Arctic Cat Fuel Pressure / Engine Operation Issue

[DonB]

Fuel Injected, 2015 AC XR550XT ATV (renamed the Alterra from 2016 on).  1300 miles.

I had written an earlier post concerning part of the problem, but a new one has arisen...

2 PROBLEMS:

1. Engine sputters & fails when throttle applied (even from idle and while in Neutral), and, now...
2. Fuel pressure reads @ "0" despite clear line and operational fuel pump.

• Unit originally suffered fire in muffler - presumably due to engine driveability problem & resulting unburnt fuel... fuel pump ultimately died when starting repairs.  
  • Installed a new fuel pump as dealer advised it was the problem.
  • Have now been chasing a proper fix for several months, as, while it generally starts fine, the engine will not take any sort of throttle - even from idle.
    • Instead, it immediately starts to miss, backfire & die.  
  • From the beginning, the dealer claimed that a new genuine AC fuel pump was all that was needed.
    • However, the replacement, non-AC fuel pump runs at 42 psi & works fine).
• NEW ISSUE:  Unexpectedly, the first replacement pump stopped registering any fuel pressure (per in-line pressure gauge).
  • This despite confirming both: (a) pump clearly pumping & (b) fuel line - all the way to the fuel injector - clear & delivering fuel.
  • Tried a 2nd replacement pump which, initially, registered pressure (engine performance issues remained).
  • But, when I tried to start it today, no fuel pressure again (and, therefore, apparently no fuel to injector).
    • Again confirmed pump working and fuel line to injector clear & delivering fuel.
    • Engine continues to start easily with starter fluid but, of course, stalls once fluid has burned off.

While cleaning/replacing the fuel injector seems the next logical step, it strikes me that, were the injector plugged, I should still be seeing a psi reading on the installed, in-line gauge I've been using (not zero)!

Any ideas before I surrender this to the dealer and a B-I-G bill?

thanx, db

[Mech]

Are you following the recommended diagnosis procedure as laid out in the service manual ?

Have you checked for trouble codes ?

Do you know where the fuel pressure regulator is and have you checked that or tried disabling it ?

Yes, a blocked injector won't cause low pressure, but a stuck open one might. Zero pressure though sounds more like pump or regulator.

A vacuum leak into the inlet could also give a lot of those symptoms), and so could incorrectly adjusted valve clearances. or an ignition problem(not zero pressure though.

You could check for the vacuum leak with the engine start.. with the engine idling spray it anywhere there could be air getting in, manifold, hoses, charcoal canister.

The suspect ignition you might spot easily by attaching a timing light and watching it as you rev the motor.

Valves.. It's in the book.

 

[Gwbarm]

Every time I have had these kind of problems I just replace the regulator first and if no go then the injector. I have had injectors so clogged that I could not get them clean. 

[Cj Winds]

Sounds like you have no fuel pressure and engine runs fine on starting fluid. Can you remove the fuel pump assembly and place the the inlet sock in a tub of fuel and watch if the pump works and if there are leaks anywhere?