intermittant sputtering follow-up

[nevets]

Not too long ago I posted a message about sputtering which would start once the car got warm. Following the advice of those who commented, I replaced the coil, condenser, points, rotor, and plugs. The result is the car now feels more responsive, however the sputtering is now not just when the car gets warm but all the time. Plus, when backing off the gas, as in coasting down an incline (in 4th, foot off the gas) I get an occasional backfire, which I assume is unburned fuel igniting from the hot exhaust pipes. And I'll also mention, though I'm sure it's unrelated, the car shifts into OD much faster than previously.

I'm thinking maybe it's one of those rather tired looking skinny wires in the dist, one of which is a ground.

Any help would be appreciated.

 

[Keoke]

I'm thinking maybe it's one of those rather tired looking skinny wires in the dist, one of which is a ground.

Well replace it and see,however, new condensers can be worse than partially failed old ones.---Keoke

 

[why]

I attacked my missing at higher RPM when hot as a fuel system problem, after new pump etc. etc etc it turned out that in the wire from coil to distributor,at the distributor end, the central wire (actually like a compressed carbon) had burned back a bit into the insulation. 2 minutes to trim insulation, reft end connector, stick it back into distribtor--all better
I think it was on this board that someone said " In old English cars most fuel system problems are electrical"
Jay '65 3000

 

[nevets]

Why
Sounds interesting, coan you please provide more details?
Thanks

 

[nevets]

After replacing the condenser again and also replacing the little ground wire inside the dist, the sputering appears to have stopped.

 

[why]

Let us all hope and pray the key phrase is not: "appears to have stopped."

As to previous post, the wire that goes into the distributor has little metal fitting at its end which makes the contact with the inner metal piece down in the hole in the distributor. When I pulled that out of the distributor, and took a look at it, the end of the wire was a bit charred, upon taking the metal end fitting off I could see that there was no inner wire, it was burned back about a millimeter up into the insulation. Upon cutting off the insulation, it was not a wire at all but seemingly a fabric-like material impregnated with carbon. I exposed about a 1/4 inch of this material, put the end fitting back on, bending the "wire" back around and up the outside of the insulation, so it was firmly clamped between metal fitting and insulation thus making good contact with metal fitting, stuck it back into distributor hole, and voila, the year long search for misfire at higher rpms when at about 180 deg or higher was no longer present.

 

[nevets]

Thanks for the detailed explanation. Although my problem was of a different nature, the effect was similar. I'm just glad the designers of the AH had the good sense to locate the distributor so that it is very accessible.

 

[TimK]

Backfiring on deceleration can result from a poorly sealed manifold to down pipes gaskets which allows air in the exhaust and incompletely burned fuel can ignite more easily. I stopped my problem with new gaskets between manifold and downpipes and tightening the brass nuts.

 

[nevets]

Good point. I'll check the nuts for tightness. Part of the fun in troubleshooting a problem is the sudden appearance of another seemingly related problem, but one which turns out to be totally unrelated. Gets you going round in circles.

 

[nevets]

I took the car out for a fairly long test drive and all seems well, almost. Engine is smooth and strong when accelerating, but when I hold a constant speed it sort of burbles...hard to explain, not a misfire, just not a smooth constant drone from the exhaust. If this was Car-Talk I think I could do a a pretty good vocalization of the sound.

Any thoughts?

BTW, Thanks for all the help with this

 

[tahoe healey]

Movement in the dizzy shaft?

 

[GregW]

just not a smooth constant drone from the exhaust.

Well, if it was a motorcycle, I'd say you were lean on the needle and to shim (raise) it a ½ notch. On a SU, maybe richen the jet slightly.

 

[Patrick67BJ8]

I took the car out for a fairly long test drive and all seems well, almost. Engine is smooth and strong when accelerating, but when I hold a constant speed it sort of burbles...hard to explain, not a misfire, just not a smooth constant drone from the exhaust. If this was Car-Talk I think I could do a a pretty good vocalization of the sound.

Any thoughts?

BTW, Thanks for all the help with this

My first thought: Balance the carbs with a unisun(spelling). With the SU tools in the dash pot and wire arms lined up, rev the engine and observe that they both rise equally and together. Then check the throttle linkage for proper adjustmentfor both carbs(this is critical and most often overlooked.
Patrick

 

[nevets]

Thanks guys, I'll look into the carbs as well...