Fuel Reserve

[Flynt]

Someday someone, somewhere will actually have to apply a little more diagnosis and research and present the facts.

We can make this a WCR project...  Wiz always needs to be in Res to run the fuel pump, so we know the pump's not getting power in Normal.  All we have to test is whether I'm getting a low signal from my fuel level sensor.  If I am, then switching to Normal position should induce a miss instantly if there is any ignition impact from the low fuel signal...  I know it doesn't do that (we'll confirm that as well however), so we would have definitive proof for a '92 ABS model at least.

Frank

[aviationfred]

 
Re: Speed Hut Multi Gauge install

« Reply #27 on: March 30, 2017, 10:32:45 AM »
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The only negative that I can take away from this project reared it's head this morning. This revolves around the reserve switch circuit. With the switch in the on position, there is no power to the fuel relay. Put the switch in the reserve position and the fuel pump is happily clicking away. At the moment I am not that concerned. The new fuel gauge has a low fuel warning light and I plan to monitor the fuel situation as the tank gets near the empty mark.



I pulled this from my aftermarket gauge install for the 1989 1300. Just like the Wizard, I am required to have the reserve switch activated for the fuel pump to work. I have not investigated the whys for this to be the case.

The empty fuel tank and the fuel sender that I will look at this weekend is on my 1990 1200 that has all OEM wiring and gauges. I am hopeful that I can submit some good answers. I think it will help, that I am an Electrician by trade.

Fred

[simi_ed]

Good morning fellas (notice I did not say Gentlemen; wanted to include everybody!).

Holy Toledo!
<snip>

Oh my, never thought I would see the day where it may be better to discuss oil – would the gentleman from southern California like to begin...?!

Keep smiling!!!

And of course ride safe,

Midget

EDIT: Mr. T: just kidding

I'll take my cue:  AmsOil is the only way to go!. If you use anything else you might as well run Harley oil!

Ed

[ZOA NOM]

What a way to welcome in the weekend with the resurfacing of this old chestnut.

Let me make it very clear. How the reserve switch functions is not and never has been in doubt. The only issue has ever been who understands it and who doesn't.

How do you like your proof served up...

Anecdotal
professional
Empirical
Scientific

It has been proven every which way.

FFS, this is kindergarten level diagnostics. I know this is an owner's forum and not a mechanic's forum but proving it for yourself for those who have even basic mechanical knowledge is simple. This idea that it is an ongoing mystery is absolute rubbish.

Some years back when this was discussed at length, I conducted some tests, not for my benefit but to demonstrate beyond doubt how it worked. The results were irrefutable, until Randy called into doubt my professional credentials and suggested that my findings were not credible unless supported by video. Errr, that would be a video showing a test light on......then off......then on......  The suggestion that I couldn't tell the difference or that I was misrepresenting the facts beggars belief.



Rich Pleinnes- there is no meat left on the bone. This is not the space shuttle, it is the reserve switch on a motorbike. Figuring out how it worked was instant, proving it took 5 mins (and has been previously posted)

Mark Olsen - the symptoms of electrical vs fuel interuption cannot be mistaken one for the other. Especially a bike cutting to 2 cylinders as opposed to running out of fuel. There is a chasm between the two. The idea you mention that it cuts to 2 cylinders was not the resolution but the myth that was dispelled. I see no point in being glad you don't have a fuel pump, it is the only way to get proper filtration and in use, are trouble free. Petcocks seem to give far more grief here than pumps.

Mike Ramos - I don't know where your reserve fuel tank is but presumably it is further away from the pump than the bike tank. Of course it's going to take longer to draw fuel from it. The time it takes is relative to the distance it has to travel and the amount of fuel it has to move).

Great White - the test has been done a number of ways. The simplest one being putting a test light on the pump when the main tank starts to splutter. Tip the bike to left so that what little fuel remains flows away from the sender unit and the light goes out. Stand the bike upright (or to the right} it comes back on. With it tilted to the left and the test light off, move the switch to "RES" and the light will instantly come on. Or, as Pat described, simply pull over when the bike stops running on the main tank, with the ignition on and switch to RES and you can hear the pump spring into action.

Randy - there is no "quick fill" function and there is no relevance to earlier non fuel pump models. The restoration of normal power is NOT instant when you flick the switch, it takes a number of seconds to regain normal operation. The time depends of the how long you have let it stumble before switching it over. If you are tuned into your bike and pick it up at the very subtle onset, it is very quick, it you wait until the thing will barely run, it takes longer after switching over (more fuel needed to fill the bowls) As for the manual not mentioning the switch in the circuit, as you know, workshop manuals have many errors and omissions. However, what you have in front in you is what it is.

Pat Conlon - you are right, it starts out so subtly you can barely pick it and gets progressively worse until it eventually dies, switching to reserve if left until this stage takes longer to restore power.

Randy (again) much of you argument seems to stem from the belief that power is restored "instantly" when switched to reserve, it's not. The longer you leave it stumbling before switching over, the longer it takes to run clean again.
I don't know whether you ride this model yourself and if so how often you run it to reserve, but the restoration of power is definitely not instant.

Zoa - maybe you could contribute your own findings on this subject.

Frank - makes sense.

The bottom line is, there is no mistaking an engine running out of fuel with one that is running out of spark.

Great stuff guys, just like the old days!

IMO

Noel

Ugh... as an electronics technician trained in TTL logic, I understand the function of a digital system and the use of square wave duty cycle to modulate fuel delivery, therefore, it makes sense that the fuel sensor that is fed to the digital computer is doing precisely that - varying the duty cycle of the ignition, not turning off the fuel pump, which in turn reduces the flow of fuel (modulates pressure), while not simply draining the bowls empty. This is why both theories have some validity.

There.

[FJ_Hooligan]

I'm confused.  How does varying the duty cycle of the ignition reduce fuel flow? 

Those appear to be totally different and unrelated outputs of the Digital Ignitor Unit.

[FJ_Hooligan]

Re: Speed Hut Multi Gauge install

« Reply #27 on: March 30, 2017, 10:32:45 AM »
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The only negative that I can take away from this project reared it's head this morning. This revolves around the reserve switch circuit. With the switch in the on position, there is no power to the fuel relay. Put the switch in the reserve position and the fuel pump is happily clicking away. At the moment I am not that concerned. The new fuel gauge has a low fuel warning light and I plan to monitor the fuel situation as the tank gets near the empty mark.



I pulled this from my aftermarket gauge install for the 1989 1300. Just like the Wizard, I am required to have the reserve switch activated for the fuel pump to work. I have not investigated the whys for this to be the case.

The empty fuel tank and the fuel sender that I will look at this weekend is on my 1990 1200 that has all OEM wiring and gauges. I am hopeful that I can submit some good answers. I think it will help, that I am an Electrician by trade.

Fred

I think I can explain this based on the first diagram that Randy posted. 

On the upper left, what is called the Fuel "Censor" (A) appears to be a variable resistor to ground.  Part of this circuit includes the Fuel Warning Light (B).  Current flows through the light on its way to ground through the Fuel Sensor.  I would assume that the Fuel Sensor has high resistance when the tank is full and gets progressively less restrictive as the tank empties.  The Digital Ignitor Unit (H) sees the fuel level as a signal that's proportional to the amount of current flowing through the Fuel Sensor via the Fuel Sensor Input Circuit (I) which converts the analog signal into something digital that the CPU uses.

As the resistance decreases and the current flow through this part of the circuit increases it begins to light up the Fuel Warning Light.  The light gets brighter as the fuel level goes down.  The Fuel Level Input Signal is evidently an input to the CPU which activates the Fuel Pump Relay (T) and keeps the pump running.   At some point, the "fuel" signal exceeds a threshold current level and the CPU shuts off the fuel pump relay.

The Reserve Switch (D) provides an input to the CPU that provides bypass logic that turns the fuel pump relay (back) on.

If you need to have the reserve switch on all the time then that means you've lost the leg of the circuit that includes the Fuel Warning Light and the input signal to the Fuel Sensor Input Circuit.  Does your fuel gage work?  I would think this signal is a derivative of what drives the fuel gage.

DavidR.

[FJ_Hooligan]

Studying the wiring diagram, the fuel gage level is a separate signal from the tank sender unit.  It's a green wire.

The input to the Relay Assembly and the Fuel Pump Relay that also runs to the Fuel Warning Light is G/R (green/red).

See if you can ohm the G/R wire from the tank sensor connector to the Relay Assembly connector.  If you don't have continuity, that would be a good place to start.  I don't think the circuit grounds through the Fuel Warning Light (although that's a remote possibility, meaning that if the bulb is not in place then the circuit is dead but that would be a really dumb circuit design)

[Mark Olson]

Noel, 
no fuel pump to go bad , I have a larger hose to fill my bowls.....
larger needle and seat that don't plug up , and living in California my fuel is good.

So yeah ,, I'm Glad.

As for the Reserve switch quest , it appears the fuel relay power is cut ...and what else? maybe it reduces power to conserve fuel to get you to the next gas station. An off the road stationary test is invalid.

Please conduct the following test for the good of the FJ collective.
attach sensors and probes to your ignition system to record input and out put voltages while operating your FJ.
now ride till you run out of gas and have to switch to reserve but don't switch till the engine dies and you can record your readings ... Like does the engine still get spark when you have stalled with the reserve switch still off.
Make sure you ride to a remote area as roadside tests are dangerous ..

I am counting on you.

[ribbert]

Noel, 
no fuel pump to go bad , I have a larger hose to fill my bowls.....
larger needle and seat that don't plug up , and living in California my fuel is good.

So yeah ,, I'm Glad.

As for the Reserve switch quest , it appears the fuel relay power is cut ...and what else? maybe it reduces power to conserve fuel to get you to the next gas station. An off the road stationary test is invalid.

Please conduct the following test for the good of the FJ collective.
attach sensors and probes to your ignition system to record input and out put voltages while operating your FJ.
now ride till you run out of gas and have to switch to reserve but don't switch till the engine dies and you can record your readings ... Like does the engine still get spark when you have stalled with the reserve switch still off.
Make sure you ride to a remote area as roadside tests are dangerous ..

I am counting on you.

Yeah, sure Mark. as soon as I finish the parabolic algorithms for re entry I'm working on I'll move onto the serious stuff. 

Mark, I don't have a handle on your sense of humour and I don't want to offend you but I will go with my gut feel and assume your suggestions are tongue in cheek.

On the off chance you are being serious......

Why is an "off road stationary test" invalid. How does forward speed effect such a test?
You agree power is cut to the fuel pump. Why would you then have reduced spark as well if there is no fuel to ignite?

There is one point that many seem to overlook, it is just a fuel reserve function on a garden variety bike. Just how complicated were Yamaha going to make it?

I say again, there is no mistaking a bike running out of fuel with one running out of spark.

As for the bigger needle and seat (which really isn't that much bigger and the bigger hose which is irrelevent), they just let bigger crap through.
The benefit from the filter the pump allows you to run is less crap in your carbies. A fuel pump should only need replacing once in the entire life of your bike, hardly a biggy.

You are lucky to live somewhere with good fuel. We are also lucky here in that regard.



IMO

Noel

[FJ_Hooligan]

If you don't charge the coil up to its rated voltage then the spark is weak(er).  Just how much spark does it take to ignite an air/fuel mixture?

If you cut the spark completely you run the risk of fouling a plug. 

I don't think either of those options are a logical design approach for a running out of fuel simulation.

[ribbert]

Ugh... as an electronics technician trained in TTL logic, I understand the function of a digital system and the use of square wave duty cycle to modulate fuel delivery, therefore, it makes sense that the fuel sensor that is fed to the digital computer is doing precisely that - varying the duty cycle of the ignition, not turning off the fuel pump, which in turn reduces the flow of fuel (modulates pressure), while not simply draining the bowls empty. This is why both theories have some validity.

There.

Rick, thanks for responding but you're attributing way too much complication to such a simple task and have ignored one very basic feature, the fuel pump DOES turn off when low on fuel, it has no power until the reserve switch is activated or fuel added. Without fuel it doesn't matter what the spark is doing, there's nothing for it to ignite.
This was a first generation step up from manual petcocks 25 years ago on a bike with a crude electronic engine management system, not an F18.

A fuel reserve function on bikes is a hangover from when they didn't have fuel gauges, not emerging technology. When was the last time you owned a car with a reserve switch? The last one I owned was a 1951 Rover.

Rick, run your bike dry on the main tank and put a test light or multi meter on the fuel pump, there will be no power. Switch to reserve and power will be restored, it's that simple.

Noel

[ribbert]

Noel, nice to see you so inclusive!  I think you covered almost everyone & some more than once!

Can't have anyone thinking their contributions are not valued and worthy of a response.

Noel

[ribbert]

... Noel, you may not believe this coming from me but I hope you are not (once again) going away...

Midget

Mike I agree with you, I don't.

Noel

[Firehawk068]

I think that there are more variables at play here with the engine "Simply running out of fuel", that may make it seem like it is losing spark energy in a couple cylinders.
Although I have absolutely No DATA on whether it cuts spark or not, I HAVE run my tank down to the point where I've had to switch it to "RESERVE" to keep going........
In each of these instances, I've noticed a very slight hiccup in the engine running. At which time I instinctively twist the throttle a little further, and that seems to clear the hiccup as well as restore forward acceleration for just a moment. If I keep riding, the hiccups gradually become more frequent, and the engine starts to run worse and worse until the point it quits.
If I catch it while the engine is still running, and switch the RESERVE switch, it does take a few seconds to restore normal-smooth engine running with no hiccups.
Each of these times that I have experienced, the transition back to smooth running was not "Instant" like it would be if Spark was suddenly restored. It has always taken a few seconds.......

This would support Pat's theory on fuel dipping to just below the pilot jet, to cause a stumble under part-throttle conditions............And when you instinctively give it more throttle, more fuel flows through the main and the engine will "Un-stumble"
I've ridden bikes with clogged pilots. They won't idle, they spit and stumble at part-throttle, but will pull all day at WOT.

But how does this explain why (at first) when running out of fuel, it only seems to stumble on one or two cylinders?

In my opinion, try as you might (especially with a higher mileage engine) you will never get all of the cylinders exactly balanced.............
There are so many variables to this: Valve clearances, piston ring sealing, valve stem sealing, variances in the amount of carbon in each cylinder, compression in each cylinder, temperature of each individual cylinder, variances in the carb bodies themselves, etc.............
You can sync the carbs to get them as close as you can, and you can try to get the floats all even or the fuel bowl levels as even as possible, but you will never get them "EXACT"
While the engine is running, there will always be some cylinders that draw a bit more air than the others, or that use a bit more fuel than the others...............You would never notice this while the engine is running, and the fuel pump is constantly keeping the fuel bowls topped up...
But once you cut the fuel pump, and the re-supply to the fuel bowls stops, there will always be one or two cylinders that run out first and start to stumble.
It is not as straightforward as instantly cutting all the fuel to the engine at once........
If you are really keen on how your bike is running, and catch it right away and hit the RESERVE switch, the 2 or 3 cylinders that are still running properly will continue to do so until the cylinder that was stumbling is re-supplied with fuel.
If you continue to ride and do nothing, the rest of the cylinders will all eventually drop out and stumble, until the engine just will not run anymore..
This is exactly what I experienced the few times that I have run the tank down to require "RESERVE".

Anyway, I'm sure this debate will continue in the future until someone comes up with some "Hard Data" on the cut-fuel/cut-spark debate, and I have absolutely NO DATA on the spark side of it.
I simply have my doubts that the engineers at Yamaha would have made the RESERVE function more complicated than simply "Cutting the power to the Fuel Pump", but I could be wrong. There are some crazy engineering stories in the world of Motor-Driven Vehicles.............

[ZOA NOM]

Ugh... as an electronics technician trained in TTL logic, I understand the function of a digital system and the use of square wave duty cycle to modulate fuel delivery, therefore, it makes sense that the fuel sensor that is fed to the digital computer is doing precisely that - varying the duty cycle of the ignition, not turning off the fuel pump, which in turn reduces the flow of fuel (modulates pressure), while not simply draining the bowls empty. This is why both theories have some validity.

There.

Rick, thanks for responding but you're attributing way too much complication to such a simple task and have ignored one very basic feature, the fuel pump DOES turn off when low on fuel, it has no power until the reserve switch is activated or fuel added. Without fuel it doesn't matter what the spark is doing, there's nothing for it to ignite.
This was a first generation step up from manual petcocks 25 years ago on a bike with a crude electronic engine management system, not an F18.

A fuel reserve function on bikes is a hangover from when they didn't have fuel gauges, not emerging technology. When was the last time you owned a car with a reserve switch? The last one I owned was a 1951 Rover.

Rick, run your bike dry on the main tank and put a test light or multi meter on the fuel pump, there will be no power. Switch to reserve and power will be restored, it's that simple.

Noel

Noel,

If it was simply a cutout for power to the fuel pump, it wouldn't need to go through the CPU. Just wire a power lead to the pump and move on. It goes through the CPU because it does more than simply restore 12v to the fuel pump. I believe it does both simultaneously - changes the duty cycle of the ignition to give the feeling of a miss, and reduces the fuel pressure so the pump doesn't force fuel when the timing is off.

Look at items P,Q & R on the diagram. They are all connected to a transformer with 12v supplied to the other side from the main switch. The CPU will modulate the current flow through each transformer (all four ignition coils for timing and the fuel pump relay for pressure), by varying the duty cycle of the waveform applied.

PS - An F-18 is 1990's technology. Now if you had said YF-22...