Mercruiser 350 L engine electrical puzzle

G

griff4

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Joined
Dec 31, 2013
RO Number
33534
Messages
34
Hi all. I have a 2007 Bayliner 325. The engines have 350 2 barrel carbs with the tks choke system. The starboard engine would not start. I found the 20 amp fuse to the engine harness blown and the diode inoperative. Upon replacing the fuse and diode, the fuel pump runs even with the ignition off! The engine starts, but won't shut off with the key! The diode must be pulled out to shut off the ignition! Has anyone gad this condition? I have checked over the engine wire harness to attempt to locate where the unwanted 12 voltage is getting into the harness, but am stumped. Any suggestions are appreciated. Thanks, Griff.
 
Check the ignition switch for power at the "I" terminal with key Off. Should be none.

What diode are you referring to? Do you mean fuel pump relay?
 
Thanks, Sandy. The ignition switch is okay. The diode is a little orange colored thing that clips into the tks harness atop the intake manifold. I am now trying to troubleshoot this problem and using the good diode from the port engine. Electric diagnosis is not my thing and have called an old technician to take a look see. Griff.
 
I had a similar problem. It turned out to be corrosion in a bunch of electrical connections behind the battery switches. Cleaned them up and all was good.
Jim
 
Sandy and Jim, thanks for your input. Will keep you posted. Griff.
 
Griff- I had not heard of the Mercruiser TKS (Turn Key Start )system before your post but it was interesting to check into that.

I think this will explain your problem & hopefully the solution:

Oops [:-propeller] .
Edit: corrected link - open the 1st google result to see the service bulletin on failed TKS system diodes:
https://www.google.com/search?rlz=1...7......0....1..gws-wiz.......0i71.zfMLNFSSQmc

It sure sounds like the new diode is defective and passing current both ways.[:-propeller][:-propeller][:-propeller]
 
Sandy...I too am interested in this post, but your link does not work. Can you post the info on here for everyone to learn from?
 
--> Sandy

I don't need to try it; I know that that link will not work... It points to a file on your computer's main disk drive.
 
Ooops- Very sorry !!! I thought I was posting directly to a cut & paste URL link, but it turns out I can only link to the google search result ( 1st return on the page) and you have to download. Or just Google " service bulletin Mercruiser TKS system Diode ".

I should have noticed the personal element of that original link I posted as Bill kindly pointed out..

I corrected my post above to help get you there this time.
 
Actually, it would have been entertaining ( and hopelessly confusing ) if I actually had a similar disk directory structure! ( I caught it, 'cause, ahem, I might have done the same thing. )
 
Thanks all, especially Sandy. Yes, it was the Diode and the 20 amp fuse. All okay now. The Merc service bulletin said it all! Griff
 
I'm glad that the gang was able to solve the problem-wish I could have been of help. The boaters on here are the best!!!!!!!
 
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