Rbrown

Hi guys, me and my dad just reassembled my mercruiser 454 mag mpi after a rebuild and are having some trouble. Engine fired right up with timing set approximate to 8* btdc and the paperclip trick in a&b pins on obd port to set timing. Like I said engine starts easily and runs well for 5-10 seconds and abruptly shuts down. Fuel pressure primes up to about 45lbs. All connectors have been plugged in. Injector wiring verified correct. Can't seem to figure out what is shutting down the engine. Any ideas?

Griff

What does it do when you give it some throttle??

Rbrown

Revs up fine but still abruptly shuts off. Also of note, it's running off of a remote fuel cell with fresh gas

Brad Christy

RBrown,

Does it shut off, as if you turned the key, or does it sputter out? Does it fire right back up or is there a delay for restart?

I have a friend that was having similar behavior out of a carbed 454 that onset at the beginning of the season last year. It would start fine, then die after less than a minute. It would be a short while that it would just crank over without even a hint of ignition, then it would fire again, and of course die shortly after. Turned out to be long-past-gone internal distributor parts that had finally just given up over the winter. I don't know if these were parts you addressed during your rebuild, but it's something to look into.

Thanks. Brad.

sutphen 30

will it stay running w/ part throttle or does it rev up and then dies off?your probably have to find someone w/ diacom/rhinda scan tool and look at whats happening.
another thought,does the shifter bracket on engine have 2 purple wires and a micro switch?

105Fountain

Choke stuck closed?

Rbrown

It shuts off as if the key was turned off. Doesn't sputter out

Brad Christy

RBrown,

Does it restart right away, or do you have to wait a bit?

I'm no expert, but my bet is on an ignition issue. It's been my observation that fuel issues generally result in a sputtering out behavior.

That being said, it's my understanding, with an electric fuel pump, there is a feedback lead from the alternator that will cut power to an electric fuel pump in the event the engine quits while the ignition switch is in the "run" position", meant to keep from pumping fuel into an engine that has unexpectedly shut down. I have no idea how the wiring is configured to accomplish this, though. With an EFI engine, I'd guess it would probably be a pretty instantaneous shut down when fuel pressure goes to zero. This might explain the delay between starting and shutting down. You might look into this.

Thanks. Brad.

105Fountain

Fuel or spark with MPI I say fuel ?

F-2 Speedy

you sure its not the choke......