[Slimm]

I am helping my boss get his 2008 Grizzly 700 FI running after sitting for an extended period. Cleaned all the electrical connections and flushed the fuel system with fresh fuel. The fuel pump turns on and flows fuel when you turn the key on. I hooked the fuel injector up to my fuel injector tester and it functions properly.
The problem I am having it the injector does not spray a priming burst when cranking to start. If you introduce some ether, brake cleaner, carb cleaner or gas into the throttle body the engine will start and run perfectly, smooth and make good power throughout the power band.
I have 39 yrs as a mechanic but have no experience with ATV's. Does this unit have a separate fuel pump relay for cranking or does the ECM manage the prime cycle to start?

 

[Ridgway81432]

Welcome from Colorado.
I can't give you an answer, but can get you to a f.s.m. that will have the answer.
Our member at 501parts.com has downloads available.

 

[89sandman]

When I come across this problem in a vehicle it is usually the efi driver in the ecm has corroded and started leaking. If you open up the ecm the corrosion and staining of the board is easy to see. Don't know if you can do it on a atv ecm.

 

[RedRocket]

The Yamaha ECU modules are sealed and should be sealed enough against weather.

@Slimm One of the first places to start is with your battery and associated electrical connections. I've learned from @reogem that the ECU must receive a minimum voltage signal before the injector will be pulsed. I experienced a non-start on my 2007 Grizzly 700 related to a physically bad battery even with the battery showing about 12.2 volts on a multimeter. Only when I brought my charged battery to a place to have it load tested did it reveal the battery was not properly holding amps. I replaced with a new, and charged battery, and had previously cleaned all of the battery terminals, chassis ground and it started right up.

If your boss' Grizzly 700 sat for an extended period of time, very unlikely the ECU went bad during that time.

 

[reogem]

X2 Get a factory service manual.
X2 Make sure the battery is in tip top condition and fully charged.
The 2008's via the display switched into Diagnostic mode. The FSM explains.
In Diag mode the function of most all EFI components can be tested. This can help pin point the issue.