Engine Firewall Wiring & Connectors


The following information describes how to accomplish the task of selecting and installing engine firewall wiring for your aircraft. For this type of application there are numerous options and this is just one way to do it. In this Tech Tip article we will show you two popular ways to make disconnecting your engine's firewall wiring quick and easy to help facilitate removing the engine.

Of the two ways presented below, soldering is the one method you really need some experience with in order to accomplish it properly. If you are not experienced in making soldered connections you could possibly get a "cold solder" connection. The term "cold solder" means you will get the solder hot enough to flow into the connector, but not get the connector hot enough to create a good bond between the connector and the solder. When the solder cools you may not be able to pull the wire out of the connector as the solder may cause a wedge effect inside the connector, however it may not have actually bonded to the connector's surface. When this happens corrosion can start forming over time between the solder and connector causing a loss of electrical flow from the engine. So for those of you who are not experienced in soldering or soldering connectors we suggest using pliers-type crimp connectors instead.


Crimp Connectors



Firewall Wiring Kit, Click to Enlarge



Quick Disconnect Wiring Connectors For Engine Wiring

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The following photos show the correct way to use crimp connectors. It is important to obtain and use "high quality" crimping pliers and "NOT" buy inexpensive ones. The cheaper crimping pliers may render poor quality crimp connections which could put you at the risk of loosing electrical flow from the engine in the air.

Note there are two crimp tabs at the rear of the crimp connector. The first crimp tab is to be crimped over the wire insulation to hold the wire in place without allowing wire movement which may cause the wire to break. The second crimp tab is to make the electrical connection crimp to the wire. Be sure to strip the wire where the end of the wire is inserted into the connector tube and ensure the insulation is just past the first crimp tab.

If you are inexperienced at crimping it is suggested you buy an extra dozen crimp pins. Use six or so to practice making the crimp connection and the other half dozen in case you need to replace a badly crimped connection.

          
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Once you have successfully made a crimped connection to your lead wire just push the connector into the connector plug housing. There are two to four wing tabs on the sides of the connector that are locking tabs which will give you a small click sound when fully inserted and will lock the connector into the plug housing.

          
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Should you accidentally insert the connector into the wrong connector hole in the plug housing and need to remove it to place into the correct hole you will need the tool shown in the photo to the right to safely remove the connector and then reinstall it without damaging it.

          
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Soldering Connectors


Quick Disconnect Wiring Connectors For Engine Wiring

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In these two photos the builder is using electrical quick disconnect terminals that are commercially available. You can source these electrical connectors at electrical supply stores or at Skyes The Limit in Arizona. Both exterior ends of the connectors use wire solder pins to connect the 18 AWG wiring from your aircraft's wiring harness at the inside half of the 6-pin connector and the outer end to your engine harness. The same applies for the 4-pin EGT and CHT connectors. Standard electrical breaker box connectors are used as feedthroughs for the two 4 AWG engine starter cables.

          
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The wiring diagram to the right shows the wiring color codes of the standard 6-wire harness to be soldered to the inside connector and its corresponding engine harness color coded wires for the exterior half of the connector. Also shown in the diagram are the EGT and CHT electrical feedthroughs and circuit breaker wiring color codes.

          
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Although this is an easy way to disconnect the engine wiring from the aircraft to make engine removal less complicated, soldering the wires to these small pin connectors may take a little time and will require good soldering skills.

          
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