Ok, just got through doing a head swap on the V8 Miata, and now the injectors aren't pulsing. I started off with the car @ one mechanic, he ended up moving & couldn't finish it, so I took it to the guys that did the exhaust on it to finish up the head/intake/cam swap on it. Everything is back together, but they can't get the injectors to pulse. They've tracked down every wire, went back to the computer, the signal is coming out, continuity between all injectors, getting power to the injectors, it's just not grounding to open the injectors. Even tried running a ground from the battery to the ground clusters to make sure there was not simply a bad connection there. Anybody got any thoughts on it?
Pics of the swap
http://www.topendfabrication.com/gallery/main.php?g2_itemId=852
Pics of the pimp exhaust
http://www.topendfabrication.com/gallery/main.php?g2_itemId=681
Thanks for your help, I know squat about wiring!!!
Make sure the intake and cylinder head are grounded.
You may have to run a redundant ground wire.
They are grounded. Even ran a wire directly from the battery ground to the intake to insure a ground, no success. 
You got somethin' wired up wrong. Most injector systems are wired up like this: Battery -> fuse -> switch (or relay) -> injector -> computer -> ground. Assuming your computer is OK, you have a break in that circuit. Pull the plug at the computer. Your injector line (ignition on) should read pretty close to battery voltage (12v). If it does, then short that to ground with a clip lead and your injector should squirt/click. If it does, your computer may not be grounded. Sometimes the computers have a separate injector ground connection. If you don't have about 12v at the computer, you have a problem between the battery and the injector or between the injector and the plug for the computer. Or the injector is blown open, but that's pretty unusual. Unless you have low impedance injectors and you tried running them without the ballast resistor pack or something.
The injectors will pulse when you ground them with a lead, tried doing a ground to the computer straight from the battery, and we've got continuity from the injectors all the way to the computer on each plug. I do have 12v at the injectors with the ignition on. I'm stumped 
Does the computer use a separate ground for the injectors? You need a wiring diagram for whatever vehicle the motor/ECU came out of and you need to wire it up just like that. You could run a ground directly to the computer but if you still didn't ground the injector ground, it won't fire, if it's wired up that way.
Yes. It's a Ford 5.0, and grounded to the injector ground. If I had more than 2 hairs left I'd be pulling them out.
Well, then, does the computer think it needs to fire? Are there any codes? Is is OBDII or blinky light or what? Pull the codes and see what they tell you. You may not have a tach signal, for example, or your computer may not fire the injectors if it doesn't see a coil get charged (Toyota's do that). In other words, your injectors may be wired up just fine but you have a problem somewhere else.
So it was running, the heads were removed and reinstalled, now it won't run, right? That means there just about has to be a wiring problem somewhere. 99% of problems like this are a connector that hasn't been plugged in because it can't be seen or it's not fully snapped together. I'd start by going everywhere in the engine compartment and check every connection. Look carefully behind the engine etc.
If that doesn't turn up anything: just about any PCM will ground the injector circuits through the main PCM ground wire, meaning the current flow is actually like this: battery> injector> PCM connector> pulsed ground circuit in PCM (surface mount electronics and microprocessors, not easily tested) > PCM ground terminal > chassis ground. I don't recommend probing the PCM unless you have a logic probe. Using a 12V test light could damage the PCM.
I'm thinking this is a sequential injection system meaning each of the injectors has a separate ground at the PCM. If it's batch fire, then a couple of injectors will share a ground at the PCM. Should be fairly simple to check; if it's batch fire somewhere along the line pairs of injectors will share a PCM pulse through a splice.
I am assuming that you are grounding the injectors with the original wiring supplying 12V to them and you are grounding the leads from the injectors to the PCM? If not, try this: disconnect the PCM connector and the injector connectors and run a continuity test from the injector to the PCM connector. Check them all, repair any open circuits.
If all this checks out and the engine still won't start and you still have no injector pulse, see if you can locate a test PCM.
Thanks guys, that's a couple more places to try than I had before :)
Dr. Hess brought up a good point: is the PCM seeing a reason to start squirting? For instance, sequential FI Fords had to 'see' #1 be ready to run before they would start working, so you could have a dizzy connection bad etc. You see that on other cars as well.
Many moons ago, we had an Isuzu Rodeo towed in that the owner had stuck a boneyard motor in and he could not get it to run. It would run on carb cleaner, though. The PCM was happy as a clam, it said everything was great but it would not run; it had spark but no fuel. To make a long story short, when the owner had swapped motors he cut the two wire wiring harness going to the crank sensor (easier, I guess) and then spliced the wires together but backwards. We wired it properly and it busted right off. Why that kept it from starting but did not set a code is one of the great mysteries of the universe.
Hopefully going to get to try these out this weekend, I know Jason & Shane (my mechanics) are going crazy on it & I feel bad for putting them in the middle of the project, I don't know if it might have been something that Billy did when he started disassembling or just a random fluke thing. Either way they've been great about it, couldn't ask for better guys. I'm just no help whatsoever when it comes to wiring
