Twins DF175A both running rough

[blbaker88]

Fuel as either starvation or quality has been eliminated as a culprit. According to the mechanic # 2 cylinder on each engine is not producing combustion. The spark plug produces spark, fuel injector sprays in fuel, and it has compression. It would seem that it is not doing all 3 at the same time. In my mind I keep going back to VV timing.

[artdf175]

I go back to my question re the engine interface cable????
yes or no??

as IF yes- disconnect it and run the engines..
Art

[blbaker88]

yes that has been done. The motors have been ran independent of the boat haresses, power, and fuel. Neither performed any different.

[Harper]

Fuel as either starvation or quality has been eliminated as a culprit. According to the mechanic # 2 cylinder on each engine is not producing combustion. The spark plug produces spark, fuel injector sprays in fuel, and it has compression. It would seem that it is not doing all 3 at the same time. In my mind I keep going back to VV timing.

VVT works by changing the rotational position of the entire camshaft. Why do you think it would affect only cylinder #2 if it were the culprit? If combustion is truly not taking place at the correct time, then it would seem more likely that the ECM, which determines the timing of ignition for each cylinder, is sending a faulty signal to cylinder #2. But you've said everything to do with the ECM has been changed with no resolution.

So ...... back to post #18 ...... Just what did they change in the way of wiring harness? Cable to #2 coil pack?

By the way, both engines beginning to act up at the same time and having the exact same cause sounds like a conspiracy to me.

[blbaker88]

i know how crazy it sounds...The tech said they swapped out the ECM, the wiring harness under the cowling, and disconnected it from the boat. They have swapped out coil packs, and fuel injectors. I suspect its either the cam shaft position sensor or VVT. VVT only because I was right in the RPM range where VVT is active when the failure occurred, and because no one has come up with a better place to look.

Maybe it is some other sensor sending bad data to the ECM and it is putting the motor in fail safe mode. One of the mechanics suggested that this may be the cause. According to the mechanic, the problem moved from #2 to #4 after he moved the adjusted the timing chain. Apparently fail-safe shuts off the even cylinders.

[artdf175]

yes that has been done. The motors have been ran independent of the boat haresses, power, and fuel. Neither performed any different.

ok but did you disconnect the engine interface cable - like completely unplug the cable itself ?

here is the reason I ask- I fought for over a year running along for various minutes and out of no where the engine would drop to 4000 RPM and not run any faster. kill the engine and would run WOT for a few minutes and then just drop back to 4000.
and would be getting a number of errors
then one day I noticed the RPM were jumping from 0 to max - not on the analog gages but the display on my Lowrance.

There is nothing anyplace that discusses 4000 RPM

Out of desperation and no other options I disconnected the engine interface cable from the connector under the cowling ...
problem solved!
The only thing I can think of was that the cable was disrupting data inside the ecm causing erroneous errors

I am unsure if it is part of the harness. I added mine to the engine years later.
Without that cable the engine runs perfectly ..

double check that there is nothing plugged in and try it again

Art 2006 DF275

[blbaker88]

Art,

I will pass this along to the tech. They said they replaced the engine harness; from their description I do not know what they connected or disconnected. They said ran it, I believe the phrase was boat in a box. I took that to mean they ran the outboards without any interface to my boat.

[Moonlighter]

Art,

I will pass this along to the tech. They said they replaced the engine harness; from their description I do not know what they connected or disconnected. They said ran it, I believe the phrase was boat in a box. I took that to mean they ran the outboards without any interface to my boat.

The interface cables are for the C-10 gauges, one per engine, they are not a part of the harness as such, but they connect to the gauge harness behind the console. Only relevant if you run C-10 gauges.

The Suzuki SMG4 gauges do not use these interface cables. So if your boat has them, ignore this post.

As Art implied, a faulty interface cable can cause feedback to the ecu that can cause the engine/s to run badly.

Its simple to test if this is the cause of the problem - as he said, you just unplug them from the engine harness behind the console. The engine still runs, just no engine data on the C-10’s. OK to run like that for the purposes of testing. If the problem goes away the solution is to replace the interface cables with new ones, configure them and away you go.

[blbaker88]

I cannot confirm whether the mechanic did this as described. However, prior to taking to the mechanic I did disconnect the harness and the engines did not perform any better.

[artdf175]

I think there is some confusion
unless they started incorporating the engine interface cable into the harness, this cable is different. It has its own programable chip built into the cable. It was this cable that caused my problem. Never touched the harness.
Again in my case, just disconnecting the harness would not have found the problem.
What I believe to be the problem was some kind of erroneous feedback this cable was giving the ECM.

Ask the dealer to ask Suzuki what causes a 4000 rpm limitation. I bet they won't have an answer.

Somebody would have to explain what "out of the box" means.
With my 175 it has to be cabled to the remote with the some type of wiring harness.

Then again the question might be -do you have an engine interface cable? Do you get the engine stats on a page on your chart plotter? Engine temp, Rpm fuel consumption?
Good luck
Art

[blbaker88]

I understood boat in a box to mean they hooked a battery, and control harness to the engine to run it without it being connected to my boat.
My gauges are the C10 and are NEMA 2000. I can also get engine data on my chartplotter.

There are two harnesses that run from the engines to the boat. One goes to the throttle/shifter, and key switch. The other to the NEMA network.

I do not believe 4000 rpm is a fail-safe setting, I believe it is just what the outboards can achieve at WOT on three cylinders. I was told that in fail-safe the ECM shuts down even cylinders meaning either No. 2 or No. 4; not sure if this is true or not.

I am stumped as to why Suzuki can't figure this out.

[Murray]

Is sabotage/prank worth considering?

[blbaker88]

I suppose it is a remote possibility. But someone would have to energize my lift then lower the boat to gain access

[artdf175]

It would be the cable that connects the engine to the NEMA 2000 network. That is the engine interface cable.
Try unplugging that cable at the engine and running it.

[blbaker88]

I have done this already. It made no difference. I connected up a laptop to the engine connector to run SDS diagnostic tool.