VP 5.8Fsi Dead in Water

[mcperrault]

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Took the boat out on Sunday. Ran GREAT all day long. On the way back to the marina, I noticed the voltage output drop to 12V. I shutdown assuming a broken alternator belt or similar. Found the alternator moving freely and belt still intact.

I went to restart and bring into port and no fire. The engine turned over fine but never fired. Initial thought is that the low pressure fuel pump went out and it's not getting any fuel on start. The hi pressure pump would take care of the engine at speed, right?

Thoughts?

BTW - Engine was running rough (sputtering and dying) at idle after being run for a while (ie, when coming back into port). I saw this happening 2 or 3 times in the last 10 outings. It always restarted immediately following dying, allowing me to pull into the docks. It also ran great on start and idled like a champ....

Thanks again for all the assistance. Don't know what I would do without you guys!

Thanks,
Mark

[gonzo]

The low presure pump feeds the high pressure pump. Both need to work at all times. A bad alternator will cause symptoms like you are describing. The voltage may be dropping too much causing misfires. Also, if the battery is low, it won't fire during cranking if the voltage is below 9V.

[mcperrault]

Understood. I have 2 batteries and when I'm cranking I'm using both. I see 12V at the engine. Is there a breaker I'm missing? Will the fuel water separator re-prime or do I have to do it manually as I did?

I'm assuming I can crank over with an shot alternator and get it to run off batteries. If that happens, then I'll see crappy output and know the alt is shot, right?

Do you know how the safety kill switches work? Will they shutdown electrical to the fuel pump (similar to how a car alarm system works)? I'm thinking that might be my problem...

[Steven Brown]

If you cruise low speed all the time you could have fouled up spark plugs.

[gonzo]

The safety kill switch cuts the ignition and fuel pump. If your engine is a MERCRUISER, the shift interrupt switch or the intermediate shift cable could be the problem.