8N Won't Start

[Phil Freeman]

I have a 1948 or 1949 8N (serial # indicates 1949, but owner's manual is 1948). It has the front mounted distributor. Last fall when I quit using it for the season, it was running, but now it won't fire at all. The wiring harness was a mess, so I replaced that and still no firing. I had replaced plugs, points and condenser late last season and the plugs look good. I pulled the distributor back off and checked the points and timing and both are good. There is gas to the carb (floods if choked) and what appears to me to be good spark at each plug. I did the 1/4" spark test with each plug wire and while I can't be 100% certain the spark is adequate, it sure appears to be. I took the carb off and squirted starting fluid directly into the manifold and still not a hint of firing. I don't know anything else to check except for compression, but it just seems unlikely to me that an engine running 5 months ago now has such bad compression that it won't fire at all. I know people always say "replace the plugs" but again, it seems unlikely they could be so bad as to keep it from firing at all. The tractor has a 6 volt system. Your thoughts or ideas would be much appreciated.

 

[AbvAvgJoe]

Did you let the gas flow out of the carb drain? Did you let it run enough to be sure the needle and seat are not stuck? If you have good hot blue spark at each plug, then it's most likely not getting fuel to the cylinders or it's flooded itself and your spark plugs need to be cleaned and dried or replaced. Hope you get it running soon. Joe

 

[HCooke]

Three things, compression, spark, fuel. Might try bypassing the resistor and ignition switch to see if that improves the spark. Since it doesn't fire with starter fluid, that would seem to rule out a fuel problem. Stuck valves? - does it have good suction when you put your hand over the carb intake when trying to start it? If you've flooded it you may have to clean the plugs or replace them.

 

[D7fever]

did you clean the points? sometimes thru the winter,especially if it is wet, they will corrode, need to be cleaned then they will spark. Did you check the resistor that is in line with the coil? Check for spark at the plugs? If you rewired without the resistor, you might have burned out the coil.

 

[Phil Freeman]

I am not sure what you mean by "If you rewired without the resistor..." Do you mean if there is no resistor?

Thanks.

 

[Phil Freeman]

I did test for vacuum at the carb, and while there was some, it seemed weaker than I think it should be. Also, the plugs seem dry even after cranking on it over a flooded carb. That makes me think it is not pulling in the fuel mix to the cylindars.

 

[Phil Freeman]

Thanks, Joe. I will check that.

 

[JMOR]

(quoted from post at 21:17:05 04/13/11) Thanks, Joe. I will check that.

f you have the 1/4 spark that you speak of & it won't even pop on starting fluid, then I would try new plugs or at least heat those a bit with a propane torch to burn off invisible deposits that can drain the energy down the insulator, resulting in no spark at gap.

 

[seaking]

try putting a shot of oil in each plug hole,,
the cylenders my be dry and not sealing the rings
to the cyl.walls...

good luck on it.....s.k.