Stick a phillips head screw driver into one of your existing wires, then hold the shaft 3/4" away from a ground point....crank it. (Or have someone crank it).

Or use an old wire if you have one, like you said.

Once you confirm a good spark, you could pull the fuses for the injectors, crank it to clear cylinders then try starting it (injector fuses still pulled.

You don't have to have gasoline shooting from the cylinders for it to be flooded; cylinders that HAVE been that flooded, that have a wet piston top, cylinder walls, combustion chamber, valve etc. all that coated w/gasoline is "too rich" to already, so if the injectors are also firing "normally" for a normal cold start...that is probably just way too much gasoline in the cylinder. It will likely remain flooded and may not start. SO, if you can confirm good spark, I would blow out the cylinders one more time, install the plugs (dried w/brake cleaner or something -a propane torch maybe), then try to start it w/the injectors unplugged. If it fired, I'd "milk it" for all it's worth to try to burn as much gasoline out as possible, then install the fuses and try again.

The plugs should be wet, if you cranked the engine w/no ignition. Probably not "soaked" as in raw gasoline filling the area between the porcelain and the ID of the threads, but certainly damp. If running correctly, a pulled plug should be bone dry....chalky even.

 

https://www.corvetteforum.com/forums...t-is-this.html

 

I already changed the FPR-

 

I tested the spark with a piece of 14 gauge primary wire to the distributor cap & the spark jumped an easy 1/2" gap between the wire and grounded jumper cable end.

Then I cleaned the spark plugs with brake cleaner, blew them out with compressed air and reinstalled.

Pulled the injector fuses and the individual injector plugs and it started right up.

It ran for about 10 seaconds, ran out of fuel and then quit.

I installed the injector fuses and connectors and tried to start it but it would not fire.

just pulled the plugs and they were all wet.

I need to go look at the fuel pressure again...

 

That was the 1st thing I did - jumpered A to G and all I got was a 74 code.

Gut feeling is that the ECM is doing weird stuff because it didn't do the 12, 12, 12 in the beginning and with full support from the manuf we could not get the ECM to communicate with the scanner.

 

Without the 12 code repeated 3 times at the beginning , the ECM is saying it's not happy as you probably know. Could be ECM or power to ECM.

So strange your initial issue was a bad coil and all these other issues you've found. Almost as if you were hit by a strong EMP (electromagnetic pulse) - any chance you were by an industrial or military site when things went awry? Seriously, I've never heard of an EMP taking out a car - but law enforcement was working on a device to do just this to stop criminals in their get away cars.

Keep diagnosing, so frustrating we know. You must be charging up your battery in-between bouts of cranking.

 

By the way, this pic:




looks like someone may have stripped the wires to make a measurement in the past - meaning that you may be on a path that someone else once went down. When I used to take my car in (before I learned myself), these are the type of nicks Bubba made to make in-place diagnostic measurements.

 

I agree on the FP test again. Wow, this car is challenging you.

Ran for 10 seconds on the gas in the cylinders only. That is longer than even I would have thought.

 

Yeah, the way it died was very much like a binary failure, just dead right NOW.

I have but will check again all fuses for ECM power, and will try jumpering the A > G to see if I can get a code. I don't think that I will, but will give it a go since finding the short.

But not being able to communicate with the scanner is another telltale sign that something is amiss. The tech & I spent 30 minutes entering vehicle VIN ID codes, trying to match the scanner to the computer but none of their guidance worked.

They said the only one who might be better able to communicate with it is a Chevy dealer, and I talked to one today. If I do end up having it towed there I will have to write a full script for the tech to read so they don't waste my $$$ looking at known good parts....

And I've kept a smart battery charger hooked to the car for the last 5 days.

 

Sorry, I wasn't being clear.

I would not proceed without first getting 1 and 2 flashing 3 times from the ECM.

At least now you have a first step !

 

I spent some more time reading the FSM and learned that I was performing the ECM Diagnostic incorrectly, so I will be running that test this morning with the correct connector pins connected ( A & B ).

I will also be hooking up my fuel pressure gauge to see what I can see.

 

With the A >B Diagnostic jumper installed, all I get is 12, 12, 12, then repeats, meaning no faults according to the FSM.

 

That is much better. The "code 74" made no sense to me.

12 - 12 - 12 sounds promising.

Have you been able to do the FP test again?

 

Ok guys, here is what is happening with the Fuel Pressure, the injectors-

Ignition - ON

- with the injectors plugged in AND the injector fuses IN, fuel pressure rises and then after the initial 2 seconds, it bleeds off to zero.

- with the fuses IN and ALL injectors unplugged, fuel pressure rises to 44 psi & then maintains 40 psi after the 2 seconds.

- with the fuses In and ANY injector then plugged In the fuel pressure will bleed off through that injector. As fuel pressure is decreasing, you can UNPLUG the injector and the fuel pressure will stop decreasing/maintain pressure.

what I know-

With no power to the injectors, fuel pressure climbs to 44 psi and then maintains 40 psi. This means that the new fuel pump, the fuel pressure regulator and all other fuel system valves/components are good, maintaining pressure as required.

As soon as ANY injector is connected to power, it is being commanded to open and is injecting fuel into it's cylinder. This is flooding the cylinders and killing the engine any time the key is on.

After the initial fuel pressure rise and bleed off, there is zero fuel pressure when the engine is cranking. I believe that the injectors are fully open and continuing to flood the cylinders when they should not.

We also know this-

- the injectors are no longer grounded by the splice short that I repaired.

- the ECM is NOT throwing any codes other than the normal 12, 12, 12 diagnostic.

- I am unable to connect to the ECM with my new Innova 3120D OBD 1 & 2 Scanner with the help of Innova tech support.

- the ignition is all new (cap, rotor, coil, wires, plugs) and is throwing a good 1/2'- 3/4' spark

So here are my conclusions-

- with the key ON, the injectors are being told by the ECM to open and the engine is being flooded.

- we do not know if the ECM is flooding the engine because of a faulty input

- if I understand the system correctly, the ECM should onlt trigger an injector to open at the appropriate time as the engine runs ie as timed. Never should all the injectors open simultaneously.

Again I am faced with a decision-

Replace the ECM, move the eprom to the new ECM and see if that fixes it-

or

Take it to the Chevy dealer down the street and see if their techs can read the ECM and other systems with their factory equipment, identify and repair the problem.

So what say you?

 

If it were me, I would do neither of your two options....yet.


1. I'm not sure that we are sure that the ECM is triggering the injectors. You did a good repair job to the harness...but did we re-test to ground for another short? Or did we assume that the short found is all the shorts? I would re-run the FP test, like you did (great testing, BTW) but w/the ECM totally unplugged from the harness. To run the fuel pump, you can jumper the fuel pump relay.

2. Probably not, b/c there is no input that I know of that would trigger the ECM to 100% duty cycle the injectors. IOW, I can't think of a sensor/input that would cause this; it's either the ECM doing it, or (another) short to ground in the harness.

3. I THINK on TPI, it fires one side, then the other, then the first and so on, based on inputs from the pick up coil in the distributor. Some systems fire both "sides" at the same time (GM TBI after CFI) but I don't think the TPI does -I believe it fires them alternately. So you are right, nothing should command them to fire at the same time and certainly, nothing at 100% on time.

Couple things you can do here:
1. RE-run the FP test w/the ECM unhooked. Same results? Another short in the harness.
2. Just ohm the harness, ECM plugged in and unplugged. Short unplugged = another short in the harness
3. Ohm the pins in the ECM that ground the injectors. If they're Grounded 100% of the time, that doesn't bode well for the ECM.

I'd want to test the whole system again though if it were me; I'd test the injector harness to ground, and run the FP test un plugged, as I'd want to "see for myself" what is going on, before replacing the ECM.

 

Good points-

I will go do the tests.

With the ECM disconnected there should be no power to the injectors. If there is then an outside short is opening them.

I will check the injector harness again for shorts to ground. I did that after the repair but will check it again with the ECM disconnected.

And I will check the FP with the ECM disconnected.

 

Incorrect. Remember; the injectors get their power from:
Battery > Ignition switch > Injector fuses >Injectors.

ECM is completely out of the loop on POWER for the injectors. It doesn't supply the power, it doesn't "know" if there is power. All it does is ground the injectors to turn them on.

Looking forward to hearing what you find next...

 

OK, here's what I found-

With the battery connected or disconnected, key on, all injector ground wires (Blue & Green) are OPEN - infinity

Same thing with the battery disconnected and the ECM unplugged.

With the ECM pulled in or unplugged, the pink/black injector wires are showing 8 ohms at every injector, and this with the battery connected or disconnected completely.

With the battery connected, ECM disconnected anf the Key ON, fuel pressure zero - the pump never comes on.

 

Also, I pulled the injector fuses and checked the injector connector pins to ground and both wires show open/infinity.

This means both wires are NOT shorted to ground between the engine compartment and the fuse panel.

It also means that somewhere between the fuse panel and the ECM connectors something else is tied into the power circuit and the ohmmeter makes it's way through that item to IT'S ground- could be a bulb or the 12v feed.

And none of the injector wires are shorted together.

 

Also-

With the ECM connected or not, there is 12V at the injectors as you said.