short in distributor keeps reappearing - any ideas?

[SDJason]

Hi there - long story short (pun not intended) - got stuck by the side of the road, traced it to a short somewhere in the distributor.

Using Les Andrews' 4-3 Troubleshooting chart, at step 5 "Turn ON ignition switch and test for 6 volts on the open point arm", the needle on the multimeter barely moved. Easy, I thought - a short somewhere inside the distributor. Taking it apart didn't show any obvious problem, so I put it all back together (and used an emery board to rough up the armored cable plunger, the indent on the tab where the armored cable makes contact, the tab where the condenser screws into, and the condenser where it makes contact with the tab).

Checking again showed 6 volts at Les Andrews' step 5. Homefree! (or so I thought). Turning the engine over still wouldn't start - and going through the troubleshooting again showed no voltage at step 5 ("Turn ON ignition switch and test for 6 volts on the open point arm").

Ughh - so, it looks like I have a magic reappearing short in the distributor - any ideas what to look for?

Thanks in advance!

[mleder]

I had a similar problem, If your using a fuse on the top of the starter that assembly can get corroded and connections at the rivets can get loose. Second if you have over oiled your distributor I've been told it can cause problems from the overflows, Third if it is a modern points, upper and lower plate other members have experienced problems leading back to a ground or loose connection between the wire or the tab on the plate. Keep us posted what you were able to find out

[lindy williams]

the tab on the lower plate could be touching the distributor housing due to popout cable being screwed in too far or a repro lower plate could be shorting between the tab and the lower plate or the wire between the upper and lower plates could be shorting to the distributor housing.

[Tom Endy]

You could have an intermittent short in the distibutor or the pop-out cable. A way to isolate as to which one is to make up an emergency by-pass cable (it is a good idea to carry one with you). It is made from the end of a discarded pop-out cable. You need just the part that screws into the distributor. Attach a wire with a clip lead to it. Remove the pop-out cable from the distributor and screw in the by pass . Remove the red wire from the distributor primary connection and attach the clip lead there. If there is no short in the distributor the car should start and you can drive it that way for a few days to make sure the intermittent has gone away. You will have to remove the clip lead to shut the engine off.

If the problem persists the intermittent is in the distributor. Take it apart and find what is shorting. More than likely the lower wire connecting the two plates together.

One of the few things I always carry with me is a rebuilt road tested distributor and a by-pass cable. I have used it more on other people's car than my own.

A shorted pop cable can be repaired. I would send it to Cal Allen the "key guy". He specializes in them.


Tom Endy

[jmeckel]

If you are running orignal type points, check to make sure that the copper strap that follows the flat spring is not too long and shorting to the case. I had this problem and it was not easy to find, simple to fix, just put a bend in it to use up the slack.

[Brentwood Bob]

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Screw the ignition cable only in far enough to make contact with the lower plate. Bob

[Mitch//pa]

knowing what kind of setup your running helps
original, modern, pop out , etc

[James Rogers]

If you are using the stock setup, check your ammeter. It acts as a fuse and can cause lots of problems if it is marginal. Next time it happens, wrap a small wire around the nuts that hold the junction box cover on and try to start the car. If it starts, the problem is not in the distributor.

[SDJason]

Originally Posted by Mitch//pa

knowing what kind of setup your running helps
original, modern, pop out , etc

Oh, yeah, forgot to mention - original setup, except that the popout switch has been replaced with a modern style (simple turning switch with two connectors on the back - much like this:


Thanks for the tips so far - I've got quite a few things to look into now...

[Karl]

I've had problems with the modern switch before can jiggle so just turned off. To all the world looks like is still on but isn't . Also can short out if and when the terminals touch the gas tank . Karl

[Tom Wesenberg]

Karl beat me to it. I was going to list those same two faults as soon as I saw the picture of the repro switch.

[Fred K-OR]

Originally Posted by Karl

I've had problems with the modern switch before can jiggle so just turned off. To all the world looks like is still on but isn't . Also can short out if and when the terminals touch the gas tank . Karl

I had same problem with terminals touching the gas tank.

[columbiA]

Those cheap ign switches are junk.I use the modern switch that is modified to look like a pop-out but doesnt "pop".They are a good quality switch.I always stick a few layers of tape on the tank behind the switch.

[BILL WILLIAMSON]

A poster that had no current to his points once mentioned that the rivet on the incoming end of the pigtail wire seemed tight & no corrosion. He took it out & set the rivet tighter & VOILLE' he had current!
On a similar theme, I've seen loss of current in junction box studs, even though they're tight & no visible signs of corrosion. Just tighten them tight & add internal/external star washers. Somebody once posted, "STAR WASHERS ARE A GROUND'S BEST FRIEND"!! The Dog is my Best Friend & helps me recomember all this crap! Bill W.

[SDJason]

Quick update - now that it's the weekend again, I had some time to troubleshoot this some more.

Started out as it was left - no voltage on the points arm, so I checked to make sure there was 6V on the armored cable plunger (there was), then proceeded to take the distributor apart again and checked for electrical continuity (and shorting) along the entire path from the tab on the lower plate that the armored cable plunger contacts, through the pigtail, to the points arm and everything seemed fine (continuity wise).

Putting it all back together, not so fine - again no voltage on the points arm.

Removed and reinstalled the condenser, and suddenly had 6V on the points arm. Trying to start the engine doesn't work, and afterwards the 6V at the points arm disappeared.

Long story short (again, no pun intended) - it appears that when the condenser is installed, a short (sometimes) magically appears, and definitely appears after trying to start the engine. (I've now checked this two more times). Visually examining the lower plate tab that the condenser screws into, it definitely is not touching/shorting out to the distributor body.

So - help! Is it possible that the condenser itself is bad and needs to be replaced? It's pretty much brand new, with less than ~200 miles on it. I checked for continuity between the condenser body and the contact on the end, and there doesn't appear to be any - but the short appears AFTER turning the engine over - maybe it needs to be in a charged state to have the short appear? I don't really know - just guessing now from what I've observed. Any new ideas on what could be the problem, given this new information?

Thanks in advance (again)

[Joe K]

So - help! Is it possible that the condenser itself is bad and needs to be replaced? It's pretty much brand new, with less than ~200 miles on it.

It's called "infant mortality" - when things break down early in their lifespan.

New condenser time. I think you can buy these at Ford still? Probably at NAPA.

I haven't done this recently but one used to be able to get "routine" small buck parts from local sources.

Although come to mention it, I haven't seen the tt10 spark plugs at AutoZone recently (although I bet they can order and have it at the store the next day.)

Yup. Napa has them http://www.napaonline.com/Catalog/Ca...FA5_0182283939

$9.99 Check your local for off the shelf.

NAPA has at least 5 pages of Model A specific stuff.

Joe K

[Fred K-OR]

Originally Posted by Karl

I've had problems with the modern switch before can jiggle so just turned off. To all the world looks like is still on but isn't . Also can short out if and when the terminals touch the gas tank . Karl

Again, did you check this situation out. The problem I had with a switch like this is that it took some time to rub the paint off the gas tank before it started to short. The way I found I had a short, and I think Tom mentioned to check this, is I found the coil was warm.

Another thing you could do would be to replace your distributor with a known good one (if you can find one) and see if that makes things better. Another thing to check may be your points-are they in good shape.

[Kurt in NJ]

Buy a condenser from A&L, sometimes listed as "burn out proof" in other catalogues, I havn't been able to cook it in 20+ years.

[SDJason]

Originally Posted by Fred K-OR

Again, did you check this situation out. The problem I had with a switch like this is that it took some time to rub the paint off the gas tank before it started to short. The way I found I had a short, and I think Tom mentioned to check this, is I found the coil was warm.

Another thing you could do would be to replace your distributor with a known good one (if you can find one) and see if that makes things better. Another thing to check may be your points-are they in good shape.

Yeah - checked that - the contacts on the switch are well-wrapped with electrical tape to preclude any shorting there; also had a bybass cable on hand (as recommended by Tom Endy - thanks, I hadn't thought of that) to isolate things a bit - still the same results - I can get the short to disappear briefly (dismantling the distributor and putting it back together), but as soon as I turn the engine over, it reappears, then removing the condenser makes it disappear.

I think my next step may be to get another condenser. A bit disheartening - the thing's only been in use for maybe a few months at most...

[1931 flamingo]

The NAPA condenser in post #16 says 36 month/36,000 mile guarantee. FWIW
Paul in CT