fuel, spark, good injectors... wont start (runs with carb cleaner)

So do you have power to the injector wire that is supposed to have power at the injectors with the key in the run position?

With all injectors disconnected and key on, there is 2-3v on one side of each connector. As soon as I connect ANY 1 injector back to its connector, there is no power at any remaining open connector.

Alright theres the problem the pink wire with a black stripe should have battery voltage with the key in the run position.Its power from the inj fuse.

I am amazed how quickly I received a response - this forum is great! thank you.

So do you mean there is a short between the fuse and the injectors? Would this include possibly the injector control module? I am somewhat confused - I thought the injector connection should read battery voltage only when the pulse signal is sent.

No here is how it works you get battery voltage from the inj fuse on the pink wires with a black stripe.That power comes straight from fuse.The injector is plused and control by the ground side of the injector circuit.That would be the light blue wires going to the injectors.Then those wires change to a dark blue color and go back to the ecm/electronic control module.That is what controls the injector pluse.Lets start by seeing what the voltage is at the inj fuse in the fuse box with the key in the run position?Also make sure the battery is fully charged.Check both sides of the fuse.It could be a crossion in the fuse box causing a bad connection even.

12v at battery, no reading at injector fuse. fuse block in general is getting power (i.e. fuel pump fuse reads 12v). I do have all the injector connectors and connectors that attach to anything related to the plenum detached, as I pulled the plenum. Do these need reconnected to get a reading?

Take that back. About .5v at the fuse (I didn't have a good ground on the tester 1st time).

Then your problem is at the fuse box then.Was that 5 volts at the fuse?

In the group of the small 2 prong fuses, where 2 are labeled something to do with injectors, there is only 0.5v on both sides of each fuse. In the other half of the fuse box, where there are larger 5 prong fuses, such as for the fuel pump, there is 12v.

Also check your crank shaft sensor conecter. That crank shaft sensor controls the pulse to your injecters. And it is common on the 3.1, 3.4, & 3.8 for the conecter to be bad. You can but it at any local part store. Part # PT5666.

I've heard there are 2 sensors. Is this the one on the back of the motor by the firewall, or the one behind the crank pully?

Heres the problem with that theroy the injectors are controled by the ground side of the injector circuit thru the ecm.So no matter what you should still have 12 volts to the wires i told you with the key in the run position.With the 5 pins those are relays not fuses.

Also bad crankshaft sensor no spark they have spark.

Shpould be fuse number 7 in the diagram in the passenger side under hood fuse box.When you think you found the correct fuse pull the fuse out and see if there is no voltage going to the injectors anymore.That way you will know you found the correct fuse.I also posted part of the wire diagram so you can see how the battery voltage runs from the fuse to the injectors.

I started by reconnecting all the electrical connectors I had pulled to remove the plenum. Now the only things disconnected are all injectors. Now I have 12v at the injector fuse. I have 2.5 volts at every injector connector UNLESS I plug any 1 injector connector back in, then the remaining injector connectors have 0v. Thank you for the all the help - this one really has me stumped!

Your going to have to start out by seeing if there is 12 volts coming out of the fuse box.If not the problem is somewhere in the fuse box area.Open terminal loose connection etc.

1. I HAD 12v at the fuse, but upon disconnecting then reconnecting the wiring harness (2 connectors) I have between 0v and 0.5v at the fuse. This leads me to believe there is a bad connector.
2. HOWEVER, regardless of the above, I have 12v on the pink/black wire coming out of the harness connector that runs directly to the injectors (the same connector I've been messing with that seems to have affected the fuse voltage).
3. At the injector, still about 2.5v and 0v if any one of them is plugged in.

Oh, and I took an ohmmeter and checked for continuity between the pink/black wire end of the harness (male connector) and each injector at the power side. It was good at each one.

That really makes no sense because as you can see the power wire to the fuel injectors gets its power thru the fuse and then too the unjectors.Look at the wire diagram i posted you see where the power wires split off from the main power feed wire?I would find that connection point and see what you can find for power there?It could be all corroded up or loose etc?

I know I am looking for 12v to flow to the pink/black side of each connector and will chase that wire. But I am confused why it drops from 2.5v to 0v when any 1 connector is plugged in. Are there 2 problems here? Also, what is the black box on the fender well right next to the fuse box, approx 4x6 inches with 2 large harness connectors going in? Is that involved in this circuit?

Its on the passenger side and has relays in it?If so there is your cooling fan relays primary and then the secondary boxes and then the ac comoressor relays they have nothing to do with the injectors.What would cause the injector wire to be 12 volts then drop down like that could be high resistance like corroded terminals etc.Its all the same problem you just have to find the reason for the voltage drop.Let me know what you find.

Now I feel stupid. After unwrapping the wiring harnesses and chasing pink/black wires around, I found I did not have a good ground with my test meter. So... I have 12v at the fuse (constantly), AND, 12v at each injector (the pink/black side). So back to square one...

Dont feel bad everyone has there bad days.Sonwhat problem are you having?

Was running fine. After shut off 30 min later cranks but wont start. Has good spark. Has good fuel pressure, HAS 12v at each injector wire key on. Did run with carb cleaner sprayed into air intake. Pulled plenum ohm'd all injectors are between 1.5-2 ohms.

All the injectors arent going to fail at the same time i would have checked for unjector pluse first.Which you said you have checked for that and its not there.Do you have a led computer safe test light?

If you mean a Noid light I can borrow one from Auto Zone. When I did that before dismantling I had no light at key on and no light at cranking. but now that I've found 12v at the wire at key on the previous light test response doesnt make sense. I have also been told by a couple people that the GM 3.1 and 3.8 in that year have a problem where if one injector grounds out, they all ground out due to the way they are wired. Would you agree? If so, how can you test that as the plenum has to pulled to get to them all?

There is two sides to your circuit a constant power and a plusing ground.You know we have power now we need to check for a plusing ground from the computer.If the wires were grounded out the noid light would stay on solid when turning the key on.You need a computer safe test light to check the ground side of the circuit while cranking for a plusing ground.

ok. assuming you are not talking about the noid light, how do i connect the test light?

The aligator clip to the positive battery post then the test light point to the non power feed to the injector connector.Then crank the light should flash check all the connectors.The noid lights tests the circuit as a hole working.This will just test the ground pluse side of the circuit.

Finally got a test light. Connected as you say and no light when cranking. Also checked ohms, neg side of connector to engine block, and got full continuity reading.

You shouldnt have a constant ground to the non power wire if you did the injectors would stay open and flood the engine with gas.Also when you checked it with the noid light it would have had the noid light on constantly with the key in the run position.Which you said it didnt.

Correct on the noid light. So you are expecting no continuity to the no power side? I am so confused - the manager at the auto store that loaned me the light suggested checking continuity and that it should be present. Maybe he was thinking the power side. FYI all injectors are still disconnected.

Yeah the computer controls the ground and pluses it shouldnt have a constant ground.That noid light should be on if there is power and ground.

So am I chasing a wiring problem or is this pointing to the computer?

Thank you for all your attention to this!

If it was the computer, would it still run with carb cleaner?

Your welcome thats what were here for measure the voltage across the injector harness with the key in the run position.Let me know what you find.

3v across hot lead and the no power lead. Same reading at all 6 connectors.

So just the power feed side to negative side of the battery reads battery voltage?

Yes. 12v