Gaurdian mode when engine is warmed up

[skyman2112]

View attachment coldstartS.mp4
View attachment HotStartS.mp4
View attachment Backflush.mp4
Hey group, my 2011 Crownline 21SS with a 6.2L 377 MAG w/cats, Bravo 1, is slow to build water pressure when engine is warmed up only. Takes over 15 seconds to exceed 1psi so it sets off the alarm and goes into gaurdian mode temporarily.
Seems like theres not enough back pressure when the engine is warmed up (thermostat open) and it starts at 0.2 psi but slowly rises to over 1 psi, which is enough to reset the alarm and continue using my boat, but super annoying waiting for the alarm to reset every time i start it when its warmed up.
When i start it cold i get 1.4-3psi (thermostat closed) immediately. See the attached videos for hot and cold starts in the water, as well as me backflushing the line that feeds the pump while the boat is on the trailer.
Already replaced everything twice, dont suggest anything simple please such as new pump housing and impeller, pressure sensor, poppet valve spring, thermostat, or inlet hose restriction, There is plenty of water flow it never runs hot.
Its been 4 years of the same problem gonna try this forum again.. Had to buy my own Rinda scan tool this boat is so touchy.

 

[muc]

Might be able to help. if you can share your serial number.
A couple of questions.
What is your water pressure and RPM at W.O.T.
What is the engine RPM when you start cold and hot?

 

[skyman2112]

Might be able to help. if you can share your serial number.
A couple of questions.
What is your water pressure and RPM at W.O.T.
What is the engine RPM when you start cold and hot?

Hello Muc, my engine S/N is 1A645849. My water pressure from about 3000-5200 is unaffected by rpm and fluctuates on the Rinda scan tool from 13-15 psi. The rpm for cold and hot starting is the same around 700rpm i think, cant remember the exact number but its non adjustable and within spec as i recall.

 

[muc]

Have you seen Bulletin No. 2015-01R1
PCM 09 Calibration Update—Optional

 

[skyman2112]

yeah i had my ECM updated last year but not to change the horn sounding. I dont have a check engine light so not sure ithis bulletin applies. Does it prevent gaurdian mode from kicking in? I didnt see anything about that
I found a temporary fix, i just rev the engine during warm startups, it gets the pressure up faster and when i go back to idle it stays up.
The backflush video seems to show plenty of water flow through the lines but it sure acts like some kind of restriction going on. If i could just fool that water pressure sensor reading by 1psi i would never have to worry about it

 

[skyman2112]

someone asked me if i have the right exhaust elbow gasket and there is 3 different ones to choose from. Well i guess if the factory put the wrong one in it could cause me to have low back pressure when the thermostat is open. That would make it hard to build pressure when warmed up.

 

[achris]

someone asked me if i have the right exhaust elbow gasket and there is 3 different ones to choose from. Well i guess if the factory put the wrong one in it could cause me to have low back pressure when the thermostat is open. That would make it hard to build pressure when warmed up.

Cat manifolds only have 2 option, raw water or closed cooling... If you have closed cooling and you put the raw water cooling gaskets in, you'll never fill the heat exchanger. If you have raw water cooling and you put the closed gaskets in, the engine would never be able to expel water, and you'd overheat within minutes.

Chris........

 

[skyman2112]

well so much for that idea. What else could make it slow to build water pressure when the engine is warmed up?
One of the marinas that viewed my video told me the alarm is going off too fast, it should take longer than 15 seconds to set off the low water pressure alarm. I reset the codes as suggested but keep getting the same code for low water pressure. Strange.

 

[Fun Times]

Already replaced everything twice, dont suggest anything simple please such as new pump housing and impeller, pressure sensor, poppet valve spring, thermostat, or inlet hose restriction.

Since it wasn't mention it would leave me to wonder if you've also inspected the check ball valves located down at the exhaust as they may have an effect to the back_flow theory...Item numbers 23 - 26,

Exhaust Manifold and Elbow

Exhaust Manifold and Elbow

www.mercruiserparts.com

Can't for sure tell by the serial number if your engine is Closed Cooling System, With Poppet Valve Or Standard Cooling With Poppet Valve.

350 MAG MPI ALPHA/BRAVO EC - 1A623185 & Up

350 MAG MPI ALPHA/BRAVO EC - 1A623185 & Up

www.mercruiserparts.com

Upon engine start-up, do you get an RPM flare-up that goes right up to around 1300 RPM then drops at a medium rate to idle RPM of what the actual engine temperature is at the moment....The flare-up is deigned to get everything pumping, flowing, charging, etc., even your newer cars/trucks have a RPM flare-up to do the same.

 

[skyman2112]

Since it wasn't mention it would leave me to wonder if you've also inspected the check ball valves located down at the exhaust as they may have an effect to the back_flow theory...Item numbers 23 - 26,

Exhaust Manifold and Elbow

Exhaust Manifold and Elbow

www.mercruiserparts.com

Can't for sure tell by the serial number if your engine is Closed Cooling System, With Poppet Valve Or Standard Cooling With Poppet Valve.

350 MAG MPI ALPHA/BRAVO EC - 1A623185 & Up

350 MAG MPI ALPHA/BRAVO EC - 1A623185 & Up

www.mercruiserparts.com

Upon engine start-up, do you get an RPM flare-up that goes right up to around 1300 RPM then drops at a medium rate to idle RPM of what the actual engine temperature is at the moment....The flare-up is deigned to get everything pumping, flowing, charging, etc., even your newer cars/trucks have a RPM flare-up to do the same.

thats a very good point. Ill have to take a look at the check valves . I think its flares up on start up. I do a manual flare up of sorts to keep the alarm from going off. Its the only thing i found to keep the alarm off so far.

 

[skyman2112]

Ended up being a restriction at the cool fuel fitting, tiny piece of impeller wedged into the opening cause its only the size of your finger