5.0 mpi shuts off while cruising! (((Update))) Still in need of help with fuel pressure specs and what to try next. Thank you!

[RichRab]

All Dodge. I did not take boat out but it looks like the vent under gas cap comes out or unscrews? Any experience with that? Thank you. RR

 

[alldodge]

Don't really know what your looking at (no pics) but open the gas cap and blow air into the vent line and see if it comes out the gas fill

 

[RichRab]

I did not take a picture and I am away from boat but when the fuel cap is off there is the big hole where the fuel nozzle goes and the vent hose has a black cap of some sort of end on it that somehow comes off. What do you mean by mud dobbers? If I can't get vent off do you think I can spray carb cleaner into vent? Thank you. Rich R.

 

[UncleWillie]

Mud Dobbers are a species of Wasps that build the nests out of Mud in small spaces.
If they have plugged up the vent line and you spray anything in there, you will flush the mud into the gas tank.
Take the vent apart and inspect the fitting.

If the vent is plugged the fuel tank will form a vacuum as the fuel is used.
When the engine stalls; if the tank is vacuum locked, you will hear a big inrush of air as you Open the fill cap.
The Fill Cap should Open quietly if the tank is vented properly.

 

[alldodge]

I did not take a picture and I am away from boat but when the fuel cap is off there is the big hole where the fuel nozzle goes and the vent hose has a black cap of some sort of end on it that somehow comes off. What do you mean by mud dobbers? If I can't get vent off do you think I can spray carb cleaner into vent? Thank you. Rich R.

You probably had a gas fill and vent all in one. The vent is under the gas fill and is a small square hole. Just run it and if it dies listen for air going in. If you have what I think you have for a gas fill and vent, then mud dobbers are not the issue

 

[RichRab]

Had the boat to dealer and all he could find is maybe a rusty ground. Will pick up boat and hope for the best. I knew the vent could not be the problem- that could be fixed for free! Thank you. RR

 

[RichRab]

Picked up boat and about 50 minutes into return trip-- you got it. Shut off and started right up.

 

[UncleWillie]

... I knew the vent could not be the problem- that could be fixed for free! Thank you. RR

We still have not eliminated a vent problem.
When it died, if you opened the fill cap, did it suck air?

Better yet, after 40 minutes of running, slow to an idle, Open the Fill Cap for a second and close it back up?
Does it still die near the 50 minute mark or closer to the 90 minute mark?

 

[RichRab]

I took off cap a few times around 40 minute time and keeping in mind we are in the water with boat running we did not hear any sound at cap and then the boat shuts off around 50 minutes and restarts right up. Then in 50 minutes same thing. Thank you. RR

 

[alldodge]

I'm thinking a bad connection and heat is the issue. Figure something has a weak connection and after 50 minutes the heat has built up to break. Doesn't take very long to cool and it can restart. The ECM is bolted to metal and heat sink. Have you removed the plugs off the ECM and checked the connections, also check bolts holding it.

 

[RichRab]

I will check again and maybe try to open hatch after a while to see what happens. Thank you. RR

 

[skippy2235]

Coil getting hot?

 

[UncleWillie]

I took off cap a few times around 40 minute time and keeping in mind we are in the water with boat running we did not hear any sound at cap and then the boat shuts off around 50 minutes and restarts right up. Then in 50 minutes same thing. Thank you. RR

Very Good! We can safely eliminate the Vent being the issue.
Now we know one thing that it isn't.

If it were something getting Hot after 50 minutes; It would not cool down to its initial temperature in the 30 seconds it takes to restart the engine.
I would expect a hot part to fail again in well under 10 minutes on subsequent cycles.
Something electrical, or mechanical, is getting a full reset when the engine stops.

Do you have anything with a timer on board?
A long forgotten, defective, mis-wired, Live Well Timer, Auto Bilge Pump, etc., that is shorting out every 50 minutes?

Try stopping the engine for a few seconds at the 40 minute mark and see if it still stalls at the 50 minute mark, or it gets reset and runs another 50 minutes before stalling.

This is a Good one! :joyous:

 

[RichRab]

I have checked everything that I can think of. A boat mechanic said he is sure that the problem is the circuit breaker under the spark arrestor and suggested bypassing it to see what happens. Boat will be in water in about a month and I will update. Thank you. RR

 

[alldodge]

If the 50 amp breaker was it then everything would not work and it should not reset automatically, but hey I'm listening all the same

 

[RichRab]

Will let you know. Thanks