Desperate for help: Bike starts stuttering after a while - repairs itself by turning engine off and on again

[jaffabaffa]

Hey Fazer riders!


My 2004 Yamaha FZ6-S has a weird problem.

If I start the engine and ride off, everything seems to work just fine, but after 7 or 8 minutes or so, the bike starts to stutter and hold back as soon as I apply more throttle.

Nothing particularly weird so far, right? Here comes the weird part…

When this problem occurs, and I park the bike on the side of the road, whereafter I shut off the engine, and turn it back on again right away, the problem disappears.
When I then ride off again, I can enjoy my Fazer for about 7 or 8 minutes again, whereafter the problem inevitably starts occurring again. I can then temporarily fix the issue by turning the bike off and on again, but it will always reappear eventually.


The things I have already done to try to fix this problem:

• Refill the fuel tank with fresh petrol
• Replace the throttle positioning sensor (official Yamaha recall that my bike didn’t undergo yet prior to the problem first occurring)
• Ride around with an open fuel cap.
• Replace all four spark plugs with new iridium spark plugs
• Added a injector cleaning fuel additive to the petrol
• Added a fuel filter on the fuel hose

Additional information:

• The bike doesn’t give any fault codes/error codes
• The bike has 9150 km or 5700 miles on the odometer.
• I have owned the bike since February 2021, and bought the bike with just shy of 9000 km or 5600 miles on the odometer, so you could say the motorcycle has had this problem since the beginning of my ownership.

I am desperate for advise on fixing this issue. I need my bike to get to college, and I can't afford to pay a mechanic to take a look at my bike.

I would absolutely love to hear whether or not you guys can provide me with some helpful tips and tricks.

I am looking forward to your reactions and answers!


Yours faithfully,

Dennis

 

[TownsendsFJR1300]

There's a re-call for your year bike for the TPS (Throttle Position Sensor):

https://www.nhtsa.gov/vehicle/2004/YAMAHA/FZ6

I would get that checked to see if it was replaced. It could very well be your issue..

.

 

[jaffabaffa]

Thank you for the reply Scott, but as stated in my post, I already had the TPS replaced by my local Yamaha dealer. Unfortunately, it didn't solve the problem. Any other ideas or suspicions?
I just went ahead and cleaned and lubed all connecters with contact spray. Will test tomorrow to see if it has any affect.

 

[Gary in NJ]

I'd remove the external fuel filter. It's not necessary and can only cause problems. I'd put my money on a clogged fuel pump screen. In order to inspect it you will need to empty the tank of fuel, remove the tank, and then remove the fuel pump assembly. Temporary fuel starvation is the precursor to total fuel starvation.

 

[jaffabaffa]

I'd remove the external fuel filter. It's not necessary and can only cause problems. I'd put my money on a clogged fuel pump screen. In order to inspect it you will need to empty the tank of fuel, remove the tank, and then remove the fuel pump assembly. Temporary fuel starvation is the precursor to total fuel starvation.

Thanks a lot, Gary! I will look into it.
Can a bad fuel pump also explain why the motorcycle works just fine again after I restart it? When I turn on the ignition, my bike temporarily makes a whining sound (like almost all modern bikes do). That is the fuel pump right?

 

[Gary in NJ]

That is the fuel pump priming. The fuel rail requires 40psi to start the engine. If cleaning the fuel pump screen doesn’t help, then a fuel rail pressure test is a good next step.

 

[trepetti]

That is the fuel pump priming. The fuel rail requires 40psi to start the engine. If cleaning the fuel pump screen doesn’t help, then a fuel rail pressure test is a good next step.

+ 1 on Gary's comment. Everything added to the fuel line will drop the pressure. There is no problem that is fixed with an external fuel filter.

This actually happened to me and although odd, should be on the table as a possibility. I had a situation where the bike seemed to respond as you describe. The idle would get rough and it would not rev. And it only happened when the bike got warm. What happened was that a part of the wiring was rubbing against the fan. When the bike was at normal temperature everything worked fine. But when bike tried to turn the fan on, the wires rubbing against it would prevent it from spinning easily, and so it would demand more current from the battery to try to spin up to speed. The fan and the fuel pump are on the same circuit, so when the fan was demanding more current, it was pulling it from the fuel pump. So fuel pressure dropped and the bike would not rev. Once the bike cooled off and the fan did not need to spin, the fuel pump got the current is needed and the bike tan perfectly.

You say that when you turn the bike off then on the problem goes away, is it hot when you turn it off and cooler when you turn it back on?

I don't know if this is what you are seeing, but it happened to me and i wanted to let you know in case your issue is similar.

 

[trepetti]

...another thing to consider and a recurring problem on our bikes is the red kill switch. When it gets dirty it makes poor contact and essentially connects and disconnects very rapidly. And that feels like an engine that loses power and will not rev.

How often do you use your kill switch? If you use it a lot, I recommend you bypass the switch to test. If the test solves the problem you can dismantle the switch and clean it like lots of us have already done.

 

[jaffabaffa]

@TownsendsFJR1300 @Gary in NJ @trepetti Thank you all for the replies and help so far, guys!

I made an appointment for coming Thursday for a diagnostic read-out by my local bike shop. I will keep you guys updated!

I do have a little theory of my own as well though, and I would love you guys take on it:

• When I turn on the ignition, my fuel pump makes a whining sound and puts pressure of the fuel system. There is now enough pressure in the fuel system, and I can ride off just fine. Due to a bad fuel pump, the pressure in the fuel system can not be maintained for longer than lets say 15 minutes. The pressure gradually decreases, until it reaches a point where the engine isn't getting enough fuel anymore - causing the symptoms I'm experiencing. Now, when I turn the ignition off and on again, the fuel pump makes this whining sound again, and restores the fuel pressure to normal. Everything is now fine again, and I can start riding again until the fuel pressure inevitably drops and disappears again. This issue puts the motorcycle in an ever lasting loop of the bike working, and then not working anymore.

Does this theory sound feasible to you guys, or is my marginal knowledge of modern fuel injected engines putting me on a side track?

 

[TownsendsFJR1300]

Sure does sound like the fuel pump is NOT keeping up with the fuel that's needed..

I've never heard of these symptoms here, for the FZ, but that doesn't mean anything.

Usually the pump just stops working, no pressure. Your pump IS priming up and initially making pressure.

The loss of pressure won't be found by plugging into anything, you need to put a pressure gauge
on the rail and monitor it till it acts up/quits. I suspect the pressure will drop. At the very least, make sure they DO a pressure test.


Depending on what their charging you, you may want to just put a pump in it first:

QFS Fuel Pump w/ Strainer for Yamaha Motorcycle / Scooter - EFI In-Tank OEM Replacement, HFP-382-Y

FREE SHIPPING, LIFETIME WARRANTY from the AUTHORITY on OEM replacement Fuel Pumps. SAVE up to 70% off on parts for your Yamaha 93-23 with HFP-382-Y

www.highflowfuel.com

.

 

[jaffabaffa]

Thanks a lot! Didn't know a loss of pressure won't be found by plugging it into anything. I will specifically ask the shop to monitor the fuel pressure. Unfortunately I don't live in the US, which means the fuel pump you are suggesting would be very expensive for me to buy due to shipping and import fees. My gut feeling tells me it has to be either a bad fuel pump, or a very dirtied/clogged fuel pump mesh.

Will keep you updated as soon as I know more!

 

[TownsendsFJR1300]

Check page 7-29 in the S1 Yamaha shop manual for pressure testing.

 

[trepetti]

@TownsendsFJR1300 @Gary in NJ @trepetti Thank you all for the replies and help so far, guys!

I made an appointment for coming Thursday for a diagnostic read-out by my local bike shop. I will keep you guys updated!

I do have a little theory of my own as well though, and I would love you guys take on it:

• When I turn on the ignition, my fuel pump makes a whining sound and puts pressure of the fuel system. There is now enough pressure in the fuel system, and I can ride off just fine. Due to a bad fuel pump, the pressure in the fuel system can not be maintained for longer than lets say 15 minutes. The pressure gradually decreases, until it reaches a point where the engine isn't getting enough fuel anymore - causing the symptoms I'm experiencing. Now, when I turn the ignition off and on again, the fuel pump makes this whining sound again, and restores the fuel pressure to normal. Everything is now fine again, and I can start riding again until the fuel pressure inevitably drops and disappears again. This issue puts the motorcycle in an ever lasting loop of the bike working, and then not working anymore.

Does this theory sound feasible to you guys, or is my marginal knowledge of modern fuel injected engines putting me on a side track?

I am not sold on the theory. If the fuel pump was not keeping up with demand from the start, I cannot see it working for 8 minutes and then fail. If the fuel rail pressure drops the engine will not run well, so I am thinking that the problem starts at the 8 minute mark.

Start the bike and let it idle for 10 minutes. See if the engine gets rough at some point. Let it get hot enough that the fan needs to come on and make sure the fan spins up to speed. And when the fan does come on, try to rev the engine and note if it sputters.

Did you remove the additional fuel filter?

 

[Macconraoi]

Hey Fazer riders!


My 2004 Yamaha FZ6-S has a weird problem.

If I start the engine and ride off, everything seems to work just fine, but after 7 or 8 minutes or so, the bike starts to stutter and hold back as soon as I apply more throttle.

Nothing particularly weird so far, right? Here comes the weird part…

When this problem occurs, and I park the bike on the side of the road, whereafter I shut off the engine, and turn it back on again right away, the problem disappears.
When I then ride off again, I can enjoy my Fazer for about 7 or 8 minutes again, whereafter the problem inevitably starts occurring again. I can then temporarily fix the issue by turning the bike off and on again, but it will always reappear eventually.


The things I have already done to try to fix this problem:

• Refill the fuel tank with fresh petrol
• Replace the throttle positioning sensor (official Yamaha recall that my bike didn’t undergo yet prior to the problem first occurring)
• Ride around with an open fuel cap.
• Replace all four spark plugs with new iridium spark plugs
• Added a injector cleaning fuel additive to the petrol
• Added a fuel filter on the fuel hose

Additional information:

• The bike doesn’t give any fault codes/error codes
• The bike has 9150 km or 5700 miles on the odometer.
• I have owned the bike since February 2021, and bought the bike with just shy of 9000 km or 5600 miles on the odometer, so you could say the motorcycle has had this problem since the beginning of my ownership.

I am desperate for advise on fixing this issue. I need my bike to get to college, and I can't afford to pay a mechanic to take a look at my bike.

I would absolutely love to hear whether or not you guys can provide me with some helpful tips and tricks.

I am looking forward to your reactions and answers!


Yours faithfully,

Dennis

I had a similar problem to yours, no fault code would ever appear when my bike had its issue. after a while a cylinder would drop out if I blipped the throttle, it was just one cylinder doing it but all of them at various times, I changed the coils, plugs, TPS, removed the throttle bodies and checked everything was serviceable, replaced all the vacuum hoses, checked the ignition timing, stator output and fuel pump pressure. I decided to open every single connector on the bike, what I found was the main ECU plug and ECU had slight corrosion on 4 mins, I cleaned all pins and connectors and it sorted the problem.

 

[jaffabaffa]

I had a similar problem to yours, no fault code would ever appear when my bike had its issue. after a while a cylinder would drop out if I blipped the throttle, it was just one cylinder doing it but all of them at various times, I changed the coils, plugs, TPS, removed the throttle bodies and checked everything was serviceable, replaced all the vacuum hoses, checked the ignition timing, stator output and fuel pump pressure. I decided to open every single connector on the bike, what I found was the main ECU plug and ECU had slight corrosion on 4 mins, I cleaned all pins and connectors and it sorted the problem.

Thank you very much for the reply!

I already checked, cleaned and lubed all connectors that I could (easily) get my hands on, and I did not encounter any corrosion.

My gut feeling still tells me it has something to due with the fuel tank. Wether that is the fuel pump itself, or the fuel pump mesh - I don't know.

We will soon find out! (I hope)

 

[Macconraoi]

Thank you very much for the reply!

I already checked, cleaned and lubed all connectors that I could (easily) get my hands on, and I did not encounter any corrosion.

My gut feeling still tells me it has something to due with the fuel tank. Wether that is the fuel pump itself, or the fuel pump mesh - I don't know.

We will soon find out! (I hope)

Low fuel pressure usually shows up as a problem when the engine is at higher revs and under load, I have my doubts its low fuel pressure.

 

[jaffabaffa]

@TownsendsFJR1300 @Gary in NJ @trepetti @Macconraoi

Hey guys!

I got an update (sort of).

So last Thursday I went to my local motorcycle shop to get a read-out (diagnostic). Today they told me they were unable to locate any read-out connector on the bike, and where therefore unable to perform a diagnostic scan.
I was rather surprised to hear this, because I understood that the Yamaha FZ6-S (FZ6 Fazer) did have such a read-out connector. The only advise they could give me, was to check and clean every connector on the bike, which I had already done prior to visiting the shop.
Can any of you guys perhaps confirm whether or not this motorcycle has a read-out connector, and if so, where is it located on the motorcycle, and what does it look like?

I managed to find a pretty cheap new fuel pump online, so i went and ordered it just to try it out. It should arrive here by the end of this month. When I do replace the fuel pump, I will clean everything inside the tank as well. If that doesn't help either, I will bring my bike to an official Yamaha dealership.

Any further suggestions or advise?

 

[Motogiro]

Since it may take time for the ECU to pop an error code 43 (abnormal voltage to fuel pump and injection) if there is a quick intermittent, you may not see a code.
If this is an intermittent event you might attach a LED on a long wire from the red wire with the blue tracer wire in the fuel pump and ground. If the light goes out when the bike shuts off it would show power to the fuel pump and fuel injectors has been cut off. This could be happening as a result of safety protocol because of a sidestand switch being activated or a failing relay in the (starter interrupt - cut off relay module)
You could also run a jumper between the red wire and the red with blue tracer wire on the module to eliminate the possibility that the relay in the module is failing.
The simplest would be to run a temporary jumper to see if the relay is at fault. There are 2 relays in that module. One is for the starter interrupt and one is for the fuel pump/fuel injectors.

There is no specific connector for diagnostics that I know of but the dealer may have a plug assembly for the ECU or other location for diagnosis.

 

[jaffabaffa]

If this is an intermittent event you might attach a LED on a long wire from the red wire with the blue tracer wire in the fuel pump and ground. If the light goes out when the bike shuts off it would show power to the fuel pump and fuel injectors has been cut off. This could be happening as a result of safety protocol because of a sidestand switch being activated or a failing relay in the (starter interrupt - cut off relay module)
You could also run a jumper between the red wire and the red with blue tracer wire on the module to eliminate the possibility that the relay in the module is failing.
The simplest would be to run a temporary jumper to see if the relay is at fault. There are 2 relays in that module. One is for the starter interrupt and one is for the fuel pump/fuel injectors.

That is very smart idea!
In case replacing the fuel pump en thoroughly cleaning the inside of the fuel tanks does not fix the problem, I will try doing that as a last resort.
Thanks for the help!

 

[Gary in NJ]

The instrument cluster is where you read fault codes. Some display when you turn on the key, and others show when you engage the starter.