496 won't start
 

I have a marine power 496 and was out this weekend, ran for probably 5 hours or more with no problems at all. Then I heard it backfiring a little at 4100 rpm's and up and lost only a little power. Then the power started falling off quick and then just shut off.

Now it won't start at all. Turns over fine, got 42lb of fuel pressure or so and will fire on starting fluid.

My first thought was bad gas, but where I got gas from over 100 boats filled up from the same place and just couldn't see just my boat getting bad gas.

I don't have a code reader but I guess I'm going to need to get one.

Any help please!
Brad

Is the SmartCraft beeping?

I would start with replacing the fuel/water separator and inline "bullet" fuel filter if equipped.

Already did.

It don't have a Smartcraft

Check The crank positon sensor. It fails and wil not start

fuel pump...been there done that...came down to the fuel pump.

I've got fuel pressure, it holds at 42 and when turning over it drops to 38-40 psi.

What do you not have??? Fuel at injector/carb? Spark? ...or air?

Suck, Squeeze, Pop, Fooey - got to have the 3 above to make it run. Don't just guess - diagnose the problem and replace only the needed parts.

Sounds like you have a fuel pressure gauge (which doesn't mean the injector is opening, by the way). Do you have a spark tester? Pick one up at Autozone and narrow this problem down to an ignition or fuel delivery issue. Then we can help from there.

I've got spark, fuel pressure and air. The only other thing it could be is injectors not opening, I don't know what or how many different things it could be. I've checked all my grounds also and seem to be good.

There was a thread about a month ago about problems and checking injectors. You should see if you are getting 12 volts to the injectors, and need to track down the grounds to verify good connections. I changed the crank position sensor on a buddy's boat last year. It would fire and even ran for a few seconds, but not firing at the correct times. OH yea, no codes ether.
Here is the thread http://www.offshoreonly.com/forums/g...cylinders.html