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At first the car ran and drove not starting issue?

Tiny
SNOWINDIESEL
  • MEMBER
  • 1991 PONTIAC 6000
  • 3.1L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 74,500 MILES
I got this car on a trade a few months ago.

At first the car ran and drove, it ran rough, would “loop” at idle. I drove it around like that until it gave me a no start. The car will fire up, you’ll hear all 6 fire off and then it shuts off. If you give it fuel trying to start it, it won’t even try to start. I was able to get the car to start by pumping the peddle like a carb but now that doesn’t work anymore

It has fuel pressure (43psi) it’ll run off ether,
I’ve replaced ICM, ECM, Ignition coil packs, TPS, MAP, IAC Valve, CPS, Fuel filter. I’ve got a used throttle body coming in the mail for my next attempt. Any recommendations?
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Friday, September 20th, 2024 AT 5:32 AM

25 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
Are the injectors getting a trigger signal? This guide can help you:

https://www.2carpros.com/articles/how-to-test-a-fuel-injector

Also, when you crank the engine over hold your hand over the exhaust pipe, you should feel the pulses of the cylinders, if not then you could have a clogged exhaust system.

Please go over this video as well:

https://youtu.be/lXLJbuAZ4CE?si=aCNzQRvsH2OFvROF

Please go over these guides and get back to us.
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Friday, September 20th, 2024 AT 11:05 AM
Tiny
SNOWINDIESEL
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I don’t have access to a multi meter right now but when I unplugged an injector and tried starting it you can hear it missing. I’d think that means it would be getting a signal? No?
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Friday, September 20th, 2024 AT 11:33 AM
Tiny
KEN L
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If you unplug the injector and it is running worse than it is probably working. Can you upload a short video of what the problem is? That way I can se what's going on.
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Friday, September 20th, 2024 AT 1:47 PM
Tiny
SNOWINDIESEL
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I’m surprised it started! When it’s running and you give it fuel it stumbles over itself for a second and then revs up.
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Friday, September 20th, 2024 AT 3:46 PM
Tiny
KEN L
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Thanks for the video, it helps. It seems like the fuel pump is weak and it needs to be replaced.

Here is a guide to help check the fuel pressure to confirm the issue:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

FUEL PRESSURE:

Ignition ON Engine OFF .................... 40.5 to 47.0 psi

With Regulator Vacuum Applied [1] .................... 3.0 - 10.0 psi Less than Ignition ON Engine OFF

You can rent a fuel pressure gauge from the auto part store for cheap or free. Here is how to change the pump out in case you need it. Check out the images (below). Please let us know what happens.

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Saturday, September 21st, 2024 AT 10:43 AM
Tiny
SNOWINDIESEL
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Replaced fuel pump. Still same issue. Could it be a bad fuel regulator that’s causing this?
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Friday, September 27th, 2024 AT 12:30 PM
Tiny
KEN L
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Hmm, when it shuts down will it run on starting fluid? We need to see what the engine loses spark or fuel? Also is the security light flashing?
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Saturday, September 28th, 2024 AT 10:15 AM
Tiny
SNOWINDIESEL
  • MEMBER
  • 15 POSTS
No security light. It does run on starting fluid when it’s shut down. It will fire for a split second and die when it’s acting up. When the car is running it runs really smooth as long as you keep your foot on the peddle. If you let off it starts to drop in rpm and struggle to idle. If you don’t keep the gas going it won’t idle.

I have a fuel regulator coming and I’ve got a donor throttle body. Those are my next guesses...
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Saturday, September 28th, 2024 AT 10:26 AM
Tiny
SNOWINDIESEL
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  • 15 POSTS
That and if you try to floor it when it’s running it will lose all power, it’ll still stay on, but you lose power until you restart the car. I found that out trying to pass a car when I was able to get it started.
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Saturday, September 28th, 2024 AT 10:28 AM
Tiny
KEN L
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The IAC valve seems to be bad for the idle problem but not the no power issue. Lets run the codes to see if any are stored.

https://www.2carpros.com/articles/buick-cadillac-chevy-gmc-oldsmobile-pontiac-gm-1983-1995-obd1-code-definitions-and-retrieval-method

You may have a clogged catalytic converter, please go over this guide as well:

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

Please go over this guide and get back to us.
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Saturday, September 28th, 2024 AT 11:05 AM
Tiny
SNOWINDIESEL
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It flashes code 12 to me 3 times and then flashes code 43 - Knock sensor or electronic spark control circuit fault.
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Sunday, September 29th, 2024 AT 8:22 AM
Tiny
SNOWINDIESEL
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Also I’m pretty sure the Catalytic Converter was deleted. This car was straight piped when I got it. I put a muffler back on it
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Sunday, September 29th, 2024 AT 8:23 AM
Tiny
KEN L
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Okay, when you installed the new fuel pump did you replace the fuel filter as well? And when it wont start can you sue starting fluid to make it run?
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Sunday, September 29th, 2024 AT 10:09 AM
Tiny
KEN L
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I have seen the ICM cause strange problem like this as well FYI.
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Sunday, September 29th, 2024 AT 10:10 AM
Tiny
SNOWINDIESEL
  • MEMBER
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I had a shop replace the pump. I’ve replaced the fuel filter before the pump was replaced. I was able to get the car to run off starting fluid before I replaced pump or filter. I’ve replaced ICM, ECM, Coil packs, TPS, IAC Valve, MAP Sensor, and CPS.
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Sunday, September 29th, 2024 AT 10:13 AM
Tiny
SNOWINDIESEL
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The car fires up no problem at times or doesn’t fire up at all. It’s bipolar. Haha
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Sunday, September 29th, 2024 AT 10:16 AM
Tiny
SNOWINDIESEL
  • MEMBER
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Here’s a video of me trying to start it this morning. It fired up. I could smell gas out of the exhaust, and it had a blue cloud leave when I first fired it up. I also drove it around and got video of how it’s acting while driving.
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Sunday, September 29th, 2024 AT 11:04 AM
Tiny
KEN L
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Yep, that is an intermittent problem, they can be tough track down, did you run the codes? This might give us a clue on what is causing it. Since it has a new fuel pump and it didn't change anything I am leaning towards the ignition system, and more specifically the ignition control module.
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Monday, September 30th, 2024 AT 9:42 AM
Tiny
SNOWINDIESEL
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Yes I ran the codes. I got a code 12 and a code 43. The link you gave me says 12 means everything is normal and 43 is a bad Knock sensor.

It does have a new Ignition control module and new coil packs on the ICM. The plugins on the ICM looked fine, no corrosion. Again, I've replaced ICM, ECM, Coil packs, TPS, IAC Valve, MAP Sensor, and CPS.
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Monday, September 30th, 2024 AT 4:16 PM
Tiny
KEN L
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Yep, those codes are typical. So when the engine does not start we need to see what it is missing, either fuel or spark. Use starting fluid for fuel and this video will show you how to check for spark.

https://youtu.be/baq_aEWNQ0Y?si=9MWDPgLYuuPAD6Ms

Please go over this guide and get back to us.

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Tuesday, October 1st, 2024 AT 9:53 AM

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