502 mpi - strange problem
 

looking for ideas, I have been dealing with this issue for way to long.

2000 502 mpi- runs perfect, every so often it just dies, most of the time when running at higher rpm but happens at idle too. Usually when it dies can tell it is a celear loss of fuel pressue, I have a fuel pressure gauge and the gauge goes to 10, all I have to do to get it re-started is to loosen the separator (I can hear a hiss of air) and it will restart and the pressure is back to normal, When I remove the separator after it died it is half full.

I removed the anti siphon, checked the tank vent, blew out the tank pickup tube and checked it the best I can (welded in tank), replaced pump, hoses from pump to separator, both relays. The injectors were all tested and redone about a year ago.

Last night it died, and I was idling it was like the key switch was turned off, no loss of pressure, it fired right back up and ran great after that.

have you ever heard of an intermittent ecm issue that could cause the fuel delivery to shut off like this? or does it sound like a tank issue??

any ideas would be great, Thanks

The first Test you should try is you need to seperate the boats fuel tank from the engine so you can find out what you need to fix. Try getting some new fuel hose and a 2.5 to 5 gal gas tank and run the new hose to the engines fuel inlet hose barb fiting and make sure the small gas tank is well vented with the hose resting in the new tank, Make sure the filter is full and hook up the psi gauge and go run it to see if it still dose it.
Qustion for you dose it do it when the tank is as close too 100% full as you can get it, Or dose it happen when the tank starts to go down some?

thanks, I tried that today and the still having the issue, so I think I can eliminate the tank,

I think my next step is to try and borrow a ecm from someone local, to see if it's a computer glitch, Not sure what else it could be, I replaced everything except the line from the pump to the rail,

is the alternator charging and battery voltage above 12v?

Also check for loose wires and loose ground wires or corroded connections. Sounds like the system is intermittant and dropping out which is just like turning the key off and on.

Best Regards,
Ray @ Raylar

I had a bad ignition lanyard kill switch that caused the engine to shut down intermittently for no reason. Replaced the switch and never had the problem again.