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Discussion Starter · #1 ·
So I’ve been dealing with this for a few months, after I thought I fixed something it still happens. my bike occasionally shuts of as if its running out of gas I believe it might be a short because I’ve changed the fuel pump and the ignition I’ve bypassed bas and the kill switch I’ve switched out fuel cut relay after doing all that I noticed that sometimes when my bike shuts off it will refuse to prime back up, after a couple of minutes it’ll sometimes either prime start and shut back off , not prime at all for another while or it will run for another two days as if nothing was ever wrong.it does this both when the bike is cold and warmed up

Please someone help and give any input I’ve read countless threads but none with my exact symptoms I will post pics and videos coming up. By the way it’s a street fighter stunt bike project no power commander or alarm or any mechanical mods besides stunts parts such as cage handbrake and sprockets

https://www.youtube.com/watch?v=tKz1TVFZzqM&feature=youtu.be

 

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WTF! sounds more like fuel starvation than electrical probs.Ya aint got shite swishin around in yer tank mebee? or some crud gettin into yer petcock(is ita vacuum type i wonder?)
 

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Discussion Starter · #3 ·
WTF! sounds more like fuel starvation than electrical probs.Ya aint got shite swishin around in yer tank mebee? or some crud gettin into yer petcock(is ita vacuum type i wonder?)
There is this tube going from under the tank to something with denso written on it I believe it’s the vent tube because the other side of the box that tube is connected to goes to the vacuum lines, now in this tube that I think is a vent tube there is fuel in it and the fuel looks orange. Does that even sound normal? I thought that the only lines that should have fuel is the pump to the fuel line and pump to regulator. The other two should be a vent for the vacuum and over flow right? Or am I missing something

If you don’t understand what I’m talking about I can post pics, and thanks for your reply
 

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That mystery box is probably a charcoal canister to capture gas vapors from the tank. When you start the engine a little valve opens and lets the vapors get drawn into the engine. Emissions thing. There shouldn't be raw fuel in this. You can just remove this whole system and cap the ports in the intake.

This bike has the regulator on the fuel rail, correct? and a return line to the tank? Those are the only ones that should have fuel. You have a small vent line for the charcoal can, and another hose that's an overflow.

Next time it acts up and the fuel pump isn't running, pull the electrical connector apart, turn the key on, kill switch on, and see if it's being supplied with power- usually runs for 2-3 seconds at key on, then shuts off until RPM is detected. You can usually hear a relay click on then off. If it is getting power but not running, your pump could be bad, or if you changed the pump motor, a terminal on the motor could be loose and intermittently losing contact, or the motor could be bad.

If there's no power to the pump, most likely the relay is bad, which could also be an intermittent problem.
 

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Discussion Starter · #5 ·
That mystery box is probably a charcoal canister to capture gas vapors from the tank. When you start the engine a little valve opens and lets the vapors get drawn into the engine. Emissions thing. There shouldn't be raw fuel in this. You can just remove this whole system and cap the ports in the intake.

This bike has the regulator on the fuel rail, correct? and a return line to the tank? Those are the only ones that should have fuel. You have a small vent line for the charcoal can, and another hose that's an overflow.

Next time it acts up and the fuel pump isn't running, pull the electrical connector apart, turn the key on, kill switch on, and see if it's being supplied with power- usually runs for 2-3 seconds at key on, then shuts off until RPM is detected. You can usually hear a relay click on then off. If it is getting power but not running, your pump could be bad, or if you changed the pump motor, a terminal on the motor could be loose and intermittently losing contact, or the motor could be bad.

If there's no power to the pump, most likely the relay is bad, which could also be an intermittent problem.

By any chance is that charcoal box your referring to something that can cause a vapor lock if its not functioning properly ive heard of vapor lock with similar symptoms so im wondering if that's something to look into
 

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No. The charcoal can is not part of the fuel system, and could not obstruct normal fueling.

Vapor lock is virtually unheard of in EFI engines since the fuel pump is in the tank, and the fuel is constantly circulating. It never has a chance to get hot enough to vaporize- and the fuel pump would still be running even if it was.

I suspect you're losing fuel pressure, either by the pump losing electrical power, or a dying pump motor.
 

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Discussion Starter · #7 ·
No. The charcoal can is not part of the fuel system, and could not obstruct normal fueling.

Vapor lock is virtually unheard of in EFI engines since the fuel pump is in the tank, and the fuel is constantly circulating. It never has a chance to get hot enough to vaporize- and the fuel pump would still be running even if it was.

I suspect you're losing fuel pressure, either by the pump losing electrical power, or a dying pump motor.
Thank you for clarifying that , im starting to think my relays are intermittent , does it vary on each bike on how to check or is there a general way to check for intermittent relays i couldnt find any threads with same bike
 

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Relays are generic, it's just an electrically powered switch. If you have a service manual for your bike it probably shows how to test it, or at least a wiring diagram so you can see what wires it should be connecting when activated.

You check them by supplying +12v to the ground and "trigger" post, and then checking continuity through the feed and load posts- release the 12v and the circuit should break.

On a common 4 post relay, "85" is the +12v "trigger", "30" is +12v supply voltage, "87" is the load, and "86" is ground. So +12v to 85 and 86, check ohms between 30 and 87. Sometimes there is a fifth "87a" for a secondary load if the relay controls multiple things. Check the wiring diagram for your bike. This relay is most likely controlled/triggered by the ECU.
 

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Discussion Starter · #9 ·
Relays are generic, it's just an electrically powered switch. If you have a service manual for your bike it probably shows how to test it, or at least a wiring diagram so you can see what wires it should be connecting when activated.

You check them by supplying +12v to the ground and "trigger" post, and then checking continuity through the feed and load posts- release the 12v and the circuit should break.

On a common 4 post relay, "85" is the +12v "trigger", "30" is +12v supply voltage, "87" is the load, and "86" is ground. So +12v to 85 and 86, check ohms between 30 and 87. Sometimes there is a fifth "87a" for a secondary load if the relay controls multiple things. Check the wiring diagram for your bike. This relay is most likely controlled/triggered by the ECU.
I seem to have narrowed it down to a very bad and hacked wiring harness along with the grounding block being grounded out. I found a good condition harness not hacked or burnt and started replacing it when I then noticed and realized it was missing two plugs , one for the sensor to exhaust and the other that goes to the evap purge valve. My 929 is one of those California emission bike models so the harness came from a bike that didn’t have cali emissions . I heard you can remove this and it wouldn’t effect my bike at all so my question is how do I do so ive looked and red tons of threads and seems that the threads with step to step guides no longer exist someone please help so I can get back on the road.

if anyone wants pictures i can try uploading in case no one knows what im talking about
 

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Just toss the evap can into the bin and cap any ports it leaves exposed, probably one on one of the intakes. Nothing is dependent on any of the emissions crap.

The ECU "might" be different on a CA bike if it has a different harness. I'm sure the bike will still run with the o2 sensor not hooked up or the purge valve missing, but the FI light might always be on.
 
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