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1G Engine out, wiring TLC underway.

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Spector5

10+ Year Contributor
274
6
Jul 31, 2011
holland, Michigan
So, engine was pulled out for mechanical issues.... while that’s out, I figured no better time than now to freshen up the 25+ year old weather beaten harness.

I’ve done plenty of wiring tuck jobs and custom harnesses for other people. However, as usual, my car always gets left out due to time.

Never being a big fan for how the factory routed the wiring and the materials they used. It left me feeling like it was put together by someone in their backyard right off the showroom floor.

Obviously, functionality and longevity trumps the visual aesthetic for anyone with half a brain when it comes to wiring.

After playing around with paper drawings and physically moving the harness how I want it to be. I came up with plan for the harness. Now the engines out and I have time. I have begun the long tedious process of building a harness how I would of like to seen from the factory.

I decided to reroute the main harness through the heater core area. I deleted the heater assy. So my harness design and routing wouldn’t work for most. However, it works for me.

Currently to date harness is out and began disassembly and marking the harness.
 

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Never being a big fan for how the factory routed the wiring and the materials they used. It left me feeling like it was put together by someone in their backyard right off the showroom floor.

What materials are you using that are better than stock?
 
I went through putting my harness together as well. Trying to clean up the bay and interior. Deleted unnecessary things like egr, ac, etc.

This is a budget build mind u but I think it came out pretty good for my first try. I used a combination of solder, heatshrink tubing, electrical tape and expandable braided sleeving for the engine bay. Also ran it through the heater core. For the interior I used tesa wire loom tape.
 
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What materials are you using that are better than stock?

The type of wiring used in 91’ compared to todays options is a no brainer. It’s the first thing that will be changed.

It’s a outdated gtp type wire. As you can see doesn’t hold up more than a decade. From the constant heat and cooling effect in the engine bay and fluids coming into contact with it. Almost all dsm harnesses I’ve ever seen to include mine are extreme stiff and brittle.

I will be using factory Oem replacement connectors and pins from Sheridan engineering.

From the factory, they sealed up the connectors but then left the battery, starter cables and other wiring exposed to the elements.

They used good material for what was available in that time frame. However it is very outdated to modern spec.

I will be using shrink tube over nylon braided loom instead of the plastic loom that falls victim to the same issues as wiring. The loom becomes brittle and then breaks off.

They used more electrical tape than 3m can make in our harnesses. That to over time unravels and becomes brittle.

No matter what we use it won’t last forever, but there is definitely more reliable and efficient materials to use over factory materials.

I went through putting my harness together as well. Trying to clean up the bay and interior. Deleted unnecessary things like egr, ac, etc.

This is a budget build mind u but I think it came out pretty good for my first try. I used a combination of solder, heatshrink tubing, electrical tape and expandable braided sleeving for the engine bay. Also ran it through the heater core. For the interior I used tesa wire loom tape.

One thing to keep in mind is solder vs butt/crimp connectors. Everyone was taught to solder their connections or repairs. I was even taught that by my tech school, mentors, etc. however, This has went from personal preference(debates) to the new performance world industry standard to crimp connections. There’s a lot of great articles that explain why that Is, I would spend all day explaining it, LOL.

I use a bare connector, and individual shrink tube. A lot of guys like the perm-seal version. As it’s already coated with the heat shrink. Most fail to realize that if not done properly. You will penetrate the heat shrink when crimping the connector. Pretty much defeating the purpose of the shrink. Causing premature wiring issues.
 
Last edited by a moderator:
The type of wiring used in 91’ compared to todays options is a no brainer. It’s the first thing that will be changed.

It’s a outdated gtp type wire. As you can see doesn’t hold up more than a decade. From the constant heat and cooling effect in the engine bay and fluids coming into contact with it. Almost all dsm harnesses I’ve ever seen to include mine are extreme stiff and brittle.

I will be using factory Oem replacement connectors and pins from Sheridan engineering.

From the factory, they sealed up the connectors but then left the battery, starter cables and other wiring exposed to the elements.

They used good material for what was available in that time frame. However it is very outdated to modern spec.

I will be using shrink tube over nylon braided loom instead of the plastic loom that falls victim to the same issues as wiring. The loom becomes brittle and then breaks off.

They used more electrical tape than 3m can make in our harnesses. That to over time unravels and becomes brittle.

No matter what we use it won’t last forever, but there is definitely more reliable and efficient materials to use over factory materials.

Sounds like a good plan. I guess I will be getting an order from you sometime soon ;)

Are you meaning shrink tube along the whole length? Or just at the joints? If the nylon braided loom is exposed, it can get dirt trapped in it. Then it will act like sandpaper on the wires. Not as big a problem on a race car thats going to be run a season or two, but a definite concern if you are trying to make something last long.

I didn't have issues with solder splices I made, but I have had them fail when someone else was building a harness I designed. The trick to getting them to live is to make sure that the solder doesn't wick down the wire. And then also to support the wire all along that, so there is no bending at all around the joint. It's easier and safer to crimp, I wouldn't design a solder splice into any new harnesses I make.
 
Sounds like a good plan. I guess I will be getting an order from you sometime soon ;)

Are you meaning shrink tube along the whole length? Or just at the joints? If the nylon braided loom is exposed, it can get dirt trapped in it. Then it will act like sandpaper on the wires. Not as big a problem on a race car thats going to be run a season or two, but a definite concern if you are trying to make something last long.

I didn't have issues with solder splices I made, but I have had them fail when someone else was building a harness I designed. The trick to getting them to live is to make sure that the solder doesn't wick down the wire. And then also to support the wire all along that, so there is no bending at all around the joint. It's easier and safer to crimp, I wouldn't design a solder splice into any new harnesses I make.

Don’t get me
Sounds like a good plan. I guess I will be getting an order from you sometime soon ;)

Are you meaning shrink tube along the whole length? Or just at the joints? If the nylon braided loom is exposed, it can get dirt trapped in it. Then it will act like sandpaper on the wires. Not as big a problem on a race car thats going to be run a season or two, but a definite concern if you are trying to make something last long.

I didn't have issues with solder splices I made, but I have had them fail when someone else was building a harness I designed. The trick to getting them to live is to make sure that the solder doesn't wick down the wire. And then also to support the wire all along that, so there is no bending at all around the joint. It's easier and safer to crimp, I wouldn't design a solder splice into any new harnesses I make.

I’m still learning how to use the nylon braided loom. That’s really good to know how it traps debri! However, the “sand paper” rubbing affect could be said for plastic loom as well.

I’m not against plastic loom, electrical tape, or even solder. I just think a lot of it is over used, better ways or even aesthetically pleasing. Also, quality of materials as in even brand of electrical tape. I’ve used expensive 3m and the cheapest possible from a harbor freight.... I’ve had bad experience with the cheaper tape as it seems to come unraveled within the same day I use it. It just seems people get carried away with electrical tape. If you can’t wrap a joint or loom end correctly it sticks out like a sore thumb. people use zip ties to secure the loom to the wiring. Nothing wrong with it, but doesn’t look very professional.

“My plan” LOL, is to electrical tape the wire harness itself to hold it together and to add a barrier. Nylon braid over top, then heat shrink joints and ends. New pins, connectors and

I should rephrase myself by saying there’s really no right or wrong way to to build a harness as long as it works for its given purpose.
 
I’m still learning how to use the nylon braided loom. That’s really good to know how it traps debri! However, the “sand paper” rubbing affect could be said for plastic loom as well.

The open braid traps the sand in the weave, and it allows the sand a direct path in. On the loom, the entrance is only at the split, which can be taped over. The sleeving I use is designed not to allow this. You can get sleeving that is rubberized that will also work, it just is very hard to use to build a harness.

The loom is risky to use for a reason you may not have seen with the old DSM harnesses. That loom is like a saw. Have it touching something else, or another loom, and it will cut through it over time.

“My plan” LOL, is to electrical tape the wire harness itself to hold it together and to add a barrier. Nylon braid over top, then heat shrink joints and ends.

FWIW, I was working on some OEM harnesses a few years ago. This was the OEM suggestion for a long lasting harness, and it isn't too far from what you are planning. Use the fabric style tape to wrap the harness. This prevents abrasion. Then put the split loom over that, and finally wrap it with the quality vinyl tape to seal the loom, preventing dirt from getting in. The overtape also helps prevent the loom from cutting through other stuff. Although you might want to add a layer of the fabric tape if it is in contact with something else, to prevent rub through.
 
The open braid traps the sand in the weave, and it allows the sand a direct path in. On the loom, the entrance is only at the split, which can be taped over. The sleeving I use is designed not to allow this. You can get sleeving that is rubberized that will also work, it just is very hard to use to build a harness.

The loom is risky to use for a reason you may not have seen with the old DSM harnesses. That loom is like a saw. Have it touching something else, or another loom, and it will cut through it over time.



FWIW, I was working on some OEM harnesses a few years ago. This was the OEM suggestion for a long lasting harness, and it isn't too far from what you are planning. Use the fabric style tape to wrap the harness. This prevents abrasion. Then put the split loom over that, and finally wrap it with the quality vinyl tape to seal the loom, preventing dirt from getting in. The overtape also helps prevent the loom from cutting through other stuff. Although you might want to add a layer of the fabric tape if it is in contact with something else, to prevent rub through.

I will most definitely keep that in mind. Thanks for the advice, nice to find someone that’s experienced the pros and cons of braided loom. Overall it’s still fairly new/rare as most stick to plastic loom and yes, the plastic is a lot cheaper.
 
I chuckled a little bit whenyou told Brad that you were going to order from Sheridan. Brad's a great guy and has helped me with wiring issues many times. Good luck, and please keep this thread updated with pictures if you can when you start building it.
 
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