire to a injector wire, and a wire to the TPS. Make sure they are all clean and have good contact. I can't see there being a problem with the Bosch injectors in the intercooler. You could test the positive wire going to the secondary injectors with a test light, but you will have to get the sled on boost to do it, so you would have to ride it.

BOOSTD · Dec 12, 2010

In the boost line to the computer, pressurize it with compressed air and see if the injectors fire. Make sure all three are firing, if not just one or two not to make sure its not a isolated injector. From there start testing wires individually.

TurboCobra · Dec 12, 2010

tx 4 reply - troubleshooters!

Franklin - yes the secondary injectors are stock. PG Yama installed the kit a year ago. Seemed to run fine last spring, but 1st ride this year is a problem...

Linc - we jacked up the sled and it revs about 9000 rpm (9 psi boost) and the all the popp'n & fartn starts, so no not overrev'n

NM - the dealer put the fuel control box on his computer (from MCX). Then we pumped 5psi into the inlet and he saw the changes on his monitor. I removed the ground at the battery and cleaned it. Will look for the wire to the throttle position sensor (TPS) today (thanks). I may take the sled out side and sling it up to the back of my snomo deck and rev it up, to see if any changes have helped....

I appreciate all your suggestions and comments (and expertise)! Mike

TurboCobra · Dec 12, 2010

how to test injectors?

Boostd - that is exactly what I want to do - test to see if all 3 injectors are firing - what is the easy way to do this without removing the air plenum box? I pulled off the BOV on the left side of the box, but can only see the injector casings. PG Yama suggested physically looking into the air box, but they said you have to pull off the headlight, and a lot of parts.... so is that my direction??

I guess I could test the Red/Black wires first... with the 5psi pumped into the computer chip. Anyone know if these injectors have ever failed? This thing is the tightest thing I have ever worked on! :face-icon-small-sad

Linc · Dec 12, 2010

9200 is hitting rev limiter, I still think you're over revving, when it hits the rev limiter, it drops the RPM and you wont see the 9200 because it's doing it's job, and you won't get full boost on a stand without loading the motor down. try adding a gram or two of weight, then take it for a ride, I think that will fix it. But without a load on the motor, you can't test it properly.

You can test to see if the extra injectors are working if you add shop air to your MCX box while it's idling ( very little air, remember it only needs 5psi or so to trigger them ) unhook the MCX signal line, plug it off, hook a temporary hose the MCX box, LIGHTLY blow air in to it, and you should stall the engine by over fuelling it, it should at least run very poorly.

Tuesday · Dec 12, 2010

I would agree rpms can be so erratic. Do you have a shockwave? Just for interest sake through more helix at it and see if the poping goes away. If you see 9k on the tac then you are probably hitting the rev limiter. Injectors failing have been very rare. Like mentioned very little air will make the injectors fire so dont hit it with 100psi compressor air hehe.

GL

TurboCobra · Dec 12, 2010

reply - tx 4 advise

thanks for advise, Link & Tuesday. I don't think it is hitting the rev limiter because when I was climbing with in last weekend it would not go over 8500 rpm and 9psi boost. Have not changed the clutch set up since last year when it ran fine, other than taking out all three small bolts at the back of the secondary to close the sheaves more (belt squeals at idle sometimes now). I have already put 5psi into the controller, so I will retest to see if there is current in the red/black wires.

TurboCobra · Dec 12, 2010

injector pressure test - failed?

I put about 5psi to the MCX computer chip (inlet port) and there was no change in the idle and it did not go rich. Does this mean the secondary injectors are not firing?

Linc · Dec 12, 2010

I would say that they are not working, unplug the injectors and add 12 volts to the injectors to see if they're working, you can do this while it's stopped, you should hear a click, if they are working, ( clicking) then start the sled and do it again and see if there is a change to the way it runs ( it should run rich, maybe even stall), if there is no change and it's clicking , then the injectors aren't getting fuel.

noob · Dec 12, 2010

If it's a 240 kit, i had the red power wire in my mc x box not making full contact. when you plug the wiring harness in, it looks fine, but the pin would push the power wire out as you tried to hook the wiring harness up. At about 5 psi, it would pop and fart as no power to mc x injectors. check and make sure youve got contact.

dexter · Dec 13, 2010

Also check the wires on the connector for the mcx box (pretty small pins for the wire size) as they tend to break.

TurboCobra · Dec 13, 2010

tx 4 advise

Linc, Noob & Dexter, thanks for the advise! All good stuff. This seems to be what Erik (MC Express - Sweden) is saying as well;

Hi Mike.
It must be something wrong with the electric parts.
It can be something wrong with your wire harness
Maybe your EFI-box is broken after all?
I assume you have checked the + an - wirest to the EFIbox already.
If everything seems O.K, borrow a box from PGY and try again.
Best regards Erik Marklund

So....... back to the shop to night - will keep you posted :face-icon-small-hap

TurboCobra · Dec 13, 2010

more electrical trouble-shooting

Well, I checked out the wiring for another couple hours on my sled and found the following;
1) I can hear the injectors clicking with the engine off and 12v. applied to the plug
2) When I put 12v. to the secondary injectors with the engine running - it floods it immediately and stalls. I have to use a bit of throttle to restart the engine after that. I can not get it to do that by applying 5psi to the MCX EFI box.
3) There is 12v. at the large orange and large red wires at the MCX plug when the fuel system is pressurizing (5 sec. or so), then only power is 0.7 volts at the large yellow plug with the key on
4) during pressuring (5 seconds after key on), and pressuring the MCX chip the fuel pump (in the tank) makes a strange clicking sound, but the secondary injectors don't make any sound.
5) there is about a 4" long pigtail with many pins on the male/female plug that looks like was installed with the kit. A blue & orange wire also leads from this to the rear turbo - should I be checking for a constant power source here (to the secondary injectors), or does it only supply power when the main fuel pump is running? :face-icon-small-dis

TurboCobra · Dec 14, 2010

reply from MC Express

If the ground a +12 volt to the EFI box is O.K, test with a new EFI-box and if it is still nor working, try a new wire harness. The wire harness inside the plenum can be bad too. Best regards Erik.

Linc · Dec 14, 2010

So, your MCX box is toast or more likely is there is a bad connection to the box or power source to it pull the plug and clean and grease the connections with di-electric grease, check for power going to the box first, but I would just go through all the plugs and make all the pin in them are connected and pushed in properly, if everything checks out then maybe you can borrow a box, just to be certain it isn't a electrical/ connection problem.

TurboCobra · Dec 14, 2010

getting close to solving problem

Thanks for that, Linc. I am headed out to the shop to run a jumper wire (+12v) from the starter solenoid to the MCX (EFI box), as per Erik's instructions - guaranteed to fire the injectors!! I hope this works, Mike :face-icon-small-win

slash · Dec 14, 2010

TurboCobra said:
Boostd - that is exactly what I want to do - test to see if all 3 injectors are firing - what is the easy way to do this without removing the air plenum box? I pulled off the BOV on the left side of the box, but can only see the injector casings. PG Yama suggested physically looking into the air box, but they said you have to pull off the headlight, and a lot of parts.... so is that my direction??

I guess I could test the Red/Black wires first... with the 5psi pumped into the computer chip. Anyone know if these injectors have ever failed? This thing is the tightest thing I have ever worked on! :face-icon-small-sad

you can get a noid light and see if theres a signal to the injectors.

MCX 240 hp - troubleshooting injectors

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