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1G Engine bay wiring repair questions

dwb

Proven Member
168
64
Sep 9, 2021
Broomfield, Colorado
I'm redoing several electrical connectors in the engine bay on my 1g, like the injectors, knock sensor, coolant temp sensor, oil pressure sending unit, etc. I have to replace a few inches of the wire due to cracking insulation and sometimes broken copper. In the past I just used whatever wire I had laying around but I want to do it right this time, so I'm looking for some advice:
  • What gauge of wire is typically used in the engine bay for sensors/injectors? They all look the same gauge but maybe I'm mistaken.
  • What type of wire will hold up to the heat inside the engine bay? Anyone have a favorite replacement wire (brand/type)?
  • I've heard conflicting information about soldering vs crimping a pigtail onto the harness. I've always soldered mine but curious what some of your opinions are?
  • What should I do about the black wire loom leading up to the injector connectors that get brittle? I'm sure none of them are going to survive. Just heat shrink them?
  • Any tips/tricks to cleaning a harness that's been exposed to engine oil leaks? I have the engine out so I have easy access to the harness.
As always, I appreciate any advice you can provide.
 

TK's9d2TSi

Supporting Member
6,303
3,294
Sep 11, 2017
Cincinnati, Ohio
There a few different gauges used. I personally like solder over crimp and that’s arguable. Jafro made his entire harness and it’s not cheap.

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danl

Proven Member
671
77
Apr 8, 2002
Severn, Maryland
This is a really great question and one that I myself had to figure out the hard way. My ass-u-me-tion is that you would like an economical solution.

Crimping is preferred. The reason is that done correctly it is a more reliable connection. The "done correctly" part is important because done poorly, it will not be reliable. The reason it is ultimately more reliable is that solder can and does crack when exposed to vibration. Crimping does not.

If you are looking for connectors its worth purchasing from here: http://connectors.sheridanengineering.com/index.htm

A lot of these connectors are no longer available and he sells them at a FAIR price.

For wire, this is an economical solution:

20 gauge is an overall good gauge for both sensors and solenoids in the car. If you want you can go even thinner for the sensors but for solenoids and injectors I like the 20 gauge.

Waytek also sells economical crimpers which are key to making nice crimp jobs. Do some research here. You will be spending $50 or more for a nice set of crimpers and may need multiple types or more than one die for your crimpers. Also order up some heat shrink, loom, and electrical tape at the same time.

If wiring seems hard, that is because it is. Don't commit to a "race spec" or "mil" spec harness first try. Just get the basics down and do simple repairs like you stated. Here is a great primer video. The 30 mins invested will save you hundreds of dollars.

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If you want some literature on why crimping is best, how to do lightweight bundling using lacing, and other general tips learned the hard way (loss of life) feel free to sink your teeth into this.


You may note that soldering is allowed in the NASA specifications, but it is under specific circumstances. Still, I'd argue that crimping is the preferred method when possible. There is a HPA video explaining how to perform a splices using crimping should you want to learn that.
 

dwb

Proven Member
168
64
Sep 9, 2021
Broomfield, Colorado
This is a really great question and one that I myself had to figure out the hard way. My ass-u-me-tion is that you would like an economical solution.

Crimping is preferred. The reason is that done correctly it is a more reliable connection. The "done correctly" part is important because done poorly, it will not be reliable. The reason it is ultimately more reliable is that solder can and does crack when exposed to vibration. Crimping does not.

If you are looking for connectors its worth purchasing from here: http://connectors.sheridanengineering.com/index.htm

A lot of these connectors are no longer available and he sells them at a FAIR price.

For wire, this is an economical solution:

20 gauge is an overall good gauge for both sensors and solenoids in the car. If you want you can go even thinner for the sensors but for solenoids and injectors I like the 20 gauge.

Waytek also sells economical crimpers which are key to making nice crimp jobs. Do some research here. You will be spending $50 or more for a nice set of crimpers and may need multiple types or more than one die for your crimpers. Also order up some heat shrink, loom, and electrical tape at the same time.

If wiring seems hard, that is because it is. Don't commit to a "race spec" or "mil" spec harness first try. Just get the basics down and do simple repairs like you stated. Here is a great primer video. The 30 mins invested will save you hundreds of dollars.

You must be logged in to view this image or video.

If you want some literature on why crimping is best, how to do lightweight bundling using lacing, and other general tips learned the hard way (loss of life) feel free to sink your teeth into this.


You may note that soldering is allowed in the NASA specifications, but it is under specific circumstances. Still, I'd argue that crimping is the preferred method when possible. There is a HPA video explaining how to perform a splices using crimping should you want to learn that.
Thanks danl. This is exactly the type of info I'm looking for. Economical is one thing but doing it right is another. I'm more a fan of the later at this stage in life, as long as I'm not getting bent over financially.

I've already purchased some of those Sheridan connectors and realized I'm going to need a crimp tool for those anyway, so if crimping is the way to go for splices, then I'll probably go that route. Seems easier than soldering anyway. I'm by no means a noob at soldering but it can be time consuming and easy to mess up. Waytek wire did come up when I was researching wire type, so I'm glad to see I was on track.

I'll try to take some time to look at your links.
 

danl

Proven Member
671
77
Apr 8, 2002
Severn, Maryland
Thanks danl. This is exactly the type of info I'm looking for. Economical is one thing but doing it right is another. I'm more a fan of the later at this stage in life, as long as I'm not getting bent over financially.

I've already purchased some of those Sheridan connectors and realized I'm going to need a crimp tool for those anyway, so if crimping is the way to go for splices, then I'll probably go that route. Seems easier than soldering anyway. I'm by no means a noob at soldering but it can be time consuming and easy to mess up. Waytek wire did come up when I was researching wire type, so I'm glad to see I was on track.

I'll try to take some time to look at your links.
Hey man, good deal. I should have used another word instead of economical. What I would rather say is don't shoot for the moon use techniques that you are comfortable with. Economical doesn't mean poor quality. What I'd rather have said is that $320 for a pair of tfezel wire strippers, $500 for a pair of DMC crimpers, and hundreds more for your consumables that meet a MIL-STD is a bit overkill. Rather you can do a fine job, better than factory even, with a set of $50 crimpers and $50-100 of supplies.
 

We're on Boost

Proven Member
1,446
330
Aug 25, 2007
Seattle area, Washington
Yeah I don't like it that the old wires get brittle. So a few years ago I finally discovered that there is such a thing as engine compartment wire, as distinct from ordinary primary wire, and I bought some engine compartment wire in gauges 10, 14, 16, 18, and 20.

The wire I'm talking about is generically called either SXL, GXL, or TXL, the difference being the thickness of the insulation. The material used for the insulation is Cross-Linked Polyethylene (XLPE) which is rated for temperatures up to 125 deg C. This insulation should go for many years without getting brittle, and physically it is tough and robust like for resistance to damage from bending.

I like 18 or 16 gauge for most things. It isn't always that you need that much current capacity. It is more because physically they are strong and robust which for me makes it easier to work with and more robust in use on the car. I don't like making connections with 20 gauge because there is so little copper there to work with.

For crimpers, if you are making up new OEM type connectors with pigtails, you will probably want a Hozan P-706. This is made for the little OEM type terminals that the OEM connectors use, like the stuff you would buy from BradS or from Ohm Racing. You can buy a Hozan from Ohm racing. Otherwise they are surprisingly hard to buy in the US. I bought mine from an eBay seller in Japan.

But then when you take your newly made connector with pigtails out to the car to attach it to wherever you have cut the harness back to, I like to use ordinary generic connectors there. Usually I use "parallel" connectors there. Those are more heavy duty and need a more stout crimper. So there I use a ChannelLock #909 crimper/cutter. It's also a nice heavy duty cutter. And one of those will only cost about $30, made in USA, and they are a really nice tool. This tool actually got me into buying ChannelLock stuff again for quite a few tools since their stuff is so nice.

I used to solder everything but got interested in crimping about 10 years ago. One day I talked to some of the people in the Boeing engineering department that designs the wire runs in the airplane, I asked them if they terminate these wire runs with crimps or solder. They said crimps, always! I was ok with that because I don't like the way solder wicks up the wire when you are using stranded wires. It goes up the wire a ways and then if your strain relief (heat shrink or whatever) doesn't go beyond that, the wire will break off at that point after a while, sometimes. I mean I've had that happen. So now I crimp these things.
 
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brads

DSM Wiseman
852
95
Oct 24, 2002
Alta Loma, California
I recommended the Hozan P706, but don't sell them. For a while, you could get them cheaper through eBay or Amazon, shipped directly from Japan, than I could get them if I bulk purchased directly from Hozan. Needless to say, I never bulk purchased, and just told people to check those sources. The last time I looked, prices were in the $55 range for them. I think they make a 707 one too. The P706 has a good variety of crimp widths and heights, so you can pick them to get a really good match to your terminal, especially for generic crimpers.

I always recommend crimp only, because I have had issues with solder joints breaking in some harnesses in the past.
 

dwb

Proven Member
168
64
Sep 9, 2021
Broomfield, Colorado
I was going to buy a couple rolls of SXL 18 AWG wire but I decided to see what wire scraps we had at work. I work for an OEM aircraft manufacture. I happened to walk in the wire shop right after the Laselec machine messed up a whole batch of 18 AWG. So I snagged that bundle of unshielded MIL-SPEC. According to the wire manufacture: "is composed of a 19/30 stranded tinned copper conductor with ethylene tetrafluoroethylene (ETFE) insulation. These cables are rated for a voltage of 600 volts, have a maximum temperature of 150°C, and weigh approximately 8 lbs/MFT."
I think (hope) this wire should be as good, if not better than OEM for sensors and solenoids. Unfortunately it's all white but for pigtails but I should be fine.

I've also decided to buy the Hozan P706 crimper and a bunch of non-insulated TC-1 copper butt connectors and seal it up with some heat shrink. That plus my Sheridan Engineering replacement plugs and I should be good to go.

Someone stop me now if I've got this all wrong! ;)
 
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We're on Boost

Proven Member
1,446
330
Aug 25, 2007
Seattle area, Washington
Someone stop me now if I've got this all wrong! ;)

Sounds good to me.
In fact, ETFE (Tefzel) should be just about as good as it gets!

I would say, do quite a few experimental crimps and shrinks on the bench first, with short pieces of wire to see how it all goes.

My heat shrink is all 2:1 shrink ratio and sometimes I wish I had 3:1 ratio so that it can go over a fat-ish connector and still come down tight on the wire OD. Use the heat shrink to give your wire some strain relief. That is, take the shrink about 3/8" or so beyond each end of the connector. I usually use a double layer of shrink. That does make assembly more complicated but it makes sure that it's all very stiff right where the connector ends. You don't want the wire being able to bend right there at the end of the connector.

I saw on my car 1 or 2 places where English Racing used slick little butt connectors that come already covered with Raychem DR-25 heat shrink. They would be really easy to use, quick, as long as you use the correct type of crimper jaws on it that don't destroy the heat shrink.
I noticed that the Raychem DR-25 heat shrink seems to be more flexible than the various more common heat shrinks I've been using. I don't have any yet myself, but I'm thinking it's probably the best heat shrink.
Anyway, just some more thoughts there to throw on the pile.
 
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