92 vette no start problem

[corvettegraveyard]

I have a 92 vette six spped has been sittting, just did some open heart surgery blew a head gasket 18months ago .....block is oem. I now have a no start problem. I tried the vats bypass solder in resistors... no luck the car will crank all day long I can hear the fuel pump turn on to, But She will start once in a while only. I believe since I get a crank, and fuel pump that vats is working? What can cause this no start. I think it is the optispark it is only two years old?? I have some car knowledge I am a dealer/mechanic ?

[gsdave]

Have you verified fuel pressure at the fuel rail and spark?

[gmjunkie]

Originally Posted by gsdave

Have you verified fuel pressure at the fuel rail and spark?

LT1 and LT4's will with you if the fuel pressure is low!! Need at least 42-47 lb at key up!!

[corvettegraveyard]

fuel pressure 45 psi , fuel is in good shape?

[CorvetteJohn]

A non codeing intermittent TPS is a possibility. It sounds like the ECM is being given a message that the engine is flooded and needs to crank without actually delivering fuel to the injectors. The other possibility is that with all the work to remove and repair the head gasket one of the wires to a sensor has become broken. I have found the TPS plug wires to be brittle because they are so small and also I have had them broken off inside the plug.

Hope this sheds some light on the tps for you
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Throttle Position Sensor (TPS)
Copied from 1993 Service Manual
The Throttle Position sensor (TPS) is a potentiometer connected to the throttle shaft on the throttle body. It is a potentiometer with one end connected to 5 volts
from the ECM and the other to ECM ground. A third wire is connected to the ECM to measure the voltage from the TP sensor. As the throttle valve angle is changed (accelerator pedal moved), the voltage output of the TP sensor also changes. At a closed throttle position, the voltage output of the TP sensor is low (approximately .5 volt). As the throttle valve opens, the output voltage should be approximately 5 volts.

By monitoring the output voltage from the TP sensor, the ECM can determine fuel delivery based on throttle valve angle (driver demand). A broken or loose TP sensor can cause intermittent burst of fuel from the injectors and cause an unstable idle, because the ECM detects the throttle is moving.

If the TP sensor circuit is open, the ECM will set a DTC 22. If the TP sensor circuit is shorted a DTC 21 will be set. A problem in any of the TP sensor circuits will set either a DTC 21 or 22. Once a DTC is set, the ECM will use a default value for TP sensor, and some vehicle performance will return.

A personal note, when my TPS failed it DID NOT set a code other than to tell me the ECM was bad.

I used a couple of straight pins through the wires to hook the meter on

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[corvettegraveyard]

So far we believe that it is the opti spark? My guy ohmed it out and it is at fault. Will be reinstalling a new one soon.

[CorvetteJohn]

You might look at the electrical connector on top of the opti to see if it is corroded it will give the same symptom for the opti.

[corvettegraveyard]

the opti was two years old but , i think it got wet when i had the heads/ waterpump, freeze plugs done. my shop mechanic is just charging parts? So far up to two hundred dollars

[shakedown067]

They make a Vent kit for the older style opti's. While you are at it, I'd highly suggest looking into doing that mod.