mk2dave Posted October 4, 2023 Share Posted October 4, 2023 I'm trying to help my brother with his 5th gen. It's been sitting for a while, and it needed a new battery. Fuel pump wasn't priming, so a new fuel pump and filter was installed. Fuel pump now primes when its supposed to, but the bike still doesn't run by itself. It turns over, and it will run on starting fluid. Fuel also comes out of the fuel return line when priming. No MIL. So Im running out of ideas here. Fuel seems to be flowing to the rail... so bad injectors? I wouldn't bet on ALL the injectors going bad. I would have expected it to run and maybe miss but still run. Is there a switch that controls if the injectors fires? It runs on starting fluid, so ignition seems not be the cause. I'm assuming fuel pressure isn't that important to get it running since it runs with starting fluid sprayed into the airbox. If FP is not correct, it wont run well, but it should run even if barely. Any ideas and suggestions would be appreciated. Quote Link to comment Share on other sites More sharing options...
Member Contributer bmart Posted October 4, 2023 Member Contributer Share Posted October 4, 2023 You need fuel, air, and spark. Have you checked those systems completely? Quote Link to comment Share on other sites More sharing options...
V4 Rosso Posted October 4, 2023 Share Posted October 4, 2023 1 hour ago, mk2dave said: I'm assuming fuel pressure isn't that important to get it running since it runs with starting fluid sprayed into the airbox. If FP is not correct, it wont run well, but it should run even if barely. Starting fluid comes out of the spray can because the can is pressurised 🤓 Check if there is fuel coming out of the injectors. Quote Link to comment Share on other sites More sharing options...
mk2dave Posted October 4, 2023 Author Share Posted October 4, 2023 49 minutes ago, V4 Rosso said: Starting fluid comes out of the spray can because the can is pressurised 🤓 Check if there is fuel coming out of the injectors. I think that is our next step. Unfortunately, pulling the injectors themselves involves taking off the throttle bodies. After reading other threads, it seems like feeling the injectors for pintle movement off of a 9v battery might be the way to go. Is there a way to see the injectors spraying fuel without removing the injectors if the throttle butterflies are held open? I am not hearing anyone suggest it may be a sensor that is stopping the injectors from firing. Quote Link to comment Share on other sites More sharing options...
mk2dave Posted October 5, 2023 Author Share Posted October 5, 2023 It would also be great to confirm if the injectors will fire with the fuel pump disconnected. I lean towards yes, but sometimes manufacturers try and be smarter than necessary. Quote Link to comment Share on other sites More sharing options...
Member Contributer Grum Posted October 5, 2023 Member Contributer Share Posted October 5, 2023 6 hours ago, mk2dave said: I am not hearing anyone suggest it may be a sensor that is stopping the injectors from firing. For the injectors and most likley the Ignition coils to be enabled the ECM MUST see a Ground at either B10 for a Neutral gear start (from the Neutral Switch) OR a Ground at B21 from the Sidestand UP while riding. If neither Ground is detected = Dead Engine. So, while in Neutral, make sure you measure a Ground at B10 of the ECM. Note - the Neutral Ground goes through one of the Clutch Diodes before reaching the ECM. Verify that you measure a Ground at B21 a Green/White wire, with the Sidestand UP. Might be worth giving both ECM plugs a good spray of electrical contact cleaner something like CRC 2-26. Assume you have fresh fuel, a healthy charged battery and both battery terminals are clean and tight! Ignition Switch to On. Make sure you are measuring battery voltage, a solid 12v, at the Black/White wire of the Injectors and Ignition Coils as well as B8 of the ECM. Try starting the bike with Sidestand UP does this make any difference? Remove the Spark Plugs. What state are they in? If they are wet, then you may have an over rich flooded no start situation. Check that you are getting a good Spark. If you're intending on replacing the plugs (worth doing), try the NGK Iridium CR9EHIX-9 type. Another thing worth checking is the FPR Fuel Pressure Regulator. Check it's vacuum hose, make sure it's dry and no fuel dripping from the FPR, any sign of fuel will mean a ruptured diaphragm in the FPR, dumping excessive fuel via the vacuum hose into cylinders 3 and 4. Have you downloaded the Service Manual? 1 Quote Link to comment Share on other sites More sharing options...
Member Contributer Grum Posted October 5, 2023 Member Contributer Share Posted October 5, 2023 3 hours ago, mk2dave said: It would also be great to confirm if the injectors will fire with the fuel pump disconnected. I lean towards yes, but sometimes manufacturers try and be smarter than necessary. The ECM has no feedback of Fuel Pump ops, flow or pressure. Provided the ECM sees the appropriate cranking pulses, and the enable logic as previously mentioned, as well as no active fault codes, power and grounds all good, then it should be firing the injectors you would think....! Quote Link to comment Share on other sites More sharing options...
V4 Rosso Posted October 5, 2023 Share Posted October 5, 2023 22 hours ago, mk2dave said: Is there a way to see the injectors spraying fuel without removing the injectors if the throttle butterflies are held open? Yo may have to remove the airbox to get a good view Quote Link to comment Share on other sites More sharing options...
rick Posted October 26, 2023 Share Posted October 26, 2023 I just found my main fuse B has a short wire to a connector, which was burned and crusty.I wire brushed it and sprayed contact cleaner and works great now! Under seat next to battery. Good luck. Quote Link to comment Share on other sites More sharing options...
Member Contributer Grum Posted October 26, 2023 Member Contributer Share Posted October 26, 2023 40 minutes ago, rick said: I just found my main fuse B has a short wire to a connector, which was burned and crusty.I wire brushed it and sprayed contact cleaner and works great now! Under seat next to battery. Good luck. Good find, but a little strange. Overheated bad connections at this fuse would normally mean no Fuel Pump ops, no injectors, no spark, also the MIL light would be fully illuminated, not flashing. Also on a 5th Gen, your headlights would either be dead or barely turning on.! Bit of a shame the Voltage on the critical Black/White wire powering all the EFI equipment wasn't measured, I'm sure that would have told a story, poor/low voltage on this wire generally (not always) goes back to issues with Main Fuse B. The wire joint you discovered and the whole Fuse assembly needs to be replaced, otherwise it WILL come back to haunt you! P.s. Buggar!.........I've just realised, rick is not the Original Poster! Oh well, the above still applies! Quote Link to comment Share on other sites More sharing options...
Member Contributer JZH Posted October 27, 2023 Member Contributer Share Posted October 27, 2023 That may or may not be something. My first thought, when you said the bike had sat for a while and wouldn't run, was clogged injectors. When I was building the Yellow Peril I had the OEM injectors professionally cleaned, but when I tried to start the engine I only had one or two cylinders firing. After a suitably long hair-pulling session I think I followed someone's advice on here and started tapping on the injectors with the engine running, and sure enough, they all came un-stuck and the engine began to run like a VFR engine should. Wooden mallet or stick. Give it a try. Ciao, JZH Quote Link to comment Share on other sites More sharing options...
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