380 MAG Mpi fuel issues

370Dancer said:
I just took a 4 month assignment in Pa., so I doubt I'll be getting much resolution on this for a while. I have not had a chance to go out and test the boat since blowing backwards on the fuel lines, and running at the dock.
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Where at in PA?

Doug
 
Quote:
Originally Posted by 370Dancer
I just took a 4 month assignment in Pa., so I doubt I'll be getting much resolution on this for a while. I have not had a chance to go out and test the boat since blowing backwards on the fuel lines, and running at the dock.

Where at in PA?


Downingtown, mostly, with some downtown trips. The tide's really low around here.....
 
370Dancer said:
Quote:
Originally Posted by 370Dancer
I just took a 4 month assignment in Pa., so I doubt I'll be getting much resolution on this for a while. I have not had a chance to go out and test the boat since blowing backwards on the fuel lines, and running at the dock.

Where at in PA?


Downingtown, mostly, with some downtown trips. The tide's really low around here.....
Click to expand...

I'm down near Center City. PM me if you have the itch to go for a ride on the Delaware.

Doug
 
PMPMPMPMPM

seriously, I'll see what this weekend brings. If I get my chores done, I may drive down and see how the baysiders live. Never been on the water up here.
 
370Dancer said:
PMPMPMPMPM

seriously, I'll see what this weekend brings. If I get my chores done, I may drive down and see how the baysiders live. Never been on the water up here.
Click to expand...

The Delaware River is a place to boat but it's nothing special, that's for sure. And it's definitely not like Florida boating!

Doug
 
370Dancer, time flies, it's now been +4 months :smt001 so are you
back in the sunshine state and if so have you spent any time pursuing our mutual fuelfeed problems?
 
If you have followed any of my other posts, you know that I am now in Huntsville, Alabama. Ahhh, the consultant's life.
Today, for the first time in a long time, I ran for 30 minutes or so, came back to a dock, and 1 hour later tried to leave. The Starboard engine ran for a minute (maybe, I wasn't looking until it didn't respond). Then it died, and proceeded to exhibit all the symptoms I have been talking about for a year. Fortunately, up here, it was cool enough (even though the engines were still around 160 degrees to mess a bit to see if I could find SOME repeatable thing to lead me(us) to a sane conclusion.

It still has the exact symptom of not enough fuel in the separator. I connected my primer bulb (the fuel line was DRY), turned the fuel cutoff to ON to bypass it, cracked the fuel water separator to allow air to escape, pumped up the system till fuel started overflowing the separator, waited 1/2 hour, ran the bilge blower for 5 minutes, and it started right up (I knew it would because I could feel the fuel flowing when priming).

SO, now I think that the fuel shutoff solenoids are getting hot from the engine room ambient temperature, and sticking closed until they cool down the next day. preventing fuel to pump during a hot start.
I can't say that I've ever had them bypassed full time, but may have.
I want to say that I'm getting closer, and I have to, or the Amiral won't go out any more unless we aren't going to stop anywhere. Any one else getting any closer?
 
Happened again yesterday. on the hook for 6 hours, running the genny about half the time, neither engine would start. Went to the engine room, primed the stbd engine, and all was well. Didn't put a bypass on the port, so had to do without until we got back to the dock. Started right up this morning like nothing ever happened.
Is it possible to create such a vapor lock as to vaporize 1/2 of the fuel in the separator, which is located at the bottom of the engine?!

If people have been putting secondary fuel pumps (at 400 each) inline, how can they help without breaking the line somewhere to allow the air to escape? I'd love to say that I have a seal or connection leak allowing air in, but the system is pressurized. Where's the air coming from? Vaporized fuel?

@#($*#$Y^&($#)$*%)*%$&^(%$#)$%!!! boats.
 
I reread the whole thread because I remember this one stumping me last year.

1. I read that you don't have the heat shields for the solenoids... still true? If so, install shields and test. You may also be able to try some heat tape wrap used on exhaust systems as a test.

2. If you're still looking towards sticking solenoids, can you bypass them totally for a test? Just run a line straight from the tank.

Still boggled and still thinking!

Doug
 
The fuel cutoff solenoids have heat shields? If they are supposed to, then the answer is no. This last time I left one of the solenoids in bypass and the other inline. Neither engine would start. The one that I had in bypass mode has the fuel primer bulb in the circuit, so I was able to pump that one up, and even at "temperature", it started right up, and ran us home. It was as hot Sunday as that boat has ever seen in Florida. The river water is 91 degrees, and feels cool when getting in. My white cockpit floor was 135 (of course the engines were under them).

I wonder if wrapping the fuel lines from the tank to the intake with heat shield tape would help?

One more thing that bugs me is that I can loosely tie this phenomena with the start of my engines steaming out of the side exhaust once the engines are up to temp a couple of years ago. My temps never fluctuate, though. 170 Port, and 175 starboard, through 2 sets of gauges.
 
That link above does not work, so I can't see what you're referring to.

I remember in the thread that someone said there were insulating shields on the solenoids? or filter assembly? and you replied that they were missing, possibly due to the fact that your boat had several engine replacements. That's what I was referring to.

Can the solenoids be bypassed completely to eliminate them? The funny thing is that when you've actuated the solenoids manually, the boat still hasn't started unless you prime it?

Still thinking....

Doug

Edit: Another thing I thought of - When you experience the problem, have you always had your generator running prior to the no start event? Is the generator fed off it's own fuel line? I still keep going back to a clogged vent line on your tank. Somehow the engine fuel lines are being bled down. Is there any vacuum break type valves on the fuel lines? Just thinking out loud again.
 
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Do you ever see any fuel residue near the filter assembly? Are the plugs tight on the non used ports of the filter assembly? Thinking of air leaks here or around any fuel fitting.

Have you tested fuel pressure when the engines are running? I also know a bad fuel pressure regulator will cause the lines to bleed down.

Doug
 
I agree with Doug, I would get a fuel preasure gauge on the rail (not easy to access on our motor but it can be done, if you don't know how to get to it let me know) and see what is happening exactly when this problem occurs, like I said I have a problem starting both of mine when the motor sits for a few hours (2-5) and the boat has been rocking at anchor a little (when it is calm water doesn't seem to happen), but I just use the WOT trick and it works everytime for me (I am not sure you are experiencing the same problem, but sounds similar). I have had an on going stalling issue at idle that was misdiagnosed by 2 different mechanics, turned out to be low fuel preasure on the rail which I finally diagosed and fixed by replacing the entire Cool Fuel pump, regulator, and cooler. I am curious to see if this fixes my other starting issue when it is warm but haven't had the scenario yet that would bring it on.
 
douglee25 said:
Do you ever see any fuel residue near the filter assembly? Are the plugs tight on the non used ports of the filter assembly? Thinking of air leaks here or around any fuel fitting.

Have you tested fuel pressure when the engines are running? I also know a bad fuel pressure regulator will cause the lines to bleed down.

Doug
Click to expand...

I have never seen, nor smelled any gas in the engine room unless I caused it (cracking the fuel water sep).

OK, let's go a little further with vapor lock. Is it possible to vaporize the fuel from the intake to an inch down the fuel water sep? That seems like a lot.
Pressure Regulator? Would it be possible for the engines to run like a champ at idle or plane if this were bad?
 
douglee25 said:
That link above does not work, so I can't see what you're referring to.

I remember in the thread that someone said there were insulating shields on the solenoids? or filter assembly? and you replied that they were missing, possibly due to the fact that your boat had several engine replacements. That's what I was referring to.

That was the link I posted again. it is covers for the filter assemblies

Can the solenoids be bypassed completely to eliminate them? The funny thing is that when you've actuated the solenoids manually, the boat still hasn't started unless you prime it?

I have not actuated them manually. I have supposedly bypassed them by manually turning the knob to the bypass position. This allows fuel to flow freely whether the ignition is on or off. I in fact have to turn them to this position to pump up the fuel line.

I like the bleed down issue. I have tried going from off to the start position (fuel pump runs for 2 seconds) about 50 times without starting, hoping that would prime the system. No avail.
When cold, they start right up.


Still thinking....

Doug

Edit: Another thing I thought of - When you experience the problem, have you always had your generator running prior to the no start event?

Yes

Is the generator fed off it's own fuel line?

Yes from the starboard tank


I still keep going back to a clogged vent line on your tank.

If they were clogged, then the engine wouldn't run once I primed it back up.

Somehow the engine fuel lines are being bled down. Is there any vacuum break type valves on the fuel lines? Just thinking out loud again.
Click to expand...
See interleaved answers and thoughts with yours above - thanks for thinking. When we figure this out, let's sell it back to Mercruiser.!
 
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I read the whole thread and I am liking Doug's tank vent theory.

If the vent were clogged, when you run the genny, it's fuel pump would be drawing from the unvented tank and probably suck the fuel right out of the fuel lines to the mains.

Try this experiment. Take a run sufficient to duplicate the problem and head back to your dock. Open the fuel fill cap while the mains are still running to provide a vent. Shut the mains down and immediately turn off the fuel solenoids to isolate the tank system from the engines. Close her up and run the genny for a "typical" amount of time. When you think she's "ready", open up the fuel solenoids (bypass mode to eliminate any potential issues with the solenoids) and see if the engines will start.
 
370Dancer said:
I have never seen, nor smelled any gas in the engine room unless I caused it (cracking the fuel water sep).

OK, let's go a little further with vapor lock. Is it possible to vaporize the fuel from the intake to an inch down the fuel water sep? That seems like a lot.
Pressure Regulator? Would it be possible for the engines to run like a champ at idle or plane if this were bad?
Click to expand...

I have seen bad regulators that exhibit similar symptons as yours, although typically the engine always has a hard start after sitting. A bad regulator can cause bleed down and then it takes a very very long time in order for the fuel pump to reprime the system. I would definitely check your fuel pressure though.

Doug
 
skibum said:
I read the whole thread and I am liking Doug's tank vent theory.

If the vent were clogged, when you run the genny, it's fuel pump would be drawing from the unvented tank and probably suck the fuel right out of the fuel lines to the mains.

Try this experiment. Take a run sufficient to duplicate the problem and head back to your dock. Open the fuel fill cap while the mains are still running to provide a vent. Shut the mains down and immediately turn off the fuel solenoids to isolate the tank system from the engines. Close her up and run the genny for a "typical" amount of time. When you think she's "ready", open up the fuel solenoids (bypass mode to eliminate any potential issues with the solenoids) and see if the engines will start.
Click to expand...

I understand what you are saying, but here's a couple of reasons I don't think that's it.
1. What about the Port side? Has the same issue, so it has to be something common between them, like ambient temperature, or time, fuel source (long ruled out because of multiple fill ups).
2. A clogged vent line would be a permanent problem, not one just associated with heat. Plus, once I have "reprimed" the engine, it runs for hours with no issue.
 
Expansion/contraction of the tank with a clogged or partially clogged vent line could still exhibit symptoms like you're experiencing.

Doug
 
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