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Discussion Starter #1
Hello everyone, newbie here. Have been working with my brother trying to get his bike started, have been consulting the forum (and everywhere else we can find to troubleshoot), but still no luck getting it going. Hoping someone here might have some other ideas to get it up and running again. Sorry for the long post in advance, but it seems like when troubleshooting stuff like this, the more details the better.

First, some details:
  • 2012 CBR250r (no ABS)
  • 5300 miles
  • Regularly serviced and maintained (until this last winter, more on that in a bit)
  • Has pretty much been an awesome bike since purchased new.
During winter it has generally been parked with good gas, and then started up a few times during the cold months to make sure all is continuing to work properly. Unfortunately life happened this last winter and this didn’t occur. Suspect poor quality gas was left in the tank, and it was left parked for about 5 months without being moved or started. We pulled it out this spring and have been trying to get it started since. While we’ve found and fixed various problems we’ve found along the way, wondering if there’s some underlying problem that’s causing the mess and we’ve only gotten the symptoms thus far.

Issues:
  • Fuel gage flashing flashing full bars (corrected)
  • Fuel pump not priming when turned on (corrected)
  • The bike won’t start :(
What we’ve troubleshooted/fixed (in order)
  • Drained the tank and filled with fresh, good fuel
  • Started with started fluid to confirm it’s getting a spark - it will run until the starter fluid is consumed and then dies
  • Replaced the fuel pump - it now primes when turned on (and function confirmed on a bench test)
  • Pulled the injector and cleaned/flushed (and function confirmed on a bench test).
  • Swapped the fuel sender (believe it’s formally called the “fuel unit”) - fuel gage is now functioning properly
  • Bike still won’t start.
Really puzzling, as it seems everything is functioning from the tank to the plug, and the only thing that I’m not quite sure how to check would be that the injector is actually getting power and fuel flowing through it when installed on the bike (not just on the bench). Wondering if there could be a sensor preventing it from functioning, preventing the bike from starting on the fuel. As well, fuses all look fine that we’ve checked, and where the fuel pump will prime and the engine will start with starter fluid, it doesn’t seem like it would be a tip-over sensor or something similar would be causing the issue, but please correct me if I’m wrong. Finally, it seems really odd that bad fuel would cause the fuel pump and sender to both go bad, and wondering if there’s something else causing the issue that also would have damaged both units, somehow without blowing a fuse.

We’re at a loss right now (plus, the weather is finally great so really want to get out), so if anyone has any other thoughts or ideas of what might be happening, would really appreciate it. If not we may just have to accept defeat and take it in to the dealer to see if they can fix it.

Thanks
 

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Sure sounds like you are on the right track.

Because it runs on Starter Fluid, it narrows down the problem to fuel.

Tip over sensor isn't an issue if it sputters with Starter Fluid.

Tank is clean inside?

Make sure the battery holds at least 12.7V before cranking and over 10V while cranking.

I'd say you need to confirm you have power at the injector. Another member bought a replacement pump and it did not supply adequate pressure. Replaced it and it started up.
 

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Discussion Starter #3
@jkv357 thanks for the response!

Sure sounds like you are on the right track.

Because it runs on Starter Fluid, it narrows down the problem to fuel.

Tip over sensor isn't an issue if it sputters with Starter Fluid.

Tank is clean inside?

Make sure the battery holds at least 12.7V before cranking and over 10V while cranking.

I'd say you need to confirm you have power at the injector. Another member bought a replacement pump and it did not supply adequate pressure. Replaced it and it started up.
  • Agree, definitely seems like something amiss in the fuel system.
  • Yes the tank is clean, no signs of corrosion/sediment/anything else anywhere
  • Battery - good point, and I guess that’s a beginner oversight. I haven’t checked it because it cranks, lights work, etc, though it has been drained and re-charged on the tender a number of times as we’ve been troubleshooting. I guess it’s possible that all that could happen but the system not quite have enough power to operate fully, or that the battery was fine when we started (and the fuel pump was bad), but that all of the cycling has caused a problem. Will dig out a multimeter and check.
  • On power at the injector - definitely isn’t getting power. I pulled it again and it clicks when powered - and it sprayed a nice cone when I bench-tested it - so the injector is functional, but it’s not spraying when connected and I start it.
  • For a replacement pump, any ideas as to what adequate pressure should be (or look like)? When the pump is connected directly to power it sends a nice steady flow, but I wouldn’t call it “high pressure”.
Will check the battery and get back.
 

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Discussion Starter #4
Was able to check the battery - 13.4V before cranking and 12.2V while cranking, so I think we can cross that one off the list.

As far as I can tell then, it seems that either:
  • The replacement pump we got is underperforming/not providing enough pressure to properly supply the injector (any recommendations for a high-quality replacement pump are welcome, as are any thoughts for how to tell if a pump just isn’t good enough)
  • There’s an electrical issue that’s keeping the injector from opening (and may also be the cause for the pump and sender dying in the first place)
Appreciate the help.
 

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Was able to check the battery - 13.4V before cranking and 12.2V while cranking, so I think we can cross that one off the list.

As far as I can tell then, it seems that either:
  • The replacement pump we got is underperforming/not providing enough pressure to properly supply the injector (any recommendations for a high-quality replacement pump are welcome, as are any thoughts for how to tell if a pump just isn’t good enough)
  • There’s an electrical issue that’s keeping the injector from opening (and may also be the cause for the pump and sender dying in the first place)
Appreciate the help.
Yup - battery is fine.

See if you can PM feliximo here. He had a similar issue and replaced a new/bad pump with something else and got the engine running again (but still has some high-rev issues).

Has the bike been tipped over? Maybe that would explain cutting power to the injector, so I'd check the sensor. Thought it may cut spark, but maybe not.

Anything been done concerning the ignition that would put it in lock-down/theft mode?
 

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Discussion Starter #6
Thanks, it was tipped once but a very long time ago, and the bike was still working fine afterwards. Nothing has been tinkered with on the ignition.

Ordered another pump to see if somehow the current replacement is bad/isn’t supplying enough pressure to the injector, we’ll see if it makes a difference.

If not, all I can assume is a poor electrical connection somewhere that is only impacting the injector, but nothing looks off on the harness or connectors.. Trying to research the various sensors on the bike, but it doesn’t seem like any of those being “unhappy” would cause the issue we’re having (no power to the injector but power to everything else). May have to throw in the towel at that point and take it to the shop.
 

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Trying to think of anything else that would cut power to the injector but still let the engine crank - but not start. Safety switches typically don't do that.

Damaged wiring would be the obvious cause of lack of power. Any connectors that could be corroded? Can you trace the wiring back and find power anywhere?

The last thing I can think of would be a malfunctioning ECU, but that seems like a long shot.
 

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Yeah, it’s super weird. 2nd replacement pump should be arriving today or tomorrow, and I’ve confirmed there aren’t any blockages in any of the lines or housing that would cause reduced pressure reaching the injector, so we’ll see if that corrects anything (if the problem is inadequate pressure to the injector)

On the electrical, no visible damage or corrosion anywhere, and working through continuity checks - looks like I can get power to the injector connector, but it’s been a while since I’ve had to debug anything electrical so needing to re-educate myself to make sure I’m checking things right.

Assuming that checks out, agree that the only thing left (I think) would be a faulty ECU. Looked at resetting it, but as far as I can tell the process requires you to have the bike running, so... 🙃
 

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Discussion Starter #9
Worked through the circuit checks - looks like the injector is getting power, but it isn’t triggering when I try to start it. Making me think it’s either a bad ECU, or a sensor preventing it from activating. Looking through what sensors are on the bike though, it looks like only the O2 sensor might cause a problem like this (though from what I can find a bad O2 sensor would cause it to run rough, but probably not prevent starting). From other reading, a Manifold Absolute Pressure sensor or Mass Air Flow sensor might cause a problem like this, but it doesn’t seem like the bike has either - please correct me if I’m wrong.

Gonna get a replacement ECU, will see in a few days (or longer given shipping these days) if that solves the problem.
 

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Swapped the Fuel Pump, and while it seems more potent on a bench test (the initial replacement makes a lot of noise but will barely pull any fuel, this one will at least pull fuel through the pump), still no change to being able to start. I disconnected the fuel line from the injector and had it flow into a jar to check the flow rate of the full system, and while I‘ve read somewhere that the pressure rating for the fuel pump should be ~30psi (though I can’t find a definitive source), it doesn’t look at all like 30 psi - it’s more like just-over-a-steady-dribble that comes out the line. Also bypassed the fuel filter to see if that was clogging it up - while there was some gunk in the filter there was no meaningful change with the filter pulled out of the system. Tried to post a video of the flow but looks like that’s not possible.

Anyone know what the flow rate should be? At a loss right now, and wondering if the Quantum fuel pumps just aren’t any good and we need to buckle down and buy the complete $300 fuel pump assembly instead of just the pump replacement.

Also tried replacing the ECU, and no change.

At this point all I can figure is some sensor flagging the bike to be able to attempt to start but not fire the fuel injector at all (seems unlikely based on the sensors I’ve been able to find on the bike), or the 2 fuel pump replacements we’ve gotten are bad/not generating sufficient flow to spray through the injectors. I’m leaning towards the latter, but would love to confirm what the PSI or flow rate should be before dropping another $300.
 

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Sounds like another bad pump to me.

See if you can find a good used pump before dropping $300 on a new one.

Everything I hear about replacement pumps suggests most have issues.
 

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Discussion Starter #12
Victory! 3rd pump was the charm (provided meaningfully more flow), and I realized there was an o-ring missing from the assembly that needed to be replaced. It must’ve fallen out the first time the fuel pump assembly was taken apart. Stupid mistake.

For anyone having a similar problem, the first 2 pumps purchased were Quantum T35 units. The first would barely pull anything on a bench test. The second unit was much better, but would only pull fluid once there was a bit of a siphon action to fill the input line. The 3rd pump was a Kemso pump that we found on eBay - it clearly listed the pressure spec (43-68 psi), they claim to test every unit, and it was the same price as the Quantum pump ~$70. It pumped great on the bench test and rapidly transferred fluid.

On the missing o-ring, when installing the kemso pump, it looked like the output side of the fuel pump should have an o-ring in place given how it mates into the plastic housing. My guess is that it fell out unnoticed the first time we disassembled the pump assembly, and has been missing since (the o-ring on the input side isn’t installed to the pump itself, so it didn’t jump out to me that it was missing until I looked more closely). This meant the output line wasn’t properly sealed, making the low flow problem meaningfully worse. Luckily the Kemso pump came with a replacement o-ring, so I added it when re-assembly and everything now works properly. Our first replacement pump probably didn’t have a chance, but the second might have worked had this o-ring been in place. I’m just happy that it’s now fixed.

Thanks @jkv357 for helping work through the issue!
 
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