Help! Help! Calling all Suzuki Engine Pro's

[indianjoe]

2005 Suzuki DF90 157 hrs.
Problem:
Motor starts and runs perfect at all rpms idles fine runs full throttle fine then at any moment engine will go into what seems like safe mode. No alarms, no lights, motor will not go over 3000 rpms after a short distance maybe a quarter to a half mile motor will go out of what seems like safe mode and then then accelerate and run perfectly. Symptoms may happen again repeatedly at that point or the motor may run all day and run fine. Recently after doing all of the below motor ran for more than 15hrs over 3 days before it happened again.
What we have done so far:
1. Changed water separator and inspected for water in fuel none found.
2. Changed and inspected low pressure fuel pump and found no debris.
3. Drained fuel from tank and refilled
4. Replaced primer bulb and Installed new fuel lines to motor and low pressure fuel lines under cowling.
5. Ran motor on separate fuel tank still had same issues with injector cleaner water removal additive made no difference.
6. Removed inline anti syphoned valve from fuel line at tank no change.
7. Took to marine repair shop and they ran diagnostics found no codes no issues while engine was in what appeared safe mode.
8. Removed High Pressure fuel pump and inspected vst found no debris everything looked like new. Did not test regulator. Did not replace high pressure filter.
9. Replaced low pressure pump.
10. Tested fuel pressure at fuel rail and it maintained 38 psi when symptoms appeared. No drop in pressure at anytime
11. Did change low pressure pump with used one made no difference.
12. Battery is new connections are good & clean
13. Tested voltage on white wire to ecu from battery replaced slightly corroded fuse holder with new one at battery removed and replaced connection on white wire under cowling with temporary butt connector. Checked for bad grounds cleaned a few questionable connections. Cleaned connector to ecu. Checked fuses for corrosion under cowling. Nothing helped.
14. Went back to marine services and they suggested ecu is next best guess ordered used one from reputable dealer and motor ran perfect for 3 days straight running very hard then it did it again a couple of times on the3rd day after about 10 miles turned around and headed home motor ran perfect all the way back.

I have completely ran out of ideas I hope someone out there can point me to a solution. Can not get into Suzuki dealer for 3 weeks they are so backed up. I really would appreciate any help on this.
Thank you
Indianjoe

[Moonlighter]

Well, you've certainly covered a lot of bases there already!

From what you've described I doubt it would be a fuel issue, as you've covered pretty well everything off in that regard.

So it must be Electrical or electronic.

There are a number of conditions that send the engine into "safe" mode or limit rpm.

The first one that springs to mind is the switch in the engine that limits rpm when the engine is in neutral. It has been reported to fail on occasions. Can be out of adjustment too. So might be possible that it is either failing or is loose and the adjustment is "on the cusp" of where it activates so that as the boat bounces along, perhaps it is losing then regaining contact???

It wouldn't throw any error codes either or record anything in the ECU when it happens because it is a normal function. Normally when the engine is in neutral, if you lift the neutral throttle level up, this switch will activate to interrupt spark and retard engine timing. So the engine runs badly at 3000rpm - a bit like a race car with the pit lane speed limiter activated!

It is a relatively inexpensive part - about $40 from memory - and quite easy to replace. Might be worth a look.

That's all I've got for you.

Good luck with getting it sorted.

[artdf175]

Indianjoe that is certainly one of the best inquiries I have seen in the last couple of years
My question would be if your have the service manual ?
The manual has what I think is s fairly complete list of situations that cause the rev limiter to activate
After everything you have already done go through the items one by one until they are eliminated
Sounds like you have checked wire connections but would go through all of them
Engine is 10 years old with low hours but a any one could have a little corrosion that can be throwing a bad signal to ecu
Good luck and keep us posted
Art

[redlowrey]

Sounds like a neutral switch problem on the engine. Start there, the switch is closed in neutral and open when in gear. Probably needs adjusting.

[indianjoe]

Thanks Moonlighter I will check that out sounds like that might be it. Will let you all know soon and thank everyone for their replies it is very much appreciated. I have an appontment in 2 weeks to take it to the suzuki stealership and am dreading it. Hopefully the neutral safty switch is it. Will be in touch soon stay tuned.

Well, you've certainly covered a lot of bases there already!

From what you've described I doubt it would be a fuel issue, as you've covered pretty well everything off in that regard.

So it must be Electrical or electronic.

There are a number of conditions that send the engine into "safe" mode or limit rpm.

The first one that springs to mind is the switch in the engine that limits rpm when the engine is in neutral. It has been reported to fail on occasions. Can be out of adjustment too. So might be possible that it is either failing or is loose and the adjustment is "on the cusp" of where it activates so that as the boat bounces along, perhaps it is losing then regaining contact???

It wouldn't throw any error codes either or record anything in the ECU when it happens because it is a normal function. Normally when the engine is in neutral, if you lift the neutral throttle level up, this switch will activate to interrupt spark and retard engine timing. So the engine runs badly at 3000rpm - a bit like a race car with the pit lane speed limiter activated!

It is a relatively inexpensive part - about $40 from memory - and quite easy to replace. Might be worth a look.

That's all I've got for you.

Good luck with getting it sorted.

[indianjoe]

Thanks for the info I will check out. Is there a way to bypass the switch to see if that eliminates the problem? On another post moonlighter also sugested it is the neutral safty switch. Does anyone know if there is another neutral switch in the control box? I read somewhere that zuks have 2 of them.

Sounds like a neutral switch problem on the engine. Start there, the switch is closed in neutral and open when in gear. Probably needs adjusting.

[Auburn02]

I believe that is correct that there is one at the engine and one in the control binnacle. I'm not sure where the one on the engine is located, binnacle switch should be easy enough to find. I also don't know if they would both cause the same behavior, but it really sounds like you're on the right track since it's throwing no code, and it always falls off to around 3000 RPM which happens to be the RPM limit when the motor is revved in neutral, as Moonlighter has explained here.

[indianjoe]

Thanks Auburn!

I believe that is correct that there is one at the engine and one in the control binnacle. I'm not sure where the one on the engine is located, binnacle switch should be easy enough to find. I also don't know if they would both cause the same behavior, but it really sounds like you're on the right track since it's throwing no code, and it always falls off to around 3000 RPM which happens to be the RPM limit when the motor is revved in neutral, as Moonlighter has explained here.

[indianjoe]

Thanks Redlowrey for the help!
As you and moonlighter and others have suggested to check the neutral switch I just did.
I pulled the connector and jumpered the switch with my ohm toner and it rings on and off just fine as you move the shifter on and off neutral position on up to full throttle nothing out of the ordinary. I guess the switch could be internally shorting out at times under certain conditions mentioned above. Am I stuck with just buying a new one to find out? Is there any other way to test the switch? Thanks again!

Sounds like a neutral switch problem on the engine. Start there, the switch is closed in neutral and open when in gear. Probably needs adjusting.

[Solarman]

Indian Joe, the neutral safety switch (nss) will not allow you to start your motor. It has nothing to do with your RPMs. And you might have 2 nss, one is in the control and the other is in the motor at the shift linkage.

The shift position switch is mounted next to the nss on the motor. The shift position switch is the one Grant (moonlighter) was suggesting you check. It limits the motor to about 3k-3.5k RPMs, and if, as Grant said, it could be just slightly out of adjustment, or intermittent and may go out.

Anyway, check out the shift position switch for you problem.

Good luck, yes, you can bypass to see if it eliminates your problem.

[Auburn02]

The shift position switch is mounted next to the nss on the motor. The shift position switch is the one Grant (moonlighter) was suggesting you check.

Ah, that's the switch I was thinking of, not the neutral safety switch. For some reason in my head I thought they were one and the same.

[indianjoe]

Well I guess I am a little confused. I went back out and looked and there is only what the manual calls a neutral safety switch on the engine shift linkage and one in the control box. I don't see another switch anywhere on the motor near the linkage at all. Are we calling the switch by two different names. On this motor 2005 df90 is there a shift position switch? If so please help me find it. Thanks for the help!

Ah, that's the switch I was thinking of, not the neutral safety switch. For some reason in my head I thought they were one and the same.

[redlowrey]

Mate there are two neutral switches, one in your binnacle and the other on your engine where the shift linkages are. The one in your binnacle stops you from starting in gear, the one on your motor stops you from starting in gear as well as informing the ecu if the gear shift is in gear. I will explain how the system works early engines and late engine. When the ignition switch is turned to the start position, battery voltage will flow through a brown wire through the switch in the binnacle to pin five on the ecu and through the other switch mounted on the engine at the linkages. In neutral the switch will be in the closed position so battery voltage will flow through it to the starter motor relay coil to earth. This will energize it and pull the main relay contacts together then battery voltage will flow to the starter soliniod pull in winding through the brushes to earth. If the neutral switch on the engine is open, the engine won't crank over plus even if you bridged the starter and got it to crank the engine it will not start because the ecu will not put a ground on the injectors. In neutral with the engine running 3000rpm max timing 8 degree's. Late engines same deal except the starter motor relay will be grounded inside the ecu , this is because when you do a iac idle adjustment the motor has to be running and you turn the starter switch to the start position five times so the iac's duty cycle is set at 15%.

[indianjoe]

Thank you for the helpful information.
I have ordered a new neutral Safty switch for the motor as mentioned above it worked fine for the neutral cut off part. I just don't know how to test for the intermittent problem of the 3000 rpm cut off part other than replacing the switch as moonlighter had mentioned. I have one ordered to be here Friday and will try that out. $37bucks. Worth a try. After calling the zuk dealer to see if they had one he said he rarely sees that switch being the problem as far as being intermittent and cutting the rpms to 3000k. He said that they usually just go bad and don't work at all. He said you can tell by the scanner if it is showing neutral gear position instead forward gear position at the time of the engine cutting back to 3000k. I said it took me 3 days to get it to do it again and he said I could not afford to pay him to ride around in the boat for 3 days holding the scanner waiting for something to fail. Cheaper to just buy the switch.
I will post back after I test to see if that was the problem this weekend. Wish me luck!
Indianjoe.

Mate there are two neutral switches, one in your binnacle and the other on your engine where the shift linkages are. The one in your binnacle stops you from starting in gear, the one on your motor stops you from starting in gear as well as informing the ecu if the gear shift is in gear. I will explain how the system works early engines and late engine. When the ignition switch is turned to the start position, battery voltage will flow through a brown wire through the switch in the binnacle to pin five on the ecu and through the other switch mounted on the engine at the linkages. In neutral the switch will be in the closed position so battery voltage will flow through it to the starter motor relay coil to earth. This will energize it and pull the main relay contacts together then battery voltage will flow to the starter soliniod pull in winding through the brushes to earth. If the neutral switch on the engine is open, the engine won't crank over plus even if you bridged the starter and got it to crank the engine it will not start because the ecu will not put a ground on the injectors. In neutral with the engine running 3000rpm max timing 8 degree's. Late engines same deal except the starter motor relay will be grounded inside the ecu , this is because when you do a iac idle adjustment the motor has to be running and you turn the starter switch to the start position five times so the iac's duty cycle is set at 15%.

[indianjoe]

Thank You!

Just wanted to say thanks to Moonlighter and everyone else that contributed to this thread. Changing the neutral safty switch has fixed the problem. I have ran about a 3/4 of a tank of gas at almost full throttle without problems.
Thanks again!
Indianjoe