[DMCForum] Re: More ignition analysis (ON TOPIC) WALT

["cruznmd" <racuti1@xxxxxxxxxxxx>]

Walt,

You may be right but I think there is another component to consider:

I spoke to Dave Stragand and John Hervey last night. Both 
conversations drifted in a remarkably similar direction. Electrical, 
fuel, electrical, timing advance, coil, voltages, resistances, and 
eventually the pulse coil.

Remember, Mike was using the alternator that's in your car without 
these symptoms. In a way, I still think you're right. There's not 
enough voltage, just from a different source. Here's why:

John read some documents to me last night describing pulse coil 
theory of operation. The pulse coil generates a stronger voltage the 
faster it turns. At idle, the signal is weaker. I think our pulse 
coils are breaking down, and not generating a good signal for the 
ignition ECU to convert and output to the coil (especially at low 
speeds). The ECU controls coil operation. Garbage into the ECU = 
garbage out. This could cause the dwell to be wrong or the ECU is 
telling the coil to output in some other incorrect way.

The fact that this is temperature related also seems to point to an 
electrical breakdown. The pulse coil is like the door solenoids. 
Wrapped wire, and if the enamel is boiled off, you have a bad winding 
just like in the door solenoid. When you idle, the engine compt. is 
just boiling away. Especially in Florida.

It was finally cooler here this morning and the car drove noticably 
better, but not perfect on the NEW COIL.

My plan today, is to get the engine good and hot, then measure the 
resistance of the pulse coil. Cold, the resistance is 550-700-ish 
ohms. The exact values are on John's website. I expect resistance to 
increase when hot but if I get something like 1.5k ohms +, or less 
than 500 ohms, I'm replacing the pulse coil. Another thing I'll try 
is measuring the voltage output by the pulse coil while cranking. If 
it's very low- again, I'll replace the pulse coil.

Walt, just to ask: Have you checked your timing advance? Failure to 
advance, or advance sufficiently or rapidly enough could also cause 
this. I'd check vacuum advance, then remove the hose from the dizzy 
and check the centrifugal advace. Both of mine are good.

Ciao,
Rich A.
#5335

--- In DMCForum@xxxxxxxxxxxxxxx, "Walter Coe" <Whalt@xxxx> wrote:
> Rich,
> 
> My car has symptoms very similar to yours: Intermittently
> the car will hesitate when accelerating from a full stop.
> Once past a certain RPM, it will take off like a scalded
> dog.
> 
> I have found that the longer I have been waiting at a
> traffic light, the worse the symptoms will be.  If I shift
> into neutral and rev the engine slightly while waiting at a
> light, then the problem isn't there.
> 
> I have concluded that my problem is caused by low overall
> system voltage.  If my a/c is off, the radiator fans are not
> running (engine cool) and the headlights are off, then my
> acceleration is great.  But sit at a traffic light while the
> radiator fans are running and the car will almost stall from
> a dead battery.  As confirmation, I watch my dash gauge.
> Once the voltage gets above 12V, all stuttering clears up.
> 
> I bet that the reason your symptoms change with different
> coils is that some coils tolerate lower voltage than others.
> I think that the best fix is a better alternator and more
> efficient radiator fans.  I would also like to see a more
> efficient a/c blower.  Those things suck a lot more current
> than they need to for the amount of air they move.
> 
> Walt

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