"James Sweet" wrote in message
news:9o75h.57$tb2.36@trnddc08...
kyle wrote:
fuel pump has been replaced .. it gushes fuel out the line when removed
from the carb. intake and i'm turning the key over...

how could it be a gas vent thing? where is the vent, anyways.. is it
between the gas tank and the fuel filter?

don't know if i mentioned but it is an I/O.

Del Cecchi wrote:

"kyle" wrote in message
egroups.com...

hi all,

i am at my wits end over this 2003 bayliner 5.0L merc.

here is the symptom:

give it some warmpup throttle action, turn key on, she cranks
beautifully. no smoke. no roughness.

10-20 seconds later, she instantly cuts off.

so.. youre thinking.. it must be a fuel thing, right?

i started small: i replaced the fuel filter. same result.

a little larger: i replaced the fuel pump (it's an electronic fuel
pump, we tested with it unhooked from carb and it was a weak stream..
after replacement she was peein' strong). same result.

a little larger: i replaced the ignition coil. same result.

a little larger: i rebuilt the carb. at this point, she showed
promise. we took her out on the lake for about an hour and she ran
beautifully!! i let her sit for a week .. then bam, same damn result
as before!! 10-20 second purr then cut off.

so i said damn it, let's look at the carb again. no fuel is getting
down in the manifold after the initial warmup throttle action!! so
figured something is messed up with carb.. went down and bought a fresh
rebuilt carb.. last night.. put it on.. same result! and i still
don't see fuel dropping into the 2 barrels after crankup. it does
make a noise like it's spraying air or something at least. but it was
somewhat dark when i was observing it this time...

the guy i bought the boat from had done a lot of wiring himself (mp3
player, gps..) .. could it be some electrical shorting after 10-20
seconds or would it only be a startup thing?

my next order of business is going at it from the distributor system.
maybe the distributor chip is bad? distributor cap? what else could it
be!! man this is driving me nuts. that engine is practically new at
this point!!

also, what do you think about some crap in the fuel? i filled the damn
tank up from about 3 gallons.. but what if there is dirt or water or
something in the tank and it keeps suckin' up dirt? should i drain the
40 gallon tank.. and clean the tank somehow (never done that.. whats
the best way to do it?) give that a shot? the one thing that leads me
to believe it isnt the tank is that when i warmup throttle action it
pushes fuel down the manifold so the fuel filter seems to be fine?
maybe just not fine all the time?

any suggestions would be great. i've had it in and out of the shop and
they had it fixed at one point but then 1 week later it died again
(without me doing anything in between then).

i'm tempted to sell the boat, get something else, but i am in it $12K
and who is going to buy an '03 bayliner 21.5ft that doesnt run for
anywhere near that?? best bet is to get it running, then sell it, i
guess, or maybe keep it since ive grown attached :

thank you so much for your time reading this,



Hook a timing light up to one of the plug wires, I like the inductive
pickup type. Fire it up and run it while holding down the trigger on the
light until the engine dies. Does the timing light stop firing the moment
the trouble appears or does it keep going until the engine stops turning?
That will help narrow down whether the ignition or fuel is the problem.


This has most likely been mentioned before, but just in case it hasn't ....
The electric fuel pumps are wired (or supposed to be) through an oil
pressure switch. Once the engine starts, the fuel pump will only run if
there is oil pressure activating the switch. (the purpose is to ensure the
fuel pump doesn't keep pumping fuel into the carb if the engine dies or is
off. I believe that when you turn the key to the "start" position, the oil
pressure switch is bypassed to allow the pump to run and the engine to start
with no oil pressure.

From the symptoms you described above, it may be that the oil pressure
switch is bad or the wiring to and from it is bad.

Eisboch