Dual Point Problem

[Stumper]

Looking for feedback on my Latest challenge. A few months back I suddenly had an issue where my engine would cut in and out under any amount of throttle. Found the problem by pulling the vacuum line off the timing advance which resulted in the engine settling to normal - at first. After a few tries of putting the vacuum back on and off it finally would run at all. Found that the primary power wire inside was broke. After I pulled the distributor to replace the wire also found the bridge wire between the two contacts nearly broke. I replaced the wires along with new points, condenser put it back in and everything ran fine for several outings. I suspected that the problem was the wires were all old originals and that the action of the advance moving the dist back and forth resulted in the wires breaking.
Fast forward to Saturday. Started the same type of skipping of the engine to the point that I couldn’t really put any load on it. Even backed fired out the exhaust a couple of times. I pulled the cap and all the wires inside looked good and tight. Tried again but same problem. I pulled the vacuum line to the advance and it runs perfect…..

A “shop” that had my car some months back replaced the vacuum advance unit with a new one from Tony’s Parts. Since the car runs good without the advance connected I’m thinking the unit is bad. Haven’t had it apart yet but anyone have thoughts? When the distributor was out a few months ago it didn’t seem to have any play and was oiled up good.

 

[493 Mike]

Do you set the points with a feeler gauge or dwell meter? Did you use good quality automotive wire in your replacement operation? Have you mapped the advance curves with a tach and timing light to see what is going on?
Mike

 

[pnora]

Sounds like your base timing is to far advanced. As said above make sure the points are set correctly first.

 

[toolmanmike]

If you are just going to try different stuff, try a different condenser. The new ones nowdays are junk. Buy a quality old part from Halifaxhops.

 

[Stumper]

I set the points first at 16-17 mil and checked dwell after and it was 29. The condenser was a HD I think Blue Streak. As I said it started and ran well up until Saturday.
I do have the timing advanced a bit to around 13 degrees but it wasn’t pinging. Unless just that bit of advance plus the vacuum advance is causing something to bind inside?

I’ve not tried running any kind of timing curve since everything is stock and I’m not looking for performance.

 

[steve340]

Try a new condenser. Make sure the points are still good - a bad condenser can arc/burn them.

 

[Stumper]

Correct me if my thinking is wrong but since the engine runs perfect with the vacuum line to the advance disconnected, wouldn’t this indicate that the distributor and components are good?

 

[steve340]

You could be right. What happens to the timing/distributor when you connect the vacuum unit?
Is it all connected right in the distributor and operating correctly?
You can take the cap off and use a hand vacuum pump to see what happens when you apply and release vacuum. Start the engine and do the same test and watch the timing marks.

 

[Geoff 2]

Is the vac adv connected to a manifold or ported source? PVA should have no effect on idle UNLESS:
- the diaphragm in the VA is leaking [ or the hose ]
- throttle blades are open too far at idle, accessing the PVA port.

 

[Stumper]

The advance gets its vacuum from the ported carb connection. Idle is fine, the problem is only with a bit of throttle applied. I’ll try seeing what goes on with a timing light tomorrow. May also try using my brake bleeder pump to pull some vacuum on the can with the cap off to see what is going on. Whatever is going on is not a tuning problem since it all worked fine, right up until it didn’t anymore…

 

[Geoff 2]

That IS the problem. [ They] all work fine until they don't anymore.....

 

[gtxrt]

I set the points first at 16-17 mil and checked dwell after and it was 29. The condenser was a HD I think Blue Streak. As I said it started and ran well up until Saturday.
I do have the timing advanced a bit to around 13 degrees but it wasn’t pinging. Unless just that bit of advance plus the vacuum advance is causing something to bind inside?

I’ve not tried running any kind of timing curve since everything is stock and I’m not looking for performance.

check your dwell at idle with advance not hooked up or on the ported side then watch it with the vacuum advance hooked up and increase your rpms. I bet your dwell will decrease.

 

[AR67GTX]

Your dwell is a little low which means your point gap is slightly too large. Combined dwell should be 31-35. A gap of .017” usually gets me there but depends on your eye and feel for setting the gap. However, that is not your current problem as long as both sets of points actually are gapped and you are not running on a single set.

From your symptoms a Catholic Priest may be in order but I think I would try another condenser and then as a real Hail Mary, another coil. It sounds like you have a broken wire in the distributor that the vacuum advance is jerking around but it seems you have looked all over that stuff and found it OK. Good Luck - pass the holy water.

 

[gtxrt]

The advance gets its vacuum from the ported carb connection. Idle is fine, the problem is only with a bit of throttle applied. I’ll try seeing what goes on with a timing light tomorrow. May also try using my brake bleeder pump to pull some vacuum on the can with the cap off to see what is going on. Whatever is going on is not a tuning problem since it all worked fine, right up until it didn’t anymore…

if on the ported side now just watch the dwell with increased rpms and if something is wrong with the plates sticking or something else wrong your dwell will go down very simple test that will tell a lot

 

[Stumper]

It may well have been the broken ground wire that I repaired the last time. I was pulling on it this afternoon and it came apart. Got the distributor on the bench now trying to figure out how to make a good connection that will last…. Will report back after I get it fixed and back in …

 

[493 Mike]

It may well have been the broken ground wire that I repaired the last time. I was pulling on it this afternoon and it came apart. Got the distributor on the bench now trying to figure out how to make a good connection that will last…. Will report back after I get it fixed and back in …

You need to use a wire with super fine/high count strands. They flex much better.
Mike

 

[AR67GTX]

You need to use a wire with super fine/high count strands. They flex much better.
Mike

Yes, I wonder what is common source for fine strand wire? Anyone found one on Amazon or EBay?

 

[gtxrt]

ebay

 

[Stumper]

Got a pretty good repair on the ground wire this afternoon - both ends soldered. Set the points and put the distributor back in and no fire….. Pulled it out again and found what looked like a broken hot wire. Replaced it and put her back in and still no fire! I tested the coil ( first time I think I’ve done this) with a multimeter. Got 1.7 ohm over the primary. Tested the secondary and got nothing - zip! I think I was testing it correctly. Odd that the primary coil is good but the secondary would be bad ? Anyway, just got back from town and picked up a new coil.. I think I’ll have a couple glasses of wine tonight and try the coil in the morning.

 

[Geoff 2]

You can eliminate 50% of dual point dist problems.....by using a single point dist...