Please help! Mercruiser 7.4L MPI will not start

[jeff67210]

The last time I used my boat, everything works fine. Three weeks later, I was going to take a friend to go fishing and it did not start. Weather had gotten colder a bit. My fuel gauge show a little below 1/4 line. My boat mechanic worked on it, cleaned the air intake, check spark plug and it sparks when ground to chassis. What we thought was fuel delivery problem. The schraeder valve has fuel flow when the pin is depressed. We removed the air intake assembly exposing the fuel injection flap, open it and sprayed starter fluid and turn ON ignition and it just turn over but no life. My boat mechanic says it is the fuel pump that is needed to be replace. I wonder if anyone else has other ideas different from my boat mechanic? I would certainly appreciate if any boater fellow can help me out. Maybe there is something else I can check or something I missed. Please advise. Thanks so much.

 

[skolbe]

Did they remove the fuel filter. You may need to just prime the fuel pump. Had an issue with my 260.

 

[jeff67210]

What I was thinking is replace the fuel filter and put more gas and add a fuel stabilizer to rule out condensation in the fuel tank. I do I prime the fuel pump? Thanks by the way skolbe for your important input.

 

[Fun Times]

Have you check to see if your kill switch at the shifter was up in the run position?

Have you try leaving the throttle open a little bit while cranking to get extra air to the engine?

Do the gauges move when you turn the key on?

Does the RPM gauge go up while cranking engine?

Have you checked for spark while cranking the engine over by either taking one of the spark wires off and put a spare plug in the wire and set it near the block and crank it over looking for spark, Or you could also use a timing light if you have one because the safest way to check for spark in my opinion is to hook up a timing light to the coil wire first and crank the engine over and watch the light to see if it flashes bright and fast, Then move it to a few spark plug wires down by the spark plugs and crank it over and see if you get a few flashish here and there while cranking it over. Do you have spark???


If you put starting fulid down the throttle body and it did not try to start even one time then that normaly would mean you have no spark.
To test fuel pressure you will need to hook up a gauge to that schrader valve And you will need to see the pressure go up to anywhere from 36 to 43ish psi.

Also you may want to seperate the starting system between the boat and the engine by removing the main wire harness going to the engine as a test to see if your problem is with in the boat or the engine itself And all you need to do with the main plug pulled off is jump #'s 5 & 6 Then touch # 6 to number 7 till it starts then pull # 7 when started, And to stop engine pull 5 or 6. Here is a you tube video of how to do this step. http://www.youtube.com/watch?v=NUoXFIo2Ab8 if you want to try this.

Also you will want to make sure you have good engine compression by doing a compression test.

Is the fuel filter new and full???

 

[jeff67210]

I meant, how do I prime the fuel pump?

 

[jeff67210]

Thank you Boat Tech for your input. The first 3 items on your comment were have been done and are fine. The rest of your input I will try next weekend as I my wife and I are driving to Northern CA to visit a friend. Again, thank you guys for your valuable help.

 

[skolbe]

You need to remove the fuel filter and check that it has fuel in it. If it doesn't add fuel and reinstall and try restarting. If it won't run but tries to run the other way requires something that is messy and you will have fuel in the bilge which you may not want to try this since you will lose fuel in your bilge which of course if flamable and I don't want discuss online. If you suspect water in the fuel filter try buying a new fuel filter top off the filter with fuel before installing and try restarting.

 

[Fun Times]

I meant, how do I prime the fuel pump?

Make sure the filter is full and cycle the key anywhere from 4 to 8 times, And if you think you have air in the fuel line system you could push the schrader valve in to help remove any air, This would be one way to do it.:smt001

 

[LTD.330]

Please excuse my tearseness, I'm not a writer and always come off like **** online.

Just to be clear, the engine will turn over, correct?

Normally, there are three things are needed for combustion: Fuel, Spark, and Air. But, since you said your motors MPI, we can throw in the ECM as the fourth thing needed.

ASSuming the engine will turn over, you said your spark plugs would spark. Did you have a good ground? What color was the spark? White, Blue, Yellow?

After removing the various ducting work for the air intake, could you see any obstructions in the plenum? Could/did you shine a light into it looking for obstructions?

Did you shoot a blast of ether down the throat of the plenum? What happened?


Please keep us informed, I've got the same motors and would love to learn from your experiences.

 

[jeff67210]

My father-in-law and I worked on the boat this weekend and got it started. We first pulled out the fuel filter, checked for water and we didn't find any evidence. We drained the fuel filter of old gasoline and refilled it with new gasoline. We then filled some fuel stabilizer about 16 oz and added more gasoline. We pulled all spark plugs and cleaned and re-installed. Sprayed fluid started with WOT and it almost want to start. What we finally did was push the knob below the throttle stick to put it in neutral and got it going. The boat starts now with every time on the first try. During this process the knob below the throttle stick got stucked in neutral and we can't seem to put the boat in either forward or reverse. Has anyone have and idea to get this knob to reset so we can engage the forward and reverse gear? We disassembled the throttle stick assembly but we still cannot get to the point to popped out the knob, any one have an idea to get this assembly taken apart properly to access the knob? Again thanks so much for those of you who had been helpful.:thumbsup: