200 HPDI ECU Issue

[boscoe99]

The power for the oil pump and fuel pump come from the main relay. Check there.

Also, I see a connector at the fuel pump that leads to the oil pump that could be the problem.

[rodbolt17]

as you have or should have seen, sometimes the actual diagram is a teat on a boar hog.

best I remember the key on yellow 12V wakes up the ECM which then applies the ground path to activate the main relay.
no 12V to the ECU no main relay activation.

any yellow/red wire will have 12 to ground anytime the key switch is on IF the main relay turned on.

remember there are a few splices from the key switch to the ECU.

[Sailorman295]

Made it back this morning to continue on this engine. Rodbolt was right about the yellow wire. It supplies wake up voltage to the ecu when the key switch is turned on which then powers the relays. Had power off the key switch but nothing at the main harness connector on the engine. Inspected all the main cable that was visible and saw nothing amiss. But upon pulling the wiring harness as far out from under the floorboards that I could, I saw that some of the outer covering had been removed. I had to disconnect from the key switch and cut several wire ties but then was able to pull the cable out far enough to see what had happened. Two things. First someone had cut away a section of the outer covering to splice together the red wire. The splice was poorly done and the wire pulled out of one of the connectors which was not a marine heat shrink. The yellow wire was chewed in several spots from a rat that had gotten into the boat when it sat at someones shop. The person who did the red wire splice never taped the harness back up so the rat had unfettered access to the wires. Five other wires were also chewed. Over a short time salt had gotten into the yellow wire and ate up the strands until it no longer made connection. I spliced all the damaged wires and used heat shrink of course. Then thoroughly taped up the harness. Turned the key and instant starting. What a sweet sound. Thanks guys for all your help and steering me in the right direction.

[boscoe99]

People apparently cannot understand or accept the concept of wires being grounded to activate circuits.

If a Yamaha marine mechanic tries to trouble shoot his home electrical system is he confused that a power wire is switched open or closed to turn on or turn off a light?

[rodbolt17]

your confusing simple DC electronics with that weird world of 115V 60Hz.

how in the ell I can turn my kitchen lights off at one wall, walk over to another switch turn it on and walk over to the 3rd switch and turn it back off? baffleing.

but I can tell you how the simple DC electronic circuits used on most outboard and I/O stuff works.

it is all mostly the same.

it is the difference from being an electritions mate and a firecontrolman.

I am a fire controlman, CIWS.

[99yam40]

Good to here you found the problem.
almost sounds like you need a new harness.
I hope your spices hold up well.

I went from being an auto mechanic to an industrial electrician back in the 70s.
It was a little confusing at 1st with wire colors and switching. but simple once you get the hang of it