FZ6 - Fueling Issue, Potential ECU Failure

BillyTheWrench

New Member
Joined
Jul 28, 2021
Messages
10
Reaction score
3
Points
3
Location
NorthEast
Visit site
Hello Folks,

I try to keep away from posting unless I think it either A) is a new problem (which is rare, I know) or B) provides value to the existing pool of information. I'll try to keep it to the facts so here's the story.

FZ6 w/ ~30k miles. Normally stored outdoors, but garaged this winter. Filled the tank and added fuel stabilizer in November. Kept the battery indoors all winter. Charged it up, reinstalled and fired right up no problems. Drove it ~5miles to its summer location sometime in late May. Upon the second attempt at riding, the bike was warming up and over the course of ~2mins it began to slowly drop in rpm until the engine stalled.

Here's what I've tested.

Crank position sensor = 292ohm
CPS should be 248-372ohm
IN SPEC

All fuses are functional

Cap should be 10k ohh
Cap1: 10.51k
Cap4: 9.95k
Cap3: 10.27k
Cap2: 10.49k
Note: probe resistance: 0.7ohm
IN SPEC

Primary1-4: 2.5ohm
Primary3-2: 2.5ohm
Primary should be 1.53-2.07ohm
IN SPEC

Secondary coil should be 12k-18kohm
Secondary1-4: 15.3k
Secondary3-2:15.38k
IN SPEC

Checking the continuity(pg375):
⁃ Main switch: continuous
⁃ Clutch: 1300-50ohm, could be replaced
⁃ Side stand: continuous, open when stand is down
⁃ Engine stop: run=0ohm, stop=784ohm
⁃ Start: continuous when pressed
⁃ Brake: 0ohm when pressed, 2ohm when released
⁃ Oil level: 400ohm to ground
⁃ Neutral switch: continuous in both conditions, ~1800ohm in gear and ~1400ohm in neutral

Intake air temp sensor:
Spec = 2200-2700ohm
Measured = 1700ohm
OUT OF SPEC

Throttle position sensor testing:
Pin 1&3 spec (red & blue)= 4000-5000
Measured = 2.49kohm
Pin 2&3 spec (yellow & black) = twist throttle and measure at min and max
⁃ min: near 0
⁃ Max: no more than 3.5-6.5kohm
⁃ Measured Min: .350kohm
⁃ Measured Max: 2.05kohm
OUT OF SPEC

All injectors should be 12ohms
⁃ all injectors test at 13ohms
note: probe resistance is 0.7ohm
IN SPEC

So that's somewhat good news to find SOMETHING broken. I replaced the throttle position sensor and intake air temp sensor. I thought the TPS could be the issue but definitely not the air temp. Neither of them changed the behavior of the running issue.

At this point I pulled the spark plugs out and grounded them to the exhaust manifold. Nice healthy sparks while cranking so no issues there.

I was still skeptical of an ECU failure because I pulled the harness connector off and it was bone dry in there. No signs of fried pins. That doesn't mean its not fried, but given that its still behaving normally I figured I'd try out the fueling system.

I splash a bit of fuel down the throttle bodies and voila, we have a bit of idling going on. Given that I can hear the pump priming the system I do not suspect it's unhealthy yet, but that doesn't mean its providing sufficient pressure. I hop into diagnostic mode and while holding the throttle bodies open I trigger the injectors two at a time. I can see fuel injecting down the intake in a pretty healthy spray on all 4 injectors. I say what the hell and pull the fuel rail off then resistance test the injectors all individually which you can see in the data above they are all within spec as well. Clean 'em up then reassemble.

So now I'm thinking alright alright maybe even with fuel stabilizer the fuel pressure regulator could have gotten jammed or something. I buy another fuel line, cut it, and splice in a pressure gauge using 5/16 fuel line from autozone and a couple pipe fittings. Dump some fuel down the intake and crank it away. I got 40psi priming the pump and a little above that for the 10 seconds it was running on the fuel in the throttle bodies. Then it proceeded to die and only crank afterwards.

From the looks of this trouble shooting, I have fuel and spark present. I understand this is a machine, not a prototype, and magic does not exist in machines. I really don't want to replace the ECU because I just don't think its behaving like the ECU is trashed.

Any thoughts on this one?

Thanks in advance for taking the time to read! Sorry if something like this has been posted already. I was scrounging this and the sportbikes forums and didn't find any similar threads.
 

Gary in NJ

Junior Member
Site Supporter
Joined
May 6, 2014
Messages
1,964
Reaction score
1,908
Points
113
Location
Amoungst the Twisty Roads
Visit site
An ECU failure is rare.

You mentioned that fuel poured into the TB resulted in a running idle for a period. That leads me to believe that either the fuel is old/bad or the fuel filter is clogged. I’d remove the tank, dump the fuel, and then remove and inspect the screen on the pump assembly. They are known to clog.
 

BillyTheWrench

New Member
Joined
Jul 28, 2021
Messages
10
Reaction score
3
Points
3
Location
NorthEast
Visit site
Alright so this is the part where everyone on this thread rolls their eyes at me :rolleyes: I looked up removing the pump and intended to inspect/clean the filter screen. Since it appeared that it could have been a laborious process I said well, maybe if it fill it up with fresh gas and some techron it might dissolve whatever is in there. So I did aaaaaaand yeah same result ALTHOUGH I did get a few more observations.

For reference: filled it up with 87 & a full bottle of techron complete. Since that Techron is intended to treat 21gal I'm hoping the concentration will be aggressive on the fuel filter.

Then I cranked it a bit and held the throttle wide open. With the throttle wide open it would run on one cylinder if I kept it at WOT. Now these are just observations from sound and smell but it seemed like it was 1) firing on only cylinder and 2) maybe backfiring out the intake? It was a bit smokey but past sundown as well so take that observation with a grain of salt. I wouldn't mind entertaining the idea of the fuel & spark systems being out of time, but that would probably be the result of a failed crank position sensor which tested in spec. (or a cooked ECU ;) )

I'm going to let it sit for two days. Tomorrow I'll take the battery out and let it sit on the tender. I was hoping for the 30s it was running on 1 cylinder that it would be enough to get fresh fuel to all the injectors but I didn't expect it to be like flipping a switch. Regardless, Plan B is to drain most of it using the fuel pump then remove the pump for inspection hoping not to break anything.
 

Gary in NJ

Junior Member
Site Supporter
Joined
May 6, 2014
Messages
1,964
Reaction score
1,908
Points
113
Location
Amoungst the Twisty Roads
Visit site
There are no chemicals that will clear a clogged fuel screen.

Back firing through the throttle bodies is an indication of a timing issue. Did any of your testing include the timing. I don’t think it’s possible to install the TPS incorrectly, but the back firing sure is curious.
 

TownsendsFJR1300

2007 FZ6
Site Supporter
Joined
Feb 7, 2009
Messages
12,516
Reaction score
1,157
Points
113
Location
Cape Coral, Florida, USA
Visit site
Should you decide to remove the fuel pump, it's much easier to pop the release tab shown below and slide the two parts apart.
It separates the fuel tank level arm from the pump itself making removal MUCH easier.

Using this method, it's really not an issue.

Re-installation, the assembly should go back in assembled, as one unit..

fuel pump #2.jpg
 

Mcdabber434

New Member
Joined
Aug 5, 2021
Messages
7
Reaction score
2
Points
3
Location
United States
Visit site
There are no chemicals that will clear a clogged fuel screen.

Back firing through the throttle bodies is an indication of a timing issue. Did any of your testing include the timing. I don’t think it’s possible to install the TPS incorrectly, but the back firing sure is curious.
If he’s reaming it and he’s only on 2 cylinders it will backfire through the exhaust and intake (ime)
 

Motogiro

Vrrroooooom!
Staff member
Moderator
Elite Member
Site Supporter
Joined
May 8, 2008
Messages
14,968
Reaction score
1,138
Points
113
Location
San Diego, Ca.
Visit site
Also backfiring can occur with a leaky or slow responding valve.
 

BillyTheWrench

New Member
Joined
Jul 28, 2021
Messages
10
Reaction score
3
Points
3
Location
NorthEast
Visit site
I removed the pump and only found large particles on the filter. This stuff was easily just brushed off, I was crossing my fingers to catch some varnish in there but everything seemed fine.


View attachment IMG_0233.JPG

Here's the weird part: I reassemble everything with some gas and give it a few cranks. It starts doing the same thing where it'll only fire on one cylinder (which I suspect is cyl 4 but its hard to tell). I open the throttle all they way and it start sputtering but gaining maybe a few rpms. Then light a light switch BOOM all cylinders light and its purring like a kitten. o_O

I've had my heart played with enough by this beast so I'm not trusting a damn thing. I rev it a bit, hold it at 2000rpm for a little. I wanted to get the fresh fuel with the cleaner to cycle through the system. I let it idle until the temp got to 2 bars. It only had a splash of fuel in there so I stopped the engine, gave the tank about a gallon of fuel + cleaner, then fired it up again. Didn't even need to touch the throttle, just fired up normally.

Now after about 1 minute its back to its normal self; one cylinder dropping out at a time it slowly decreases in rpm and sputters until it dies out.

What did I learn? For some reason, disassembling parts of the fuel system and reassembling seems to bring it back to life. I don't think its the fuel delivery from the tank, I suspect there's some kind of obstruction in the fuel rail. The fuel rail is a log manifold so I'm thinking maybe its dropping cylinders farthest from the fuel pump one at a time which is why when cranking I can only get cyl 4 to spark?

I'm thinking the next step is to pickup a fuel rail assembly from Ebay and see if trying someone else's fueling components does the trick.

Does anyone have any thoughts on ultrasonic cleaning btw? We have been experimenting with ultrasonic cleaning at work (unrelated field) and I have access to large quantities of isopropyl alcohol and ultrasonic cleaners large large enough to fit all this in. I'm not sure how cleaning injectors works but I assumed they would need to be plugged in and cycling. I can't do that, but I could submerge everything in alcohol and run the cleaner for a bit.
 

Attachments

  • IMG_0233.JPG
    6.2 MB · Views: 9

TownsendsFJR1300

2007 FZ6
Site Supporter
Joined
Feb 7, 2009
Messages
12,516
Reaction score
1,157
Points
113
Location
Cape Coral, Florida, USA
Visit site
Just for s..ts and giggles, try hot wiring the red kill wires together, (by passing the switch on the right side handle bar).

If that connection is bad/borderline, you can get all kinds of weird stuff going on till it finally quits..

That switch, especially if old/used a lot can /will fail.. It is one known weakness for the bike..
 

Motogiro

Vrrroooooom!
Staff member
Moderator
Elite Member
Site Supporter
Joined
May 8, 2008
Messages
14,968
Reaction score
1,138
Points
113
Location
San Diego, Ca.
Visit site
Is there a way you can look at fuel pressure between the pump and injectors?
 

BillyTheWrench

New Member
Joined
Jul 28, 2021
Messages
10
Reaction score
3
Points
3
Location
NorthEast
Visit site
I don't think the strap/stop switch was in terrible condition. I jumpered the two solder terminals with an alligator clip and didn't observe any new behaviors. I had a hard time with the plastic coming out so I'll replace it anyways if its a weak point to begin with.

IMG_4218.JPG

Strangely the bike has been more responsive lately. All that's changed since I last started it a few days ago is theres ~.5gal of fuel/cleaner mix in the tank, fully charged battery, and I fiddled a bit with that start switch. I did the usual where I crank it a bit and twist the throttle open 1/2 way. Today it slowly lit all cylinders and idled low for a bit. It will usually drop in RPM until it dies, but it idled low enough to come up to two bars of temp before I shut it off. I let it sit for a couple of seconds then hit the start switch again and it came right on. It Idled on its own all the way up until the fan came one (four bars of temp). I let it sit for a while just to let everything run hot before shutting it off again.

I took a vid this time:

As I was watching it idle I was on a call with another biker friend. He suggested checking the valve clearances. He's in the dirt bike scene and said the 4 stroke guys will have trouble starting their bikes once the valve clearances come out of spec. I'll entertain the idea, but at 21k miles I would be a little annoyed if it was that critical of a service. This is a Yamaha after all, not a Ducati.

Any thoughts on this? If not valves, or the starter switch, I'm leaning towards bad fuel/fuel clog that is gradually clearing itself out.
 

Gary in NJ

Junior Member
Site Supporter
Joined
May 6, 2014
Messages
1,964
Reaction score
1,908
Points
113
Location
Amoungst the Twisty Roads
Visit site
The bike sounds good in the video. Don’t crack the throttle during start - let the computer use its cold start map.

There is a temperature sensor in the throttle body assembly that controls warm idle. The coolant rail can corrode and as a result the sensor never sees warm coolant.
 

BillyTheWrench

New Member
Joined
Jul 28, 2021
Messages
10
Reaction score
3
Points
3
Location
NorthEast
Visit site
Images on forums always seem to be labyrinth. That said, many threads are useless without pics. Even more so down the road when someone has a similar problem and can't see the pics in a good writeup. Is the max image size documented anywhere on this forum? I did a forum search for "image size" and found nothing of anyone having any problems. I'll try capture as much of my findings in text in case anyone wants to look at this later.

From Gary in NJ:

The bike sounds good in the video. Don’t crack the throttle during start - let the computer use its cold start map.

Gary, I appreciate the feedback and its hard to fully understand why I did that from the limited text I've posted. 1) it won't start unless I crack the throttle on its cold start map, 2) it runs "better" if it can get warm which it usually needs help with.

That said, I took your comment and thought about it's cold start map. A couple of years ago I swapped a Ford 5.0L (from a ford explorer) into my BMW E36 and it wouldn't start when it was warm. This was due to the 02 harness being garbage but it ran my memory and I though maybe it doesn't know what temperature the engine is! This affects both fuel and I'd imagine timing? Correct me if I'm wrong for the sakes of documentation.

A quote from page 1-3 in the FZ6 manual:

The injection duration and the injection timing are controlled by the ECU. Signals that are input from the throttle position sensor, crankshaft position sensor, intake air pressure sensor, intake temperature sensor and coolant temperature sensor enable the ECU to determine the injection duration. The injection timing is determined through the signals from the crankshaft position sensor. As a result, the volume of fuel that is required by the engine can be supplied at all times in accordance with the driving conditions.

If the engine is hot, it does not require as much fuel to run which would be a low injection duration. I suspect that coolant temperature sensor may be out of spec so I looked up the procedure to confirm the coolant temp spec in the manual, Page 8-46. In brief, you take out the coolant temp sensor, put in a pot of water at 80[C] and measure the resistance between the terminals which should be ~0.29-0.35kOhm.

I performed the test and measured 0.38kOhm. I was also seeing 1.81kOhm at room temp, 27[C], which if you look at graph in the manual could be a little out of range too. I'm going to say, it could be replaced but once again, I really don't think it could cause a problem like this. If the temp sensor is giving feedback of a higher resistance than actual conditions, that would correspond to running rich. And we're not talking much here, I'm out of range by 30Ohm, the engine should be able to handle a little extra fuel. Especially at a cold start. But, lets say this is true, I should have spark plugs covered in black residue.

I pulled out cylinder #4's plug (its the easiest to get to) and I'd say its looks fine. It certainly does not look like its been fighting though waves of rich combustion cycles.


210821_sparkplug.jpg

View attachment 210821_temptesting.jpg

I should also mention that I did replace the start/stop switch on the bike and didn't notice any particularly different behavior. I think the old switch was fine, the starter button was a bit soft but I don't think it contributed to the problem here.

I think the next steps here would be to run a leak down test. I would run a compression test but it would be difficult to get the engine to temp. Also, it may not hurt to replace the coolant temp sensor.

I'll be honest though, I'm not going to do either of those things. If I was in absolute love with this motorcycle, I would bring it to a shop and have them use their expertise. But, I have had many personal and professional projects follow this same course where is $50 or $100 at a time and it snowballs into something much more than you wanted. I think I'm probably $300 and maybe another 10hrs of diagnosis away from having this figured out, but that's not a definite answer. What I do know is that if I can get $300 from parting this out, I'd be happy. I missed a season of riding which kinda hurts so I might just be bitter, but ultimately I've lost interest. It is a machine, and it can be replaced. I don't think this project is a failure, I learned a lot!

You guys are great, and I'd love to help you out with your projects. Please message me for parts you'd like to have off this thing and we can find a fair price together. If it's not fully parted out by mid October I'm going to throw it in my truck and have it recycled.
 
Top