Need distributor help

[Bob Claffie]

I have random spark at cylinder #1. New cap and rotor and reasonable wires. I do notice quite a bit of play in the dist shaft. Distributor in the car is marked "DM6A 40662B". (This is a '59 100/6) I have a spare "core" marked "DM8A 40581A" with no perceptible play in the shaft. Can these two distributors be mixed and matched? Or does anyone have / install bushings in these things? I assume the bushings wear and not the shaft, let me know if I am wrong on this, or if there is an alternate fix I haven't thought of. Thanks,Bob

 

[Keoke]

HI BOb, I do not know those Dizzy'specifically.However, if they appear physically identical.then you can switch the advance weights ,springs and the action plate from the DM6A- to- the DM8a.But first I would move the #1 sparkplug to a different location and see if the problem goes away or if it moves to the new location. If the problem follows the plug move it probably indicates a defective plug-rare but it does happen.

OPTIONS:

1] install a pertronix ignition module

2] Send dizzy to Jeff at Advance Auto see the archives here for a rebuild.

3] Purchase a new Dizzy from Retro Rockets if available.

------Fwiw---Keoke

 

[Dave Russell]

[ QUOTE ]
I have random spark at cylinder #1. Thanks,Bob

[/ QUOTE ]
Hi Bob,
You didn't say if the "random spark" was actually causing engine miss fire or just showing on the timing light. By connecting the timing light to cylinder #6 instead of #1, you should get the exact same timing picture. Cylinders #1 & #6 just fire exactly one revolution apart.

It's not unusual for a timing light to show "missed sparks" or varying spark locations on the damper, even when nothing is actually wrong.

Some folks may disagree, but I have found that I get a much more stable timing light "picture" by temporarily substituting a length of resistor type plug wire for the wire core type on the cylinder being used for measurement.

One problem that I can think that would cause low rpm spark scatter is that the centrifugal advance springs exert zero tension at the low rpm fully retarded position & allow the advance to jump around. If this were the case, things should stabilize as rpm is increased. A loose spring can be checked for by carefully turning the rotor to advance & retard by hand & feeling for any slack in the spring. It could be visually checked by removing the point plate & observing the advance & spring motion.

It's a little hard to isolate this condition since centrifugal force will tend to stabilize the wobble of a loose distributor shaft at higher rpm also.

I would experiment with the timing light triggering first.
D

 

[Bob Claffie]

It is a serious misfire, not just a scatter . I have an inductive timing light and have connected the plug lead to each plug wire and get about 95% +/- steady blips except on #1 which is at around 50 %. I have attached the plug lead as close to the distributor as possible to try and eliminate possible wire failure. Plugs look good , even #1 and the compression is a solid 150 across the board. Bob

 

[Keoke]

Bob!,does the engine actually Miss?. Is the idle uneven and creating a splashy exhaust note?---Keoke

 

[Dave Russell]

It's still not clear to me if there is actually a missfire as detected in the exhaust note, or just missing flashes on the timing light.

In either case, it appears to be confined to cylinder #1. This would indicate a defective plug wire or plug itself on the #1 cylinder. It should be easy enough to replace the wire & or plug if necessary.

Attaching the inductive pickup closer to the distributor cap will not help if the wire or plug is defective.
D

 

[Keoke]

GUN NIGHT!!---Keoke- /ubbthreads/images/graemlins/laugh.gif

 

[Keoke]

Re: Need distributor help *DELETED*

Post deleted by Keoke

 

[Bob Claffie]

I will be more specific! The car is running on FIVE cylinders. If the engine was running OK I would not have asked for help just to cure a timing light problem. There is visible side to side play in the shaft, it puzzles me why it only seems to affect the #1 cylinder. If the timing light stutters 1 inch from the distributor cap I do n ot see how it can be the fault of the wire or plug.
Would a Pertronic NOT fix the problem? Doesn't that system rely on a rotor and cap similar to stock with the only change a switch from points to electronics? Bob

 

[zblu]

sounds like something is not centered, ie its running an elliptical path all things being equal

 

[Keoke]

BOB! you have a PM check it NOW!!---Here it is see attachment. Regarding malfunctions of a timing light when operated in close proximity of the ignition wires: The timing light contains electronic circuits that may be susceptible to the radiated fields generated by the igntion system. These radiated electromagnetic fields can make the light malfuncton and they radiate out to significant distances away from the car.---Keoke- /ubbthreads/images/graemlins/yesnod.gif /ubbthreads/images/graemlins/hammer.gif

 

[Dave Russell]

[ QUOTE ]
If the timing light stutters 1 inch from the distributor cap I do not see how it can be the fault of the wire or plug. Bob

[/ QUOTE ]
I don't understand your reasoning. I must be getting very dense. The plug wire & plug are a series circuit. Anything that "happens" near the distributor also happens anywhere along the wire & at the plug. Why are you so reluctant to replace the wire & plug?
D

 

[Bob Claffie]

Oh boy, is my face red. Now we know who the really DENSE one is, and it is me. All this time the concept of CIRCUIT has been missing from my thoughts. I thought I had a pile of electricity inside the distributor and the problem was getting it from the rotor to the contacts inside the distributor cap. WRONG! Ultimately I did test for wires and plugs and had both defective on #1 cylinder. Using a spare plug from my Mustang and an old wire courtesy of my former MG the Healey now, for the first time in my ownership, function with six working cylinders. Thanks to all especially Dave and Keoke for putting up with me. Bob

 

[JeffS]

Bob, if there really is a significant amount of play in your distributor shaft, Take a look at the terminals inside the cap. As it gets worse, you will actually see where the rotor begins to contact the terminals on the cap.
Otherwise its possible that the play is only in the points cam assembly, not actually in the shaft.

'Glad to hear you found the major problem!
Jeff