380 MAG Mpi fuel issues

Could the gas lines be collapsing due to the E-10 softening the fuel lines? The heat adds to the softening and collapsing?
 
370 Dancer, You're right about the ECM on Merc's simple 2 channel EFI motors not allowing a real WOT start. But, my dad has the older gen 502 EFI with a VST tank. It has vapor lock problems, but will fire if the throttle is held steady, wide open. It cranks for maybe about 5-10 seconds, but will catch without backfire.

DC380 might be on to something as well.

You mentioned having that miss while running... I'd be curious to see what a fuel pressure gauge would show during that.
 
Worth checking the fuel vent as Doug suggests. There's little reason that fuel would be drawn back into the tank. I don't think that the solenoid valves would permit fuel to pass in either direction with the valve not powered and set to the "off" position. But I never checked them or their specs so they might not resist reverse flow.

I see where you said the fuel filters were only half full when you checked them. That there is no fuel in the system when you attempt to start the engines rather makes sense. That the formerly empty system is full when you attempt a cold start the next day does not make sense.

The vapor point pressure of fuel these days is pretty awful, but I doubt the pressure is high enough to force the solenoid valve open to drain the system of liquid fuel and again low enough when the engine room cools to rapidly draw the fuel back into the system for a cold start. Normally takes the electric fuel pump quite a long time to fill the fuel filter when the system is dry.

Pretty sure I remember reading in my FSM, the ECU for MEFI-1, -2, and -3 is programmed to flow fuel at start between idle position and about 1/2 throttle. At about 1/2 throttle, fuel is cut-off and remains cut-off until near WOT, where fuel flow is again resumed.
 
Not sure if this helps, but the WOT trick worked for me this weekend. My mechanic suggested that as a way to reset the ECM. Apparently, it also shuts off the injectors and the pump to allow a start in a flooded situation (my problem). Prior to that the mechanic suggested checking the fuel pump and (surprise) the coil. He said these two are weak points on the 380 7.4 MPI engines that are in our late 90's 370s. Both seemed to be fine though.

Gene
 
Short story: run the engines for 30 minutes or more, cruise or idle, doesn't matter. Shut it down. Anywhere from 30 minutes to 4 hours later, the engine will not start, or starts and dies right away. This is an intermittent issue, and moves from port to starboard, and sometimes both (as in get towed in). Without fail, the engines can always be started the next morning as if nothing ever happened. Been going on now for 8 months.

Clue: spin off the fuel water separator, and the fuel level is down 1/2" or more. Now we know why they won't start.

It seems to be related to engines coming to temperature, or perhaps time. Last weekend we ran 120 miles without incident, but no temporary stopping and then going, except when we broke from the raft up, idled for 5 minutes, anchored, and then 4 hours later pulled the hook, and both fired right up. AUUUGGGHHHH.

Casual mechanic conversations think it might be vapor lock, but both engines, moving randomly from port to starboard? A Rinda showed no codes thrown on either engine.

I have watched both fuel vents when filling up for blockage. Last week, the port vent was clear, and the Starboard acted clogged. I cleared the Starboard vent thinking I had solved my problem. Nope, yesterday idled across the bay to take a small kid fishing, and cut both engines to drift. Port wouldn't start. Idled 1/2 mile to another spot, and cut the starboard engine (dumb). Now neither start. 2 hours later, the Starboard finally started. Port never did. Made it back, and this morning, both engines start like nothing ever happened. Double AAUUGGHHH.

The fuel is fresh, the tanks have been treated with StarTron (double dose) and I am at my wits end. So, what's causing my fuel level in the separators to be low? Why does it eventually get better over 8+ hours?

I know this is a little late. I had the same problem with my engine, more so with the starboard engine. My dealer install some heat shields right above the fuel cooler (fuel,water separator filter). The problem is no longer there. I live in Covington,La, across the lake from New Orleans.
 
I have the same problem on my 370. Really frustrating. I am to the point that i know it is a fuel pressure issue. I took a fuel pressure gauge with me last weekend. When the starboard engine would not start i hooked to the orfice and no pressure. I already had the solenoids bypassed to the on position. Has anyone ever figured out what the problem is yet?
 
The StBd engine has now graduated to not starting, no matter how long I wait. Today, I spun off the fuel water sep, filled it with fuel, and put it back on. Started, idled for about 30-45 seconds, and died. No more starting. I think I have a restriction in the fuel line coming from the tank now, or the fuel pump is making noise, but not pumping. I am thinking about swapping the gen and engine pickup lines to see if the gen dies and the engine runs. Then, I'll know if it's in the line, and pickup tube. If not, then it's probably the high pressure pump has failed. And, the Port engine pump is intermittently failing....?
ARRGH.
First, though, I'll just replace the fairly new water seps again, and see if that improves life.
 
I see where you said the fuel filters were only half full when you checked them. That there is no fuel in the system when you attempt to start the engines rather makes sense. That the formerly empty system is full when you attempt a cold start the next day does not make sense.

Couldn't agree more. This has been the wierdness. To be clear, I only checked the Stbd engine sep as that one is easily accessible from the center hatch. I never checked the level cold to see if it "filled back up" until today, where it was still low, but now the engine never stays running, so I'll never know for sure. I suspect that previously, it got filled up "enough" to run and catch up when the high pressure pump was working, or there was not a complete restriction in the tank to sep fuel line. Speaking of which......

One thing I haven't mentioned previously, is that I have Navman fuel flow senders between the tank and the fuel/water sep. I'm starting to wonder if the Ethanol might be attacking the spinner blades in the senders, or something gummed them up. Pulling tomorrow for an inspection.
 
Fuel flow senders? Do you have filters between the tank and the sensors? If so, how many filters are in line for each engine?
 
Just a suggestion but have you checked your fuel coolers for blockages ? Not sure of age of your engines but there was a corrosion issue with some , think they were called KOOL FUEL 3 ? might be worth a look - I think they were made of alumininium & are prone to blocking causing the symptoms you describe, hope this helps :huh:
 
Just a suggestion but have you checked your fuel coolers for blockages ? Not sure of age of your engines but there was a corrosion issue with some , think they were called KOOL FUEL 3 ? might be worth a look - I think they were made of alumininium & are prone to blocking causing the symptoms you describe, hope this helps :huh:

Not on a 1998.
 
Where you spliced in your fuel flow sensors, is there any chance that you have a leak which causes air to enter the line?

Doug
 
Thanks for continuing to hang onto this saga.
Here's a new thing....

Stbd engine graduated to not starting at all. I disconnected the fuel line from the cut off solenoid to the flow sensor, and guess what? Dry as a bone. So, now, it's the cutoff not ever opening, or blocked line. Did some testing of voltage presence at the solenoid, which is not really possible, because voltage is not present unless the engine is running. Confirmed this on the port engine. So, back to putting the solenoid in bypass manual mode (ON). Multi primes with the 2 second pump prior to start led to no avail. So, I went and bought an outboard fuel line kit with a primer bulb. Tried to prime it manually. That did nothing. I decided to try one more thing before going between the solenoid and the tank. I turned the primer hose around and blew air into the tank. If I got nothing, then the solenoid was "stuck closed", or the line was completely blocked. If I could hear air bubbles, then the line was clear, and the solenoid passing. Well, it took about 20 pumps, and suddenly I could hear bubbling in the tank. Not sure where the obstruction was, but I'm guessing at the tank pickup. turned the primer hose back around, and started filling the fuel lines, and sep filter with very little effort. turned the solenoid back to the "OFF" position to rule it out. Started the engine right up, and ran it at various speeds for about 15 minutes. Yippe, and, damnit.

so...... maybe I've been getting build up of crud in the tank from the Ethenol scrubbing everything. Maybe the Port engine is just behind the Stbd in failure by a bit. Maybe it's not temp related at all. Maybe I just checked into the looney farm.
Next course is to put Stbd back together, and move my hose clearing tool to the port side and do the same treatment. Then, out to do a real test.
 
Frank, to answer your question about a filter before the flow sender, I broke the rule and did not put a filter between the tank and the senders. I figured the worst that would happen is that the paddles would quit, and I'd see that right away on the display.
My circuit is tank pickup to cutoff solenoid to flow sender to fuel water separator to cool fuel to rail.
 
Interesting. Would never have guessed that. The pickups on old boats would foul, actually the antisyphon valve at the top of the tank. Never heard of one like yours. Well, always good to learn something new. Thank you for the update!

Best regards,
Frank
 
370Dancer, pls let us know what's going on regarding your fuel problems.
I'm very intrested as I'm also experiencing very similar problems that are driving me nuts.
Best of luck and regards,
/Robert
 
370Dancer, like you I connected a primer bulb to the fuel supply line and in my case I could always get the engine running steady by pumping the bulb, sometimes every 5 minutes and sometimes once a day. To save my self the trouble of removing my home made cockpit table to be able to stretch down in the engine romm to pump that bulb I installed an electric low pressure suction pump near the fuel tank in the engine room, It's curing the symptoms alright and the engine has since performed flawlessly, the real problem behind this is yet to be figured out. I'm sorta counting on you for that to happen :smt001.

/Robert
 

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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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