To DIY'ers-how not to wire things

[jkstill]

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.

[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.