Rebuilding Beru plug connectors

[rswannabe]

In the process of sorting out a poor running condition on my 911 recently, I came to the conclusion my ignition system could use improvement. The motor is a 2.8 short stroke with twin plug distributor, MSD 6AL, and twin blaster coils. All that worked well and didn't need to be addressed. What did need to be improved were the plug wires and connectors. When I tested them with with a multimeter, I found 8 out of 12 of my plug connectors were shoring zero continuity, when they should have been reading 3,000 ohms (3kohm) resistance. This is not uncommon for them to increase in resistance over time. I borrow another twelve of these a friend had lying around and tested them as well and found only 2 of the 12 showing the correct resistance. The rest were showing no continuity.

My car was using the Belden 7.5mm carbon core plug wires, with Beru plug connectors with the 3mm threaded connectors that were used on the 3.2 carrera. When I went and tested my wires and their threaded ends, I also found too high resistance (as much as 50kohm on on wire). I think this was due to the carbon wire core breaking and not being a good match to the crimped on beru threaded wire ends.

Here is a typical Beru plug connector. This is the earlier style with the wood screw connector that bored into the plug wire.



Here is the 3mm threaded Beru wire end. You feed the central conductive core of your plug wire into the stud portion of connector and crimp that, then crimp the body onto the wire insulation. They are designed for 7.5mm diameter wires.





Now, I could have just bought a new set of Magnecore or similar wires with their end connectors and probably been done. I could have also bought new Beru plug connectors, but They are $26 each and I am a cheapskate. I had not seen any threads about rebuilding the Beru style system, so I wanted to try that.

I stripped off the top and bottom rubber boots and the air flow seal. What you are then left with is the phenolic resin (Bakelite) body exposed.



The factory assembly of these is sealed with a touch of resin on the top (by the threaded connectors the wire screws into). I removed the dollop of resin with a power sander and exposed the top of the brass threaded connector. I then forced the brass threaded connector out of the body, invariably breaking some of the surrounding Bakelite body. That is not a problem as you will see later. You can then dump out the contents of the body. What you will find is an aluminum spacer rod, one to three resistors (depending on intended resistance), and a spring to keep them all in compression.



I found if I clean the connections lightly with sandpaper I could then assemble the connector and it it would then read the correct 3kohm resistance. These had resistance to reduce radio frequency and electromagnetic interference generated by the car's ignition system. These were designed to work with solid core plug wires that had no RFI and EMI suppression. Modern solid core spiral wound wires are able to suppress RFI and EMI on their own, so the resistors in the plug connectors are not needed when used with modern plug wires. So I decided to rebuild the plug connectors without any resistors. I measured the length of the combined resistors and spacer rod and then made a new single spacer rod to replace them out of 3/8" diameter brass rod. I used brass for its better corrosion resistance.



I then rebuilt the plug connectors with the new rods inside, still using the stock spring to maintain internal connections, reassembled everything, and sealed the tops back up with JB Weld. Now I had a set of good connectors with zero resistance.



I then rebuilt the plug wires using Taylor spiral core 8.0mm plug wire. I bought the Taylor wire in bulk on Summit, and a bunch of new Beru threaded wire ends from auto parts warehouse. I then cut and crimped new wires. Because the 8.0mm diameter was a little large for the Beru wire ends (remember they were intended for 7.5mm wires) I simply reduced the outside diameter of the Taylor wires at the end until they fit inside the connectors. I used a bench grinder to do this. Overkill, but it worked fine.

With my new wires made up and threaded into the Beru plug connectors I again checked the resistance of all my wires. Now my longest wire (#6 cylinder lower plug) has a total resistance of less than 2kohm.

I put this all back together and fired up the car and it now runs and idles SO much better. It is a night and day difference. It is clear my ignition system was having to work really hard to overcome all the resistance and jump the gaps in my previous system. Now all that energy can go to the plugs and creating a solid and regular spark.

If you are running Beru connectors, I recommend checking them periodically to make sure they are still in spec. If they are not you can then replace them or rebuild them.

[Rich Gas]

Nice detail. Highly overlooked but essential maintenance. I took the easy route and ordered new Beru wires but ran into some problems when I separated the ends to install them. Found a few ends at a local shop...they charged me $5 a pop.

Rich

[al lkosmal]

nice work brooke

I'll have to do this to my stash of beru connectors.

regards,
al

[Larrybrook]

What about where it connects to the spark plug, any cleaning or modifications there?

[rswannabe]

Originally Posted by Larrybrook

What about where it connects to the spark plug, any cleaning or modifications there?

There is a lug that is in the bottom of the plug connector and snaps onto the end of the spark plug. I popped them out of the body as well (used a long skinny screwdriver through the body of the plug connector and tapped on it with a hammer), cleaned the end with a wire wheel to remove any accumulated oxidation, and then reinstalled it into the housing with a little JB Weld around the body of the lug (careful not to get any on the surface that spring and rod bare on) just to make sure it was fully bonded in as well. I don't think this was really necessary, but certainly should not hurt.

[ozracer]

Rswannabe great article any chance of showing a step by step guide of how you check them with the multimeter explaining it for the electrically challenged?

[rswannabe]

Originally Posted by ozracer

Rswannabe great article any chance of showing a step by step guide of how you check them with the multimeter explaining it for the electrically challenged?

All you need is an electrical multimeter that can measure resistance (ohms). Most can do this. Flip the dial on your meter to the resistance setting and touch the two leads of your meter together. With the two leads touching, you should get a reading of zero ohms. This means there is no resistance and is also called perfect continuity.

Disconnect your plug connector from the spark plug in the head of your motor. It just snaps on and off of the spark lug. You then unscrew your plug wire from the plug connector where it goes into the rubber boot at the top of the connector. You should now have in your hard the plug connector as shown in the first picture in my original post. Touch one lead of your multimeter to the lug that connects to the spark plug on the bottom of the connector. Touch the other lead to the brass fitting the plug wire connects inside the rubber boot at the top of the connector. While touching one lead to each end of the plug connector, you then look at what reading your multimeter is giving you. If your connector is in good shape, you should see your meter reading between 1,000 ohms (1kohm) and 3,000 ohms (3kohm), depending on the year and model of your car. If the plug connector is not working correctly, you will get a readying of infinite ohms which indicates there is no current passing and thus no continuity between the two ends (no electrical connection). This tells you the connector needs to be rebuilt or replaced.

[ozracer]

awesome exactly what I was looking for most appreciated thank you very much

[rswannabe]

I had someone reach out to me asking for where to get the 3 mm threaded crimp on wire end connectors. I got them from Auto Parts Warehouse. You can find them here:

http://www.***********************/shop_brands/beru/ignition_wire_end_plug.html

[stormcrow]

Brooke,

Did you change your wires to resistor wires? I did mine exactly the same way you did yours with the brass rod. I changed my plug wires to 7mm resistor wires and replaced my rotor from a resistor rotor to a solid copper rotor. The P-car never ran so great and I improved my gas mileage to 22 mpg on the highway as I was only getting 19 -20 mpg before. Also changed the boots on the distributor cap to brass.

[rswannabe]

The only reason the old wire ends had resistance was to suppress radio frequency interference. Modern spiral wound wires are able to do this without resistance. I went to new Taylor 8mm wires.

[70basket]

Great info, subscribed!

[jlex]

Instead of taking the plug connector off the wire to check resistance, couldn't you just check resistance on the entire length of the wire by measuring from the plug connector to the connector at the distributor end?

[rswannabe]

Originally Posted by jlex

Instead of taking the plug connector off the wire to check resistance, couldn't you just check resistance on the entire length of the wire by measuring from the plug connector to the connector at the distributor end?

Absolutely, that is the first test you can do, but if you find high resistance or no continuity, then you need to separate the plug end from the wire to see specifically if the problem is in the wire or the plug connector.

[PZSPEED]

Does the wood screw portion have treads in the other end that can be unscrewed from the top brass piece? Where did you source the brass rod from?
Thanks,Patrick

[rswannabe]

I've never handled the screw type connector myself, so I can't answer your question there. I purchased the brass rod at my local hardware store. Hobby shops should also have similar 3/8" diameter rod. Copper and aluminum would also work.

[Kraftwerk]

This crazy, but good, Crazy-Good! I love the project... might be on my list of 'stuff to do'. Thanks for sharing.

[PZSPEED]

Originally Posted by rswannabe

I've never handled the screw type connector myself, so I can't answer your question there. I purchased the brass rod at my local hardware store. Hobby shops should also have similar 3/8" diameter rod. Copper and aluminum would also work.

What year/model Beru plug connectors are you using that have the threaded hole?

[rswannabe]

I believe the wood screw models were used in the long hood and SC cars, but they went to tot he crimped end with machine screw with the 3.2 Carrera. I might be wrong on the transition point though.

[bobsmyuncle]

Old thread, however I'm wondering if anyone has experience with the 'wood screw' ends. I'm about to build new wires. Do these just get screwed right into the end of a flush cut wire?