troubleshooting electircal system

[tom888fish]

I know this has been discussed many times, but I'm struggling with the Search feature. Can someone point me to electrical system troubleshooting? After rebuilding the carb I couldn't get so much as a pop. There was spark when I pulled the plugs, but I figured I'd go ahead and rebuild the distributor plate, points, cap rotor and even wound up putting on a new coil. Now I've got no spark whatsoever.

 

[Dell (WA)]

Tom..........gonna make a WAG (wild A$$ guess) yer talkin' bout the weird 4-nipple front mount dizzy. Points are 0.015. The 2-bolt dizzy is designed to be removed from the engine and points are adjusted (0.015) or replaced on the kitchen table. Just un-snapple yer capple and remove the two-bolts and walk. Installation is a reversal of the removal ...except... finger start the 2-bolts. Now install the rotor and rotate the rotor until the OFF-SET tang on the back of the dizzy fits the OFF-SET slot in front of cam shaft. Now tighten the 2-bolts and re-snapple yer capple. Simple, eh? Remember to POLISH the INVISIBLE corrosion from between the points. Me? I clamp the corner of $1-bill (cheap) between the points and pull. Remember, with the 2-bolt scheme, you kenn NOT install outta time.

As fer yer carbie, adjust the down-pointing MAINJET to 2-turns and LEAVITT!!! Adjust the side-pointing idlemix fer FASTEST idle, NOT SMOOTHEST idle. Understand the difference??? Remember the side-point idlemix is BASSACKWARDS; out fer lean, IN fer ENRICH. Usually ends up about 1/8-1/4 turn.......HTH, the amazed Dell

 

[tom888fish]

Dell - you're correct on the front mount. I've had it off and on a number of times no troubles there; I know the drill on aligning etc. I had previously rebuilt it and it was running but not outstanding and then I couldn't get it to start at all. So this time since I had one, I put in a new plate and replaced the bronze bushing as well. Also a new coil. The points and capaciter probably have 4 hours on them since I replaced them last summer (tractor doesn't get used a lot, and typically doesn't start unless I don't really need it to. So essentially everything but the housing is new and adjusted. Now I get no spark at all. I pulled the lead to the top of the coil and my unresearched assumption is that I should be able to see voltage going to that but I don't. Where to go from here?

 

[Bruce (VA)]

What has also been discussed many times is providing some minimum information about the tractor you're working on.

What model tractor is it?

Is it 6v or 12v?

Does it have a front or side distributor?
75 Tips

 

[tom888fish]

Bruce, yes; sorry, I was actually originally just asking for where to find some information on self-diagnosis and planned to do my research first before asking more specific questions here. However, since we're on it; its a 1948 8N, 6V front mount.

 

[Bruce (VA)]

Re below, if you do not have battery voltage at the top of the coil w/ the points open (and about half that w/ them closed) the problem is not in the distributor.

Google " wiring diagrams JMOR" and find the diagram for your tractor. Then get out your multimeter & follow the voltage from the battery.

HINT: pay careful attention to the ignition switch.

Post back w/ results or more questions.
75 Tips

 

[tom888fish]

Thanks Bruce!

 

[Dell (WA)]

Tom.........since the weak sister ignition key feeds the "infamous" ballast resistor which feeds the wire at the top of the 1-terminal coil. I'd suspect the ignition key first 'cuz its eazy to gitt too. Try wigglin' the key around. Surprizingly enuff, the 1-terminal square can coil is semi-bulletproof. Its not as robust as the 3-terminal roundcan coil which is oil cooled. Most squarecan coil problems are the points. (0.015) In 60yrs of futtzing with ignition systems, I've NEVER had a BAD condenser. I'm an electronic engr and I have the test equipment to check condensers. Ittza almost always been BAD points. The rubbin' block wears and closes up the gap (0.015) and suddenly NO SPARKIES. .......HTH, Dell, yer shade tree electrician and self-appointed sparkie-meister

 

[tom888fish]

Dell - Is the engine turning over any proof that the ignition is working correctly or is turning over and spark not necessarily linked?

 

[Dell (WA)]

Tom........there is NO relationship between the engine turning and yer sparkies sparkling. Iff'n the ignition switch ain't ON, you gitt NO sparkies. The tranny mounted starter switch must be in NEUTRAL. Hint: the ignition switch is a weak sister 5-amp shyneez look alike. The tranny starter draws about 150-amps. Normal ignition draws about 3-amps. Donna worry about yer amp-meter, it is voltage insensitive. And while the N-tractor came from the factory 6-volt positive (+) ground, the starter motor still turns the correct direction with negative (-) ground. There is some technical advantage fer positive (+) ground fer yer sparkies, but modern sparkie design negates that. Recommend AutoLite 437's gapped 0.025........Dell, yer self-appointed sparkie-meister