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-   -   Help, Motor won't start. Merc 454 Mag EFI (https://www.offshoreonly.com/forums/general-q/311838-help-motor-wont-start-merc-454-mag-efi.html)

dmaxximus 05-07-2014 09:31 AM


Originally Posted by onesickpantera (Post 4117598)
You dont have to swap them. There are three posts on the back of the switch. One has 12 volts all the time, one will have 12 volts when you turn the key to on and the third will have 12 volts when turned to start. Check the first post with a test light when the key is turned to on(and make sure the wire is connected).

Ok thanks again to everyone, I will just replace the fuses in the VST box even though they all appear good, I can't find any other fuse boxes in the boat to check then try the volt test on ignition switch. Something is not allowing the fuel pump to turn on. Again I double tested the pump and it spun up fine, I even ran power to it (not a great idea) while cranking and no start. Communication issue for certain :confused:

dmaxximus 05-07-2014 09:35 AM


Originally Posted by FIXX (Post 4117633)
OK BACK TO THE BOX....If you test for power their at all 3 fuse leads on both sides,,all those leads are triggered from the ecm...the landyard safety tether that goes to your wrise also goes to the ecm which powers up the ecm..check the circuit brakers and what ever side of the tether feeds power to the tether or lantyard to power up the fuel side of the ecm that provides power to the fuel pump..like i said some boats have more then one fuse panel..

if it all checks out either your ignition module is bad or your ecm took a crap..

Ok good idea and thanks, can't get to it till memorial weekend so hopefully I get it figured out or it's gonna be a $hit weekend!

Knot 4 Me 05-07-2014 09:39 AM

Is your boat on a lift at LOTO? If so what MM?

onesickpantera 05-07-2014 11:16 AM


Originally Posted by dmaxximus (Post 4118351)
I even ran power to it (not a great idea) while cranking and no start. Communication issue for certain :confused:

I didn't catch this the first time. If you powered the pump with 12 volts and it turned on and still wouldn't start there are other issues. Did you unplug the main harness and check for corrosion?

dmaxximus 05-07-2014 02:27 PM


Originally Posted by onesickpantera (Post 4118407)
I didn't catch this the first time. If you powered the pump with 12 volts and it turned on and still wouldn't start there are other issues. Did you unplug the main harness and check for corrosion?

I went through all the elec connections and fuses I could find, my boat has never seen salt water and has never sit in the water overnight. Not to be egotistical but its pretty dang clean everywhere. I have a few wiring diagrams and troubleshoot flow chart now so hopefully will lead to prob. I have the VST and removed the elec pump and it was clean inside, so going to back track electrical as the guys mentioned. Ignition Switch isnt talking to ECU and Fuel Pump so I'm guessing it's somewhere between there. They were both running 3 weeks ago after de-winterization. Thanks for your suggestion :traurig001:

onesickpantera 05-15-2014 02:42 PM

Any updates?

dmaxximus 05-15-2014 02:53 PM


Originally Posted by onesickpantera (Post 4122609)
Any updates?

No man I have been out of state since that weekend. I called a local tech and hes gonna try and diagnose it and see if it throws a code. He seems to think ECM by what I was telling him but I know that story so won't fall for it just yet. I ordered a new ignition and kill switch just incase it's one of those. I had battery problems that day and had to charge battery, I was wondering how sensative EFI is to weak battery. It was plenty to crank it and shock the **** outta me checking for spark but doesnt mean it's enough to power the system right?

dmaxximus 05-23-2014 05:01 PM

Ok gents back at it again and down to no power to starter relay or fuse. Maybe a bad ECM on memorial weekend when I can't get one would be just great. F@ck

dmaxximus 06-03-2014 12:10 PM


Originally Posted by onesickpantera (Post 4122609)
Any updates?

Swapped ECM with good motor and it fired right up. Sent ECM to Bob at MEFIBURN and he said it's cooked. $1100 for a new one or around $850 for a used one on Ebay. Not sure it's worth the risk of buying a used one, any suggestions?

Pismo10 06-03-2014 01:24 PM

Crazy expensive. That would be a $30 part if it was not for a boat.


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