Charlies 86 SE

[Raydar]

We'll try.
All measurements are made with the (-) meter probe connected to ground.
The injectors... One of the pins will have a continuous 12V. The other pin will show 12V except when it's pulsed.
This is measured with the injector plugged in.

If you need to measure just the injector connector (unplugged from the injector)... Again, you will see 12V on one side. The other side will show 0V.
You will need to switch your meter to the ohms setting. Probably the 1K scale. As the ECM pulses, you should see the resistance pulse towards 0. 
As an alternative, you can leave the meter on "volts". And just connect both leads to the injector connector. You should see 12V "pulsed" as the ECM tries to fire the injector.
Keep in mind that you should see exactly the same signals on 1,3, and 5.
You will also see the same on 2,4, and 6.
(I'm told that all 6 fire at the same time, but I think it alternates between banks.)

With all of that said... I would be inclined to unplug one of the other injectors, and swap connectors between the two. For our purposes, it really doesn't matter which one, but one from the same bank is preferable.
The problem should either stay with the injector (which is how we seem to be leaning) or with the connector. If it stays with the connector, the problem is likely in the injector harness.
You or Charlie should have a spare injector harness laying around. It's the large flat connector that's near the MAP sensor and thermostat housing. Has leads that (duh) go to each injector.  It's only about 15" long.

Edit - I forgot about the cold start injector. It's in a circuit by itself, in that harness. (although it may share 12 V.) Ignore it. 

[GTRS Fiero]

The injectors fire in batches, one bank at a time.

[Raydar]

The injectors fire in batches, one bank at a time.

That's really what I thought, but then I'd read some other stuff that seemed to indicate they all fired at once. Thanks.
(One bank at a time would seem to make more sense, but yeah...)

[Fierofool]

You can test the circuit with a test light connected to the ground on the battery and the probe inserted into the positive side of the harness.  You can change the test light clip to the positive terminal and insert it into the ground side and with the engine running you should get a pulsed light.  If there's a good circuit and the exhaust manifold is cold on that cylinder, it has to be the injector. 

Noid light test kits can be rented at the auto parts store to test the circuit, too.  I checked AutoZone and none of them seem to have the test kit but it can be ordered for purchase online.  I also checked Advance but the spybots in my computer sets me as Jefferson and won't let me look at the availability of any other stores. 

[scottb]

thank you Steve and Charlie, I will give it a shot

[Raydar]

You can test the circuit with a test light connected to the ground on the battery and the probe inserted into the positive side of the harness.  You can change the test light clip to the positive terminal and insert it into the ground side and with the engine running you should get a pulsed light.  If there's a good circuit and the exhaust manifold is cold on that cylinder, it has to be the injector. 
...

Yes. If you have a test light, this sounds like the easier/better way.

[Fierofool]

Mike said they ran the circuit test with a multimeter and they had the pulsed signal when on the ground side.  Later, Scott ran some more tests and is again leaning toward the harness.  Mike said that the plan is to take the harness from the other engine and see if that fixes the problem before sending the injectors back to FIC.   

[GTRS Fiero]

Well, the harnesses are 30+ years old.  I found parts of mine were brittle, so cut those pieces out and spliced in new wire.

[Fierofool]

Scott has pulled the injectors and is returning them to FIC to be corrected. 

As he pulled them, I asked that he give me the numbers from the refurbished 3.1 injectors and the original 2.8 engine injectors.  Turns out they are the same injectors.  I wanted to be sure that the injectors were large enough to support the engine.  The stock 2.8 injectors flow 14.65 lb/hr and with just a few more HP , they are maxed out and would run lean. 

With the 2.8 rated at 140 hp and the 3.4 rated at 160, I have been assuming that the 3.1, being exactly in the middle of the 2.8 and 3.1 would also have HP in the middle.  About 150.  Man, was I wrong.  The early 3.1 engines only had 120 HP.  Various applications accomplished 129 HP.  Even the Beretta GTZ initially had only 135 HP.  It wasn't until the later years that the Generation II LHO or T Series 3.1 developed 140 HP. 

Since I have a T Series engine, developing 140 HP, same as the Fiero 2.8, We're satisfied that the injectors are sized correctly for the engine. 

[GTRS Fiero]

I went back and looked at my April newsletter.  The 3.1 T transverse V6 had the following specs:

Size	RPO “VIN”	Years	Lbs.	Orient	HP	TQ	Disp.	Comp.	Bore	Stroke	Fuel Delivery
3.1 CIB	LH0 “T”	'88-'96	340	T	140	180	192	8.9:1	89	84	MPFI

Looking at the numbers, Pontiac did make some effort to make the Fiero V6 have some power.

[scottb]

You forgot to mention that I changed the injector wiring harness first, but that resulted in no change in the way the engine was running.

I also threw a couple more injectors into the bag in case the bad one cannot be fixed.

[GTRS Fiero]

Were these injectors from this engine, or the previous one?

This would seem to be the 3rd engine in this Fiero.

[scottb]

The failed injector was on the the 3.1 orginally...... I dont think it matters though, they are the same on both engines

[GTRS Fiero]

I'm just wondering if the injectors from the 2.8 would work.

[scottb]

As I said they are the same, same numbers on both sets. And both the 2.8 and 3.1 are rated at the same horsepower.  Only reason not to use the original 2.8 injectors is the fact that we don't know the mileage on them and how much dirt has built up restricting the flow. Besides, the rebuilder should stand behind his work and make it right