47 ran rough then not at all. Need ideas.
 

On a two hour cruise Saturday engine started skipping a beat hear and there. Was kind of annoying then got worse over the weekend so I thought I'd try to fix it. Here's what I've done so far. What have I missed?

1. Monitored spark coming out of coil while driving. Although not smooth, misses in spark didn't seem to correspond to engine misses.

2. Replaced the condenser with new one that tested within specs (since that's the easiest fix). Didn't help.

3. Checked for voltage at battery side of coil. That was good.

4. Checked all of the sparkplugs and cleaned them. Checked spark in each wire to each plug. Most were smooth and consistent. Some were irratic but did not seem to correspond to engine misses.

5. Removed the distributor and dismantled, cleaned and lubed and checked all shaft/bearing clearances for any wear. All were good. Replaced the rotor and points, double checking their gap. Checked for their proper operation at distributor side of coil with test light. Light went on and off appropriately indicating points were opening and closing. Didn't help

6. Tried different timing settings. Didn't help.

7. Bypassed the resistor in case it was the problem. Didn't help.

[Seemed the more I did the worse it got.]

8. Tested the coil that seemed OK but tried two other coils just in case. Didn't help.

[By this time the engine would hardley start and if it did would only run for a short time before dying.]

9. Checked for adequate fuel flow and pressure to carburetor. Accelerator pump was not pumping so replaced my Stromberg carburetor with a Holley 94, whose accelerator pump worked perfect, in case the carburetor was at fault. Didn't help.

So, here's where I'm at now: If I plug a spare spark plug wire into the bottom of the coil and hold it near a head stud nut I get consistent bright spark. But, if I plug in the wire to the distributor and put my timing light on it to monitor spark I get very sporadic spark, then steady once in a while enough to idle for a few seconds, then nothing and the engine dies.

What else can I do or check before removing the entire spark plug wire harness and replacing all of them? That is the hardest thing to do and my last resort only if you can't think of anything else.

Any ideas?:confused:

Re: 47 ran rough then not at all. Need ideas.
 

Hows the cap and rotor?? What point setting was there?? ken ct.

Re: 47 ran rough then not at all. Need ideas.
 

We had problems with our 47 that we converted from 6v to 12V.
Ran good, than not at all.
We had a bad resistor.
Good luck,
Bob

Re: 47 ran rough then not at all. Need ideas.
 

Points were set at spec: 0.014 to 0.016 in.

Re: 47 ran rough then not at all. Need ideas.
 

I've bypassed the resistor just to get a stronger spark for diagnosing. It's still good.

Re: 47 ran rough then not at all. Need ideas.
 

Someone with real expertise will jump in here soon. The steady coil spark when disconnected from the distributor and then intermittent when connected to the distributor confuses me. If the distributor is functioning correctly it should charge the coil the same no matter what the coil wire is connected to. Also, you didn't mention bypassing the ignition switch with a jumper from the battery to the coil. My guess is that you have a breakdown in the feed to the coil or a bad distributor.

Re: 47 ran rough then not at all. Need ideas.
 

I'll go with bad dist or dist cap might need a good cleaning

Re: 47 ran rough then not at all. Need ideas.
 

From what you've said, I suspect a bad high tension lead between the coil and distributor. also, carefully check distributor cap and rotor as suggested by KenCt. Good luck.

Re: 47 ran rough then not at all. Need ideas.
 

I would try a another condensor after checking the OHMs to see if it's on the money. Hopefully Bubba will chime in here to point us the right direction.

Re: 47 ran rough then not at all. Need ideas.
 

Bypassing the ignition switch, as mentioned above, would be something to try. Contacts in the switch could be a high resistance connection that heats up and becomes a worse connection as it gets hotter. This also applies to other connections in the ignition circuit. A stranded wire with most or possibly all the strands broken, but still touching making contact, will eventually get hot enough to cause an open circuit. Sometimes a terminal poorly crimped to a wire will cause a high resistance connection that gets worse with heat.
A coil with shorted or burned open windings may seemingly check okay with an ohmmeter but fail to work properly as the windings heat up. Sometimes while trouble shooting problems like this we inadvertently replace defective components with other components that are also defective.

I had a similar situation with my '35 fordor last month and the problem turned out to be a poor/intermittent solder connection of the grounding strap to the back of the condenser. Repaired that and completely went through the distributor, cleaning, oiling and resetting everything. It has been running great for the last 200 miles.

Re: 47 ran rough then not at all. Need ideas.
 

Henry,
Try replacing the coil. An intermittent coil will drive you nuts while trying to isolate the problem.

Re: 47 ran rough then not at all. Need ideas.
 

Sorry. I double posted.

Re: 47 ran rough then not at all. Need ideas.
 

I agree that this is a good source to suspect. I had the identical problem Old Henry tells of, and (after much parts changing and hair pulling), it turned out to be a bad primary voltage connection between the coil and distributor.

Re: 47 ran rough then not at all. Need ideas.
 

If the secondary high tension wire from the bottom of the coil is not attached to anything that will complete a circuit on the other end buried down deep in that crazy two layer distributor cap, no spark would go through it for the timing light pickup to detect. One more indication that it's probably in that distributor cap from heII - a nightmare to deal with - gotta remove the fan, generator, and the entire sparkplug wire harness. Hate it. Don't wanna do it. Just wanna drive it. But, looks like that's the next step.:(

Re: 47 ran rough then not at all. Need ideas.
 

I would convert it to a crab cap and rotor much easier to work on and only 1 cheaper cap to deal with, ken ct.

Re: 47 ran rough then not at all. Need ideas.
 

Ken has a good point. Change what you are calling the distributor cap from hell, that's a nightmare to deal with, to a crab cap setup, but making sure you have a good gasket seal between the cap and the casting, and good sealing rubber boots where the spark plug wires enter the cap. Should be much easier to work on as compared to your existing double cap system.

Re: 47 ran rough then not at all. Need ideas.
 

Henry i have the cap,rotor,clips,nipples and corect gasket if you want to change it. All USA made parts. ken ct. 1-203-260-5945 or PM me.

Re: 47 ran rough then not at all. Need ideas.
 

I appreciate the suggestion of a crab cap. I am, indeed, sorely tempted but am probably too committed to authenticity to change to that. This will be the first time that I've had to work on the cap and wires since I put them in 5 years and 35,000 miles ago so I'll probably keep it authentic. Will probably replace all wires and both caps while I've got the whole mess out of the car.

Re: 47 ran rough then not at all. Need ideas.
 

The first thing I'd do is a compression check, you may have stripped the fiber gera??

Re: 47 ran rough then not at all. Need ideas.
 

OldHenry, check coil to distributor wire, the one that runs from the condensor side, if you haven't already maybe a break or shorting out?