2004 Mountain Cat 900 EFI Fuel Issues???

Dec 6, 2015
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Have a 2004 Mountain Cat 900 EFI that will not run more than 20 feet before it bogs out and dies. If I give it anything more then a 1/4 throttle it will die before it even moves. Sometimes it will start right back up and others times I can not get it to start without adding starting fluid to the air box. I have changed out the fuel pump, checked all my grounds, fuel pressure is 41 lbs @ the fuel rail, cleaned out the smart vales in the tank, had my injectors cleaned at the local arctic cat dealer. Have spark on both cylinders, changed out my servo. Have tried everything I can think of to get this sled to run but nothing has worked.. Any tips or ideas for me?

Current Sled Set up
1. SLP Single Pipe & Can
2. Boondocker Control Box with SLP recommended settings
3. RK Tech Torque-Line Head
4. V-Force 3 Reeds
 

Idcatman3

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Nov 26, 2007
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I'd pull the boondocker box off and try the sled for a minute or two to eliminate that as a source of error.

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kiliki

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Dec 27, 2008
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cut the wire to the throttle safety switch and put on a tether, or use a multi meter to test is.
 
Dec 7, 2007
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Elkhorn NE
Ground wire, I had issue with m1000, had spark when doing pull test, would start on occasion then die, or produce a large back fire, Turned out to be shorted out wire in the exhaust temp sensor, I know you do not have a exhaust sensor but I would check all connections for rubbed wires.
 
Dec 7, 2007
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Elkhorn NE
Another possibility, I know on my 02 800 efi mt cat I had the wires cracked right at the injector, the crack was real close to neck of connector, might be an area to see if it is large enough to cause a short.
 
Dec 6, 2015
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Pulled the Boondocker box and had the same issue.

Pulled the TSS and that did not fix it either.

I changed the stator as I have read that being an issue on these sleds.

Nothing seems to help correct the issue.. Is there a "limp mode" on this sled? Almost acts like it goes into a limp mode and will not supply fuel any more. So I have to supply it through the air box with starting fluid
 
Last edited:

kiliki

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Replace fuel pump. Also there is a screen on the uptake side on the fuel pump. At idle you might have good fuel pressure but not have enough flow for more rpm. You can use a 9v battery to run the pump in reverse to help flush it
 
Dec 6, 2015
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Is there any chance my problem could be oil related? I wonder if I am getting too much oil and that is what is causing my sled to bog down and quit? Which could also make it hard to start?
 
Dec 6, 2015
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Took the sled out yesterday and fought it bogging down for hours, added fuel with the boondocker box and finally took off and ran...Shut it down to cool off then when I started it back up same bog. Feathered and limped it along played with boondocker settings then it took off again.(this situation repeated it self multiple times) So decided to let it cool off again but when I started it up I let it idle for 10 minutes or so. It still had a little bog in the mid range but ran fine... Just seemed To run better if I let it idle longer than normal to get up to temp.


****Side note had a stock 05 king cat 900 efi that ran great all day then when we fired it up to head to the truck would not run.. boggy bottom end, would not idle... if I feathered it along I could eventually get it to clean out and run.. but as soon as the RPM drop to 3k it would bog down.. could hold the throttle constant and the sled would surge.. take off then bog down... any ideas????
 

Idcatman3

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My main thought is "this is why I stick to carbs..."
Sorry nothing better is coming at the moment.

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Dec 6, 2015
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ECU

Bought a second 900 EFI and swapped the ECU. Sled ran great and put the bad ECU on second sled and had the same issues of my other one. My thought are the ECU is bad.

Does anyone know if you have get those rebuilt/repaired?

Also read on another post that an 03-05 600, 700, or 800 can work on a 900 after it is re flashed?

What options do I have to replace the ECU without having to pay OEM price for a new one?
 

Readymedic

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Nov 6, 2013
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As far as I know, they cannot be reflashed. More than likely, an electrical problem within the ECU. And plus being the age, may be against you.
Watch Ebay. Just make sure it is an EFI. I have had several 900s, but they were carbed. Makes things a lot easier.
It has been a while, but I do not remember if the circle, triangle or square type ECUs are applicable to the 900 efi/carb.
 
Last edited:

Idcatman3

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Nov 26, 2007
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As far as I know, they cannot be reflashed. More than likely, an electrical problem within the ECU. And plus being the age, may be against you.
Watch Ebay. Just make sure it is an EFI. I have had several 900s, but they were carbed. Makes things a lot easier.
It has been a while, but I do not remember if the circle, triangle or square type ECUs are applicable to the 900 efi/carb.
I wouldn't be surprised if they can be reflashed, but the plugs are actually different between the 8 and 900 at least. I don't remember for sure about the 6, but I think it's like the 8.
It looks like the M7 one is probably the same hardware that the 900 is, but I don't know for sure. You might be able to contact someone at the Cat race department.

You could run an 800 ECU on it, if you also changed the wiring harness, and but a boondocker box or equivalent on it, but that's asking for trouble IMO.

Unfortunately, I'd just look for a replacement 900 ECU. The circle/square/triangle thing does technically apply, but the difference between them is small enough that it's not a big deal to mix/match.
 
Jan 8, 2019
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1
Have a 2004 Mountain Cat 900 EFI that will not run more than 20 feet before it bogs out and dies. If I give it anything more then a 1/4 throttle it will die before it even moves. Sometimes it will start right back up and others times I can not get it to start without adding starting fluid to the air box. I have changed out the fuel pump, checked all my grounds, fuel pressure is 41 lbs @ the fuel rail, cleaned out the smart vales in the tank, had my injectors cleaned at the local arctic cat dealer. Have spark on both cylinders, changed out my servo. Have tried everything I can think of to get this sled to run but nothing has worked.. Any tips or ideas for me?

Current Sled Set up
1. SLP Single Pipe & Can
2. Boondocker Control Box with SLP recommended settings
3. RK Tech Torque-Line Head
4. V-Force 3 Reeds
I'm having the same problem, did you figure it out?
 
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