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Injector Pulse problems?

Tiny
BRENT CATALENA
  • MEMBER
  • 2002 CHEVROLET TRUCK
  • 8.1L
  • V8
  • 4WD
  • AUTOMATIC
  • 140,000 MILES
What sensors and functions does the PCM use to supply injector pulse to the injectors? What would cause the computer to stop sending an injector pulse 3 to 4 seconds after the engine starts?
Monday, July 15th, 2019 AT 6:49 AM

34 Replies

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Hi Brent,

The PCM uses various sensors to determine how much fuel is needed. There is no way to measure fuel volume from the injector so it measures pulse width, or how long it opens the injector for based on a spec that the injector can spray X amount of fuel in X time. It looks at the MAF/MAP to determine how much air is coming in, RPM, throttle input, Baro, ambient temp and uses this info to determine how much fuel to add in order to maintain 14:7 air/fuel ratio. This guide can help us

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

It then looks at o2 sensor data to determine how it is doing with the calculation and adjusts pulse width to lean out or fatten the ratio.

Just so I understand the engine starts and then 3-4 seconds later it cuts off the injectors? Does the engine stall? Just looking for a little more detail as to what the issue is. Thanks
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Monday, July 15th, 2019 AT 4:44 PM
Tiny
BRENT CATALENA
  • MEMBER
  • 4 POSTS
Yes, the engine just shuts off, but it will start right back up and then shuts off again in 3 or 4 seconds.
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Tuesday, July 16th, 2019 AT 4:05 AM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Okay and you have a scan tool and monitored the injector pulse width shutting off and then it stalls? I just want to make sure we are going down the right path but if you are assuming that is why it is shutting off then it could just be stalling and the injectors are shutting off as a result of the crank not sensing the engine RPM any longer so it shuts off the injectors.
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Tuesday, July 16th, 2019 AT 1:19 PM
Tiny
TGLASS720
  • MEMBER
  • 2 POSTS
  • 1998 CHEVROLET TRUCK
  • V8
  • 4WD
  • AUTOMATIC
  • 120,000 MILES
I was just wondering what is the best injector cleaner on the market. I've heard that sea foam was a good choice. Also what is the best way to clean cloged injecters.
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Friday, February 12th, 2021 AT 11:36 AM (Merged)
Tiny
MASTERTECHTIM
  • MECHANIC
  • 4,749 POSTS
The best way to clean these injectors is by using high pressure injector cleaner through the fuel rail. I dont know of an inexpensive way to do this. To do it right it will cost you about 100 bucks. It takes almost an hour to do. They have updated the injectors with a different style due to the problem of the original ones clogging with carbon.
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Friday, February 12th, 2021 AT 11:36 AM (Merged)
Tiny
BMRFIXIT
  • MECHANIC
  • 19,053 POSTS
All will work but they will have to be as an additive in your tank
and your asking for the best way to do it
so you have to fuel injection cleaner throw stopping the fuel pump and running the cleaner only and that’s require special equipment
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Friday, February 12th, 2021 AT 11:36 AM (Merged)
Tiny
BLAISE1986
  • MEMBER
  • 1 POST
  • 1996 CHEVROLET TRUCK
  • V8
  • 4WD
  • AUTOMATIC
  • 235,689 MILES
1996 Chevy K1500 350 Vortec 4x4
I think there is something wrong with the spider fuel injector. The truck starts but as soon as it does it revs up to about 2500-3000 rpm and then back down, then cuts off. The injector moves up and down when I press the gas. It goes down so far that the clips on plug that sits on top are busted up and only one clip works. Both sides don't go down the same amount. One side goes as far as it can, and the other only half way. The one that only moves half way moves up and down. The other doesn't. It only moves down and then stay there. When someone presses the intake down and holds it there it starts and stays running. It idles above 2000 rpm though.
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Friday, February 12th, 2021 AT 11:37 AM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
The injectors should stay in place when you throttle it-not moving up and down-best inspect what's going on-could be O-rings. Also pressing down on the intake makes it starts and idles-could be a vacuum leak due to the manifold is not sealed properly causing the high idle-
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Friday, February 12th, 2021 AT 11:37 AM (Merged)
Tiny
BERK
  • MEMBER
  • 3 POSTS
  • 1994 CHEVROLET TRUCK
  • V8
  • 4WD
  • MANUAL
  • 255,000 MILES
I have no power to the injectors (test light dosn't light). I replaced the pick up coil, had the igntion module checked, and then replaced the ecu. The only things I haven't replaced is the personality chip in the ecu and the harnes. The fuses were good when I started. End to end wire check is the only thing I can thik of. I hope you might have some ideas I am running dry.
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Friday, February 12th, 2021 AT 11:37 AM (Merged)
Tiny
KHLOW2008
  • MECHANIC
  • 41,814 POSTS
Hi berk,

Thank you for the donation.

The injectors gets it power source from the ignition and through a fuse. If there is no power supply, it is either a blown fuse or open circuit in wiring.

Can you please provide me with the following.
1. Engine type and capacity.
2. Actual model name and code if any.

There are many variants and they uses different systems and circuits so I need the above to gather the required information and advise accordingly.
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Friday, February 12th, 2021 AT 11:37 AM (Merged)
Tiny
BERK
  • MEMBER
  • 3 POSTS
Morning KHLow

Sorry I have 11? Somthig going to the injectors just not getting the gnd or control from the pcm.

The truck is a k2500, 5.7l v8, vin #1gcgk24k5re182469. It has the heavy duty manuel transmission. It isn't a silverado and never seen a model designation just thougt it was the work truck model.

I will recheck the fuse and the voltage I could have lost it over the last 2 weeks of digging in there.
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Friday, February 12th, 2021 AT 11:37 AM (Merged)
Tiny
BERK
  • MEMBER
  • 3 POSTS
Hi
well I checked the voltage again I have battery voltage at the injectors, with the key on. I found my meter was bad giving me incorrect ohm readings. Both injectors are shorted and I think I may have lost my new pcm.
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Friday, February 12th, 2021 AT 11:37 AM (Merged)
Tiny
CHEVYGUY72
  • MEMBER
  • 1 POST
  • 1992 CHEVROLET TRUCK
  • V8
  • 4WD
  • AUTOMATIC
  • 168,000 MILES
When at idol injector b goes on and off while injector a stays working properly. It also does this going down the highway. Thanks for any help!
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Friday, February 12th, 2021 AT 11:37 AM (Merged)
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Hi, if you suspect a faulty injector, swap places with injectors, if the problem follows the injector, maybe a faulty injector. If problem stays where it was, you need to do some testing on wiring circuit. Are there any trouble-codes?
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Friday, February 12th, 2021 AT 11:37 AM (Merged)
Tiny
MX12BRAD
  • MEMBER
  • 5 POSTS
  • 1990 CHEVROLET TRUCK
Engine Mechanical problem
1990 Chevy Truck 305 V8 Two Wheel Drive Automatic fuel injection throttle body

My Question is how can I get Fuel to spary out of my injectors? Is there a injector module?
I have used a Noid tester on my truck to no avail the light did not blink so I then tried to replace the computer with a new one. Still nothing. Prior to all this I have put new fuel pump, fuel filter, cap & rotor, plug wires, idle position sensor, had both injectors cleaned they said one was 100% other was 97% so they are good.

Thank you.

Brad Leyden
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Friday, February 12th, 2021 AT 11:38 AM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Check and test injector A fuse.
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Friday, February 12th, 2021 AT 11:38 AM (Merged)
Tiny
MX12BRAD
  • MEMBER
  • 5 POSTS
I checked under the dash. Fuses in fuse box all seem to be fine. Is there another fuse location?
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Friday, February 12th, 2021 AT 11:38 AM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
The fuel injector A fuse is the 10amp in the fuse block-if okay could be open from the fuse to the injector wires
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Friday, February 12th, 2021 AT 11:38 AM (Merged)
Tiny
MX12BRAD
  • MEMBER
  • 5 POSTS
It was the distributor module
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Friday, February 12th, 2021 AT 11:38 AM (Merged)
Tiny
COOLCATPAT
  • MEMBER
  • 1 POST
  • 1989 CHEVROLET TRUCK
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 160,000 MILES
Why would the throttle body spray too much fuel?
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Friday, February 12th, 2021 AT 11:38 AM (Merged)

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