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'66 Ambassador no spark again
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Trog View Drop Down
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    Posted: Jun/13/2011 at 9:33pm

Unable to search back to May 2009 when I first posted problem with '66 Ambassador V8 no spark wherein we discovered it was poor remanufacture of either the rotor or the cap (cannot find my notes either) wherein the gap was too large between the rotor and the cap contact. Well, we struggled with it and got the car running via new rotor or cap, but now again the no spark has hit us.  I can get a instant spark each time I try to restart the engine but that's it and it's weak.  Thinking maybe (as may have been suggested previously) of going to the Pertronix ignition but then looking through some of the postings on that subject do not appear to be all that encouraging with problems still persisting and then there's Ignitors I, II, III.....at this point not sure what to do. I did use local (national) parts suppliers for the rotor and cap, but as stated earlier had problems with manufacture of those and perhaps it has manifested itself again.  Is there a particualr brand or source I should try to get for the cap/rotor or should I try to acquire a Petronix. I see Ignitor I on ebay for around $77.

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What brand points/condenser are you using?
Also, new or old coil?
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Trog View Drop Down
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NAPA or CarQuest for all ignition parts. I just cannot yet find my notes of exactly which was the problem previously, the rotor or the cap but I believe it was the rotor whose contact end point was visibly recessed too far to allow contact.  Took us a while to find that after we had checked points, condensor, and coil. This is the third occassion of no spark on the car and we are talking less than a few hundred miles between times. The car is driven only occassionally like once a month or six weeks for short distances.

Edited by Trog - Jun/13/2011 at 9:56pm
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Think I would start at the beginning again. New point/cond., rotor, cap, wires & plugs. There has to be a reason why the rotor & cap lugs got eaten up and it is resistance from plugs or wires. Now what gets me is “I can get a instant spark each time I try to restart the engine but that's it and it's weak.”? Are you getting a full 12 volts when cranking and do you get power to coil with key on? If not could be a bad IGN switch. If that checks out ok then as PMM said maybe a bad coil for the weak spark. What if you hot wire it will it start/run?

Motor grounded to the body if not this may cause a weak spark because you do not have a full path. If you do go for the IGN kit after the parts you bought only thing not used would be the points/cond. I would go with new parts to get it running then replace with the kit.

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Points: 16611 		Post Options Post Options   Thanks (0) Thanks(0)   Quote purple72Gremlin Quote  Post ReplyReply Direct Link To This Post Posted: Jun/14/2011 at 11:23am
Check that little ground wire on the breaker plate?   the coil???  Id sure take a look at it.  getting 12 volts to the coil?  another thing, was the cap and rotor the same brand?   sometimes theres a mix match.  I can remember years ago a cheapy points and condensor and a rotor kit  would be $1.97................the better caps use copper terminals.....Accel, blue streak, mallory, and a few others I cant think of.
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Trog View Drop Down
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OK, all I could do this evening was check the coil.  12.5+ volts both sides but both sides drop to 8.2-8.5 volts when cranking.  This car has a new coil with internal ballast resistor.  I thought the voltage step down to 6 Volts on the car would not be until after ignition, the idea to prolong the lifr of the points.  One time the car actually momentarily tried to start.  (And for clarification, the first new rotor replaced was from NAPA and we found the rotor contact button on the brand new rotor to be too recessed to make contact with the cap.  At the moment I do have a CQ rotor and a NAPA cap.)
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As an FYI, try a new condenser.  There have been a large number of them that don't work right out of the box from the big name stores.  My friend has an old 6 cylinder Chrysler and has been bitten by the condenser Gremlin several times.  I know of several others with the same issue and we've duplicated it here.  Seems like about 1/3 of the condensers we get aren't doing what they're supposed to.  Crappy parts are laying around on shelves it seems.
 
 
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Originally posted by Traveller Traveller wrote:

As an FYI, try a new condenser.  There have been a large number of them that don't work right out of the box from the big name stores. 
 

Not much better in the 70's either. Probably the only spare part I kept in the glove box.
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Trog View Drop Down
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OK, guess that's the first thing I'll try, a new condensor.  The worst part about this whole thing is that rear distributor cap screw jammed in up against the firewall that is barely accessible. I can usually get it loose but then getting it tightened back on is a real effort.  I guess they are Delco intended for GM perhaps and adapted to AMC, but if the screws had been rotated 90 degrees it would make it so much easier.  May be a few days before I can get to this.  Thanks
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Originally posted by Trog Trog wrote:

OK, all I could do this evening was check the coil.  12.5+ volts both sides but both sides drop to 8.2-8.5 volts when cranking.  This car has a new coil with internal ballast resistor.  I thought the voltage step down to 6 Volts on the car would not be until after ignition, the idea to prolong the lifr of the points...
The coil primary should be at 12V when the points are open, and 0V when the points are closed. The voltage you measured is the meter trying to average as the points open and close while the engine is turning. Since the internal resistance of the coil primary is very low, you will see the about same voltage at both the + and - terminals.

You didn't say anything about the plugs. If they got fouled for any reason, they won't fire even if cleaned.

BTW, I found your old thread:

http://theamcforum.com/forum/66-amc-ambassador-no-spark_topic9239.html
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