502 stalling problem

I have a 97 502 efi. once in a while the boat at 2500-4500 rpms the motor just shuts off. then when the boat comes to a stop it will start right up and run fine for weeks. Once it stalled, started up. went 100yards and stalled, started up fine and ran the rest of the day. Just had motor rebuilt, new fuel pump shortly after it did the same thing. its only happened 3 time in 7 yrs. so whats up?? i put a new water fuel filter in every year. lucky for me it never happened in a poker run. OTHER IDEAS ?

[steve]

could be the fuel pres regulator. I had a mustang do about the same thing a few years ago. It would work fine, then shut down. let is set and it would go again. was also veery sparatic

Thanks,

where is the regulator located? also i had the marina check for codes in the ecu and nothing there. could it be water in the gas tank?

COME ON, NOWBODY HAS AN ANSWER?

Even I have some more ideas, but Im not a mechanic, ps (i also can not spell) just have common sense some times.
Hope some one is more knowledgeable than me?

[obnoxus]

What do your guages do when the motor shuts down,,, do you hear the warning buzzer or do they all shut off like the key was turned off?

Check valve on the tank! Just had the same problem. I got some real nice check valves from the local speed shop. works great now.

CS

OBNOXUS,

The motor just shuts off, no buzzer and no throttle responce either. the last time it happened the motor started and ran very erratic, no throttle response, shut down, and started a few seconds later than ran fine the rest of the day. thanks for the support

[Raypanic]

Once I had a gasoline attendant drop the little metal seal off a 2 cycle oil bottle down the gas tank. It would block off the fuel flow every once in a while and shut down the engine like you said. Just an Idea. A second hose to the tank would fix this.

Thanks RAYPANIC

can I drain the tank, to suck the foreign object out?
also, if it is a fuel reg problem, where is it an a 502efi 1997. Is the reg elect or vacume?

[Poorsche]

Check fuel pressure at various points in EFI rails. I had similar problem--posted reply to similar problem today.

Pressure should be around 40 PSI and there are some Schrader valves where you can test.

We replaced IAC motor, Ambient Air Pressure sensor among other things before we landed on the fuel pressure regulator because the syptomes were so wierd.

My engine is a 97 MarinePower EFI.

You won't see anything on codes from ECU. Mine ended up being a regulator that had corroded under factory paint.

The thing is inline near the fuel pump usually at end of fuel rails and it's on a rigid metal fuel line with threaded fittings.

It's available from any parts store--if you can find a guy that really knows GM EFI systems he'll give you the number off the top of his head.