Ignition wires...replace just one?...how?

john baldwin · john baldwin's Garage

'89 3.2, seems to run on 5 cylinders...rough off idle up til 2,200 rpm. Steady idle 1K @ cold start, 800 warm; all vac hoses connected; Wilke's AFM mod performed; speed, reference, CHT sensors all in spec; injectors all working, resistance values good; all wires (Beru) plug to plug @ 2.5K, except for cylinder 6...the new copper plug has fouled, and wire plug to plug resistance jumps all over the place...how do I remove the connector at the spark plug from the wire to determine where the issue is? If it's either the wire or the connector, am I OK to change out just that component or spring for a whole new set of 6 cables? If a new set is recommended, how do I determine the best gauge, 7mm? 8.5mm? other?
New cap and rotor is on order (see pics)...all contacts pitted no record of there having been replaced. I plan to do Gunther's distributor cleaning regimen too...

88-diamondblue · 07:50 PM

If the plug wires are the original it is time to rplace them. Mine lasted 17 years and one day just started bucking on acceleration. I put the Magnacore 8.5mm wires. The only thing that needs to be done is to make the wire holders slightly larger. Have worked great for me. Also use oil to lube the distributor, no way to comletely disassembly without drilling the pin holding the drive gear on. Check this thread out. Carrera Distributor taking apart and reassembly

stlrj · 06-10-2009, 03:46 AM

[QUOTE=88-diamondblue;4713160] . The only thing that needs to be done is to make the wire holders slightly larger.
QUOTE]

You could have save yourself the trouble of using the wire holders since the Magnacores would have worked just fine all bundled like most OEM istallations. The wire separators are specifically designed for the Beru wires that stranded copper inside with resistors on both ends that have a high failure rate.

jmohn · jmohn's Garage

A new wire set may be a good idea, however, you certainly can replace just one wire. Stock gauge would be fine (7 mm, I believe).

Jerry M
'78 SC

john baldwin · john baldwin's Garage

jmohn,
Do you know how to remove the connector at the sparkplug from the wire? I don't want to damage these further by experimentation.
Also, Pelican says that these wires may be either carbon or solid core...what's the difference?

ossiblue · 06-10-2009, 06:36 AM

Since your resistance numbers are jumping around you have most likely found the problem area. You should be able to remove the plug connector by unscrewing it. I don't know what type Beru connector you have but the end screws into the wire with either a "wood screw" type thread (early wires) or a machine screw thread which taps into a fitting that is crimped to the end of the wire. Either way, the connector can be replaced.

If you don't want to spring for a new wire set, test what you have once the connectors are removed (plug end and cap end.) Test the continuity of the bare wire to see if there are breaks that cause the resistance numbers to jump. The probable culprit is the Beru connector for the plug. Test it separately for resistance and tap it as you test (should read around 3Kohms.) If you find the resistance numbers fluctuating, replace only the connector. Do the same for the cap connector (around 1Kohms) though it is not a likely suspect.

Don't know what kind of wires you have. Solid core have twisted copper wire in the center and carbon core have what looks like a thread covered in carbon in the center.

john baldwin · john baldwin's Garage

L.J.
Thanks for the reply...I'll get on it tonight! First, I'll see if the connector at the sparkplug has twisted off the wire end...a loose connection may account for why the R values were jumping all over the place. If after tightening, the R values stabilize within spec, problem may be solved.
If the bare wire has breaks, wouldn't I have seen the "light show" when checking in the dark?
As you suggest, I'll bet it's the connector...even after contact cleaner, things looked a little dubious deep inside....

jmohn · jmohn's Garage

Quote:

Originally Posted by ossiblue

Since your resistance numbers are jumping around you have most likely found the problem area. You should be able to remove the plug connector by unscrewing it. I don't know what type Beru connector you have but the end screws into the wire with either a "wood screw" type thread (early wires) or a machine screw thread which taps into a fitting that is crimped to the end of the wire. Either way, the connector can be replaced.

If you don't want to spring for a new wire set, test what you have once the connectors are removed (plug end and cap end.) Test the continuity of the bare wire to see if there are breaks that cause the resistance numbers to jump. The probable culprit is the Beru connector for the plug. Test it separately for resistance and tap it as you test (should read around 3Kohms.) If you find the resistance numbers fluctuating, replace only the connector. Do the same for the cap connector (around 1Kohms) though it is not a likely suspect.

Don't know what kind of wires you have. Solid core have twisted copper wire in the center and carbon core have what looks like a thread covered in carbon in the center.

Precisely as Ossiblue says.

I think the later cars (like yours) have a carbon core wire while the earlier cars (mines a '78) have a stranded copper core. I know cars earlier than mine used the "wood screw" appearing connection from the plug connector to the wire (it just screwed into the center of the wire, my car had the machine screw connection that fastened to a crimp on fitting on the end of the wire (as ossiblue referred to). While I haven't experienced it myself, apparently the resistors in the Beru plug connectors can be a problem. You could pick up a cheap set of wires (be sure at least one is long enough) with the proper extended plug connectors (I've heard some sets for Chrysler products work in fact some guys use them instead of OEM) and just disconnect both ends of your problematic wire and substitute a new wire to verify it's a plug wire problem. Also, the Beru plug connectors are available individually.

Jerry M
'78 SC

ossiblue · 06-10-2009, 09:59 AM

Quote:

Originally Posted by john baldwin

L.J.
Thanks for the reply...I'll get on it tonight! First, I'll see if the connector at the sparkplug has twisted off the wire end...a loose connection may account for why the R values were jumping all over the place. If after tightening, the R values stabilize within spec, problem may be solved.
If the bare wire has breaks, wouldn't I have seen the "light show" when checking in the dark?
As you suggest, I'll bet it's the connector...even after contact cleaner, things looked a little dubious deep inside....

Not necessarily. Breaks in the core will cause loss of continuity and possible arcing but if the insulation is sound or the the arc is going directly to ground on the engine metal, you may not see the light show. Many have had bad wires that do not display the arcing.

john baldwin · john baldwin's Garage

Twisted both connectors off the wires, emery cloth on all the male threads, contact cleaner on all. R values of plug connector, wire and cap connectors @ 3K, 0.1, 0.4 respectively; reassembled with cap plug and wire with dielectric grease, continuity checked; reconnected plug connector with dielectric grease; 3.04K ohms for the entire cable now (stable). This is a bit higher than the others (2.5-2.64), but we'll see how she runs once distributor has been cleaned and new cap and rotor installed. If still stumbling, time for new Magnecors (or should I opt for Clewett's?)