Fools Injection Computers - Randy’s Electrical Corner - Jp Magazine

Fool's Injection Computers - Randy’s Electrical Corner

It’s funny what is OK to say as time goes on. I was in the theatre watching that movie where the kid got busy with a pie in the kitchen and that redheaded band chick said, “This one time, at band camp, I stuck a flute…” Well, you know the rest. Anyway, almost everyone watching the movie said something like “Oh!!!” or “Dang!!!” or some other unprintable words. The point is that we were all shocked, but today something like that goes past and almost no one says boo. It takes more to shock us today than it used to.

Nothing is the same anymore, and that’s true of fuel injection, too. So when I got a question last week about where to get fuel-injection computers and harnesses, one thing led to another and pretty soon I was going down old memory lane. I’m not sure what address I stopped at on that lane, or even why they call it a lane, but I was remembering the bad old days when even a drop of water might kill the computer. You can dunk practically any of today’s computers in water and they will live. What computer you have makes a big difference in where you can put it in the Jeep.

Well, really you can put any computer just about anywhere except for on the exhaust because computers don’t like heat. Electronics get hot, so computers need vents. The computers of old got really hot and needed huge vents to keep them cool. Even today’s computers have vents, but they have gotten smaller over the years. So when you pick your computer and want to mount it, in addition to heat, you goofy Jeep guys need to be worried about water and mud because either inside is just not good.

The old computers were barely enough to keep the engine going, and today’s wristwatches have more computing power than the old fuel-injection computers ever did. I used to call them fool’s injection, because back then everyone knew that a carburetor was better and more reliable than injection. Only fools swapped to injection. Today’s computers have no problems running the engine and are very reliable. To program the old computers, you had to remove a chip, send it off, wait a few weeks, and hope it was right when you got it back. Today we can program them in real time from our laptops, dedicated controllers, and maybe even by the time you read this, our cell phones.

So what computer do you have? Where should you put it? How can you tell? What do you need to look out for when figuring all that out? Let old Randy help you out. I’m not really that old, it’s just something people say.

PhotosView Slideshow This is a very early fuel-injection computer from the late ’80s or early ’90s. They were originally mounted inside the vehicle and have basically no sealing from the elements whatsoever. Factory Jeep computers in the Wranglers from these years were mounted above the glovebox under the passenger-side dash grab bar for that reason. Even a few drops of moisture might kill one of these, so they need to be mounted high inside the Jeep behind the dash. The closer to the cowl you can get it, the better off you will be. Much like how our phones have more computing power than the first manned space flight had onboard, comparing today’s fuel injection computers to the ones from 20 years ago is kinda funny as well. This computer is from a Holley self-learning HP EFI TBI system. It is half the size of the other computers, has vibration-reducing feet, and no heat sinks. This shot from the end shows how it is fully potted, and under that blue cap is a mini USB programming plug. The arrow shows the tiny little vent. While I wouldn’t hesitate to dunk this computer, I’d mount it with the vent pointing down. If repeated dunkings are in the future, you might want to mount it inside a Tupperware food container. If you still aren’t sure what you are dealing with, a rule of thumb I’ve been using for years is this: If the plugs that plug into the computer have O-rings or seals (arrows), then it is safe to put it under the hood. If the plugs have no seals, it needs to go inside the Jeep behind the dash as I mentioned earlier. Another thing to mention is that aftermarket fuel-injection computers from those years follow the same basic ideas as what I was talking about, both above and with the O-ring plug thing. I just mention it in case you score a used aftermarket setup and get to wondering. Generally the mid-’90s transitioned to a computer more like this. The computers were sealed with O-rings and/or gaskets, usually got heat sinks to help with cooling, and were most often found under the hood. This is an OBDI Chevy computer, but many of them (even early OBDII) were this size and shape. Jeep computers of this period were about the same size, but had many more vents on them and were painted black. Notice the two small vents this one has for cooling (arrows). If possible, it is best to mount the computer with the vents facing towards the firewall, but leave some breathing room.