To DIY'ers-how not to wire things

[railgun]

Sorry for the long winded post...

When you think that you did the most awesome wiring job, regardless of what it is, you probably didn't, or missed something that's way too obvious.

I had wired in an FJO injector driver box about two years ago out of necessity as well as what I had read on various forums indicating their benefit. I did a somewhat hack wiring job at the time in that most of my wire lengths were way too long and not exactly neat. Most of my connections were just crimped and just kind of hanging around the box itself, which was mounted where the ABS unit sat.

Fast forward to this early spring and I had rewired my engine harness including the rewire of the FJO to better integrate it into the main harness. I soldered everything, cut to the proper length, covered every solder joint with heat shrink, then wrapped with some high temp vinyl tape, then some self vulcanizing tape. Everything was perfect.

Fast forward again to last weekend when I'm sitting at a stop light not 10 miles from my house on the way to Indianapolis when I start 1-rotoring it. WTF? So we pull into a Speedway gas station on the corner at which we were sitting. Spark, and make shift compression check are good. So in the middle of said gas station, we pull everything out. I can't pull my primary injector clips due to my installation, so we pull the fuel rail. Boiling fuel on top of a motor isn't something I recommend many people to mark off as something they've accomplished, but out of necessity it was pulled.

Long story short, the front primary injector wasn't firing. The injector was good by giving it some power directly, so either the FJO unit was toast or somehow the PFC.

Initial wiring testing showed that the FJO was suspect.

A tow home and further testing the following week showed that I in fact had a short between the ECU and the FJO. While the heat shrink was great and all, due to it's placement (proximity to the exhaust and the fact that they were all bunched together at the same point), as some know, the heat softened the tubing up enough that the solder points (admittedly not the cleanest) started to poke through and the front primary and the 12v touched.

Didn't take much...





Needless to say that I got extremely lucky that it was the primary. Had it been a secondary and I didn't know and I romped on it...bye bye motor.

So another rewire, an extra helping of tape around the heat shrink and a relocation of the unit away from the exhaust and were NOT back in business. That short, and running the motor long enough after it happened, caused the PFC's front primary channel to fry. But, I found a somewhat unscientific method of testing the injector channels.

Just behind the connector block and those four pins, there are four resistors and four capacitors along the edge of the PCB. One of those cap solder points and the ECU pin will show a resistance of about 440 ohms. The front primary gave about 13k+ ohms. I'd call that a failure. That and the fact that the car woudn't start.

So the moral of the story? When you wire something like that up, pay attention to where the installation is. Offset your connection points, whether crimped or soldered. And ensure that it's secure; that heat and vibration won't cause that connection to fail. Common sense? Sure. But if you'd seen the original wiring job, I think that you'd agree that it was a really good job. It's those little things that you don't realize that'll get ya.

[Nopis1O]

ha way to scare me. im finishing up the wireing on a birds nest right now.

[speedjunkie]

Damn, this scares the shit outta me haha. From what it sounds like mine is currently set up pretty similar to the way you had yours when you first installed it, and at some point I was planning on redoing it to make it clean, along with soldering with heat shrink and all that. Thanks for the heads up! Mine unit is over by the ABS, but my connections are all over the engine, close to the injectors, and all that is wrapped up in heat shielding. Hopefully that helps. Now I'm freaked haha.

[theorie]

ouch! yeah you really gotta make sure you use high quality shrink...and avoiding exhaust definitely helps. lol

[Brent]

Glad nothing too bad happened. Very informative post.

[Garfinkles Motor Works]

I always double the layers of heat shrink tubes .Some times using the same size if the wire is small or I use two different sizes one over the other .Never leave a bump in the solder joint,reheat the bump or press it down with pliers .

[railgun]

Originally Posted by Garfinkles Motor Works

Never leave a bump in the solder joint,reheat the bump or press it down with pliers .

Heh...believe me. Lesson definitely learned.

[88turboii]

yeah i dont trust heat shrink alone anymore, usually follow it up with a layer of electrical tape also

[jkstill]

Another post that makes the assumption that soldering is better than crimping.

It ain't so.

High quality crimps make a very good connection.

Solder connections have a tendency to break in high vibration environments.

In the pics in this thread, the soldering was not done properly if is sharp enough to poke through the heat shrink.

The wire needs to be heated with the soldering iron, and the solder melted on by touching it to the wire, not by touching it to the solder tip.

Want the best of both worlds? Use some cheap bare crimps, and flow a little solder into it. You can get these at radio shack, and it makes it easier to make a good solder connection.

[railgun]

Originally Posted by jkstill

Another post that makes the assumption that soldering is better than crimping.

It ain't so.

Nowhere did I assume that crimping was substandard to soldering. And those solderpoints weren't sharp per se, but rather not exactly straight and due to how they were bundled, and as tight as they were...you get the idea. And I know how to solder. The method you described is exactly what I did.

[joff]

Originally Posted by jkstill

Want the best of both worlds? Use some cheap bare crimps, and flow a little solder into it. You can get these at radio shack, and it makes it easier to make a good solder connection.

Actually, contrary to common sense, this is not the best of both worlds. Its identical to soldering only and has none of the benefits of the crimp. The only reason to favor a crimp connection is when temps are over 400F (solder melts) or when the wire is under tension/stress.

The copper/solder alloy is more brittle than the regular copper and doesn't bend much before it will fracture. Many non-engineers will fixate and overreact to this fact but the truth is it usually doesn't matter as none of the wires in our wiring harness are under significant stress. Vibration alone does not matter as the flexible wire before and after the joint flex before the solder/copper alloy flexes -- it needs to be high vibration and under tension in such a way that the joint "feels" like its being bent. For instance, voice coils in speakers are soldered and they are under extreme vibration -- BUT -- there is slack in the wire so the solder joint is not effected and there is no stress to the copper/solder.

When you crimp + solder, your crimped connection now contains the brittle solder/copper alloy. All you did was waste time and a perfectly good crimp on a soldered joint and you didn't even save any time.

[jkstill]

Originally Posted by joff

When you crimp + solder, your crimped connection now contains the brittle solder/copper alloy. All you did was waste time and a perfectly good crimp on a soldered joint and you didn't even save any time.

I appreciate the input. I've had a few years practice and do know how to solder.

The issue of not soldering a crimped joint doesn't seem that clearcut.

Here's a couple articles, one clearly against the practice, and one that tells how to properly do it. Granted, the second article is for larger wire than you will probably find in a car.

It may or may not apply to smaller wire.

http://www.ch601.org/resources/crimpsolder.htm

http://www.connex-electronics.com/?u...imp_guide.html

Personally, that's all the time I have to spend on looking up info on it.

Anyone else have anything?

[joff]

Originally Posted by jkstill

I appreciate the input. I've had a few years practice and do know how to solder.

The issue of not soldering a crimped joint doesn't seem that clearcut.

Here's a couple articles, one clearly against the practice, and one that tells how to properly do it.

Good info.

Yeah, I agree its definitely not clear-cut. :-) There are places for both.

I remember hearing NASA mostly uses crimp connections because anybody doing a solder joint has to be certified. A good crimp connection that is 99.9% the same as a solder joint is easy to make with the proper tool, proper hardware and proper prep and requires no skill (which is usually good for quality).

Being in the electronics industry though, its hard for me to imagine there being any question as to the reliability of soldering. We employ 3 full time soldering professionals for prototypes and repair work and have product lines with 20 years of production history and 100s of thousands of boards built so one can imagine the cumulative reliability data acquired. If there was anything wrong with solder joints, we would see it in our repair dept and in production yield stats and I'd be (as well as the rest of the industry) trying to find alternative ways to manufacture electronics.

Some further useful facts to contribute:

One of the biggest surprises to be learned about soldering is that rosin flux residue becomes corrosive at high temperatures. It is very important to clean the solder joint (acetone works best). It is not apparant immediately, but over the course of several years an invisible amount of flux can eat heat shrink, wire, and cause problems.

Also, the electronics industry recently got hit with B.S. (IMHO) Eco-legislation (RoHS) that requires us to take the lead out of solder. Soon it may become difficult for Joe Blow to get leaded solder which is superior in every way to the new "Greener" solder. Without the lead in solder, a phenomenon called "tin whiskers" causes solder joints to grow metal "hair" which can cause shorts to anything nearby. They take many years to grow such that the real hit to electronics reliability probably won't be known for 5-10 years. It also requires a hotter iron, easier to make a cold joint, doesn't flow as well, and is more expensive. It is also interesting to note that high reliability industries such as military and aerospace, have been given convenient exceptions to this new lead-free solder legislation.

[REVIT93RX7]

There are tools for every application. It is a matter of determining the environment one is using the wire in. Crimping will work is some applications and solder works for others. In the auto industry I think either one is fine. It just comes down to the skill of the person doing the work. Space I think is some cases dictates which method to use. Solid wire verse stranded wire is also an issue.

[RIZZXX7]

I follow mine with tape also, this type of thing happened to my mr2 and I kept on blowing fuses, shit drove me nuts