Suzuki 140 Neutral Safety Switch location

[buyslake]

I brought my 2013 Suzuki df140a motor into the Suzuki dealer, they had it a few hours and now want $450 for diagnostic services. They said my problem is the Neutral Switch assembly part number 37721-93J00

They want another $200 to install this switch. Therefore I ordered the switch and I am going to install it myself. However, I do not know where this switch is located to replace. Please advise, photos welcome.

Is it on the motor? if so where? Or is it located in the hand control near the driver's seat?

[artdf175]

well get a service manual first!!!
yes there are two - one on the remote where your throttle control is and one under the engine cover where the throttle and shift cables are
Find another dealer
shop rates should not be over $70 - $80 an hour at the most

[buyslake]

This dealer is high $125/he however the next dealer is 80 miles away. You say there is two neutral switch assemblies. Are they both the same part number? Can you tell if this one 37721-93J00 is in the motor or in the throttle control box?

Is there a free service manual for 2013 140hp Suzuki PDF download somewhere? All I could find is for an older 2003 year

[Moonlighter]

Lets back it up here a bit ....

What were the problems/symptoms that prompted you to send it to the dealer in the first place? Please explain in detail what it was doing and the circumstances.

This info is probably going to point us to the answers.

Anyway, the link below takes you to the parts diagram, and shows that the part number you have is on the engine. Its attached to the linkages and plugs into the ecu.

https://www.boats.net/catalog/suzuki...it-df140at-e03

The symptoms of this switch having failed would be that the engine starts and idles fine, but when put into gear, it will not accelerate past about 3000rpm - this is because the signal that tells the ecu that the engine is in gear has not been sent, so the ecu thinks the engine is still in neutral. So it restricts fuel supply, spark and advance to prevent over revving in neutral.

[buyslake]

Lets back it up here a bit ....

What were the problems/symptoms that prompted you to send it to the dealer in the first place? Please explain in detail what it was doing and the circumstances.

This info is probably going to point us to the answers.

Anyway, the link below takes you to the parts diagram, and shows that the part number you have is on the engine. Its attached to the linkages and plugs into the ecu.

https://www.boats.net/catalog/suzuki...it-df140at-e03

The symptoms of this switch having failed would be that the engine starts and idles fine, but when put into gear, it will not accelerate past about 3000rpm - this is because the signal that tells the ecu that the engine is in gear has not been sent, so the ecu thinks the engine is still in neutral. So it restricts fuel supply, spark and advance to prevent over revving in neutral.

When I start the motor it runs fine, then when I put it in gear it dies immediately. I can get it to go fast if I start it and slam in forward really fast bypass slow speed then it works fine at high speed, when I go back to slow speed it dies.

I wish I found this forum earlier before I took to mechanic and lose $400 in diagnostic troubleshooting. I somehow didn't see this forum before when I was looking for help.

The part is coming today so I will try and see if it works!

[Moonlighter]

That does not sound like a neutral switch issue to me.... but anyway, proceed. Do report back the results so we know,

[buyslake]

I installed the Neutral Switch Assembly Part no. 37721-93J00 in the motor and took the boat to the lake for testing. This part replacement did not fix the problem. The problem is still there. Now I wonder if I should place the other neutral control switch in the remote control? Part number 37721-95500

The motor starts and runs, however as soon as I put it in gear it dies. If I start it and thrust forward very quickly the motor will take off but when I get it back down to near neutral it will die.

Here is the Suzuki tech notes from when I had it in the dealer....... "Checked fuel pressure 42 PSI at fuel rail when key is turned on. 51 PSI of fuel pressure at idle (all in spec). Ran in test tank for half hour. Would die as motor was shifted into gear. Tech depressed switch and shifted motor into gear by hand. Motor did not die . Determined problem to be neutral safety switch on motor to be faulty"

Therefore, I replaced the neutral safety switch in the motor as the tech. suggested that as being the problem, however it was not the problem. Therefore, I am wondering if it is the neutral switch assembly in the remote control box??????

Is it worth ordering the neutral safety switch in the remote control and trying that? Or what do you experts here suggest?

[noelm007]

Have you checked the switch adjustment? maybe it was not actually faulty, but appeared to be, so, replacing it did not fix it, because it's still out of adjustment, that said, the symptoms are not exactly what a neutral switch would give, but so far, it's just guessing.

[buyslake]

Have you checked the switch adjustment? maybe it was not actually faulty, but appeared to be, so, replacing it did not fix it, because it's still out of adjustment, that said, the symptoms are not exactly what a neutral switch would give, but so far, it's just guessing.

Thanks for the advice,
could you specify more clearly what you mean by switch adjustment? And where is this located?

[buyslake]

Another observation......

I noticed when I go fast, then come back down to slow speed really slow on the throttle it will keep running and now it will run slower then it did when there was not a problem. I can get it to go 2 mph and before I had a problem it would never run under 3.3 mph. So this makes me wonder why am I able to go slower now. When I keep moving it toward neutral it eventually dies because it seems it runs so slow the motor can't handle it anymore and dies.

Is it possible there is something out of adjustment in the remote control throttle box or in the motor that would cause it to run slower then before in slow speed and therefore is the reason it shuts off????

[buyslake]

Another thing I notiiced is when I kick it down to fast speed then come back down to slow speed if I back off the throttlle fast it dies. However if I back off the throttle real slow toward neutral, I now see that the motor runs very slow like now the boat will go 2 mph and before it there was not a problem the boat never moved under 3.3 mph at the slowest speed. So this makes me wonder why am I able to go slower now? It seems like the closer I get to neutral it gets the idle so slow that it can't handle it then shuts off. Maybe it can run in neutral because there is no load on the motor? but when I put in gear it dies because the engine isn't running enough to handle the new load???? Is it possible there is something out of adjustment with the remote control throttle at the drivers side or in the motor?????

[Moonlighter]

Idle speed is set by the ecu. It has nothing to do with either of the neutral throttle switches. They are simple on/off switches. The one on the engine simply tells the ecu whether the engine is in gear or not so it controls whether the engine revs above a safe level at idle (about 3000rpm). The one on the binnacle is to stop the engine being started if it is in gear. Eg in neutral = allows engine to be started, or in gear = engine not allowed to start.

Idle speed is controlled by the IAC valve. IAC = Idle Air Control.

A faulty IAC valve will usually see the engine idle speed jumping around and/or the engine stalling when started or when brought back to idle. But because the IAC only controls idle speed, if you jump quickly to more throttle the engine will run fine at greater revs but is likely to stall when brought back to idle speed. (Is this sounding at all familiar to you??)

If you google IAC valve you will see that it is a common part used on many car engines etc and you will see explanations of what it does and how it works.

The IAC valve when replaced or removed to be cleaned will need to be reset and the idle speed adjusted by following the procedure set out in the service manual. If you search this site for posts regarding the IAC you are sure to find the procedure, I cant remember it offhand. You will also find how some people have cleaned the IAC valve and the little air hole that sometimes gets blocked and can cause poor idling situations that are not unlike your engines symptoms.

I am being extremely kind with the following comment, but maybe the Suzuki mechanic mistakenly wrote down the wrong part name in his report, when he wrote that the neutral switch needed replacing, when he really meant to say the IAC valve....?

Again if you use the parts section of this forum and put your engine details in, you will find your engine’s parts page, and a bit of searching there and you will find the IAC valve and see where it fits.

[buyslake]

*** thanks for that information. I will look into the IAC Valve

[redlowrey]

I was just reading this post and was going to reply by saying that your problem has got nothing to do with the neutral switch. Early engines had what they called a closed throttle switch that would inform the computer when the throttle was in neutral and depending on temperature would control the amount of air bypass and ignition timing so the engine did not stall.
Your engine has a variable voltage throttle position switch to inform the computer at what position the throttle is at any position, so when you pull back on the throttle it will monitor the timing and air bypass so the engine don't stall, your symptoms sound like iac valve problems, but I would do other checks in the system before you spend more money. That fuel pressure seems high, I think there are other problems besides the iac. Does it run smooth when it is cold or a little rough,
Very poor service from the Suzuki dealer, they cant even diagnose a simple problem.

[buyslake]

Ir seems to run good when cold at idle. But After run it at full speed across the lake and drop throttle quickly it dies. Then I start it and it runs for just like 3 seconds and it dies. So I start it again and quickly accelerate fast to keep it from shutting off.