916spd

I have a 94 base 6sp
it just shuts off and won't restart
Dies like you shut it off
Spray a little starting fluid while it won't start and it fires up, once fluid is burned it dies again.

New parts installed
Opti
I'm

FAUEE

Security light blinking? It sounds like either vats, your ignition coil, or your I'm.

Google for shbox's lt1 no start troubleshooting guide. It will help a lot.

pcolt94

If it cranks and starts, or just cranks and does not start it is not VATS. VATS will not cause an engine to stop for any reason at all.

"I'm"……….I guess you actually mean ICM.
It could be a bad fuel pump and poor fuel pressure.
Possible ICM problem temperature related but probably not if it starts with starting fluid.

What you need here is actual data. Measuring fuel pressure would be good too and that requires a pressure gauge. Checking for good spark would be good to know also.

FYI
If you have a aftermarket ICM they are not as good as the GM ones. Regardless, just cause it's new doesn't matter, anything could be defective.

Don’t be guessing, get some real data to start with rather than thro parts at it and work in the dark.

MatthewMiller

This is a great reply, very on target. I agree that if the car will run on starting fluid then it is not a problem with ignition/spark, but rather fuel.

PatternDayTrader

If it runs on starting fluid then you have a fuel delivery problem.
Start by testing fuel pressure. Its probably zero.

Tom400CFI

X4. The diagnostic path seems pretty clear.

FAUEE

This is NOT correct. If the starter kill portion of vats is disabled (commonly done), the second stage that keeps the injectors from firing CAN AND WILL still keep it from starting. The car will crank endlessly, sometimes nearly start (even on starter fluid) but notbrun because Injectors are not turned on.

I chased intermittent no start issues for years, replaced the whole fuel and ignition system, and finally realized the issue was the ecm portion of vats.

Tom400CFI

But the car won't start when VATS is intervening and the start enable relay has been jumped. The OP said: "it just shuts off and won't restart
Dies like you shut it off"

TO me, that implies that it started and ran normally for a period of time...which VATS wouldn't allow. But...it's not totally clear either. OP could provide a little more detail, helping us to help him.

pcolt94

In the strict troubleshooting and engineering world you are correct.

This is the basic operating parameters of VATS for people who need an basic understanding of how things work. There are always ands, ifs and buts and exceptions to the rule. Other things can always go wrong that don’t conform to the norm. But if you explain every left field diversion to a person who might have a limited knowledge of system, electronics , mechanics, signal flow and digital systems it would get so complicated the actual focus on learning and presenting a concept could be lost.

Aside from that, most PCMs don’t have the screwy problems you described that ECMs have.

dizwiz24

Tom400CFI

How are you coming to that conclusion with no test data to indicate anything like that...and the OP said this:If the opti don't work...car don't start on ether or any fuel.

FAUEE

It doesn't sound like an opti to me. To really know, we need more info. Does it run, you key it off, and it IMMEDIATELY will not restart? Does it take 5 minutes? Does it cut out while running and not restart? If it doesn't start and you wait 15 minutes, does that make a difference?

When it won' restart, does it crank or does it just not even crank? Engines require 3 main things, air, gas, spark. Air is easy to get. Spark is relatively easy to test for, as is fuel. Finding WHY you'e not getting one is the trick, but you need to know what you'e looking for first.

916spd

Security light seems to be fine. Blinks when it should. New I'm coil tests fine. But it wouldn't fire with starting fluid if those were out. I thought maybe oil pressure sensor since it ties into the fuel pump?

916spd

Ignition control module is new. @#$king spell check.
im at a loss with this one

MatthewMiller

The ICM can certainly work properly cold and fail when it gets hot (and they do get hot quickly). But I agree, if the car will run on starting then I don't see how it could be the ICM or any other ignition-related issue. Get it into failure mode and then check fuel pressure, and put a noid light on one of the injectors to ensure it's getting a signal to cycle when you crank it.

Tom400CFI

Check fuel pressure when the symptom occurs.


Oil pressure switch is a redundant back up power supply to the fuel pump...so if that failed it wouldn't affect anything if the fuel pump relay still works.

FAUEE

Does the car still die after the starting fluid burns off?

What happens if you try to start it with the pedal to tje floor (flooded engine mode)?

If you unplug the Icm does it react or sound any different?

Kevova

Carry what I call a no start kit : Noid light, spark tester, fuel pressure gauge, and DVOM.
VATS is only in play at start up. It is the only time key is read is when cylinder is turned to "start". When it quits install fuel pressure gauge and noid light see what is not right. If injector wont blink. You will need to check opti although it should set code if it fails. There should be 12v on term C yellow wire and term D black ?pink wire is ground on pcm side of opti harness. On opti side terminal D should not have continuity to ground.

916spd

Car dies after starting fluid burns off. I will try the other tests this morning. Problem is sometimes it can go 100 miles or sometimes 100 feet before it happens. Ignition control module is new. Tried three different ones.

Thank you all and I will update this afternoon on progress

916spd

Okay so car started fine. Let it warm up in my driveway. It died check and relay is clicking and fuses fp1 fp2 lose power. Cooled down for a couple hours then fires back up and fuses show power.