I'm running an MSD 6A box with a TFI coil, along with a DS 2 distributor and Taylor Thunder Bolt wires.

Today I forgot to replace the metal breather oil cap on my valve cover and it fell atop the distributor while driving. Right away it started missing and running rough. I had spent the afternoon dialing in the carb, so thought the carb was acting up. I drove for 4 miles like that.

Got home and opened the hood to see the cap sitting atop the dizzy. The engine was running and I thought about possibly getting zapped, but thought that with such nice plug wires that couldn't happen. I thought wrong. It shocked the heck out of me. I tasted the fillings in my ... teeth. My bare stomach must of been touching the grill making ground, because it bit me there too.

Anyway, my question is if I fried something in the dizzy. It still runs as though on 5 cylinders (it is an inline 6). I was quite surprised to see that the cap contacts look like welding slag, bumpy and white. The rotor the same. Any chance I toasted something in the dizzy?

While timing the engine, the marks were jumping all around, which, I've learned, is par for the course for an MSD. But, when I shut down I moved one wire that lay across the #1 wire, and the jumping stopped. Is that caused by the sensitivity of the t.light, or the power of the wires/ignition box?

 

Third thread's a charm!

https://www.ford-trucks.com/forums/1...-shooting.html

https://www.ford-trucks.com/forums/1...-question.html

 

Yes, I do have 2 threads going. When you mentioned in the original thread that the problem may be with the msd box, I opened another thread with 'MSD' in the title, hoping to attract members with knowledge that could guide me with trouble shooting the msd box.

Since this repair is very important and on a critical time clock, I am utilizing all means available to get it resolved.

 

I would start by replacing the cap and rotor because of the damage you mentioned.

If the new cap and rotor doesn't fix it, and it's only running on 5 cylinders I would suspect a bad plug or plug wire.

Check the resistance on each plug wire. Make sure they all have a similar resistance per foot of plug wire. If any of the wires are touching each other check them for any marks or damage from them arcing out to each other. This shouldn't happen with good wires but I have had it happen in the past.

A new set of plugs wouldn't be a bad idea either. If you don't want to replace them check for spark at each plug. You could also close up your plug gaps to 0.050" and see if that makes any difference.

 

Thanks, Ted. I know I have to replace the cap and rotor. Isn't it odd that when I cheap out and buy the $25 cap instead of the $62 cap it lasts half as long. Just can't make myself pay that much for a cap!

Anyway, I'm wondering if I should be using the plugs that were used with the TFI coil? Now I'm running the '75 plugs. Of course I'll check, but would the longer efi plugs handle the extra power better? interfere with the larger valves? Thanks. kevin.

 

Do you think it's possible that one of the wires pulled on a plug too hard and cracked the porcelain?

And what cap are you even getting for $25? The one I've had on mine for several years was 8!

 

My Explorer did that to 3 plugs before I changed the wires

First dead give away is that you got fried touching the wires while it was running
Start it and run it in the dark, you should see what plugs and wires are bad.

 

What they said. I get the spendy dizzy cap with the brass contacts. I think they last longer than the less expensive ones.

The EFI plugs will not be a problem for clearing anything and they might help in establishing a good flame front in the cylinder. At any rate, they don't hurt a thing nor do they cost much more if any over the older style plugs.

 

AB--I could see how that could happen, but nope, the plugs are good, but two were not as tight as they should be. I gapped them down to .050 and put them back in.

Yes! I was shocked as heck to see the price of distributor caps! I saw a motocraft one for sixty something bucks! I noticed a rotor for forty something!! The $25 dollar one I mentioned before was toward the low end of the price range, and I'm talking AZ and O'reilley's, not a speed shop. I went with a $18.99 one from AZone, which included a rotor too, and came with a life time warranty. The guy said 'no questions. You can replace it every year if you want.' For that price I'll throw an extra behind the seat on long trips.

Dusty--It's good to see you back. Obviously there was a short somewhere. Maybe it was the cap or a loose wire that got corrected when I replaced the cap and rotor. I did check it in the dark and saw zero sparks, arcs, shorts. And the miss is gone.

I do have a slight surging, but that, I believe, is the carb.

Thanks for the help, everyone.

 

Glad to hear the miss is gone.

Rockauto has the Motorcraft dist.cap for $30.79 and the rotor for $27.99. Still not cheap but better then prices you mentioned. But there is also the shipping cost.

 

I thought that for comparison, I would take a quick look at Amazon.com for the same two parts that fordman75 looked at on Rockauto.com.

The ones from Amazon offer free shipping, but cost more.

Cap DH367B $35.58
Rotor DR379A $33.18

These parts are original equipment [Motorcraft].

 

"The ones from Amazon offer free shipping, but cost more."

Yup...at some point there is going to be a trade-off.

 

But once you figure in Rockauto's shipping charges it's probably pretty close. But the difference is you would get it much quicker from Rockauto. I buy quite a bit from amazon. And with their free shipping you never know if it's going to take 3 days or a month to receive the order.

 

That is funny. I have three guys showing prices for better versions of the parts I already bought. I think my peers are trying to tell me to buy better quality parts.

Thanks, guys. Certainly you are correct.

q

 

Just some more options if you need to replace them again down the road.