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Hello,
I'd like to ask about known failure modes of the older (1973-1977) CD-4 powerpacks used on the V4 engines (85-140hp).
I'm trying to diagnose intermittent issues encountered with a 1973 115hp motor.
Primary symptom:
At both idle & low to moderate rpm ranges the engine will periodically kick up/down in rpm's by approximately 20 to 30 percent (no tachometer is available for actual figures). The cycling between up/down events is irregular but typically will occur within about a 10 to 30sec time frame window, and these events will also last in duration for perhaps 10 to 20sec as well.
Aside for (except for) the symptom described above, the motor will otherwise idle relatively smoothly & regular... even at a surprisingly low&steady rpm of around 250-300rpm. In other words the motor doesn't actually 'seem' to run rough or in a ragged (e.g. unbalanced) fashion in either state.
Virtually all of the typical DMM & DVA ignition system readings appear to be within range and normal. For example, ohm's readings & outputs for stator, timer-coil, powerpack outputs, ignition coils, etc. all seem to check out ok.
* Carbs have been carefully cleaned & reassembled with new kits.
* Compression is very good with variance below 10psi between cyls.
* Ignition coils are fresh without hardly any runtime on them at all.
So the main question here is this:
Is it (or would it be) unusual to have a powerpack that [might] intermittently drop spark on one or more cyls every so often (i.e. 10sec to 30sec)... but that would otherwise seem to provide good consistent spark *some-or-most* of the time?
OR... what other possibilities might exist for this type of symptom?
Thanks for your thoughts.
Charlie
I'd like to ask about known failure modes of the older (1973-1977) CD-4 powerpacks used on the V4 engines (85-140hp).
I'm trying to diagnose intermittent issues encountered with a 1973 115hp motor.
Primary symptom:
At both idle & low to moderate rpm ranges the engine will periodically kick up/down in rpm's by approximately 20 to 30 percent (no tachometer is available for actual figures). The cycling between up/down events is irregular but typically will occur within about a 10 to 30sec time frame window, and these events will also last in duration for perhaps 10 to 20sec as well.
Aside for (except for) the symptom described above, the motor will otherwise idle relatively smoothly & regular... even at a surprisingly low&steady rpm of around 250-300rpm. In other words the motor doesn't actually 'seem' to run rough or in a ragged (e.g. unbalanced) fashion in either state.
Virtually all of the typical DMM & DVA ignition system readings appear to be within range and normal. For example, ohm's readings & outputs for stator, timer-coil, powerpack outputs, ignition coils, etc. all seem to check out ok.
* Carbs have been carefully cleaned & reassembled with new kits.
* Compression is very good with variance below 10psi between cyls.
* Ignition coils are fresh without hardly any runtime on them at all.
So the main question here is this:
Is it (or would it be) unusual to have a powerpack that [might] intermittently drop spark on one or more cyls every so often (i.e. 10sec to 30sec)... but that would otherwise seem to provide good consistent spark *some-or-most* of the time?
OR... what other possibilities might exist for this type of symptom?
Thanks for your thoughts.
Charlie
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