the low pressure pump wont run at all at key on.
the HP pump runs about 5 seconds at 12V. 5 seconds most digital meters cant buffer enough to get a good treading.

once running and below 1200 RPM the LP pump runs at 10 seconds on 20 seconds off.

remember the ECU does NOT control supply voltage.
it controls the ground path.

So as soon as I key on both pumps run continuously. How can I trace the fault? I can't decide whether to blame a faulty E.C.U. or the Driver Modual... a shop had bypassed the module and tapped into a hot wire coming from the Y.D.S. plugs hot wire and when I tried to help the pumps were running all the time and now when I've put them back to where they originally go I get the same result pumps running constantly but with less voltage?

From Yamaha? You have got to be kidding.

What there is, is there in the service manual. Pathetic isn't it?

Are you a trained marine mokanic? Just wondering what you level of expertise is. Don't want to offer some suggestions if you won't be able to understand them.

Whenever the key is on there should be battery voltage on the red wire with a yellow tracers. More voltage with the pump not running than when the pump is running due to normal voltage drop but what you are reporting is excessive.

seems like an interesting problem - but with a nasty wildcard history..

"a shop had bypassed the module and tapped into a hot wire coming from the Y.D.S. plugs hot wire" - wtf?

as the experts explained, both pumps are supplied with 12V+ at key on -

they run "only when grounded by the ECM".

My guess has been that the "pump driver" acts as a "relay", so that the pumps are actually grounded there,
switched by a "control" ground through the ECM.

But that's just an assumption.

It would appear then that the L/R and B/W are the "control grounds" to the ECM.

I would think a "bench test" would be to apply 12V power to R/Y, and ground black:

L/W (LP pump - "1") should not then test as grounded nor should L (HP pump - "4")

but then grounding L/R or B/W should result in either L/W or L being grounded as well.

That's the way I imagine it, anyway..

But since my $375 "drive unit assembly" is working just fine, thank you,

I won't be playing with it just for fun....

Fairdeal - I see the lack of voltage on the red wire with a yellow tracer as being a real problem. Might be why some backyardigan (thanks rodnut) tried to bypass the driver. Shitty input in so shitty input out so they tried to do an end run around it.

I wonder what voltage is being seen on the other red wires with the yellow tracer.

Driver seems to be Yamahaspeak for a relay. I like your idea of simply testing the driver by grounding the input leads and letting us know what output leads they ground to run the pumps. Yamaha makes no mention of this.

Damn good looking diagram by the way.

Yes I'm a trained outboard tech. My best guess is that the signal coming from the ecu at "key on" we got was the hp pump ground and that part of the ecu is fine. the relay is stuck or grounds must be melted together inside the driver. If I was getting a signal on a frequency test that lasts 5 seconds when key on, I would assume to rule the ecu out I should start the motor test both ground paths from the ecu and see if they give the correct signals at the correct intervals. Then it would have to be driver or harness which I have tested continuity with a fluke 88v. We tested wires coming from cpu with a power probe set to frequency. And yeah a shop told him buy a computer it might fix it? but then wired from the hot off yds port and grounded with a ring terminal straight to the block. First thing I said was good idea if your 20 miles from shore dead in the water then yeah....great bush fix. But the reality is the hp pump was running straight 12v and even though the lp pump was running constantly as well it was building an air pocket in the filter and would die until you pumped the ball. So new fuel hoses to the brand new water separator, new lp pump, cleaned out the vst checked float not sure if they got him for a new hp pump all to say maybe a cpu? Only to Bush fix it and send him out on the water... if I had a spare cpu and driver I could quickly fix this but I really think to keep up doing research is the best way. Just little out there about the driver and without a schematic of the inside I would be afraid performing any bench test on someone else's part.

And would be beyond me to throw electricity through the part not knowing what's inside... when we tested the pump wires we had a good ground on the hp pump and not on the lp pump at key on.....but when you plug the lp pump in it runs and has ground. Not sure if that sheds any light to my situation? I would assume also if I preformed a running test I could tap into the cpu wires and see if I get ground hits at the proper times and pulse width that may rule out a faulty computer?

I'm guessing that the two wires from the cpu are a separate circuit that flip a switch to light up the pumps so that if there is a pump failure it can't surge back and fry the cpu?

I think we found a compatible running motor we can swap parts to figure this out tomorrow, but learning the exact path of the failure and a better understanding of why it failed would be a better option for me.

By the way the driver for this model is only $317 on boats.net not $375 i thought i would let you know just in case the $58 extra bucks was stopping you from figuring out a bench test haha... I'm kidding thanks for all the input from all three of you! I'm new to the forum and it's great to bounce stuff off of people who are in the outboard world.

Just stabbing in the dark, by passing "stuff" and measuring voltages and circuits means absolutely nothing at all unless you know what you are measuring, why, and what the result should be, without that info, 50 Fluke meters and all the tools in your kit are worthless.

as a trained tech, your doing it wrong.
a frequency test HZ, would be ok for some tach signals,not Yamaha but some, certain A/C signals but NOT a lift or HP pump signal.
ANY red/yellow lead will simply have 12v between that point and engine ground any time the key is on.
NO frequency or Hz involved here.

simply use the DC volts setting on your meter and that big round tool on your shoulders.

just by looking at that diagram and understanding a touch of electronics and knowing that ANY red/yellow wire has 12V + anytime the key is on we can test this.

we know R/Y is 12v anytime the key is on.
we know that black is engine ground always.
we know tha blue is HP pump ground PATH(current flow).
we know that blue/white is LP ground path.
that leaves two wire to check.

there is a nice diagram in the 2013 electrical systems traing manual.

but the low pressure pump should NOT run at key on,just the HP pump for 3-5 seconds.
means you will see a HZ signal.

the fuel filter cup level should rise and fall at idle and stay about 1/2 full above 1200 RPM.
it will NEVER EVER stay full.

if it runs out of gas at speeds below 1200 RPM then check the inline relief valve between the VST inlet and the LP pump intake.

on Volvo EFI they turn both pumps on at the same time.
Yamaha does NOT.

remember the lift pump cycles.
20 seconds off/10 seconds on any time the engine is running below 1200 RPM.

the ECU has 2 inputs to the driver(relay).
one controls the relay actuation for the HP ground path the other controls the LP relay actuation for the LP ground path.
both yellow red pump wires have 12V+ anytime the key is on.

look on pages 2-23 thru 2-28 of the 2013 electrical training manual.

or do the FC training program in the USN and then fix outboards and stern drives for about 30 years.

before I did training for warrenty work on mercruiser,Volvo,suzuki,tohatsu,Force, and Yamaha I did BE&E,FC(A) and the CIWS FC (C) schools.

the only Yamaha motors that used a reduced pump operating voltage at low speeds was the OX66 motors.

I am failing to understand the use of the word frequency coming up in a simple DC circuit.

Although Yamaha has failed to provide any information at all about operation of the driver in the SM (damn Yamaha) it should not be that difficult to understand and to formulate a test procedure for it. It appears to be the electronic equivalent of two independent relays within the component.

With the driver on the bench, provide it with 12 volts to the appropriate terminal as depicted in the SM. Apply a ground to the appropriate terminal.

Check the terminal for the blue wire for the presence of a ground. There should not be one. Check the terminal for the blue wire with the white tracer for the presence of a ground. There should not be one.

Perform a continuity check to verify that the blue wire and the blue wire with the white tracer are not connected to each other, which if there is would indicate an internal fault.

With two multi-meters set on the continuity setting, one connected to the driver output blue wire and one connected to the driver output blue wire with the white tracer, ground first the black wire with the white tracer and then ground the blue wire with the red tracer. Make a note of which wire grounds the LP pump and which grounds the HP pump. Let us have that information please, because no where in any Yamaha documentation can I find which input wire is supposed to ground what output wire. With one driver input wire grounded only one output grounding wire should indicate continuity. If both output wires are grounded by one input wire the driver is defective.

You might also want to check both the ground input wires from the ECU to make sure that only one wire is grounded when the key is first turned to the ON position. Not sure which wire it will be. You can tell us. The other wire from the ECU to the driver (for the LP pump) should not be grounded. If both wires are grounded there could be an ECU fault or a wire fault.

See below and hope it helps. Rotsa ruck as the japs would say.

well, here's some information "from the field"

sadly it does not support what I assumed would happen...

I detached the "drive unit assembly" on my F225TXRD from the harness connector

with test leads, supplied 12V+ to "R/Y", grounded "B",

connected one lead of a digital voltmeter to 12V+

and the other to "L": as expected, no voltage measured

then used another test lead to take "L/R" to ground :

bingo! "L" is now grounded, meter shows 12V !



So it appears grounding the L/R wire "turns on" the VST pump.

Now here's the problem:

I then moved the meter lead to "L/W" - fully expecting to see continuity there once I grounded "B/W"

didn't happen. Grounding neither B/W nor L/R had any effect on L/W.

Tried it three times, making sure I didn't just have a problem with my leads or connections.

It occurs to me, now, that I should have also tried grounding B/W and L/R simultaneously - didn't think of it.

Back to the test bench for you.

Enquiring minds need to know.

ehhhhh - I don't know.

If they weren't my own parts, I wouldn't hesitate - but I really don't want to lose any of the "magic smoke"

Here's another curious fact:

While I had the driver disconnected, I played a bit with the harness side; the L/R and B/W wires.

I had "key on"and YDS connected; I planned to use it to run each pump to see the ground "turn on".

I connected one side of the voltmeter to 12V+, and then probed the L/R and B/W contacts (going to the ECM)

I expected to see no voltage - at that point, neither pump would have been running, so the ECM would theoretically "not be providing a ground".

Well, I measured ~10V on L/R and ~4V on B/W. Going to ground, through the ECM.

That spooked me, I didn't go any further, didn't see what happened if I had YDS run the pumps.

There should be nil concern with grounding both the B/W and the L/R wires at the same time. That is exactly what the ECU does continuously when the motor is running and the RPM is above 1200.

Perhaps the circuity is designed such that the lift pump wire will be grounded only if and when the VST pump is being grounded, since the latter happens first and the lift pump only happens later. And intermittently at that if the RPM is below 1200.