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No fuel injector Pulse

Tiny
ERIC MUHLHAUSEN
  • MEMBER
  • 2000 CHEVROLET SILVERADO
  • 100,000 MILES
I have 55 PSI fuel pressure at fuel rail. Strong spark from all coils. There is power going to all injectors, but there is no injector pulse.
Saturday, June 26th, 2021 AT 5:39 PM

8 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,170 POSTS
Hi,

I need to know what size engine the truck has.

As far as the injectors, there is 12v to them at all times. To complete the circuit, a ground path is provided via the PCM. Without the PCM providing the ground, the injectors won't function.

Let me know which engine you have. That way, I can look at specific schematics to help you determine what to check.

I will watch for your response.

Take care,

Joe
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Saturday, June 26th, 2021 AT 9:21 PM
Tiny
ERIC MUHLHAUSEN
  • MEMBER
  • 6 POSTS
4.8 L V8 sorry phones going nuts.
.
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Sunday, June 27th, 2021 AT 8:00 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,170 POSTS
Hi,

No problem.

If you look below, I highlighted the wires from each injector to the PCM. Each of those wires is to receive a ground path from the PCM. So, all pink wires are power, and the highlighted ones are the ground.

Before you take anything apart on the PCM, I want you to locate the black/white wire on the rear of the engine. That is the primary ground for the PCM. If that fails, it could be the cause. It is identified in the first pic at the very top. I circled and highlighted it.

First, locate the ground on the rear of the engine. These grounds are known to fail. Also, there is a splice in the wire which could fail as well. The easiest thing to do would be to check for continuity to ground via that wire. If there isn't, then we need to find where the open is in the wire.

Here is a link you may find helpful:

https://www.2carpros.com/articles/how-to-check-wiring

If the ground is good, then I need you to disconnect the battery and then disconnect the PCM to see if there is corrosion or any damage in the connector.

Let me know what you find.

Take care,

Joe
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Sunday, June 27th, 2021 AT 9:24 PM
Tiny
ERIC MUHLHAUSEN
  • MEMBER
  • 6 POSTS
I found the ground wire in the back of the engine like you were talking about, I inspected the wire and I tested the wire everything was fine. I connected it back up to back of the engine next I went around to the ECU I unscrewed the plug from the ECU there was oil standing in the connection about 1 inch deep it was covering the bottom six or seven sets of pins. I took the ECU out and clean the pins up on the ECU and the plug in the best I could I put everything back together I just I've reconnected the negative ground on the battery I tried to start to pick up it acted the same as it has been previously it will not start it doesn't act like it wants to. Please help guys.
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Monday, June 28th, 2021 AT 3:17 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,170 POSTS
Hi,

There was oil in the connector? That is a potential problem. Do me one more favor. We know there is power to the injectors. Check if there is a ground path/pulse to the PCM. The PCM may have been damaged.

Let me know.

Joe
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Monday, June 28th, 2021 AT 7:55 PM
Tiny
ERIC MUHLHAUSEN
  • MEMBER
  • 6 POSTS
Please tell me how to find the ground path, pulse to the PCM. I am unsure what to do here.
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Wednesday, June 30th, 2021 AT 7:30 PM
Tiny
ERIC MUHLHAUSEN
  • MEMBER
  • 6 POSTS
I think I may know what you are asking I connected the clip on a test light to the batt. + Then the other end I connected to the injector plug on the opposite side of constant power.I checked 2 of the plugins on driver side and 2 on pass. Side. I got nothing from either on drivers side. First one on passenger side I got a sporadic pulse, at first it seemed to flash about 8 times for every engine revolution, then nothing then a flash once in a while, but not consistent. With other pass side inj. Plug I got 2 or 3 flashes in 5 or 6 engine revolutions not consistent. So what next? I don't know that what I did was of any help to you. I just wanted to let you know that is what I did. Even though I have good battery voltage, it seems like the starter is suddenly struggling to turn engine over, like maybe there is compression where there shouldn't be. I am not sure this is even possible. I'm pretty sure that I have not pushed the starter to hard.
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Wednesday, June 30th, 2021 AT 8:05 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,170 POSTS
The injector should pulse every 4th revolution of the engine. Is that happening? It seems random. Also, if you are getting a ground signal via the PCM and power to the injector, the engine should be getting fuel.

If we have a ground path and power, something isn't making sense. I feel we may need to remove the injector to see if they are working. Take a look through this link and let me know if you feel comfortable performing the procedures. Some, you have already done.

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

Let me know.

Joe
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Thursday, July 1st, 2021 AT 8:18 PM

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