Why no fire?

Distributor ground? An easy check with a booster cable from the battery negative to the distributor case or stalk.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's - Gone to the rust pile... Canadian Off Road Trips Photos: Non members can still view! Jan/06 (More Off Road album links at bottom of the view page)

didn't try that - - going to the garage right now!

Thanks - all ideas appreciated

Darn -- no joy

Happy Canada Day , eh?

"derek sollows" wrote

When did English cars switch from positive to negative ground? Not that (Lucas) English (Lucas) cars (Lucas) have (Lucas) electrical (Lucas) problems.

I once put some new points in a 1971 Chevrolet van I used to own.The engine wouldn't start up.I cleaned the points with some rubbing alcohol and then the engine started up and ran fine. cuhulin

Erm, first, there shouldn't be any spark at the points in the first place - points are in the low-voltage side of the circuit. Having them open (and thus, having the magnetic field in the coil collapse) is what causes the spark over on the high-side.

My first try would be putting a meter set to read resistance or continuity on the primary side of the coil - Check for (relatively) low resistance or just plain continuity. Second try would be doing the same for the secondary - If either says "no juice getting through, boss", the coil is crap (despite being new). Take it back and tell 'em you want one that works. Both show a complete circuit? OK, now it's time to set up a spark plug on the end of a cable, nicely grounded, with the other end of the cable plugged directly into the secondary post of the coil. Now jumper straight from the battery to the primary side - just "tap" the jumper to the primary terminal while observing the spark plug gap. Got spark? If yes, then the problem is someplace else. If no, then the coil is crap. Take it back and demand they replace it with a working unit.

Next thing I'd do is check the continuity of the points - Hook a jumper from battery to one side of a meter set to read volts, the other side of the meter to the usual "input" terminal of the points, and the other side of the points to ground. Now crank the engine. Meter should jump (to about battery voltage) and drop (to close-enough to zero) as the points close and open, respectively. Doesn't happen? You've got something hosed in the wiring to the points.

Next step, assuming those pan out: Disconnect the wire between the points and coil. Attach it to one side of your meter, set to read volts. Other side of your meter goes to ground. Everything else wired "as normal". Crank engine. Meter jumps up and down as points close and open? All is well. Otherwise, you've got troubles in the wiring feeding the points. Perhaps in the harness between the ignition switch and the points, perhaps in the switch itself, perhaps elsewhere, but regardless of where it is, you've got a problem.

Give it a go and let us know how things work out.

Did it do the same before the new points and condensor? Sure 12vdc is reaching points? (1)No voltage to points, yielding no spark (2)12vdc getting to BOTH sides of the points, yielding no difference in potential between contacts, resulting in no spark (3) #2 can be caused by points being shorted: both contacts grounded to each other (4) I'd try new condensor & assure it is bolted tight AND new points. Check continuity between the 2 contacts when NO voltage is applied. When checking for spark, first ensure points are 'broken', and use a screwdriver to intermittently touch both contacts while watching for spark. If all else fails, remove dist. and test with 12vdc applied on workbench. When all this has been done, your problem should become apparent--else get a pro to do this same bench test. Hope this helps, s

Is there voltage on either side of the coil primary?

--scott

Im going to be very fundamental here and hope it doesnt offend you.

Kettering systems, as yours appears to be, are dead simple to work on. Your ignition switch allows 12v to the coil and points, both in Start and Run position. Note that the coil has a + and - terminal, usually. These are not interchangeable, but if hooked up backwards, they will run after a fashion...usually.

The coil causes a spark when the points OPEN, not when they close. Just wanted to be very clear on this.

In the ignition key Start position, full voltage (and therefore current) is available to saturate the coil field and allow a hotter spark.

In Run, the current is limited so that the ignition components will hold up longer. (Sometimes this resistor fails, and the car will try to start, but cannot run when the key is moved from Start to Run)

I have seen bad condensors right out of the box. Shorted, or out of capacitance spec. I have also seen new points that shorted to ground because they were improperly assembled or installed. Be sure those two components are in good shape and that the points gap (when the distributor cam follower is on the top of the distributor cam lobe) is accurately adjusted. (resistance to ground should be essentially infinite when the points are open, and essentially zero when closed)

As others have mentioned, one side of the points/condensor is grounded. The other side should measure ca 12V when the key is in Start or Run position.

If all is in order, then start looking at the coil.

You should look for the spark at the wire coming out of the coil, not yet at the sparkplug. If, for example, you have a bad rotor or distributor cap, the spark can short to ground and never get to the plug.

I am repeating some things others have already said, I am sure, but my point (which I probably didnt make very well) is to understand how the system works and to go through it systematically.

Only a meaningful question if/when the points are closed.

With points open, there should be no voltage at the primary - on either the hot or ground side.

Au Contraire. With the points open, a voltmeter should show full voltage at BOTH the hot and ground sides of the primary. The points GROUND the ground side of the primary when they close.

No, other way around. The hot wire from the ignition switch goes to one wire on the coil primary. The other wire on the coil primary goes to the points, which short to ground.

SO, with the points open, you should measure 12V on both sides of the coil primary. And if you short the second side of the coil primary (the wire that goes to the distributor) to ground, you should get a nice fat spark off the secondary.

--scott

With one exception, my experience has been that the circuit is battery

--> ignition switch --> points --> coil --> ground. Of course, it should work just as well with points between coil and ground, but as noted, will definitely change the meter reading!

But I've only seen it that way personally once - on a Ferguson TO-30 tractor from about 1949, which had been rewired (poorly) by someone in the process of converting it from a 6 volt positive ground system to a

12 volt negative ground setup. I assumed that the points being on the ground side of the coil was a (mostly harmless) screwup on the part of the person who did the conversion/rewiring, since I'd never seen things set up that way before, and the rest of the rewiring job was so hideously bad. (I'll never understand why that tractor's entire electrical system didn't simply go up in smoke the first time somebody hit the switch...)

1968 Lotus Ignition System

Well, I don't know, you might find something there.Or go to an Autozone or similar auto parts store and see if they have a Haynes and or a Chilton's manual book for your car. cuhulin

I've NEVER seen that setup on any American car, nor any of the (few) foreign cars with points I've ever worked on, though I'm sure it has been done occasionally. For starters, doing it that requires TWO wires to the distributor plus fully insulated point contacts on both sides. Its much more complicated and harder to manufacture than simply grounding the non-moving breaker point contact in the distributor and running a single wire from the coil "-" terminal to the distributor.

I think memory might be playing a trick on you. I've owned quite a few American cars with points and a few foreign ones with points. None of these cars were wired the way you describe above. They have all been battery -> ignition switch -> voltage dropping device (resistance wire or block) -> coil -> points

Steve B.

Many years ago, the contact points were screwed on to the two pieces that holds the contact points.Replaceable contact points were sold in stores.If the old contact points were burnt out, you simply removed the old contact points and replaced them with new contact points. cuhulin

I have to agree. I've never seen a set of points that had provisions for insulating the body of the point set from ground.