01' Yamaha tachometer(multiple questions)

B

Brenardo

Cadet
Joined
Apr 15, 2013
Messages
16
Been reading and studying hard for this info and can't seem to find a solution anywhere on the interwebs.

Engine runs really good especially above idle.

The (new analog) tachometer doesn't register at idle. Teleflex set to 6P. If throttle is slightly engaged it will start to read at a minimum of 700-800 rpm (correct idle?) and the engine sounds better at this point. All connections have been checked and double checked and I feel extremely confident all is well there.

Engine has been known to stall when putting into gear, but as of this afternoon it has also began to almost stall when coming from higher RPM into neutral. I feel this is directly related to the fact I cleaned the Idle Control Valve(wasn't very dirty).

So my questions are:

What are the correct voltages on the green sending wire for the Tach coming from the ignition and ECM.

How does the ECM determine the RPM of the engine? Crankshaft position sensor? Coils?

Can the idle speed be adjusted without having to adjust the TPS?

Sorry for the novel but I am at wits end and have trust issues when it comes to letting others "work" on my any things.
 
Last edited:
C

Capt Ken

Commander
Joined
Jul 30, 2002
Messages
2,269
Re: 01' Yamaha tachometer(multiple questions)

You failed to give the most important information. Model number?
 
C

Capt Ken

Commander
Joined
Jul 30, 2002
Messages
2,269
Re: 01' Yamaha tachometer(multiple questions)

Sorry but you are going to have to get past that trust issue being you need to have the engine checked with the diagnostic system and I would guess you don't have one.
 
9

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,874
Re: 01' Yamaha tachometer(multiple questions)

Yamaha service manual for you model motor and the proper test equipment are what you need to start out with if you plan on working on it yourself.
The manual will give you the steps, and specs to do the service and will let you know what equipment is needed I believe,
And then you will have to understand how to use the test equipment.

Or take it to a very good Yamaha shop with trained techs

Good luck
 
B

Brenardo

Cadet
Joined
Apr 15, 2013
Messages
16
Re: 01' Yamaha tachometer(multiple questions)

Thanks for the reply.

When hooked up to YDS everything comes back with in spec. RPM fluctuating but all sensors are OK. Maybe some suggestions as to what you have seen personally that are similar to my existing issue?

Service manual's only reference to a tachometer is testing throttle valves. External tachometer to be hooked to plug wire #1.

Again, nowhere in the service manual does it refer to the correcy voltage reading of the green sending wire for the tach that originates from the ECM.

Also again where does the ECM gather RPM information to be sent to the tachometer on the dash? Not readily accessible information. When I talked to Yamaha dealer they suggested that I contact the engineers in Japan as they had no idea.

As far as being able to learn how to use testing equipment and read a service manual I feel more than confident in my mechanical ability to do so.
 
Last edited:
B

Brenardo

Cadet
Joined
Apr 15, 2013
Messages
16
Re: 01' Yamaha tachometer(multiple questions)

99yam40 said:
Yamaha service manual for you model motor and the proper test equipment are what you need to start out with if you plan on working on it yourself.
The manual will give you the steps, and specs to do the service and will let you know what equipment is needed I believe,
And then you will have to understand how to use the test equipment.

Or take it to a very good Yamaha shop with trained techs

Good luck
Click to expand...

Perhaps you could explain the proper testing procedure as to finding a "very good Yamaha shop" in my locale.
 
S

speed_demon

Petty Officer 2nd Class
Joined
Mar 20, 2012
Messages
111
Re: 01' Yamaha tachometer(multiple questions)

The green wire pulls a tach signal from the stator. The ECU has nothing to do with it. When you say 6p do you mean 6 pulse or 6 pole? Your tach should be set to 6 pulse or 12 pole.

If you adjust the idle you need to check the TPS output voltage at idle and WOT and compare to the specs in the manual and adjust accordingly. I would guess .5v at idle and around 4.5-5v WOT but I'm not specifically familiar with your motor. Set to idle spec, check for WOT spec, and for good measure make sure the voltage increases linearly and there are no spikes or dips.
 
B

Brenardo

Cadet
Joined
Apr 15, 2013
Messages
16
Re: 01' Yamaha tachometer(multiple questions)

It is a Teleflex gauge and is set to 6pulse. And it functions above idle.

The wire that ohms out from the tach is one of the green wires that is located in the 10pin connection to the ECM. But I don't disagree that the ECM gets the output from the stator.
 
S

speed_demon

Petty Officer 2nd Class
Joined
Mar 20, 2012
Messages
111
Re: 01' Yamaha tachometer(multiple questions)

The 10-pin cable isn't an ECM cable. With the exception of the tach signal it is just power inputs and outputs. Inputs: ignition on/off, start, trim up/down and Outputs: tach signal, +/- power, low oil/overheat buzzer +, ect... Although the ECM may get rpm info from the same place your tach is receiving a raw stator signal. Now if you were running a newer motor with command link gauges data would be sent from the ECU but over a separate data cable, not the 10-pin cable.

Have you tried another tach?
 
9

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,874
Re: 01' Yamaha tachometer(multiple questions)

on the Yamaha's I have played with the signal from stator to the tach is a pulse and the tach counts the pulses,
I have read some motors tach signal comes form ECU but I have no idea where your signal comes from or what voltages they would be
 
S

speed_demon

Petty Officer 2nd Class
Joined
Mar 20, 2012
Messages
111
Re: 01' Yamaha tachometer(multiple questions)

If the signal is coming directly from the stator it will be unrectified and unregulated. Meaning it will be AC and voltage will fluctuate with RPM. Depending on configuration you may vary from 13-50v from idle to 6k. The tach doesn't really care about voltage, just pulse frequency. Now if you have a bad stator and it's producing nil at idle maybe that could be your problem. Check charging voltage at idle. Unless your not getting any increase it's probably fine.
 
B

Brenardo

Cadet
Joined
Apr 15, 2013
Messages
16
Re: 01' Yamaha tachometer(multiple questions)

New tach installed.

Rectifier is charging the battery .

I am confident that the rectifier is not where the tach signal is from. Three wires from stator/lighting coils and a red and black.

I am gonna search thru the service manual and test the stator output at idle.

I was told by a tech rep at V3 who builds the tachs for Teleflex that the tach requires 3.5AC volts to operate.
 
B

Brenardo

Cadet
Joined
Apr 15, 2013
Messages
16
Re: 01' Yamaha tachometer(multiple questions)

Just doing regular maintenance this afternoon. Changing oil and plugs. I decided to mess with this tach issue again.

Tach seems to be functioning better today, but only after initial throttle increase. When initially started the tach will not register after revving the engine it reads what sounds and appears to function properly even at idle. (Well mostly) A few times the engine seems to drop below normal idle.

Now because of this I started poking around and I stumbled on to the ISC and that booger was HOT to the touch. I mean hot like rectifier hot. I assume that the ISC could be the cause of the Tach not reading due to RPMs being to low to produce proper stator voltage?

So basically what is normal operating temp of the ISC? I have read horror stories about ISC valves failing and burning up ECMs.

I unplugged the ISC for the time being. Is this acceptable for a short period of time?

What do you guys think?
 
S

speed_demon

Petty Officer 2nd Class
Joined
Mar 20, 2012
Messages
111
Re: 01' Yamaha tachometer(multiple questions)

It sounds like the ISC is binding up or shorting out. It shouldn't get hot. I would pull it out and see what it does when you cycle the ignition. It should move in or out smoothly. If it twitches or doesn't do anything it may be bad. It's not a cheap part. If you leave it unplugged you could manually adjust your idle but keep precise track of the turns so you can put it back when you get it fixed right. Your tach may not have a problem. Just a bad ISC causing really low idle.
 
Silvertip

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,762
Re: 01' Yamaha tachometer(multiple questions)

That would also account for why idle rpm fluctuates and the engine is tending to die coming off high throttle or going into and out of gear.
 
B

Brenardo

Cadet
Joined
Apr 15, 2013
Messages
16
Re: 01' Yamaha tachometer(multiple questions)

With the ISC disconnected can anyone verify this will NOT cause issues with the ECM? I would hate to burn up the ECM over $350.

But the specks are on fire! And I need a tug on my line.
 
S

speed_demon

Petty Officer 2nd Class
Joined
Mar 20, 2012
Messages
111
Re: 01' Yamaha tachometer(multiple questions)

Unplugging will not damage the computer. Leaving plugged in very well could. Worst case scenario your motor throws a code or goes into limp mode.
 
B

Brenardo

Cadet
Joined
Apr 15, 2013
Messages
16
Re: 01' Yamaha tachometer(multiple questions)

I am not fimilar with limp mode, although I have heard many people reference it.

What would I look for in limp mode? I would assume loss of power anything else?
 
S

speed_demon

Petty Officer 2nd Class
Joined
Mar 20, 2012
Messages
111
Re: 01' Yamaha tachometer(multiple questions)

It depends on the motor. Limp mode can be an rpm limiter (usually when you have an oil issue) or safer fuel/ignition maps. I'm not super familiar with your particular motor but the ISC would probably just throw a code. Try it and see if it has good power and gets up to rpm. I would focus on determining 100% if the ISC is bad and start looking for a cheap replacement.
 
You must log in or register to reply here.
Top