380 MAG Mpi fuel issues

Gotcha. I was thinking you had a crossover between the tanks. Just trying to come up with something out of the box since you've already done the "standard" stuff.

Time to get serious with this. Tell your mechanic that its running fine now, and as a thank you for all of his hard work you would like to take him and his family out for a dinner cruise. Run her for an hour and shut her down somewhere on the hook. Do this preferrably after dark (so you don't get much help) and in a remote area if possible. Be sure to have loaded up the boat with spare parts and tools first.
 
i haven't read all 7 pages of this thread. but if you have the cool fuel module under the engine mount next to the oil pan, has any of you bought the kit from mercruiser that is a vapor lock kit. which is a low pressure fuel pump that hookes up before your spin on fuel filter. any boat that has this problem, the kit fixed the boat not starting in hot weather 30 min. to a few hours of sitting after running. if anyone needs the part number just pm me.
 
Hi guys! Time to resurrect this thread. Yes, it's a year and a half later. I'm a little smarter, but just a little.
I convinced myself that the fuel solenoids were sticking due to being out of heat range spec since new (they are good to 170 degrees, and my engine room in the summer is 180) I coughed up 150 or so each, and replaced them. Anyone want to buy some perferctly good used solenloids?
I finally got a hold of and read the tech service bulletin from Merc (Boat fix dot com/merc/Bullet/99/99_07.pdf) that clearly states a case for vapor lock, and recommends the low pressure pumps between the tank and spin on fuel filter to mask the problem as there is no particular cure. I took the advice and added the pumps. So far, that has eliminated the no start when hot issue.
As I was approaching this issue, another has developed, which is probably related, but let's see.

The Port engine has always surged up and down a hundred or so rpm when idling cold since 2003. It would always calm down after a few minutes, and no one had a particular answer for it, so I let it go. This year (2011) this issue has worsened to this:
Start and idle, it hunts a couple hundred rpm. Put under load and run between 1000 and 1900 rpm and it runs ok. At 2000, and up, it started to swing wildly, like 500 - 800 rpm. Back it down to 2000 or under, and all is fine again. If I try to come up on plane, it would bog down almost linear down to 1000 rpm or less, and then backfire.
It was time anyway, so I changed out the dist cap (contacts were pretty corroded), rotor, plugs, wires. This made the hunting go away or at least not be anywhere near what I just described. However, if I go past 2000 rpm, the engine bogs down, almost linear.
So, I take the advice of the 2nd post of this thread 3 years later and put a fuel pressure gauge on the rail. Pressure is good at pre-start prime around 38lbs. After start, it drops to 30-32, and holds steady as a rock. No surging. put it under load, and run up to 1800. steady as a rock. Right past 2000 rpm, the pressure drops to 20lbs and stays there. The engine bogs down, and finally pops, so I bring it back to under 2000, and the pressure returns to 30lbs. got back to the dock, shut down, and the fuel pressure held long enough for me to get bored and go home. Came back the next day, and it still had 5-7 lbs on it. Reading through FSM 23, all troublehooting indications point to the fuel pressure regulator, or the vacumn line.
Before I pull the Cool Fuel II assembly, does this symptom point to something else I should be checking?
 
just a guess...what about a bad fuel pump?...when the demand for fuel is low (below 2000 rpms) the pump is able to keep the pressure at a fairly normal reading...as the demand for fuel rises (above 2000 rpms) the pump cannot supply enough fuel to feed the engine and maintain the proper fuel pressure....or a partially clogged fuel filter or a restriction in the fuel supply line can cause the same symptoms...i have not read the rest of the post so i apologize if this has already been suggested and explored...
 
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Sounds like a fuel pump or regulator to me.

Does this regulator have a vacuum reference signal? If so, unplug that and fuel pressure should rise. If not, you're regulator is bad. Also try the residual fuel pressure test. After the engine is running, turn off the engine with the gauge still attach. Observe the gauge and see if the pressure bleeds down. There may be a spec out there which to compare it to. What is the fuel pressure spec at idle? How does your compare? It seems low.

Doug
 
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it sounds like the boost pump is not pumping. I would check the fuel pressure between the vapor fuel pump and the spin on fuel filter. I have seen this problem and that pump wasnt pumping. It will give you the same symptoms. You can even pull off the fuel line going to the fuel filter and have someone turn your ignition on and see if the pump is running and pushing fuel out of the line( make sure you have a bucket to catch the fuel). Check also the fuel lines going from the fuel filter under the engine to the fuel module. if the one is kinked it will do the same also. Do you have a inline fuel filter before the vapor pump? if so pull it out and blow thru it and make sure its not clogged. (you can even put a vaccum gauge before the fuel pumps and see how much its pulling. to much will give you a restriction lower fuel pressure at higher speeds)
 
it sounds like the boost pump is not pumping. I would check the fuel pressure between the vapor fuel pump and the spin on fuel filter. I have seen this problem and that pump wasnt pumping. It will give you the same symptoms. You can even pull off the fuel line going to the fuel filter and have someone turn your ignition on and see if the pump is running and pushing fuel out of the line( make sure you have a bucket to catch the fuel). Check also the fuel lines going from the fuel filter under the engine to the fuel module. if the one is kinked it will do the same also. Do you have a inline fuel filter before the vapor pump? if so pull it out and blow thru it and make sure its not clogged. (you can even put a vaccum gauge before the fuel pumps and see how much its pulling. to much will give you a restriction lower fuel pressure at higher speeds)
I am having trouble following your terminology:
Boost Pump?
Vapor Fuel Pump?
Fuel module?
Vapor Pump?
The application is a 454 Magnum Multi Port fuel injection system with a Cool Fuel II pump. I think you are giving carb engine advice.
 
Sorry. If you have the fuel pump that is before the fuel filter that helps out with the vapor lock condition some people call it the boost pump vapor fuel pump or vapor pump. Fuel module is the cool fuel II. You dont have any of those pumps on a carb engine.
 
Ran the boat a couple of weeks ago (between freezing fronts) and pulled the vacum line to the fuel pressure regulator under load. No change, so that points to the regulator.
While pulling the cool fuel assembly, I discoverd that whomever put it on the third time (3 sets of Horizons before Sea Ray redesigned the exhaust system with water lifts), had the fuel feed and return lines to the spin on separator kinked. The feed line became soft right at the fitting from hose to metal, right where it was kinked. So, I ordered a new feed line too (70 bucks).
Installed them both, and waited for another reasonable day to run it out. That was yesterday. Upon starting, the engine no longer surges at all, and sounds as good as it ever has. Ran out and came right up on plane.

So it's solved. Not sure if it was the kink in the fuel line, the regulator, or both, but the fix was both. I hope I save someone else 4 years of chasing gremlins.

https://picasaweb.google.com/111218...&authkey=Gv1sRgCJ66_KGYjevUUg&feat=directlink
 
Hi from Sweden,
my problem finally proved itself to be a fuelpump-failure, the performance of the pump just gradually detoriated to level zero. After installing a brand new pump it all worked perfectly again and I could remove my feeder pump and reinstall the Garmin GF10 fuelflowsensor again. Imagine the pump slowly becoming less and less effective until zero suction/pressure effect was a fact.
I've always been told that a fuelpump that sounds also works but that is not always the case, a very long and tough lesson learnt.. :D

Just about 7 weeks before the boating season starts again in the Stockholm-area!
 

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