340 Not firing on all cylinders

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You should GROUND spark voltage if you pull a wire out of the distributor. This is not about getting yourself zapped, it's about not crossfiring open circuit spark voltage, or causing damage, here's why

If you are "testing" for cylinders firing, and pull a wire off either at a plug or the distributor, the open "spot" in the distributor goes to VERY high voltage when the rotor comes to that disconnected wire and fires.

This can kill an ignition module and there is caution about this in modern shop manuals

This can cause crossfiring to other cylinders which will make your test results improper. In other words you can cause a miss in ANOTHER cylinder while you are attempting to evaluate the disconnected cylinder

Especially with modern high energy systems, this can drill holes right through caps and rotors, or carbon track them, and otherwise damage secondary components

So when testing "cylinder balance" by disableing cylinders, do this:

Either stick small thin brads down beside the wires in the cap, so you can just ground them with a probe, or.........

Use insulated fuse pullers in one hand and a grounded probe in the other. As you lift each wire out with the fuse pullers, slide your grounded probe in under the wire so the spark "has a place to go."
 
Most of us on FABO don't have modern high energy systems. We drive old Mopars. :)

Irrelevant. You should still ground the spark even if you are working on a 1936 Packard. Even Ma went electronic ignition in the early '70's. How long ago, again, was that?
 
This is what I have found to work for me in this very situation...

Make sure cap and rotor look good, then...
Use the aforementioned timing light and hook it to each individual wire while running, looking for consistent strobing of the light. Make note of good cylinders as you will swap the plug wire (and plug if necessary) into a suspect cylinder. This will enable you to rule out first the plug wire, and then the plug, as a cause. What you are doing is taking a KNOWN GOOD part and swapping for the suspect part.

Do not just throw new parts on it and expect a miracle. I can tell you from experience that new parts often times are bad right out of the box. In fact, I went through 3 new sets of 8 spark plugs (thats 24 plugs total) using this troubleshooting method to get one complete set of 8 that worked.

Failing this troubleshooting session will unfortunately point toward a mechanical problem as mentioned earlier.
 
Started the Dart up on the weekend for the first time since the winter and noticed it just didn't sound right (Didn't sound the greatest when I put it away in the fall to be honest!). So I took my infra red temp guage and took some readings at the manifold. Atleast one cylinder is definitely not firing (The readings on the left side back 2 cylinders were much colder but the back left was considerably colder than the rest).

I bet I know what is the problem......the gas in the carb jelled up over the winter and clogged the carb jets. Could be wrong, but I've got a hunch.....try spraying a little starting fluid in the carb while it's running and see if it perks up.
 
Well 6 and 8 were reversed! So I swapped them and voila....it doesn't run at all!!! Piss me off.....

I must have knocked something loose at the cap, but I'm pretty sure it's flooded so I will wait to fight with it tomorrow night. I only had a few short minutes to fight with it.

What seems odd though is the entire distributor moves pretty freely and I knocked the vacation hose off. What is the purpose of the hose? To auto set the advance?
 
Take the air cleaner off and post a good clear pic.
Also to a left and right side one, It should not be to hard to find the problem.
 
I can't upload pics from my phone sill need to do it tomorrow from work...damn! One of those nights...
 
Wonder if the cam is worn out? Any unusual valve train noises? Oil these days does not support flat tappet cams very well. That is another long story. You do need to purchase a compression gauge. We all need one from time to time. Takes the guess work out of the equasion. Maybe, you can check the reluctor air gap [electronic ignition] maybe the trigger wheel is a bit too far away from the pick up coil. Sometimes by reducing the air gap, you can pick up the cylinders that were missing. .008 I believe is spec for the air gap, and this is checked with a non metalic feeler gauge. as stated earlier, you may be able to "fuzz" the gap some and achieve the necessary signals for all 8 cylinders. just some additional help in different directions which will affect cylinder firing.
 
Ok so on closer inspection I realize the entire distributor is turning...the retainer plate must have been loose.so in a nut shell I am pretty sure I buggered up the timing! Oh and by the way it does have an electronic ignition...so if I can't get the motor to start how do I set the timing? Basically need a process for initial timing...
 
you mention "the distributor moves very freely". It sounds you might have moved it when you switched the wires and it's not starting now since the timing is off. Make sure you reset the timing (10 degrees before top dead center is pretty safe for initial timing) and that the distributor is bolted down properly.

What type of carb do you have? On an Edelbrock the vacuum hose goes on the ported side (passenger side) of the carb.
 
It's an Edelbrock. I have put the hose back on I just wasn't sure of it's purpose but I assumed it was for an advance.
 
Do you have a timing light?
Since you don't know where the timing is at the moment do the following:

- make a mental note (or put a mark on the distributor base, just below the cap) of the location where the number 1 spark plug is plugged into the distributor cap.
- Remove the distributor cap and rotate the engine by hand until the rotor points to the number 1 spark plug location that you just marked (the mark on the balancer should now line up with the 0)
- you are now at 0 degrees initial timing
- install the distributor cap and tighten the distributor down (enough so it doesn't turn freely)
- start the car
- use your timing light to reset the initial timing to somewhere around 10 degrees initial this should get you in the ballpark.
 
yes the vacuum hose activates the vacuum advance canister that is connected to your distributor. Just make sure all other vacuum ports on the carb are in use or capped, so you don't have any vacuum leaks.
 
Sweet! That makes sense....unfortunately my wife is asleep directly above the garage so I can't try it tonight.
I will give it a shot tomorrow an if it works I will owe you SEVERAL beers.....You just have to come up here to get them!
 
Actually 67Cuda I am planning on making it to the Rock for the first 2 weeks of July so maybe will drop them off to you!!!!
 
Find TDC on #1. Hook up your timing light, back the balancer up to 15* BTDC by rotating the engine. Turn the key to the run position, Turn the distributor until the timing light flashes..... Bam you are at 15* BTDC. Tighten the dizzy just snug so it still moves. Start the car and do your tuning from there.
 
A year ago when I still lived in Toronto I would have taken you up on that offer :)
Good luck, I'm sure it's a simple fix :)
 
Find TDC on #1. Hook up your timing light, back the balancer up to 15* BTDC by rotating the engine. Turn the key to the run position, Turn the distributor until the timing light flashes..... Bam you are at 15* BTDC. Tighten the dizzy Start the car and do your tuning from there.

Hm, that's a neat little trick, so simple why didn't I ever think of that LOL
 
Do you have a timing light?
Since you don't know where the timing is at the moment do the following:

- make a mental note (or put a mark on the distributor base, just below the cap) of the location where the number 1 spark plug is plugged into the distributor cap.
- Remove the distributor cap and rotate the engine by hand until the rotor points to the number 1 spark plug location that you just marked (the mark on the balancer should now line up with the 0)
- you are now at 0 degrees initial timing
- install the distributor cap and tighten the distributor down (enough so it doesn't turn freely)
- start the car
- use your timing light to reset the initial timing to somewhere around 10 degrees initial this should get you in the ballpark.

You may get close to 0 degrees but it will not be exact.... I got an easier solution check out my post above.
 
If you use the method Mad Dart described, just make sure you are on the compression stroke, not the exhaust stroke (180 degrees out) when you get the number 1 cylinder to TDC. Easy way to check is to make sure the rotor is pointing towards the front of the engine.
 
Ok so I don't think I am getting any spark at all right now! Pulled a plug and grounded it while cranking over and no spark. Tried another plug wire or 2 just to be certain.
Checked the out put at the coil...with the ignitin in the run position how many volts should I be getting? Currently around 10v
 
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