Here's the previous thread.
https://www.thirdgen.org/techbb2/sho...hreadid=328911

I got a sheet from Trickster a long time ago that outlines an "Engine Cranks But Will Not Run" situation. On it, it says to:
1) Disconnect all injectors.
2) Ignition "on"
3) Probe one injector harness on each side of the motor with a test light connected to ground. (That's the short of it.) There should be no light. If light is "on", repair short to voltage.
4) If OK, check the resistance of the injectors.
5) Should be 10 ohms or more.
6) Check injector harness connector. Be sure terminals are not backed out of connector and contacting each other.
7) If all OK, replace ECM.

I have a short to voltage. When I probe, I am getting a light on both harnesses. I have a few questions if anyone would be so kind as to point me in the right direction.

1) Does anyone know exactly where I should start looking?
2) What exactly is the injector harness connector? Is it the harness that plugs into the ECM?
3) Are there any other connectors or points of contact along this circuit that I should check?

Thanks in advance! Looks like I'll be spending the rest of my week tracing this booger down.

 

I read your original post, sounds like something is leaking. First thing I would do is a fuel pressure test. I copied this off a message board a year or so ago, can't remember where, it may help.


1.Install a fuel pressure gage on the schraeder valve.

2.Pressurize the system by cycling the key on for a few seconds.

3.Turn the key off, and time the pressure reduction on the gage. Initial pressure should be approx. 40 PSI,
note the time it takes for a 20 psi. pressure drop. If the time exceeds 20 min, check valve, regulator,
and fuel injectors are free of excessive leakage.

4. If the system pressure is reduced by 20 psi. or more in 20 min. or less then one or more of the aforementioned are
suspect.

5.Turn the key on for a few seconds to repressurize the system and clamp the rubber portion of the supply line
using a pair of vise grips.

6. Turn the key off, and again note the time it takes for a 20 psi reduction of pressure. If the time is a lot
longer than noted in step 3. then replacement of the fuel pump is indicated. Could also be a torn diaphram in the pulsator valve.

7. If the times are similiar, then repeat steps 5 and 6, only this time clamp the return line instead of the supply.
Again note the time it takes for a 20 psi drop. If the time is a lot longer than noted in step 3, then the fuel regulator
needs to be replaced. If the time remains shorter than 20 min, leaking injectors are suspected. To confirm that the
injectors are leaking, raise the fuel rail slightly out of the manifold without disconnecting any fuel lines and place a
small napkin or piece of paper under each injector. Pressurize the system again, then turn the key off and allow to sit
for about 10 minutes. If a leaking injector is indicated by the fuel on the paper, replace all 8 injectors

 

Thanks, man. I'll go about doing that as soon as I get this short figured out.
I believe the only thing it could be according to your post is maybe the check valve or leaky injectors.
On the bright side, I've almost got a 100% brand new car again. Been diagnosing and replacing parts for a couple years now.

 

I think you interpeted something wrong.
The injectors have power to them always, The wire from the injector (banks) to the ECM will also have power on it.
The ECM grounds the wire to make current flow and fire the injector.
If you simply probe the wires both sides should light your test light if the light is grounded.
A "noid" light is what you need. It takes the place of an injector just to indicate the ECM is in fact "grounding" the wire to fire the injectors.
By having power on both sides of the noid light (No ground) the current can't flow so the light will not come on.
When one side is grounded, it will light up just like an injector firing.
HTH

Edit: Put your test light in series.
Wire from one injector connector to the test light (the powered wire)
Connect the ground of the test light to the other pin in the connector(should be the wire to the ECM)
That will be the same as "noid" light.

 

Also, when testing your injector wiring, make sure that you unplug all of the other injectors on that bank as well.

The injectors have little electromagnets, which are basically just a peice of wire wrapped around inside of the relay a bunch of times.

So, if you leave them plugged in, both terminals on the plug will read 12 volts.

The best way to test your injectors is with a noid light, as mentioned. You can rent them from most parts houses, usually for free. If you don't wanna bother, just get an old dash light (one of those ones you slide in) and a socket for one from an old marker light or something, and just hook that up, it'll work just as well.

Just watch to make sure that both banks are pulsing when the ECM detects a distributer reference pulse, and not that it is staying on constantly, or not coming on at all.

If it is staying on all the time, then you've probally got a short in the wiring as you are thinking, if it doesn't come on at all, I'd be suspecting the ignition module from the dizzy.

The injector harness is comprised of 4 wires. 2 for each bank of injectors. One of those wires goes to a source of power that is either on all the time, or is on both when the ignition is on, and the engine is cranking. the second wire goes to the ECM, and is the ground wire.

Once the wires reach the intake, each one is split into 4 different wires, for a total of 8, which makes 4 injector connectors.

To test the harness, unplug the harness from each injector, check for continuity between both poles of the injector connectors. If there is no continuity, your harness should be fine. Also, check to make sure that one pole on each connector is hot when you go between the poles and ground, the other should have no continuity between the pole and ground

If that all checks out, then check to make sure that the ignition module, and TPS. If those things are all good, then look into it possibly being a burnt out injector driver in the ECM. However, do that as a last attempt, as they don't regularly burn out as far as I am aware...

 

That's exactly what's happening. According to the sheet I posted about, it just says that if I get a light, then there's a short. By what you just described though, the harness should be in good shape. One pole lights, the other one doesn't. Apparently, the sheet I have doesn't get as in depth as it should.
I have used a noid light on them and they blink like they should. I would do the continuity test, but if there were continuity between poles, I should be getting a light at both poles, right?
I've swapped in another ECM and had the same results, so that theory's ruled out. I've also tested the injectors by holding the fuel rail up while the key was on and none of the drip whatsoever.
The only part of the fuel system that hasn't been replaced is the check valve. I'll do the fuel line pinch test this afternoon to test it out. The entire ignition system has been recently rebuilt as well with all new components and it's working fine.
I'm getting spark, fuel, and air. It fires right up after the first turn of the starter, then runs for about 10-15 seconds, then dies if I don't keep my foot on the gas. I just can't figure out why the car keeps doing this. Every once in a blue moon (every few months), it'll start right up and run just fine.