No fuel suddenly

[Brandon5778]

Hello, I have a 1975 mercruiser 5.0 and just recently finally got it running great.. It's actually got a new carb, fuel pump, and filter. Okay, so the boat has been running pretty good, I just got it on the water last week for the first time of the season and she ran great, missed a little bit at high rpms. Anyway last night I took the boat over to my brother's house to do a compression test and change spark plugs and wires while I was at it. I disconnected fuel line right above gas tank, going to fuel filter and I ran the boat till it had no gas and wouldn't start anymore.

After doing test and changing plugs etc, I hooked the fuel line back up, tightened up both the hose clamps and tried to run it on the muffs, well she wouldn't start after cranking forever. Usually starts right up.

So, I took off the fuel line right where it hooks up to the carb and put it in a jar. As I suspected no gas came squirting into it when I turned it over! Does anyone know what would cause it to just stop? The above is all I did to the engine and I don't understand what is different.. I know there's about half a tank of gas.. Anyway I had to stop because my battery finally died from cranking it so many damn times so now I'm waiting with it on the charger..

 

[Bt Doctur]

I disconnected fuel line right above gas tank, going to fuel filter and I ran the boat till it had no gas and wouldn't start anymore.

So why do this?
remove the filter, fill it and reinstall, add 2 oz in the carb throat

 

[Brandon5778]

I disconnected fuel line right above gas tank, going to fuel filter and I ran the boat till it had no gas and wouldn't start anymore.

So why do this?
remove the filter, fill it and reinstall

The way my brother explained it you should disconnect fuel prior to compression test

 

[Bt Doctur]

you remove all the spark plugs, disable the ign coil, pin throttle wide open and crank for 3 rev`s on each cylinder
And if MPI ,unplug the fuel pump . With the engine off and the throttle wide open, the injectors are disabled

 

[Brandon5778]

Thanks Bt I guess my brother doesn't really know how to do one

you remove all the spark plugs, disable the ign coil, pin throttle wide open and crank for 3 rev`s on each cylinder
And if MPI ,unplug the fuel pump . With the engine off and the throttle wide open, the injectors are disabled

I'm not sure what MPI stands for. It's a mechanical fuel pump. Sorry I am new to working on an engine

 

[Fishermark]

The MPI stands for multiport injection - in other words fuel injection. Since you have a mechanical fuel pump that means you have a carburetor.

 

[Fishermark]

As the Doctur ordered, , you can simply pour a little gas down the throat of the carb and then start the engine. Assuming you have everything hooked back up correctly, the pump should prime itself and everything run just fine. If it doesn't you will have to make sure the hose you disconnected is tight. A vacuum leak will cause the pump not to pull the fuel. (Think of sipping through a straw that has a hole in it).

 

[Scott Danforth]

no need to disconnect the fuel on a carbureted motor for a compression test. on an MPI yes, carbureted, no