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Tan
Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 10621
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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I have a 2001 mercruiser 5,7 liter EFI throttle body. turn

Customer Question

I have a 2001 mercruiser 5,7 liter EFI throttle body. turn key, fuel pump comes on, engine starts. It runs about 30 seconds and shuts off. I assume that the fuel pump is shutting off. ther is a purple wire coming out of the ignition switch which goes to the kill switch. A purple wire goes out of the kill switch to a round black cylinder about half the size of a small spool of thread. a white wire with a blue stripe comes out of that cylinder and goes to the back of the boat. The kill switch has been wired around,so the purple wire goes directly from the ignition switch to the little black cylinderI'mwondering what the little black cylinbder is and if it might be bad, Or any other ideas. Happy to pay for advise if we fi the problem.
Submitted: 10 months ago.
Category: Boat
Expert:  Jason replied 10 months ago.

Hi Jeff, my name is Jason.

Is the wiring on the engine all original or has somebody monkeyed with it?

I assume that the fuel pump is shutting off.

If we start assuming things your engine will never get fixed. Can you hook up a fuel pressure gauge and see if it is actually dropping fuel pressure as the engine stalls?

Customer: replied 10 months ago.
I am the second owner, so I can not say for sure. As I said before, the "kill switch" was wired around. It also looks like the radio may have been added after manufacture. Other than that everything looks original.
I do not have a fuel pressure gauge. Is there another way for me to check this? I made the assumption that the fuel pump had shut ff because I can keep the engine running by pumping the throttle.
Expert:  Jason replied 10 months ago.

I do not have a fuel pressure gauge. Is there another way for me to check this?

No

When you say you can keep the engine running by pumping the throttle, Will the engine stay running at a higher rpms?

Customer: replied 10 months ago.
no. I have to keep pumping it
Expert:  Jason replied 10 months ago.

Will it stay running if you pump it?

Customer: replied 10 months ago.
I'm going to go try it now
Expert:  Jason replied 10 months ago.

OKay

Customer: replied 10 months ago.
It will stay running only if I keep pumping it. I requested a phone call, but I have to leave the boat now. Can we continue this tomorrow morning?
Expert:  Jason replied 10 months ago.

Tomorrow is fine, I actually am about to leave for the evening. Can you get the serial number off of the engine for me.

Customer: replied 10 months ago.
engine serial # 0M071834
In a previous email, I mentioned a black cylinder about half the size of a spool of thread. It is at the end of a purple wire that comes off the ignition switch and the kill switch. I believe that cylinder is an alarm. It beeps twice when I turn the ignition key to "on" position, and I hear the fuel pump come on. I then turn the key and start the engine, and the cylinder beeps two times when the engine starts.
I'm a "shade tree mechanic", and I think this may require more knowledge and testing equipment than I have. I had hoped it might be something simple in the wires by the ignition switch and that with a little advice I could fix it. If you have some things you think I can try, I will do so. Otherwise, I can take it to a mechanic tomorrow.
Expert:  Jason replied 10 months ago.

Got the serial number. The engine is going to need some troubleshooting in order to figure out the problem. Tools required are a compression gauge, fuel pressure gauge, timing light, and because this is EFI, possibly a scan tool. I know you said you didn't have a fuel pressure gauge, so what would you like to do here? (I don't know what you have for tools or abilities)

Customer: replied 9 months ago.
I have a compression gauge and timing light, but no scan tool. I think I should take it to a mechanic.
Thank you.
Expert:  Tan replied 9 months ago.

Hello. My name is Tan.

Do you have a volt meter to test for voltage at the fuel pump when the engine quits?

You could very well have a bad ECM. The ECM sends voltage to the fuel pump when engine starts initially. If you are loosing voltage to the fuel pump after it starts you have to replace the ECM. They had some issues with these ECM's.

What you can do to verify this as the problem is connect 12 volts to the fuel pump see if engine continues to run.

There is a kit you have to buy to replace this ECM as your ECM is no longer available.

Post back with findings.

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