641 Firing

G Archer · Nov 10, 2013

Hi folks, I have a 641 that will not fire at the plugs.New points and condenser,coil, dist. cap, wires,and rotor.When I turn engine over I have a crisp blue spark from coil wire when I touch it to a ground.I can touch it to the coil post on the dist.cap and I get nothing.Do I have a bad cap or rotor? It does not make sense to me. Thank for any help. Glenn

Bruce (VA) · Nov 10, 2013

Do you have battery voltage across the points when they are open? Verify the gap on the points. Then, dress the points by running a piece of card stock or brown paper bag through them. New points sometimes have an anti-corrosive dielectric coating on them & old points can corrode or pick up grease from a dirty feeler gauge or excessive cam lubricant. (I always spray my feeler guage blade off w/ contact cleaner.) Make sure you have voltage across the points, as in past the insulator on the side of the distributor. That is a very common failure point, along w/ the attached copper strip. It's hard to find a short there because it is usually an intermittent . So 'wiggle' the insulator & the copper strip a bit when you are doing your checking. If you just replaced the rotor & lost spark, put the old one back in. Insure that the rotor fits firmly on the shaft & that the little clip is there. Make sure the distributor cap is not cracked & doesn't have carbon tracks. Check continuity on the secondary coil wire. Make sure it is firmly seated in both the cap & the coil. In fact, replace it temporarily w/ a plug wire.
75 Tips

old · Nov 10, 2013

Sounds like your throwing parts before trouble shooting.
If your saying you have good spark from the coil wire when you spin it over but no spark from any of the plug wires you have one of 3 problems.
#1 you do not have the spring clip on under the rotor so it is not tight on the shaft.
#2 Bad rotor which now days is not uncommon for new part
#3 bad distributor cap.
If I where you I would put the old cap on and check spark then if you still do not have spark try the old rotor

G Archer · Nov 10, 2013

Thanks for the replies.This is a restoration project.Engine caught fire from leaking fuel line and destroyed all wires and such.Installed new parts and the engine was running fine but stopped like the key was turned off and has not started since.Since I have good spark from coil I was leaning towards dist. cap or rotor.I ordered parts on the internet(wires,cap,rotor,points) so maybe I got some China made parts. Replaced points with NAPA brand but not cap and rotor. Thanks, Glenn

souNdguy · Nov 11, 2013

good psark for coil wire held NEAR block.. but not touching it?

if so.. then double check as old said.. rotor, clip and cap..

make sure your plug wires and plugs are ok as well.

G Archer · Nov 11, 2013

Update. Installed new Standard brand cap,rotor, and condenser.Still no fire to the plugs when cranking the starter.Loosened the dist.and rotated base where rotor lined up with # 1 terminal on dist and it will crack blue spark on tester attached to # 1 spark plug.Turn starter over and no spark.What could be killing the spark? Glenn

souNdguy · Nov 12, 2013

during restore.. did you remove the distribuitor?

G Archer · Nov 13, 2013

Found the problem.Centrifigal weight support plate broke loose from the distributer shaft.Weight was striking the post in the dist grounding it out.Got to spot weld it back in place.Thanks for all the replies. Glenn

641 Firing

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Bruce (VA)

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