No Spark on #5 S225 OX66 EFI

[ddog]

New to the board, tried the search and didn't find a match. Engine is 1999 Yamaha S225TXRX OX66 EFI.<br />The engine has spark on all six cyclinders when it is first started. After about 1 minute, will lose spark on #5. Using a timing light to check spark and confirm with a gap style spark checker.I have swapped coils around and #5 stays dead. If I disconnect the knock sensor, Spark on #5 comes back.Replaced knock sensor, but didn't fix problem? Any Ideas??<br />Thanks!

 

[blackcreek]

Re: No Spark on #5 S225 OX66 EFI

My 1997 225 ox66 does the same thing because it is designed to. I am not sure about yours but at idle mine drops #5 and #6. The computer does this to help save gas,your motor will shake at idle if it runs ok at higher rpms your motor is fine. I can feel my cylinders kick in as I accelerate. If your #5 sparks above 2000-2500 rpm it is working fine.

 

[bigbrownbuku]

Re: No Spark on #5 S225 OX66 EFI

what black creek says. not the smoothest idling engines ever built for mainly that reason.

 

[rodbolt]

Re: No Spark on #5 S225 OX66 EFI

see ya just thought you had a problem. the computer will selectivly drop #5 and #2 depending on engine RPM. but #5 is between 850 and 2000 RPM. it should not drop #6.<br /> I would suggest reading the manuals on how the v76 smart ign system works before testing. when you disconect a sensor on that motor the ECU will fix timing at 7*BTDC and the O2 sensor feedback is ignored and injection map goes fixed.

 

[ddog]

Re: No Spark on #5 S225 OX66 EFI

Thanks for the reponses. Normal, That's good to hear. Rodbolt, I have the correct Yamaha OEM Service manual but it does not give a descrption or theory of operation on the ignition system. Is the ignition system manual your referring to a separate part number or publication? Interesting you mention # 2 dropping out also. At one point I had no spark on 2 and 5 and it was actually running very smooth on four cylinders(makes sense since 2 and 5 are opposite). I had found a couple plug caps out of spec and changed them all. Since then #5 is the only one dropping out.Just trying to verify proper ignition operation since this is a powerhead replacement. Don't want a new powerhead taken out by a dead hole.Thanks again for the responses, I remember reading that the HPDI motors would cut 2 cylinders at idle to help reduce emmissions, but didn't know that about the OX 66 EFI motors.<br />ddog

 

[rodbolt]

Re: No Spark on #5 S225 OX66 EFI

hello<br /> not all Ox66 motors operate like that just the 3.1L V6 Ox66. also known as the V76 motors. there are many variations of the CCS and SMART ign systems. so far you have gotten off cheap. best to learn how why and what each sensor does before it costs you a bundle. the two most common failures that take out pistons on 3.1 motors is a bad O2 sensor or a bad low pressure fuel pump diaphram. the filter in the VST needs periodic cleaning as well. it can drop as many as 4 cylinders depending on what conditions exist.

 

[ddog]

Re: No Spark on #5 S225 OX66 EFI

Rodbolt, Thanks for the information. I already replaced all three low pressure fuel pump assemblys, Cheap insurance IMO. For the price of the diaphragms and parts, not worth rebuilding.Cleaned the VST tank and filter, surprisingly clean when opened up, also checked the filters on the injector inlets. I originally condemed the O2 sensor based on the heater resistance spec of 100ohms in the OEM yamaha manual. The O2 passed the voltage drop test using the torch test.Got the new O2 sensor and the Heater resistance value for the new one and the old one were the same, around 5 ohms. Must be misprint in the OEM manual, but now have an extra O2 sensor.Checked the specs, it is a 3.1 v76 ox66.The OEm service manual gives troubleshooting for the sensors but is lacking on theory and functionality. Is there another yamaha Publication available for the Ignition System?<br />Thanks,<br />Derrek

 

[rodbolt]

Re: No Spark on #5 S225 OX66 EFI

no good pubs but its there in spots. the flame test for the O2 sensor is a teat on a boar hog. dont use or trust it. I use the test harness and back it over them nmanually close and open the air bypass hole on the throttle plate while watching the O2 sensor voltage.