Engine dies and won't restart.

[Tpop]

Ongoing problem.....1997 150 EFI sn 0G478636.
Engine dies and will not restart. No high pressure fuel pump with key on. Pump will run when jumpered but engine still won't restart. Will fire with carb cleaner sprayed into air intake. Ecu repaired/upgraded by Simon Motorsport. Had issue before and after ECU sent to Simon. High pressure fuel pump replaced. There is nothing I can point to that gets ECU/fuel pump operating again. Happened last Sunday and had no fuel pump until Wednesday. Ran it today and it stopped after approx. 20 min of idling and running at 5k rpm. I'm running out of ideas.

[David - WI]

Have you read this thread, good info... bad key switch, maybe?

https://www.screamandfly.com/showthread.php?306443-1995-Mercury-EFI-Fuel-Pump-Issue-Power-won-t-work (https://www.screamandfly.com/showthread.php?306443-1995-Mercury-EFI-Fuel-Pump-Issue-Power-won-t-work)

[flabum1017]

:iagree: could also be a dopey lanyard switch

[axle_26]

If it fires when you spray flammable stuff in the carbs it couldn't be the lanyard because that would kill spark, so if it fires when you feed it fuel then there is spark, then it is a fuel delivery issue. They key switch I guess could be a possibility but I doubt it being that, it sounds like based on your description that it will crank so I don't think it is the key switch either, but I could be wrong. I think there is a fuel delivery issue here. Do you have 12 volts at the high pressure pump with the key on?

[LakeFever]

Check grounds and wiring to fuel pump. Add some grounds couldnt hurt. Use noid tester to verify injector firing to rule out ECU issues. Should also check ECU is commanding fuel pump on. Check/replace fuel pump relay ( if there is? ) Check tank filter. Check for fuel line delamination caused by ethanol. Change fuel filter.

[Tpop]

I have 12 volts to both terminals of fuel pump and negative drops to 2 volts when key on and operating normally. When fuel pump does not come on at key on both terminals stay at 12 volts. Appears like ECU issue but I can't explain why it fails and then takes a day or more to begin working again. It failed this past weekend so I parked it and checked for pump working at key on each day and today(Wednesday) is first time it's worked since it failed.

[LakeFever]

Is there an oil pump safety ( cars call this an oil pump relay or safety switch ) on the fuel delivery system? Is there and Anti-theft system in place?

If no id start by verifying continuity on all pins to the ecu. I have fallen into the trap of blaming the computer so many times and almost never has it actually been the computer. I did work on a fiends SeaDoo once that was towed and filled with water that fried the ECM on that one but it sure is not common. Most ECU's have a ground wire that goes in with the main harness plug. You need to find a pin out diagram and pull the connector out of ecm and check with a test light from the pin at the plug to 12v+ bat using a test light. Test lights are excellent tools for verifying continuity in 12v dc floating ground systems. Use a beep meter to check pins from fuel pump to co-responding pin on ecu

Ever have a switch on the dash of a boat that only works when you wiggle it a bit? Lights etc? Need to rule all the wiring out before chasing your tail and spending potentially a lot of money on parts.

[flabum1017]

They key switch I guess could be a possibility but I doubt it being that, it sounds like based on your description that it will crank so I don't think it is the key switch either, but I could be wrong. I think there is a fuel delivery issue here. Do you have 12 volts at the high pressure pump with the key on?

Just because it cranks, that does not necessarily mean it's getting power to the purple wire....

[eli]

The only thing you should be spraying into motor. Is fogging oil it will fire on it spraying Non oil mixture could score cylinders