Unknown Fault code on a 496HO
 

During acceleration coming onto plane my 496HO went into Guardian mode and was cutting away power without any obvious reason. After reset (ignition off/on) everything was fine again. As I read out the PCM Data there was one faultcode in the history that I couldnt find in the Merc Book: FUEL PUMP RLY CK
Apparently something to do with the fuel pump relay circuit.....but what?
That situation happened twice in this season and I would like to get a fix on it over the winter.
Any experiences out there ? Thanx for your ideas!

Re: Unknown Fault code on a 496HO
 

I had a similar problem a few weeks ago. Were you get two short beeps per minute? When I run a scan I show that the Fuelpump Rly CK was triggered once. That was about 10 run hours ago and I hasn't occured again. I'm not sure what it is. May be Dave_N will chime in soon. He knows all these codes pretty well.

Re: Unknown Fault code on a 496HO
 

Yes, Dave M, forgot to mention I had beeps from the audio warning when the problem occured.....

Re: Unknown Fault code on a 496HO
 

fuel pump relay is correct if you take the cover off the top of the mtr the relay is on the port side top

Re: Unknown Fault code on a 496HO
 

First of all, are you sure that the drive lube resivoir is full?

That fault code could mean there is a bad fuel pump relay or open circuit somewhere in the fuel pump relay circuits. Checking the freezframe memory, Does the time of the Fault coincide with the time you heard the alarm?
What is the frequency count?

What scan tool are you using?

Dave

Re: Unknown Fault code on a 496HO
 

Hi Dave,
drive lube is not the problem, always filled to the mark. My scan tool is the original merc scanner by Rinda, the little blue one.
I had reset the fault history on the tools memory before I went out last weekend. Normally only the common 4 or 5 codes appear as "active" in the data (all that Pitot and fuel level info that comes up when the smartcraft monitor is not installed).
So I am sure that the entry in the history list was new and was caused by the described situation. As mentioned, after an reset the engine functioned normal again, the code FUEL PUMP RLY CK being no longer active, BUT new in the history, along with the code GUARDIAN....
Maybe I should change the relay.........I was just taking off to race another boat as the malfunction occurred...Murphys Law, embarrassing! :-)

Re: Unknown Fault code on a 496HO
 

I have had my 496 go into Guardian mode also when the engine apparently revs up too fast. I never have the problem when I accelerate more gradually and "sneak up" on full speed. My Rinda scan tool only shows Guardian mode has been triggered and it also shows I don't have 100% power available until taking the engine back down to idle. Must be some strange programming "protection" in the ECU that can be frustrating. I have heard that Factory I racers have encountered this issue too.

Re: Unknown Fault code on a 496HO
 

...maybe injector syncho's??