2017 Quicksilver 855 Weekend powered by Mercruiser 3.0L 260HP Diesel - won't start properly

[Stevethelight]

Hi all. I am unable to start, or at least keep running, the engine on my boat. All fine one day; then, after fiddling with the non-working radar interface, the engine now won't start. The Mercury Smartcraft dials also lack power although other ancilliary equipment is fine, so no problems with the batteries. Note that if I turn and hold the key at the 'start' position (against the spring) and at the same time push and hold the additional (separate) start/stop button on the throttle lever housing (i.e. two simultaneous methods of starting), the engine will start and the Smartcraft dials work. But as soon as either the key or the button is released the engine stops. Normally, the engine starts and runs by using either the key as usual, or by turning key just to the on position and then pushing the above-mentioned start/stop button on the throttle lever housing. I have checked every fuse I can find including the two located in the engine control module housing. I can find no loose wiring at the helm. Interestingly, when the key switch is operated the trim tabs reset themselves as usual. Any ideas what I should be looking for or doing? Thanks.

 

[rafiki_]

It could be an earth wire issue? Check for corrosion in your connectors.

 

[billskip]

Check the stop solenoid circuit, ?

 

[spannerman]

Firstly this engine doesn’t have a stop solenoid as its common rail injection. It sounds like you are not getting the live feed to energise the ECU so I would check the ignition switch. Its giving the ECU a feed in the crank position so it runs but when the key returns to the RUN position the feed is lost, you can check this with a test light or multimeter . Purple wire is the 12v feed you are looking for, yellow/red is the crank signal wire. This is where I woukd start.

 

[KevinV]

As with all such "I did something completely unrelated..." problems, I'd go back to the original problem and go through everything you did. Odds on you've disconnected /dislodged something in the area you were working - don't ask how I know

 

[Stevethelight]

Firstly this engine doesn’t have a stop solenoid as its common rail injection. It sounds like you are not getting the live feed to energise the ECU so I would check the ignition switch. Its giving the ECU a feed in the crank position so it runs but when the key returns to the RUN position the feed is lost, you can check this with a test light or multimeter . Purple wire is the 12v feed you are looking for, yellow/red is the crank signal wire. This is where I woukd start.

Spannerman. Thanks for your advice. The problem was a hard-to-detect inline, blown fuse between the key-switch and the ECU. Not sure the colour of the wire. Replacing this restored the ECU feed, the speed/tacho dials and also restored power to the bilge air blower. I shall be looking at installing a separate feed for the accessories leaving this one purely for the engine ECU.

 

[Whippersnapper]

Spannerman. Thanks for your advice. The problem was a hard-to-detect inline, blown fuse between the key-switch and the ECU. Not sure the colour of the wire. Replacing this restored the ECU feed, the speed/tacho dials and also restored power to the bilge air blower. I shall be looking at installing a separate feed for the accessories leaving this one purely for the engine ECU.

If this is the same problem as I once had (my boat has the same engine), the tech installed a self resetting fuse. Apparently it is a known issue. Haven’t had any repeats.