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George Constantine
New User
Username: theo

Post Number: 31
Registered: 06-2012
Posted on Tuesday, 08 September, 2020 - 09:29:   Edit PostDelete PostView Post/Check IP

Weak spark on No 3 & 4 A & B bank, also what is the gap on the ignition module on 1979 shadow, please
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Hubert Kelly
Frequent User
Username: h_kelly

Post Number: 405
Registered: 03-2012
Posted on Tuesday, 08 September, 2020 - 11:37:   Edit PostDelete PostView Post/Check IP

George, clean the dash pots of carbon buildup (oil same) it may very well solve symptoms? .
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Robert J. Sprauer
Frequent User
Username: wraithman

Post Number: 641
Registered: 11-2017
Posted on Tuesday, 08 September, 2020 - 12:26:   Edit PostDelete PostView Post/Check IP

If the air gap was off within the Opus module, it would effect more than 2 cylinders.

I would look at the cap and definitly the wires if original.
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George Constantine
New User
Username: theo

Post Number: 34
Registered: 06-2012
Posted on Wednesday, 09 September, 2020 - 07:30:   Edit PostDelete PostView Post/Check IP

Hi Hubert

Checked the dash pots, they were clean but cleaned them anyway, no change.

Robert,

I did change over the HT leads and clean rotor and cap etc but no change?
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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 2223
Registered: 05-2012
Posted on Wednesday, 09 September, 2020 - 08:21:   Edit PostDelete PostView Post/Check IP

Have you checked for wear in the distributor spindle.
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Larry Kavanagh
Frequent User
Username: shadow_11

Post Number: 663
Registered: 05-2016
Posted on Wednesday, 09 September, 2020 - 08:41:   Edit PostDelete PostView Post/Check IP

Gap at ignition module in UK/Europe designation cars is 0.76mm/0.03". Australia, Canada, Japan & USA gap is 0.89mm/0.036". Use a plastic feeler gauge. Distributor dwell angle @ 1000 PRM should range between 33 to 39 degrees. Ignition timing using 97 octane petrol should be set at 25 degrees BTDC @ 1300 RPM. I generally use 95 octane petrol and set the timing at 25 degrees BTDC at around 1600 RPM and sometimes have to make slight variations to find the sweet spot.
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Larry Kavanagh
Frequent User
Username: shadow_11

Post Number: 664
Registered: 05-2016
Posted on Wednesday, 09 September, 2020 - 09:01:   Edit PostDelete PostView Post/Check IP

Geoff's suggestion regarding possible wear on the distributor spindle could be on the money. Firing order is A1, B1, A4, B4, B2, A3, B3, A2. Your weak spark would appear to be mostly from one side of the distributor cap. If you have a dwell meter you can get the dwell angle reading from the coil and if the reading fluctuates a lot the chances are that there's wear at the distributor spindle. The reading should be fairly steady at about 36 degrees but any number from 33 to 39 degrees is acceptable provided the reading remains steady.
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George Constantine
New User
Username: theo

Post Number: 35
Registered: 06-2012
Posted on Thursday, 10 September, 2020 - 07:30:   Edit PostDelete PostView Post/Check IP

Thank you all for your input.

I'll make a few more checks as per your recommendations
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Larry Kavanagh
Frequent User
Username: shadow_11

Post Number: 665
Registered: 05-2016
Posted on Thursday, 10 September, 2020 - 07:58:   Edit PostDelete PostView Post/Check IP

Or, if you're lucky it might be something as simple as the rotor arm not being seated properly.
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Robert J. Sprauer
Frequent User
Username: wraithman

Post Number: 643
Registered: 11-2017
Posted on Thursday, 10 September, 2020 - 21:55:   Edit PostDelete PostView Post/Check IP

Remove the plastic pick up and check the 3 ferrite bits. Make sure they are not loose and intact.
Pertronix is far more reliable than the original circuit board and related parts.
Re-set the airgap.

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