Need Help What Am I Missing

Have a 48-49 8n that runs on 2 cylinders.

105# comp. on all 4 holes
Firing on 1 and 2
4 new H12 Champ plugs
Blue spark at end of fire 1/2" long
plus wet on 3 and 4, will not fire
replaced 3 & 4 plugs with different plugs, will
not fire.

Got my camera scope out pulled 3 and 4 and took a
look, little wet, both valves opening and closing,
gas on end of plug.

Someone in the past has put a new FRONT
distributor on this tractor. Guessing this has
been a problem before, but not sure.

This not my first rodeo working on tractor, but
have to say I am a bit perplexed.

Let me know what you think. Thanks.

Have you checked cap and wires on 3/4 and for the heck of it, you know it is 1-2-4-3 fire order

Sounds like a bad cap or bad wires,you said you have a good spark,is that at each plug or just the coil?You might try swapping some wires to see if the firing changes to a different cyl. but it sounds like cap or wires to me.

Do a compression and/or a leakdown check.

Two adjacent cylinders not git'in 'er done can indicate a failed head gasket.

Did a comp test, 105 each hole.

With tractor running on 2 cylinders i removed plug wire from top of plug and get about 1/2" deep blue spark on EACH plug.

If all plugs were firing and you pulled a wire of it would drop that hole, correct, 3 and 4 make no difference, they are not firing.

If the cap or wires were bad you would either get poor (yellow) spark or none at all, not the case here. You touch the spark on any of them and it would put you into last week.

(quoted from post at 11:01:29 11/14/14) Did a comp test, 105 each hole.

With tractor running on 2 cylinders i removed plug wire from top of plug and get about 1/2" deep blue spark on EACH plug.

If all plugs were firing and you pulled a wire of it would drop that hole, correct, 3 and 4 make no difference, they are not firing.

If the cap or wires were bad you would either get poor (yellow) spark or none at all, not the case here. You touch the spark on any of them and it would put you into last week.

Click to expand...

Reverse the 3 and 4 plug wires and see what you get!

Was it previously working? If so ignore this suggestion, as it shouldn't have changed unless you have had the distributor off.

If you are just getting her going I would confirm she is set to fire at or near TDC. for #1 cylinder. You can get them to run otherwise...albeit not well.

Sounds like 3&4 are switched.

The tractor was brought to me for brakes and reseal
rear axles. It ran so poorly that I checked into
why and came up with it firing only on 1 and 2.

How do you check for TDC on an 8n, where are the
timing marks ( crank front pulley, fywheel, ???) and
how do you adjust timing on a front distributor.
May need to walk me through this one.

Bob.......check yer #3&4 wires. Make certain that they are old fashioned COPPER core wires 'stedda modern "string" fiber core wires. The string can "break" inside the insulation and yer sparkies will NEVER sparkle.

You do know the weird 4-nipple front mount dizzy is designed to be removed from the engine and points (0.015") installed/adjusted on the kitchen table, don't you?

Just un-snapple yer capple and letter dangle. Remove the 2-bolts and walk to the table. After installing/adjusting/checking the points (0.015"), remember to "polish" the invisible corrosion from between the points. Me? I clamp a $1.00 bill between the points and pull. Iff'n yer really cheap, tear a strip from HEAVY brown paper grocery sack and use that. Now finger start yer 2-bolts and install yer rotor. Rotate yer rotor so the dizzy OFF-SET tang will fit the camshaft OFF-SET slot. Now tighten yer 2-bolts and re-snapple yer capple. Simple, eh?

Because of the OFF-SET design you can NOT install outta time. BTW, timing the 4-nipple dizzy is 1/4-in. Check yer I&T FO-4 manual ($19, cheap) fer picture on timing the 4-nipple dizzy. Unlike the later 5-nipple 8N side mount dizzy, there are NO external timing marks for the 4-nipple dizzy.

BTW, compression specs fer the 6:1 low compression N-Engine is 90psi (min). New rebuilt N-Engine is about 125psi. 105 compression is GOOD numbers. ........sparkie-meister, Dell