Running on one cylinder...

[motopreserve]

First post here on the site, but I have gotten a ton of knowledge here in the past. So thanks! I searched a bunch, but did not find anything that dealt directly with the issue I am having.

Attended a track day where I intermittently lost and gained power over the course of several laps. I was able to ride through it by smacking the throttle. This would bring back power for a bit, then it would lose it again. Now at the shop it is consistently only running on cylinder #2 (haven't tried it again under load). After researching a bunch of tests to narrow down the issue - I am still coming up short.

• So far I have tested and ruled out: compression, bad coils, battery, air filter.
  
• Cleaned the fuel injectors, tested the FI resistance, FI power source and FI output voltage.
  
• I have swapped cyl #2 parts to cyl #1: coils, fuel injectors.
  
• I have spark when the plug is grounded to the engine.

All this has turned up the same thing - cylinder #2 runs regardless of which FI/coil etc are in it. And #1 does not, despite swapping known working parts. My thoughts are leaning toward fuel pump or throttle bodies. It's obviously getting fuel to cylinder #2. But is there a way that the pump would not produce enough pressure to push it to cyl #1 down the pipe? Or perhaps there is some reason that the healthy FI is not passing the needed fuel to the cylinder?

Tomorrow I will remove the throttle bodies and check to see if anything on TB #1 is acting different to the working side.

I'm looking for some guidance on what to check next. Any help is much appreciated.

Scott

[DannoXYZ]

Hi Scott, Greetings & Salutations!!

Anything that is shared between cylinders is fine: battery, airbox, air-filtre, petrol tank, fuel-pump, fuel-filtre, fuel-hoses, fuel-rail, FPR.

Problem is most likely in wiring between ECU to sensors, injectors and coils. If you've swapped injectors and coils and they all work in #2, problem is wiring somewhere.

1. Very first thing always, is measure valve-clearances. Are they within spec? Adjust all to large end of tolerance range.

2. It's possible fuel-rail has clog and not delivering to one injector. Remove rail and inspect end-to-end

3. measure fuel-pump flow-rate. Disconnect fuel-hose from rail, aim into measuring-cup. Crank engine for 10s. How much petrol did you collect? Photo of different bike, but same procedure:


4. measure pressure in fuel-rail. Crank engine for 10-sec. What is pressure in fuel-rail? Again, picture from different bike, same test and procedure


5. Inspect all terminals in all connectors on harness for looseness, bending and corrosion. Sometimes, terminals can get tweaked and pushed out of connectors when plugging in.

6. Measure all wires end-to-end for breaks


7. Disconnect all injectors and coils. key ON, measure voltage at each terminal of every injector and coil connector. Post your results here; 8 separate measurements

8: functionally verify coils and sparks. Pull coils and insert plug. Ground case of plugs, to engine or with jumper cable to battery -neg. Crank engine, is there strong bright blue spark on both plugs?

9. verify injector functionality. Pull fuel-rail with injectors attached, leave clips on. Put little cups under each injector. Crank engine for 10-sec. How much petrol did you collect in each cup?

10. measure ECU signal to each injector & coils with oscilloscope. Should look like following trace (4 separate measurements).



11. inspect each sub-throttle for proper operation. Although they really only make difference coming just off-idle, if one was stuck open or closed, it may cause issues. But really only at partial-throttle/low-RPM. I usually disable them completely when replacing EFI system anyway.

[motopreserve]

Thanks so much Danno! I have to apologize. I checked back to see if this thread had posted (my first, so being reviewed). After a couple days of it not showing I forgot to check back to report my solution.

I ended up doing several of the tests that you laid out here. But this is an amazing amount of info - and I’m happy to have it for the future. Hopefully others can benefit from this as well.

I did end up finding the issue. And feel pretty pissed at myself for not finding it sooner. It turned out the spark plug was bad. After doing so many tests (the first or second being the spark against the motor), it was the one component I didn’t swap to the other side. This would have told me immediately that the plug was the issue. But once we saw spark, we moved on to the other tests.

I finally just put a different (used) plug in the dead cylinder and it popped to life. I believe what gave the false positive was that the plug was not properly grounded during the test. Once the replacement plug worked we checked the good/bad plugs with a multimeter. And sure enough, it appeared the bad plug was shorted internally. But it had showed spark against the motor??? My guess was the way my buddy held the plug allowed the spark to jump to the motor - but when threaded into the bike it was shorting and not making proper spark.

The plug looked perfect physically. And I had cleaned it to make sure buildup was not preventing spark. But trusted the test - and really should have been thorough and swapped it to the other cylinder. Dumb mistake.

Needless to say, I have run the bike multiple times to make sure both cylinders are working correctly. And have a 4 pack of plugs, plus 2 new ones in the bike now. So hopefully I’m all set for the next session. Fingers crossed.

Really appreciate your help.

Scott

[DannoXYZ]

Awesome job tracking that down!

Sometimes, it's simple things!

BTW, it wasn't Champion spark plug was it? They've had errors in their cross-reference tables for past 30-yrs. Using those plugs in your bike can cause engine-damage.
https://faq.ninja250.org/wiki/Changi...rands_to_avoid

[motopreserve]

Not Champion, but thanks for the heads up. They were (and still are) stock NGK.

We will see how it goes tomorrow at the track. Fingers crossed!

Really appreciate the help.