Ok, I've been studying up on all the posts regarding falls-on-its-face-at-3800 rpm.
I suddenly have that problem with my 88 vert. Tonight, I plan to put the ol' fluke on the ECU. I know I should read 12-14V until the secondaries attempt to work. My question is, If the voltage doesn't change..what? If it DOES change and the secondaries don't open..that is likely a wiring problem, right?
I just want to be clear in my head what to expect when reading the joltages.
Thanks!

 

Yeah, you'll see a definite voltage drop the instant those guys "come on line". If you see a drop on one, but not the other, then you have an injector problem (or a broken wiring connection in that one circuit), BUT- your ground is good...

If both injectors show no voltage drop, it gets a bit more complicated, because now you've got to worry about what the boost sensor is doing, and the wiring, and why the ECU isn't doing its thing.

If she runs strong otherwise, it's probably NOT your rotor housing ground, either...But it could be in the harness that runs to that ground. Fun stuff, eh?

 

Actually, the thing has been running really well (recent K Landers TII Conversion and rebuild ) till this happened just lately. I've been using a meter since helping my dad work on TV's for 30+ years, so that's no problem.
Oh yeah, the black wire on the boost sensor reads 1.4 ohms to the battery ground...should I go ahead and run a ground to that? I've read mixed messages on that.
BTW, Kevin installed several grounds while he had it, so I assume that's not an issue.

 

If the meter is perfectly zeroed with the leads shorted, 1.4 ohms ain't perfect, but it ain't bad, either. It also depends on what you're reading through- remember that boost sensor ground makes a run through the ECU first, before it finds its way to an actual chassis ground (probably the rear rotor housing ground) in the OEM wiring scheme of things.

Actually, the "several" grounds that Kevin installed could be the issue. Are they acting as bonding jumpers, or it is feasible that they're acting as current carriers?

 

Ok. looks like I'm on to something. The 2nd wire on the plug reads 14v, then drops to around 8-9 when I get to 3800 and goose it a bit. The 3rd wire (other secondary) reads .6v, then drops to .4.
No joltage on that injector! Am I looking at an ECU, or maybe a ground on that particular injector?

 

First things first- you sure the paper clip, meter lead, or whatever you were using is making contact with the ECU pin, right? I know you sound like you know what you're doing, but sometimes it's a bitch to make good contact with those guys (especially on the bottom pins, and the vibration from driving around), and I don't want to lead you on a "wild goose chase" for nothing...

What's this "second wire on the plug". The bottom second wire, right? Just want to make sure we're on the same page here, lol...

Now, IF the meter's not lying to you, this is probably not an ECU problem. Even if the ECU is not there, you should have voltage down at that pin, key on, and it looks like you don't...And you know your main relay is good, or nothin' would be working. So, we're down to the wiring run between the area that the wiring from the main relay splits into 4 for the injectors, through the injector, and the run to the ECU...I'd guess injector connector at this point, or maybe a fried injector coil...

 

Yep, I'm sure the connection is good. It was the third wire from the left, bottom of the plug.
Also, I tried ohming out the wiring per another thread, using the plug just to the right of the ECU, black and yellow wire. On the working injector(2nd wire), I get around 12, zilch on the 3rd wire.
Can I get to these plugs/wires without pulling the UIM?

 

Title has been corrected... please do not post forum names in the titles. It is against forum rules.

If you want a single persons help or opinion, please PM them.

 

Oops, my bad. Consider my pee pee whacked.

 

I wouldn't think so, heck I can't even see mine with the UIM on, much less get to them...

All right, at least you've got it down to a stretch of wiring, now. I was going to mention that other thread that I posted on, looks like you found it anyway At this point, if I had to make educated guesses, here they are, in decreasing order of likelihood...

1) Bad connector on the injector, or bad connections in the "boot"
2) Bad wiring joint at the point the power supply wire splits into 4 runs (I've heard that these splices are located somewhere around the oil filler tube, inside the harness)
3) Bad injector (coil has opened)