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MPI Stalling at Higher RPM

G

gabrielgiggs

New member
Hi.

I'm having some problems with my engine and there are no proper mechanics in my area so I'm pretty in need of some help now.

I have a 7.4L MPI Mercruiser 1998 Engine that runs well, but stall when it went to about 3000RPM.

Following which;

1) I had problems starting right back up.

2) Cranks fine but doesn't start.

3) A short rest later, it managed to start, but dies off almost immediately.

4) Situation improves after awhile, able to start and idle, but dies off after a while.


What could the problems be? I have a few suspects in mind but please, let me know if you guys have a good way for me to sort this out.

1) Clogged Fuel Vent?

2) IAC Valve faulty?

Thanks in advanced.
 
A failing fuel pump and/or relay. Can you hear the fuel pump running when it won't start? Some engines had a wire corrosion issue at a junction in the harness. Follow the pump 12 vdc fedd wire to a taped junction and inspect it. Is the fuel cooler working? Hot fuel can turn to vapor and not inject worth a s...t. Feel the fuel line when it quits.
 
guyjg said:
A failing fuel pump and/or relay. Can you hear the fuel pump running when it won't start? Some engines had a wire corrosion issue at a junction in the harness. Follow the pump 12 vdc fedd wire to a taped junction and inspect it. Is the fuel cooler working? Hot fuel can turn to vapor and not inject worth a s...t. Feel the fuel line when it quits.
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Fuel pump seems to be working and fuel pressure was right when the engine couldn't start.

Does this actually rule out a plugged fuel tank vent?

So, what would you think would be the most likely cause thus far?

How about the spark plugs?
 
You can start w/the basics: spark plugs, check under the dist. cap for worn parts, check the timing. Is the engine temp. correct? The cooling system needs to be working properly. Make sure the cool fuel sytem is working. Next time it won't restart dump some lake water on the fuel lines and try again.
 
guyjg said:
You can start w/the basics: spark plugs, check under the dist. cap for worn parts, check the timing. Is the engine temp. correct? The cooling system needs to be working properly. Make sure the cool fuel sytem is working. Next time it won't restart dump some lake water on the fuel lines and try again.
Click to expand...

Thanks for the contributions so far.

Yes. The engine temp seems fine.

Is there any recommended material that you would suggest to a first time boater? I'm keen to know more about the basics, and simple troubleshooting but all the information seems to be all over the place.
 
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