Reference: For additional reading & forum comments, here’s an Auto-FAQ in the archives that covers this topic as well: Click Here >> La-Z-LinkOne of the things I’ve noticed over the years is how carelessly some engine bay electrical connections are done, especially in exposed areas. Unlike inside the cabin or under the dash, the engine bay is a pretty hostile environment due to heat and moisture. One key thing to do is to make sure any exposed wires are securely connected, well covered and protected. Below are some tips that I’d like to pass along…
Usually this is how two wires are connected in an engine bay FI connector splice:
Next, the wires are soldered together to make a solid permanent connection. 
Note: I use a temperature controlled soldering station for all of my work. It has an upper heat limit of 900 degrees F and that pretty much guarantees no cold solder joints. At the very least – I’d recommend using no less than a 45-50 watt iron for this type of work. It also helps to apply paste type soldering flux to the joint before soldering.
For wires in awkward locations or under some tension, I prefer to use non-insulated crimp style butt connectors. They make it easier to get the wires connected -- once crimped, I solder everything together for a final tight connection.
Buying Them: Radio Shack carries these as part #64-3036 (20 pack, Non-Insulated Crimp On Butt Connectors)
Regardless of the way that the wires are connected – it’s still necessary to protect them. I like to apply electrical tape over the wires or butt connectors.
Next, I apply a length of heat shrink tubing – the tubing keeps the tape from coming undone over time. Just don’t forget to slip the right sized tubing over the wires before connecting everything together (yes, sadly – I’ve forgotten a few times myself and had to pull everything apart!!!).
Note: They also make a type of shrink tubing which has heat activated sealing adhesive applied to the inside walls. This is a nice way to go as well, here’s a place where you can get it, but it ain’t cheap! – Click Here >> La-Z-Link
Although this is the minimum that should be done – I prefer to finish off exposed bay wiring with an over-covering of heat rated split wire loom. If the wire loom is in a moisture intense location it can be covered using COLD seal tape. Cold seal tape chemically bonds to itself in a short period of time and can only be removed via cutting. Cold seal tape can also be used in place of shrink wrap tubing – but it’s much thicker and makes the spliced junction bulkier in size.
Buying Them:
- Good quality wire loom can be found at this web site: La-Z-Link
- Cold seal tape can be found here (@ Eastwood Company): http://www.eastwoodco.com/shopping/product/detailmain.jsp?itemType=PRODUCT&RS=1&itemID=1387&keyword=25051&cm_mmc=undefined ]">La-Z-Link
Here’s a picture of my refurbished FI harness. All the spliced portion of the connections were multi-sealed using tape, heat shrink, split wire loom or a finish layer of heat shrink and finally some portions were finish “dress” taped (yes, anal to the max!!!).
Last tips: When installing crimp connects in the engine bay be sure to use a type that fully seals when pushed together. There are some connectors, like the bullet ones or car store insulated butt connectors, that don’t seal. It’s also a good idea to apply some dielectric grease to the fittings and contacts before they are pushed together. The grease helps to seal out dirt and moisture. For heavy duty applications (i.e., high current lighting wires, etc) I’d recommend getting a good quality male/female multi-wire auto plug rather than using individual crimp type connectors.
When I assemble a quick disconnect to its wiring – I use a little dielectric grease on the insulation end (before final crimping) to seal as well.
Lastly – I finished off the ends of the crimp connector with heat shrink tubing and then a top covering if needed.
DISCLAIMERS…
READ AND FOLLOW ALL SAFETY PROCEDURES RECOMMENDED IN THE NISSAN SERVICE MANUAL FOR WORK ON THE 300ZX Z32 ENGINE. MAKE SURE THE CAR’S ENGINE IS COLD TO AVOID BURNS AND DISCONNECT THE BATTERY BEFORE STARTING ANY WORK. ALWAYS TAKE PROPER SAFETY PRECAUTIONS AND USE COMMON SENSE WHEN WORKING ON THE ENGINE AND ELECTRICAL SYSTEM.
YOU ARE RESPONSIBLE FOR YOUR OWN SAFETY WHEN WORKING ON YOUR CAR. THIS WRITE-UP IS AN EXAMPLE OF ONE WAY TO PERFORM THIS MAINTENANCE, IT MAY NOT BE THE SAFEST OR BEST WAY TO DO IT. YOU ARE RESPONSIBLE FOR DETERMINING HOW THESE REPAIRS SHOULD BE EXECUTED IN A SAFE AND CAUTIOUS MANNER -- AUTHOR IS NOT RESPONSIBLE FOR ANY HARM TO YOU, YOUR CAR, FUTURE GENERATIONS, YOUR PROPERTY OR TO OTHERS WHILE OR AFTER PEFORMING THIS OR ANY OTHER AUTOMOBILE SERVICING... .
How-To: Installing GM Style Injector Connectors - 
