1987 C4 Corvette crank, no-start

I'm diagnosing a crank, no-start on an '87 C4 Corvette.
The car has been stood many years and was bought incomplete as a project.
The previous owner had never managed to get it running.
I was told that someone had looked at it previously, replaced the missing distributor cap/coil and rotor arm. They had left a jumper wire from the coil frame to the engine block. Still being a no-start they determined it to be a VATS problem.
I went equipped with everything I would need to bypass the key resistor and even a 30Hz signal generator I made up for the purpose.
However the problem was nothing to do with VATS at all.
I had good spark and also injector pulses.
I checked for fuel pressure and there was none.
The fuel pump was replaced , I now had KOEO prime and obtained 45psi once I had cleaned the fuel pump fuse and obtained good voltage under load at the pump.
Cranked the engine, it attempted to start.
Feeling around the headers I found only Cyl 3 and 5 had fired.
Checked the firing order and found 3 leads transposed.
Now I had all Bank 1 firing but none of Bank 2.
I checked the condition of the plugs on Bank 2, they were black but not wet.
I checked for corrosion on the Inj 2 fuse, it was quite bad so fitted a new fuse.
The jumper wire previously left was because the metal strip connecting the HEI coil frame to the centre pin (ground) of the 3-pin inner connector was missing.

Here's where I'm confused.
Next time I turned the key on, the cooling fan started up and after the first pulse of the check engine light it was flashing 12 then 11 alternately. I had not jumpered A and B on the ALDL.

I've checked for short to ground on ALDL pin B, which is clear, OL Megohms with the computer disconnected and 5.0V KOEO.

I checked all other circuits and found 4.95V on the TPS signal line.
The TPS had an internal short (33 Ohms) between 5V Ref and the signal line.
I substituted a test potentiometer to achieve 0.54V on the TPS signal line but no matter what I do now, the computer is stuck in a loop flashing codes 12 and 11.
I can't find any reference to code 11.

Also I now have no injector pulse, I can understand that with 5V on the TPS line for clear flood crank, but still nothing when I give it 0.54V.

Because I did origially have injector pulse, it leads me to believe the TPS failed while the engine just-about ran.

I've checked for shorted injectors (resistance only) and I'm getting about 4.5 Ohms each bank between the fuse and the ECU pin.

Is the computer dead?

The scan tool I have access to has a GM 12-pin ALDL adapter but only has European software.
I'm trying to obtain a scan tool with suitable software for my next visit.

Any advice please?

Simon.

Hey Simon! Welcome to the forums.

The flash codes are weird... Code 12 is supposed to be 'No problems', but I can't find any reference for Code 11, either. As a test of the ECM, you could try unplugging another 5V reference sensor and see if you get a new code. Or, short across the ECT sensor terminals. Both sensors have specific high/low circuit codes, so the ECM *should* notice immediately.

I see that you now have no injection pulse at all, but do you still have spark? Lacking both would potentially suggest a new input problem. Nice find with the TPS short, by the way

For my information, does this have a MAF or MAP? Or both? The BBB Industries diagram says MAF, but I think it's lying. Last C4 I saw was a '91, MAP with no MAF.

Hi Tyler,
It is the TPI system with MAF.

The HEI ignition system is self contained within the distributor so as long as those components are good there will be a spark.
The ignition module within sends a reference signal to the ECU which it uses to determine RPM. The ECU sends back a timing control signal for the timing advance, which the module will use as long as it has a 5V signal on the bypass line.
Even with no ECU installed, you will still get a spark which will be at the base 6°BTDC if the distributor is correctly aligned.

I doubt I will get any code for another sensor - in theory I should have expected something for the TPS line being pegged over 4.5V

The diagram I have is from Bentley Publishers and completely matches the vehicle.

Simon.