arvindc

Hi guys,

I have a 1974 Corvette in which I installed a 1994 LT1. I purchased a standalone wiring harness from icsamerica on eBay and had the same company reprogram my PCM.

The PCM reprogramming has EGR delete, smog pump delete, and A/C delete on it, as well as the VATS removed.

Everything is now wired correctly, with the exception of my two oxygen sensors not being hooked up yet. I also installed a new optispark before I dropped the engine in. I have the correct AC Delco fuel pump for 94-96 Corvettes in tank and my fuel pump relay does send signal to the pump.

Upon KEY ON/ENGINE OFF, my fuel pump pressurizes the system at roughly 44 PSI and once the system is pressurized, it drops to around 40 PSI +/-.

So I go to start it up, takes a few cranks but it eventually does catch. It runs for a few seconds, maybe 5-10 seconds, then dies. It doesn't shut off in an instance. It feels more like it's gradually shutting off

I did try cleaning the throttle body and the IAC while on the car. That didn't help.

Any insight is greatly appreciated.

Regards,

Arvin

antfarmer2

hook up the 02s and what does the fuel pressure do when this happens?
keep the optispark!!!!!!!

arvindc

Will the O2 Sensors have a lot to do with fuel pressure?

antfarmer2

no not the pressure but amount.

arvindc

I see. I'll try that over the weekend. Any other possible culprits? I did learn that the donor engine sat for about 6-8 months, not more than a year. It sat inside the car until the car was parted out about a month ago.

antfarmer2

I would ohm the injectors and smell the fpr vacumme hose for fuel for starters.

arvindc

What resistance reading should I be getting from the injectors at this point?

antfarmer2

I believe 12 to 16 but all should be close to one another.

arvindc

Anyone else wanna chime in?

93Rubie

If it runs we can safely rule out any engine mechanical issues. I would focus on fuel/spark for now. Does the fuel pressure drop as its running? Get an inline spark checker and hook it to the coil. Is it loosing spark during this time?

The 02's won't come into play until closed loop ECM operation if it ever goes into it anyway. I don't know what they programmed into the ECM.

Is there anyway for you to hook a scan tool to the ECM? OBDII port in the harness?

pcolt94

The LT1 has a temperature sensor (ECT) in the water pump. On our cars it displays it as a digital temperature reading and the same time that input from the sensor goes to the PCM. It is a major factor for air fuel ratio. If the sensor is not connected to the PCM so the signal can be inputted, the mixture will go extremely rich to the extent the engine will die.

If you do not have this connection if could be you problem as to why it does not continue to run. The ECT connects to C25 of the PCM. You may not need to know the temperature but the PCM does. ECT - Engine Coolant Temperature.

csthews

Sounds like the VATS, but you said it was programmed out. Are you certain of this?

TorchTarga94

If it was the VATS it wouldn't even crank and run.

antfarmer2

pcolt94

Obviously.
And its a 73 and I doubt if he installed a CCM in the installation with the PCM. I sure the 30hz waveform is compensated for.

TorchTarga94

csthews

My '95 does that exact thing on occasion. When it shuts down the security light flashes. I can get it to stay running by moving the key around in the ignition switch, so I assumed it was VATS shutting it down.

TorchTarga94

Even if that was the case, this is a 74' in question. No VATS in the ignition cylinder.

desertmike1

This is a very good Question!