Vette Work

"CaptDale - is secretly British" (captdale)
02/18/2020 at 19:56 • Filed to: Corvette, C4, Sparco

Finally getting the Vette back on the road. Replacing the Optispark, water pump, and Hopefully all the bushings if I have time before the rally at the end of the month. Also got these, admittedly worn, Sparco Evo 2 Plus seats for a steal. A little work on the covers till I can replace them made them look much less ratty.

Water Pump

Front of engine and optispark

New seat mounting testing

I still have to figure out exactly how I want the seats mounted.

Turns out my gamble on the opti being a MSD upgrade was wrong. I had assumed since they had installed the MSD ignition box that they would have done the Opti too as that is a common upgrade. I guess not. I’m going to ditch the MSD box as the wiring has been an issue in the past.

DISCUSSION (6)

SBA Thanks You For All The Fish > CaptDale - is secretly British
02/18/2020 at 20:17

What year? I’m just going through my own Opti-Hell

CaptDale - is secretly British > SBA Thanks You For All The Fish
02/18/2020 at 20:41

95 LT1. Not as bad as I thought it was going to be. What is wrong with yours and car?

SBA Thanks You For All The Fish > CaptDale - is secretly British
02/18/2020 at 20:49

It’s a 96 Impala that we put a 96 Grand Sport motor into. I’ve replaced everything fuel, regulator, pump, spark-Opti related. I “think” the Immobilizer is unhappy with something out of the HF signal from the Opti— even though the unit is new and the harness interconnect is new.

Runs 7 seconds. Then dies. No codes, no CEL. Have plenty of spark, but the ECU cuts fuel over sumpin’ it don’t like.

I’m going to have to admit defeat, drag it over to the Chebby dealer and have them Tech-II it when it dies to find out what it’s unhappy about. It’s gotten profoundly annoying— although when I do find it I should be good for another 120K miles, since I’ve replaced everything.

I’ve combed the threads-- 100 different theories, but no proof-of-life. Sux.

Ben > SBA Thanks You For All The Fish
02/18/2020 at 23:22

Doesn’t doesn't the ECM shut off fuel pump pressure after 5 to 7 seconds if it doesn't sensor pressure? Maybe it's the fuel pump sensor and our connection to the ECM.

SBA Thanks You For All The Fish > Ben
02/18/2020 at 23:35

yeah, according to the FSM there’s a whole bunch of stuff that factors in...

I have replaced fuel pump and filter (tank drop required. ugh), and then instrumented both the Fuel Pump Relay (stays ON to the bitter end) and FUEL PRESSURE at the rail (stays UP to spec to the bitter end).

I also see spark from the Opti all the way to the end, but I also see the injectors STOP firing— so I’m 99% sure the PCM decides to pull the plug on something it’s grumpy about. Possibilities:

Oil Pressure— checks out fine
Coolant Temp Sensor apparently— wired a new one into the plug, i s fine
A complicated set of stuff with VATS
I’ve checked the VATS resistor— and it’s fine into the harness

Opti HF signal may be out of spec, but it’s a new Opti and stub harness.

I’m worried that something in the VATS circuit may be fried (all fuses fine), either on the Anti Theft Box or the input to the PCM that needs to confirm signals...

It’s a mystery, but I’m getting sick of this one.

SBA Thanks You For All The Fish > Ben
02/18/2020 at 23:45

I should add that my copy (two copies, actually) of the FSM both omit the chapter with the in-depth discussion on the Immobilizer box and the way it works with VATS. So,that’s annoying.