black... signs of running rich.


I'm waiting on a compression testor in the mail. Once its here I'll get to work

 

If it's running then you have enough compression. Compression gauge will only tell you what we already know based on your posted info. You have enough compression since its running.

You have a fuel system problem. I'm not familiar with the FI system on that particular ATV but am familiar with FI. I'd investigate that injector. There isn't much to go wrong with FI. Excess fuel is highly likely to be an injector that's not closing all the way when it should and allowing excess fuel in.Most likely problem is a leaking injector.

 

Not necessarily on the compression issue iv seen lots of machines that will run but not well with low compression. The lower the compression the harder it can get to start and run smoothly as it does not have enough to cycle air into the system.

 

All the OP's symptoms scream excess fuel. For carburetors, there are several ways to get excess fuel into the intake. For a fuel injection system, as far as I can tell looking at his machine's fuel system diagrams, the only way he would be getting excess fuel in would be through the fuel injector.

The term fuel injector implies that the injector itself actually pumps fuel. But, the fuel pump in the tank is what actually pressurizes the fuel. A fuel injector is nothing more than a variable valve that opens a little or a lot based on how much fuel the engine needs. If it was running rough but starts fine, I'd be inclined to suspect something like the throttle position sensor is sending bad info to the ECU (or a bad ECU is sending bad info to the injector) causing it to send inject excess fuel at the wrong time....or something similar.

However, in this case, it's clearly sending fuel into the intake even when stopped and shut off. The only way that would happen is if the injector is leaking the pressurized fuel into the intake. When the OP goes to start the engine, the fuel pump has to repressurize the fuel lines and he has to hold the throttle wide open to bring in enough air to overcome the excessively rich mixture in the intake and cylinder head....causing hard starting symptoms.

I don't like throwing parts at a problem (been there-done that...it gets expensive!!) but I would start by replacing the fuel injector on the OP's machine.

I had a similar problem on a vehicle of mine a few years ago. More random but still similar. I replaced all the injectors and never had the issue again.

 

No point throwing a injector in it until he tests the fuel system.

I have also seen machines with low compression show same issues.. far less common but does happen... easier to test it all and the tool is cheaper than a tech

 

The black carbon deposits on the plug is the big clue. Compression issues won't cause that. A bad oil ring will cause black oily deposits which would lead me to suspect the rings and it could have low compression....but the OP hasn't described that. The OP has described classic fuel system problems. There's nothing wrong with checking compression but nothing the OP has described says low compression.

The OP has a fuel system problem. The overwhelmingly most likely source of his problem for his machine (now that I have looked at his machine's diagrams) is a leaky injector. His symptoms are classic leaky injector issues. Most likely, the problems are intermittent but becoming worse with time as the injector weakens. Injectors have seals and moving parts inside. They are mounted where they get hot. Over time, they do fail. The OP has described raw fuel leaking into the intake. The ONLY way that would happen on this particular machine is through a leaking injector.

Fuel injection is typically far more reliable than carburetors for a variety of reasons but it can and does malfunction. In this case.....it is malfunctioning.

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Maybehonda did you can atv fixed?

 

Sorry everyone... My son got very sick last week. It was miserable. He's only 1 year old. He's on the mend now so I just came in from the garage. I opened up my compression tester to find that it didn't include the right adapter. I'll blame this on amazon's crappy product descriptions.

I will run to town tomorrow to see if I can get something to make it work. I think I can get the adapter in town.

I didn't read outdoor explore's post until now, but I am very thankful for his contribution. It really seems to line up with my issues. I will might just grab a new fuel inject in town. I know they aren't expensive.

Thanks again and I'll update tomorrow night.

 

oh and I did reset everything as far as the TPS etc.. no codes and everything seemed fine with I checked by jumping the plug with a wire.

 

Dealer didn't have fuel injector in stock. IT's 180$ so the parts guy told me to check it before I buy a new one.

He said when I turn the key, it should pressure up, but not spray.... if anything comes out at this point it means the fuel injector is leaking and stuck open.

He said when I turn the key it should spray. Spray should be a nice spray.


He also said if its not the fuel injector he said it could be the fuel regulator in the pump. BAsically if its faulty the fuel pump could be forcing too much fuel to the injector. If this is the case its a expensive fuel pump.

No where in town had the adaptor for the compression tester. I ordered one and should be in tomorrow.

I will pull the fuel inject and test it today.