FH680V-BS29

[ILENGINE]

Could be flooded, yes. But, heat is not likely the issue unless the routing of the fuel line has been changed from where MTD originally routed it. I still suspect the coils or if there is spark.

For a little more information If I replace the Champion RN14YC plugs with BPR5ES because I can't get the recommended BPR4ES it will start hot or cold. Or if I replace the hot Champion plugs with prior ran cold plugs will restart hot. 6 brand new plugs are failing hot.

 

[txmowman]

This model does not use an oil pressure switch, at least not from Kawasaki.

Couple of things which come to my feeble mind. First, I checked the service manual and it calls for a Champion RCJ8Y plug. Second, I know you’ve done a leak down test, but I would perform a compression test, should have a minimum of 57 PSI. I wonder if it is different hot and cold. I know the oil pressure switch only triggers a warning light, but if I remember right I did have one that shorted out the ignition switch when it got hot. Replace it and problem went away that time. Manual says the fuel solenoid and pressure switch connect to the same terminal on the key switch. If that were the case I doubt you would hot spark. IL, I know you have been around the block at least one time, but I’ve got to ask a stupid question, please don’t be insulted. Have you checked for hot spark with an adjustable spark tester and can get it to jump at least 3/16”? I’ll keep thinking, keep us posted. I hope this is not a test, if so I failed.

 

[txmowman]

Hot or cold plug would be no issue. The "heat range" is the plugs ability to remove heat from the cylinder. Not the actual "burn" of the fuel mixture.

 

[Rivets]

Sorry I posted the wrong plug number, NGK #BPR4ES or the Champion IL posted. About the oil pressure switch, doesn’t mean someone could have added one? Did come up with another stupid question. Have you tried to remove one or both of the kill wires, to see if you get a bang when hot?

 

[ILENGINE]

Sorry I posted the wrong plug number, NGK #BPR4ES or the Champion IL posted. About the oil pressure switch, doesn’t mean someone could have added one? Did come up with another stupid question. Have you tried to remove one or both of the kill wires, to see if you get a bang when hot?

Actually as part of my testing have removed the kill wire one at a time and both at the same time. No change. Everything is leaning toward the new Champion plugs are shorting internally when hot. I could see a one doing it but 6.

 

[bertsmobile1]

Well the closests to this I have come across was with a Toro Titan fitted with a Kohler
The first one did a similar thing and the quick & desperate solution was to slip some platinum plugs I had on hand for the LPG van .
Very embarassing as the customer came to collect, did a trial run up & down the front lawn, shut it down, paid the bill then it would not start to get put on the trailer
Mindful of that the other one they have I used the colortune on and it confirmed what I suspected when thinking about it latter on
The carb was just too lean so I drilled out the jets , next size up & problem vanished .
How ever in both cases it would restart on carb cleaner down the carb throat but not unassisted .
And FWIW I fitted platinum plugs to it as well
I really do not know the specific difference between an XC12YC & an RC12YC which is what I originally replaced the plugs with but nothing that specifies an XC plug will run properly on any other plug so I now keep XC's as well .

 

[StarTech]

You may have a carburetor problem. Try this the next time fails to start. Loosen the carburetor. Basically you to create an air gap between the carburetor and the intake manifold and see if the engine will fire up.

Just went something similar except it was a single barrel carburetor on a Honda engine. It was taking three pulls cold to start up but no matter how many times you pulled when hot it would not start. Since the carburetor was cheap from Honda I installed a new carb and everything worked as intended. One pull cold or hot would fire it up.

Now I assume I had a fuel leak of some kinda in carburetor but since I behind a few weeks here once the engine was running I when on to the next problem. Just was n't the time to explore a $15 carburetor problem.

 

[ILENGINE]

Second, I know you’ve done a leak down test, but I would perform a compression test, should have a minimum of 57 PSI. I wonder if it is different hot and cold.

Compression around 105-110 on both cylinders on a warm but not hot engine. Ran a couple minutes and then pulled the plugs.

And something this is interesting, but may not meet peoples approval. Took my ohm meter and checked the resistance of the Champion both used in this engine and a new RN14YC plug. And compared it to the NGK both new and the plugs that are currently installed. The Champion plugs that were used are reading 12-15M ohms. The new Champion RN14YC plug is reading 83k ohms. The NGK both new and used in this engine are testing around 5k ohms.

 

[Rivets]

I haven’t seen an entire box of Champion plugs bad since the early 80’s. Now you are starting to fry my brain! To me nothing is making sense. At this point, if I had this engine, I would run the NGK BPR5ES plugs until it gets HOT. Then I would look at the plugs. If the plug has a little black tint to it I would run those plugs. If the porcelain is bright white, I would say those plugs are too hot and I’m back to square one. Just my opinion, but read my signature.

 

[ILENGINE]

I haven’t seen an entire box of Champion plugs bad since the early 80’s. Now you are starting to fry my brain! To me nothing is making sense. At this point, if I had this engine, I would run the NGK BPR5ES plugs until it gets HOT. Then I would look at the plugs. If the plug has a little black tint to it I would run those plugs. If the porcelain is bright white, I would say those plugs are too hot and I’m back to square one. Just my opinion, but read my signature.

Already had done that before you even commented. The BPR5ES have slightly darkened porcelains after having put about half an hour on them. This sets up the issue that I use the Champion plugs and the customer starts the mower and mowers their entire yard before shutting off will never see the plug issue. The ones that mow for a period and then shut off the mower to go get a drink and come back will have a no start.

I have a similar engine in the shop right now that takes the same plug. I may pull the plugs out of it and then run it and see if I can duplicate the no start engine with the suspected faulty plugs.

Just tried resetting the air gap on the modules from 010 to .014 and tried the Champion plugs again. Started cold but would only pop but not start hot. Dropped the NGK back in it and fired right off.