<VV> No spark

[djtcz at comcast.net]

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original message From: virtualvairs-request at corvair.org 

Subject: <VV> No spark 

1967 Monza coupe, pg, 95 h.p. I took this car out on a drive this week and it started missing, sputtering. I pulled into a station and filled her up with gas. The car ran better so I just thought I had some poor gas. Later drove it some more and started the missing, bucking at highway speed, and some times quitting for a moment. Today I cranked her up and it ran poorly in the garage. Then it wouldn&#39;t start. There is fuel going to the carbs as I cracked the lines at the carbs and cranked it. I have a weak voltage on the positive side of the coil. Points, condenser, rotor, and cap are new. I put my timing light on it and didn&#39;t have any spark. Tried a new coil on it, too. Any suggestions? Thanks, Ernie in Louisville, ky. 

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the list of suspects is long. 
So far neither fuel nor ignition have provided the slightest alibi. 


Ignition suspects are Dirty ("new") points, worn closed ("new") points, carbon tracked cap, rotor or coil, flooded soaked spark plugs, problems with the low voltage circuit, and more. Some problems require replacement, some just require maintenance (classically defined 10,000 mile/annual tune up), but most can be positively identified by thoughtful but simple testing, and corrected far quicker than the blast-the-symptoms-with-a-shotgun-stuffed-with-cash approach employed by many enthusiasts and some pRofESSiOnALZ. 

Were the points open or closed when you checked the voltage at the coil? 
How many volts is "weak"? 
I don't know what is the correct voltage value, but the purpose of the resistor wire in the harness is to drop the voltage supplied to the coil. Voltage drop only exists when current is flowing (points closed). 


The timing light test is a good one. 
But a passing grade requires the spark being generated by the points, condenser and coil forming an LC circuit, then making it from the coil, into and through the coil wire, thru the middle dist cap terminal, into and thru the rotor, back out the appropriate dist cap plug terminal, thru the plug wire and into the spark plug to ground. Issues in ANY or ALL of the way points 
I am not sure if severely fouled/flooded plugs would spark at such a low voltage as to fool SOME inductive timing light. 


I'd start with tests that break the ignition system into smaller sub-systems. 
Cranking with a grounded test plug (NEW plug with a 3/16" gap) in one spark plug lead is a more specific pass/fail test for the bulk of the ignition system. A snappy blue spark there would make me suspect the spark plugs enuff to remove and inspect them for condition and serviceability. While cranking, a dwell meter would confirm if the point gap is proper. 
If there is no spark at a plug lead I'd repeat the test, cranking with the test plug in the dist end of the coil wire. That would get the cap, rotor, and plug leads out of the picture to focus the test on the spark creation portion of the ignition system. 
If there is no spark with the test plug in the coil wire then I'd remove the cap, and check the point contact condition visually, then rotate the engine, first to check the maximum point gap (if the swell dwell meter, then to stop the engine with the points closed. Then, with key set to "run" I'd open and close the points with a popsicle stick, looking for an excellent spark at the test plug each and every time the points are opened. Some sparking at the points is normal. 


I'd expect the culprits behind a "no spark" condition (or at least the location of their hideout) would be identified at the conclusion of this test sequence if diligently applied . 


Once the ignition system is exonerated I'd look into fuel quality delivered to the carbs, and existing in the carbs. Just one or two fat droplets of water can effectively block the tiny metering holes in carburetors. Debris jammed in the float needle seat can dump fatal quantities of fuel into the float bowls. Soaking wet spark plugs suggests this kind of problem