Electronic Ignition...Warm misfire...another thing to check!
Posted: Sun May 16, 2021 12:05 pm
I offer my recent experiences for anyone trying to troubleshoot their car when it has a misfire ONLY when warm.
My Car is equipped with a crane Cams XR700 electronic ignition system. Late last year I took the distributor out to tidy up the (optical) pick up wiring & check the advance mechanism.
Over the winter I replaced the cylinder head, replaced the electric fuel pump & pressure regulator, had the distributor out & serviced the Webers ; i.e. lots of changes to both the fuel & ignition systems.
After pulling the car out of storage it ran perfectly cold, but after 15 minutes or so started mis-firing quite badly & would not continue to idle.
I checked fuel pressure & fuel delivery, both good. Checked ignition timing ... good. The issue sounded like a ignition component failing when hot, ignition module, cap, rotor, ignition wires, plugs or coil... most were replaced last year... replaced cap... rotor...wires again one by one with no change.
Thoughts went back to touching the distributor last year. In a fit of desperation I read the instructions & fault finding & see
"ROUGH OR INTERMITTENT OPERATION "
1. Improper phasing is the most likely cause of rough running on new installations. Check phasing according to instructions in the section on Completing the Installation.
What the heck is "phasing??" Reading back through the disjointed 20 pages of instructions I see a section I had not noticed before:
OPTICAL TRIGGER ADJUSTMENT PROCEDURE
1. The new diagnostic LED greatly simplifies the optical trigger adjustment procedure. The LED illuminates at the firing point and can be used as a static timing aid.
2. Reconnect the battery. Turn ignition key on, but do not crank engine. Timing marks must remain aligned.
3. Refer to Figure 25. Select the appropriate orientation depending on direction of rotation previously
noted. Slide trigger assembly around the edge of shutter in direction opposite to distributor shaft rotation.
When the light beam from the optical trigger reaches the leading edge of a window in the shutter,the diagnostic LED will illuminate.
At this point, stop sliding the optical trigger. Tighten all screws to maintain this position. If necessary, repeat sliding procedure until you are sure optical trigger is aligned properly. You can position the mounting arm
either to the left or to the right of the mounting foot as required for proper alignment.
4. This alignment procedure assures that the rotor is pointing directly towards a spark plug terminal when the leading edge of a shutter window reaches the optical trigger. Correct alignment assures maximum
spark energy by reducing the gap between the rotor tip and cap terminal.
5. blah blah
OK.. I know I did not do that when I had the distributor out, so I go through the simple procedure & thankfully everything is now good!
I'm not an electronics whiz, I don't know why this is important, "Correct alignment assures maximum
spark energy by reducing the gap between the rotor tip and cap terminal." makes no sense to me... you do this procedure with the engine at TDC & then set the ignition timing at something like 8 degrees before TDC... Anyway you have been warned!
My Car is equipped with a crane Cams XR700 electronic ignition system. Late last year I took the distributor out to tidy up the (optical) pick up wiring & check the advance mechanism.
Over the winter I replaced the cylinder head, replaced the electric fuel pump & pressure regulator, had the distributor out & serviced the Webers ; i.e. lots of changes to both the fuel & ignition systems.
After pulling the car out of storage it ran perfectly cold, but after 15 minutes or so started mis-firing quite badly & would not continue to idle.
I checked fuel pressure & fuel delivery, both good. Checked ignition timing ... good. The issue sounded like a ignition component failing when hot, ignition module, cap, rotor, ignition wires, plugs or coil... most were replaced last year... replaced cap... rotor...wires again one by one with no change.
Thoughts went back to touching the distributor last year. In a fit of desperation I read the instructions & fault finding & see
"ROUGH OR INTERMITTENT OPERATION "
1. Improper phasing is the most likely cause of rough running on new installations. Check phasing according to instructions in the section on Completing the Installation.
What the heck is "phasing??" Reading back through the disjointed 20 pages of instructions I see a section I had not noticed before:
OPTICAL TRIGGER ADJUSTMENT PROCEDURE
1. The new diagnostic LED greatly simplifies the optical trigger adjustment procedure. The LED illuminates at the firing point and can be used as a static timing aid.
2. Reconnect the battery. Turn ignition key on, but do not crank engine. Timing marks must remain aligned.
3. Refer to Figure 25. Select the appropriate orientation depending on direction of rotation previously
noted. Slide trigger assembly around the edge of shutter in direction opposite to distributor shaft rotation.
When the light beam from the optical trigger reaches the leading edge of a window in the shutter,the diagnostic LED will illuminate.
At this point, stop sliding the optical trigger. Tighten all screws to maintain this position. If necessary, repeat sliding procedure until you are sure optical trigger is aligned properly. You can position the mounting arm
either to the left or to the right of the mounting foot as required for proper alignment.
4. This alignment procedure assures that the rotor is pointing directly towards a spark plug terminal when the leading edge of a shutter window reaches the optical trigger. Correct alignment assures maximum
spark energy by reducing the gap between the rotor tip and cap terminal.
5. blah blah
OK.. I know I did not do that when I had the distributor out, so I go through the simple procedure & thankfully everything is now good!
I'm not an electronics whiz, I don't know why this is important, "Correct alignment assures maximum
spark energy by reducing the gap between the rotor tip and cap terminal." makes no sense to me... you do this procedure with the engine at TDC & then set the ignition timing at something like 8 degrees before TDC... Anyway you have been warned!