Fuel Reserve

[ribbert]

Deep breath & relax, repeat gently until the anger fades away or your until sanity returns...
                                                                                       

Mike, I'm sorry you missed the humour in my post of the irony in yours - maybe a bit subtle.


Deep breath & relax, repeat gently until the bias fades away or until your humour returns....



Noel

[PaulG]

The FJ1200 fuel reserve system used in later models is unusual in that when the fuel level reaches approximately 5 litres remaining ignition is cut to two cylinders giving the impression that the vehicle is running out of fuel, a reserve switch mounted in the fairing restores the cut cylinders allowing the rider to continue normally.[7][8]

That's weird.     A couple of times I have run the tank almost dry on my '92 - refill with 20L (capacity 22L apparently).  I've never experienced the above scenario. So that means.... I dunno'.  Guess I'll just keep riding instead of worrying.   

[ribbert]

.....The FJ1200 fuel reserve system used in later models is unusual in that when the fuel level reaches approximately 5 litres remaining ignition is cut to two cylinders giving the impression that the vehicle is running out of fuel.

Rick, I don't know when you joined the forum but this idea was dismissed years ago, even by the diminishing spark believers, for reasons that everyone agrees on. The behaviour of the engine when low on fuel is not consistent with this happening. If this was the case, the engine would smoothly (sort of) run along on 2 cylinders until it drained all the fuel in the tank, it doesn't.

One thing everyone agrees on is that it starts out as a barely perceivable loss of power and progresses through to stumbling, major rough running and eventually dies completely. Just cutting from 4 to 2 cylinders would not do this.

I believe this statement was originally attributed to a journo whose source of information may have been no more than his own speculation and it then took on a life of its own.

Maybe the spark has been programmed to mimic the power being cut off to the fuel pump so it feels like it's running out of fuel?  But hang on, if you were going to that, why wouldn't you just .......

Noel

[ribbert]

Before my coil relay mod, I was seeing ~11.2 volts at the coil thru my oem wiring harness.
After the coil relay mod, I'm seeing a full 14.4 volts (Transpo VR mod) at the coils above 2k rpm.

.... so, with the relay mod. the coils are now seeing 23% more energy .....
Are not the coils potentially subject to overcharging and possibly overheating?

Pat, normal charge rate for a 12v system is ~14.2 V. That is what your coil was designed to operate at. It was not designed to operate around voltage drop through the harness (11.2V).
You have not exceeded the voltage by 23%, you have returned it to it's normal operating specs.

IMO

Noel

[FJ_Hooligan]

Well, I didn't say they were digital devices, but the internal components of the CPU are, and the outputs to P,Q & R are not simply grounds. They are square waveforms that determine duty cycle by placing and removing the grounds to those devices. Also, the windings of the Fuel Pump Relay, and the Coils are indeed transformers, as you described above.

In any event, it remains a mystery, and mine has never worked as far as I know, and the bike runs fine.

Rick,
I apologize for misinterpreting your original statement.  My response appears to be harsh, I did not mean to insult.

When you say yours doesn't work, do you mean that you must have the reserve switch on all the time?  If so, do you know if your low fuel light still works?

DavidR.

[great white]

.....The FJ1200 fuel reserve system used in later models is unusual in that when the fuel level reaches approximately 5 litres remaining ignition is cut to two cylinders giving the impression that the vehicle is running out of fuel.

Rick, I don't know when you joined the forum but this idea was dismissed years ago, even by the diminishing spark believers, for reasons that everyone agrees on. The behaviour of the engine when low on fuel is not consistent with this happening. If this was the case, the engine would smoothly (sort of) run along on 2 cylinders until it drained all the fuel in the tank, it doesn't.

One thing everyone agrees on is that it starts out as a barely perceivable loss of power and progresses through to stumbling, major rough running and eventually dies completely. Just cutting from 4 to 2 cylinders would not do this.

I believe this statement was originally attributed to a journo whose source of information may have been no more than his own speculation and it then took on a life of its own.

Maybe the spark has been programmed to mimic the power being cut off to the fuel pump so it feels like it's running out of fuel?  But hang on, if you were going to that, why wouldn't you just .......

Noel

LOL! A wiki page using Haynes and Clymer manuals as a reference.

Not exactly what I would call "reliable" sources......

[aviationfred]

 

Rick,
 
When you say yours doesn't work, do you mean that you must have the reserve switch on all the time?  If so, do you know if your low fuel light still works?

DavidR.

I know that on my '89, since the Speed Hut gauges were installed. The reserve switch is required to be activated and yes, the OEM low fuel level still works as designed.

I didn't get a chance to remove the fuel sender over the weekend. The weather was too nice to be stuck in the garage. I actually rode both of the bikes this weekend.

Fred

[Firehawk068]

The Wiki page that is referenced, was actually written initially by one of the Forum members here.
I forget his name, but believe he was in Texas???
I'm pretty sure he mostly used information that had been circulated around this forum.
He went by nickname "Fintip" or something like that?

[FJmonkey]

Alan, you are correct. Kyle AKA Fintip started the page and used what information he had access to.

[ZOA NOM]

Well, I didn't say they were digital devices, but the internal components of the CPU are, and the outputs to P,Q & R are not simply grounds. They are square waveforms that determine duty cycle by placing and removing the grounds to those devices. Also, the windings of the Fuel Pump Relay, and the Coils are indeed transformers, as you described above.

In any event, it remains a mystery, and mine has never worked as far as I know, and the bike runs fine.

Rick,
I apologize for misinterpreting your original statement.  My response appears to be harsh, I did not mean to insult.

When you say yours doesn't work, do you mean that you must have the reserve switch on all the time?  If so, do you know if your low fuel light still works?

DavidR.

No harshness perceived, Dave. I actually have no idea which position it's in. I exclusively use the trip meter, and I don't believe there's a low fuel light on my 93.


I see now why this topic was abandoned....

[ribbert]

My last comment on this (maybe)

I liked this topic when it was originally brought up because it had all the elements of a good thread. Of interest to many, a mystery to all and solveable by most and would therefore lead to a conclusion.

I have just two questions:

For all the speculating, circuitry analysis, theorising and hypotheses offered up....

Q1 - Why didn't anyone conduct their own tests? and be done with it.

Q2 - Why was my test not conclusive?   and can anyone point out where it was flawed?

.......In any event, it remains a mystery.......

An opinion it seems still shared by many.



Noel

[great white]

...Q1 - Why didn't anyone conduct their own tests? and be done with it....


Noel

I can only answer this Q for myself: too busy, haven't gotten to it yet.

I'm going to isolate the fuel supply to my 4gas/synch testing/maint fuel tank. It's a gravity feed tank I hang of the bars/triples (IE: fuel pump out of the loop).
Then manipulate the sender to give the low light. If the bike stumbles, then manipulate to turn the low fuel light off. Repeat the process a couple times to ensure it actually is repeatable. Probably try a couple RES switch on/off cycles too.

Since the debate seems to be whether it's the ignition or the fuel, seems logical to isolate the systems from each other and test. Since you can't isolate the ignition and expect the bike to run properly, that just leaves the fuel system to "inhibit".

If the bike stumbles with the light on and recovers with the light off, that's evidence enough for me as to what is happening.

But that will also only confirm the ignition has a part in the aforementioned "stumble", it won't disprove there's not something happening with the fuel pump at the same time. That's for others to debate, I have no interest in it past my own little "test" for curiosities sake.



Just gotta get some free time to give it a try!

[Pat Conlon]

Even with the gravity feed directly to the carbs, with the low fuel level in the tank, you will hear the pump cycle on when you click on reserve. Just run a hose from the pump output to a gas can.

That's fine. Rule out ignition, then the rest is obvious.

We know the fuel pump is involved (at least some of us)
The question: Is the ignition *also* involved? Will be answered.

[great white]

Even with the gravity feed directly to the carbs, with the low fuel level in the tank, you will hear the pump cycle on when you click on reserve. Just run a hose from the pump output to a gas can.

That's fine. Rule out ignition, then the rest is obvious.

We know the fuel pump is involved (at least some of us)
The question: Is the ignition *also* involved? Will be answered.

I will try to listen for the pump. But when my "box o' rocks" is running, it's hard to hear anything at all......

Pump won't have fuel in it, tank will be off the bike. Multi-meter or test light would be a better indication and what I will probably use. It will also do away with the "5 seconds and no pressure = pump shut off" logic of the pump itself...

Not sure if I'll get to it this weekend. Sat I'm picking the VentureMax up from storage, Sunday or Monday we're towing the camper to the seasonal site. FJ is running OK so sync and CO2 is kinda low on the "to do" list. I also have the RPM filter adapter, new gauge lens and chain/sprockets (and a bunch of other little things) to do as well...Plus, I have to find some time to get back to modifying the VentureCruise system to the FJ.

[Pat Conlon]

What I enjoyed about the fuel pump FJ's is the long fuel hose running from the filter to the fuel pump.

When it was time to sync the carbs, I left the tank connected and simply rotated the tank 180 degrees and rested the tank on the subframe. This allowed plenty of room to the carbs.

Looking forward to your results .... Thank you in advance, for taking your time to do this.