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Discussion Starter #1
Ok so at first car started died while driving and wouldn't start,didn't hear the fuel pump so I replaced fired right up ...I let it idle for about 5minutes hit the gas and died ..and did not want to start. Next day started died after 3 minutes got tired of it sent it to the shop they did diagnostic said it was the distributor aka opti spark had it replaced picked it up today drove about 15 miles died pulled over started up again then died 30 seconds later waited 10 minutes started right up drove to o'rileys they said my battery was bad so bought a new one died again twice later on then drove it about 10 miles home and it did not die .....I dont know what else to do guys any ideas out there ?
 

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...... any ideas out there ?
1. Go to a very very different shop.
2. Don't use car parts stores for diagnostic work.
3. Search on here and/or google the large amount of information on exactly your "runs and then doesn't" condition. Hint: look into issues that come about as the car comes up to temp: resistance issues, grounds, ignition coil and ignition coil module, there's more
 

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A fuel gauge eliminates guessing and costs only $30. I always keep one in the trunk. Honestly, I never hear fuel pump running when I sit in the driver seat.
 

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Sadly this is what happens when parts are thrown at a problem instead of actual troubleshooting.

Don’t ever use that shop again. They tossed out a perfectly fine Opti that was probably a GM unit and installed a cheap Chinese one from car quest/Napa that will most likely fail soon.

I would be looking at the ICM and Coil.
 

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I agree with the above, get the GM Optispark back if you can and find a different shop.
I had a similar issue, turned out to be the fuel filter. Can't recall if the OBD II threw a code or not, bad gas plugged the filter, it would run dry under demand, stall, and the fuel pump would trickle enough through to restart, only to run dry again down the road. I change fuel filters every 20,000 miles now, never occurred again. Don't know if you changed the filter when you installed your new pump, but it's a cheap part and easy fix, before spending a lot more cash. I disengage the fuel pump's electric line, start the car and run it dry to relieve the pressure. there's less spillage of fuel when disconnecting the lines that way. The filter is under the driver's side chassis, GM has a special tool for the lines, but a pair of needle nosed pliers presses the line locks to disengage the filter from the lines. I hope this is helpful.
 

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Discussion Starter #6
I agree with the above, get the GM Optispark back if you can and find a different shop.
I had a similar issue, turned out to be the fuel filter. Can't recall if the OBD II threw a code or not, bad gas plugged the filter, it would run dry under demand, stall, and the fuel pump would trickle enough through to restart, only to run dry again down the road. I change fuel filters every 20,000 miles now, never occurred again. Don't know if you changed the filter when you installed your new pump, but it's a cheap part and easy fix, before spending a lot more cash. I disengage the fuel pump's electric line, start the car and run it dry to relieve the pressure. there's less spillage of fuel when disconnecting the lines that way. The filter is under the driver's side chassis, GM has a special tool for the lines, but a pair of needle nosed pliers presses the line locks to disengage the filter from the lines. I hope this is helpful.
Thank you for the advice I've been driving it around today and has not acted up or thrown any codes yet but I think I will go ahead and install a new fuel filter just to be safe thanks again
 

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I would be looking at the ICM and Coil.
the description screams bad ICM … which can also take out coil or vice versa
use heat sink paste under ICM on install
Once you take care of the fuel filter, grab a spare Ignition Coil Module, and a spare coil, just in case.
 

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I agree with everyone else. And don't assume that since you got a new fuel pump, all is well. I've had infant mortality with the pumps recently, aftermarket brands, Delco and Delphi. Tried them all. They are all hit or miss. Worse off, I had a Delphi pump + sending unit combo fail after a month because the internal line split. And the filter was replaced at the same time as the pump (they should always be done together).


193970


Go to Harbor Freight, buy a fuel pressure gauge and test your fuel pressure. Rule that out. It's not hard to do.

Then move on to ignition issues as they are harder to diagnose.
 
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Ok so at first car started died while driving and wouldn't start,didn't hear the fuel pump so I replaced fired right up ...I let it idle for about 5minutes hit the gas and died ..and did not want to start. Next day started died after 3 minutes got tired of it sent it to the shop they did diagnostic said it was the distributor aka opti spark had it replaced picked it up today drove about 15 miles died pulled over started up again then died 30 seconds later waited 10 minutes started right up drove to o'rileys they said my battery was bad so bought a new one died again twice later on then drove it about 10 miles home and it did not die .....I dont know what else to do guys any ideas out there ?
 

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Discussion Starter #12
Well guys I've replaced fuel filter,fuel pump,ignition coil & module opti spark and it still does the same thing ...I can drive to work park it and drive back home and park it but if I take it out after that it will die with in 10 to 15 minutes the dumb thing that I forgot to mention is that my passkey fault light is on and stays on...but been reading alot and supposedly that cats cant shut the car off while running but could prevent it from starting back up ...I'm lost but will try to delete the vats system this weekend and see if that might be it 🤦‍♂️
 

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Search 'Engine Coolant Temp Switch' on the water pump, and its harness.
 

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If the coolant temperature sensor is involved, you can monitor the temperature while driving to see if something is odd. After starting engine enter onboard diagnostics and chose option 08.
 

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Well guys I've replaced fuel filter,fuel pump,ignition coil & module opti spark and it still does the same thing ...I can drive to work park it and drive back home and park it but if I take it out after that it will die with in 10 to 15 minutes
As others have said use diagnostics to isolate the issue.
1. Fuel pressure gauge. Do you have pressure?
2. Is there a spark when it stops running and you are cranking it. Get a old spark plug and use it.
3. Are the injectors being signaled. Get a "NOID" light or use a rod to hear the injector click.

No fuel pressure check wiring and pump.
No spark OPTI, ICM, and coil. There are simple OPTI, ICM, and coil tests. A bad ground will make new parts useless.
No spark AND no injectors may be OPTI. There are simple OPTI tests.
No injectors but spark maybe VATS.

Would you explain again what you mean by "if I take it out again it will die with in 10 to 15 minutes". While you are at speed on the road? When stopping for a light? While idleing? When you put the pedal down after stopping? When you put it in gear? Or not starting after running?

If the VATS is lighting up it may be A problem but you might have more than one. There are threads that explain how to test the lock cylinder and key at the same time.

Just like a lawnmower engine the LT1 needs spark, fuel, and air. The LT1 has a lot more sub systems and just replacing them can be very costly. There are tests.
 

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I agree, I think you need more thorough diagnostics here. Definitely pay attention to what people are saying above. We need to start monitoring live parameters, anything affecting fuel, air metering and spark (MAF, O2 sensors, knock sensors, spark advance, etc.).

Get a Harbor Freight fuel pressure gauge and extend the hose. Run the gauge out from under the hood and either tape it to the cowl or run it into the cabin through the window to monitor fuel pressure at all times. If you do this, do it safely with high-pressure hose and fittings. This will diagnose a sudden fuel pressure drop either due to a fuel pump/wiring/relay issue or the regulator going bad.

Keep in mind that throwing parts at it, especially of unknown "Chinese" quality may actually hurt more than it helps.

As for VATS, you can pull the PASSKEY fuse (#14) to the module with the car running and it won't stall (but it won't restart in this state). The PASSKEY light on the dash will not be lit or blink with fuse #14 pulled. The module is completely dead in this state. There is another PASSKEY fuse (#34) but you can pull that one or both at any time and a running car won't stall either. But when a VATS module malfunctions like this, it will set hidden code 46 (on OBDI '94/'95) but won't set the CEL.

Once the PCM gets the "go" signal from the VATS module, it doesn't pay any attention to VATS after that until the next key cycle. In fact, on the old 9c1 forum from many years ago, I posted a How-To procedure to build a theft deterrent system around this hidden feature on 9c1 cars that do not have passkey programmed...but all '94-96 9c1 cars still have the module in the unlearned (bypass) mode, and you can take advantage of it.

So...I don't think VATS is the problem to be honest with you.

What it could be though is bad wiring or connections to the PCM (or worse, a bad PCM, but that's rare). Bad grounds or wiring problems at the PCM can cause all kinds of gremlins, including stalls and no-start conditions if the PCM loses power or ground. So rather than spending time on the VATS rabbit hole itself, I would actually pull the PCM and inspect/replug the 4 connectors and look for broken, corroded, or worn wires there. Again, using a live diagnostic tool will tell you this because you will get a DLC signal drop or see more than one sensor drop out when the car stalls.
 
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If it's an intermittent / bad wiring situation …

Several years ago, my wagon had a strong tendency of threatening to stall or completely stall if a right turn was made like a coward; that is, with brakes applied while steering into right turns.
(The side benefit of this problem was that it pushed me to learn to finish braking early, check the turn, and then accelerate gently into the turn every time.)

I could only replicate it by wiggling several wire bundles under the hood till I found the suspect wire bundle.
Since I could say to my mech, "look right here", he only charged me to fix the problem, instead of also charging me to search for several hours to find it.

Not the 1st time I suffered from wiring issues either.

H2Opump temp sensor's wiring was intermittently working or not working, which I noticed by popping the hood to find both fans turning on and off unpredictably, then wiggling the temp sensor wires to make the symptom come and go by hand.

Long story medium: our wires were a lil bit too thin in the 90s off the showroom floor. 25 years and tens of thousands of heat cycles later …
 

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Marky, that's very true. And what you saw could be happening for any number of sensors. A broken wire to the MAF, for example, would likely result in a random stall. Same goes for anything in the ignition circuitry.

Usually intermittent sensor wiring issues should set the CEL and store a code. Did you have a code set for the water temp sensor?

I can't express the importance of reading the codes off these cars and watching live data if you can. If a person is serious about keeping these cars on the road, spend the bucks and either get the proper scan tool or laptop hookup. A little money spent up front does indeed save yourself much frustration and money (thrown at unneeded parts) later.
 
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Discussion Starter #19
I agree, I think you need more thorough diagnostics here. Definitely pay attention to what people are saying above. We need to start monitoring live parameters, anything affecting fuel, air metering and spark (MAF, O2 sensors, knock sensors, spark advance, etc.).

Get a Harbor Freight fuel pressure gauge and extend the hose. Run the gauge out from under the hood and either tape it to the cowl or run it into the cabin through the window to monitor fuel pressure at all times. If you do this, do it safely with high-pressure hose and fittings. This will diagnose a sudden fuel pressure drop either due to a fuel pump/wiring/relay issue or the regulator going bad.

Keep in mind that throwing parts at it, especially of unknown "Chinese" quality may actually hurt more than it helps.

As for VATS, you can pull the PASSKEY fuse (#14) to the module with the car running and it won't stall (but it won't restart in this state). The PASSKEY light on the dash will not be lit or blink with fuse #14 pulled. The module is completely dead in this state. There is another PASSKEY fuse (#34) but you can pull that one or both at any time and a running car won't stall either. But when a VATS module malfunctions like this, it will set hidden code 46 (on OBDI '94/'95) but won't set the CEL.

Once the PCM gets the "go" signal from the VATS module, it doesn't pay any attention to VATS after that until the next key cycle. In fact, on the old 9c1 forum from many years ago, I posted a How-To procedure to build a theft deterrent system around this hidden feature on 9c1 cars that do not have passkey programmed...but all '94-96 9c1 cars still have the module in the unlearned (bypass) mode, and you can take advantage of it.

So...I don't think VATS is the problem to be honest with you.

What it could be though is bad wiring or connections to the PCM (or worse, a bad PCM, but that's rare). Bad grounds or wiring problems at the PCM can cause all kinds of gremlins, including stalls and no-start conditions if the PCM loses power or ground. So rather than spending time on the VATS rabbit hole itself, I would actually pull the PCM and inspect/replug the 4 connectors and look for broken, corroded, or worn wires there. Again, using a live diagnostic tool will tell you this because you will get a DLC signal drop or see more than one sensor drop out when the car stalls.
Thanks for all the procedures and advice I am going to spend my weekend doing all these tests so thank you all and I will keep everyone posted again thanks a bunch guys
 

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I can't express the importance of reading the codes off these cars and watching live data if you can. If a person is serious about keeping these cars on the road, spend the bucks and either get the proper scan tool or laptop hookup. A little money spent up front does indeed save yourself much frustration and money (thrown at unneeded parts) later.
Thank you I am tired of typing this. BUT general diagnostics can almost be done with a 12V bulb tester. Thank you for what sounds like "hands on" VATS information.

So...I don't think VATS is the problem to be honest with you.

What it could be though is bad wiring or connections to the PCM (or worse, a bad PCM, but that's rare). Bad grounds or wiring problems at the PCM can cause all kinds of gremlins, including stalls and no-start conditions if the PCM loses power or ground. So rather than spending time on the VATS rabbit hole itself, I would actually pull the PCM and inspect/replug the 4 connectors and look for broken, corroded, or worn wires there. Again, using a live diagnostic tool will tell you this because you will get a DLC signal drop or see more than one sensor drop out when the car stalls.
G104 on the ICM side of the head will mess up the PCM and or the ICM if it can not handle all the current that several things that ground at that point use.

The ground information is useless to post unless we know what is wrong fuel or ignition or both. I would not unplug the PCM without doing basic testing FIRST. Once you unplug you lose codes, reset fuel trims and basically erase a host of clues.
 
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