When ignition systems break, do they die or malfunction?

[DeepBlue2010]

I read some threads in which the boat owner complains about erratic behavior at certain RPM and it turns out that it is the ignition system and by changing it, everything is back to normal. With the way distributor based electronic ignition systems are constructed, if the break, I would expect them to stop working at any speed. The switching frequency should be irrelevant but apparently in some threads it is!

I am wondering what make an ignition system misbehave only at higher RPMs despite idling and operating just fine at lower RMPs. Can anyone shed some light on the possible reasons?


The primary reason I am asking is that if the malfunction only at high rpm, how can we reliably diagnose them on the dock at idle?
They will spark and fire just fine showing no sign of malfunction. The problem will not be solved until someone takes the leap and through a new ignition into it and try it out. While I have no problem with this approach, I am basically wonder if there is another reliable and predictive method to diagnose them.

 

[gm280]

WOW Deep, that is a good question and it will take some basic knowledge of how those electronic systems actually work.

A lot of ignition systems use either a hall effect device or a photo diode device to trigger the initial firing. And then some take the standard 12VDC and chops it up to convert it to a higher voltage. I won't get into how that actually happens. But it does take some frequency devices to allow that conversion.

So the trigger device electronically allows the primary voltage to flow the spark plug coil(s) to fire the plugs. However, at lower RPMs all those parts can accomplish that with relative ease. But as you increase the RPMs, now you are forcing those same parts to work harder and of course faster. That is when suspect parts will start breaking down. Speed and heat are two things electronic parts really have a harder time doing in any circuit. Faster working parts create internal heat as well as the external sources of heat. And heat is the number one destroyer of any electronic part...period!

So what seems like normal operating ignition at lower RPMs can break down when forced to do their job faster with more heat. Hope that helps a little. Going into the actual theory of how everything works in these ignition systems would take a lot more space and bore a lot of folks to tears. JMHO!

 

[StarTed]

I 2nd that gm280.

Such problems are very difficult to diagnose and come in many forms. I've seen hall effect devices that drift over time and become a problem for measuring devices. Accuracy drifts along with them. Similar problems also affect other components such as capacitors. Electrolytic capacitors are especially vulnerable to ageing. Resistors can change with heat. The modern integrated circuits contain many of older components in miniature form and should be more stable but heat is still the common enemy.

I don't know of any one answer to the question. Sometimes we just need to replace and see in order to save time and sanity.

 

[keith2k455]

There are specific test procedures for most specific components. I have found it best to try to test specific components and replace as necessary. To the original point, I know of no specific way to guide you towards where to look.

Best of luck.

 

[gm280]

There are specific test procedures for most specific components. I have found it best to try to test specific components and replace as necessary. To the original point, I know of no specific way to guide you towards where to look.

Best of luck.

keith, yes you are correct. There are test(s) you can do to help isolate suspect components. However, you have to really understand electronics AND have such equipment. And the fact is, most folks either don't have the equipment and/or understand the components well enough to test such things. If you could rig up some high voltage generators to test for part break downs then you can maybe pin point defective parts. With a heat gun and proper voltage supplies you can accomplish that. But to get all those things would cost the average consumer way more then replacement parts. So it is what it is. JMHO!

 

[keith2k455]

Gm280, I agree. My ability limits me to only doing voltage tests. I once thought I diagnosed my Mallory points conversion in my old Buick, only later to find out it was the hy fire box. I guess I just haven't posted anything in a while...lol