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Injector not working

Tiny
LEVI1515
  • MEMBER
  • 1989 CHEVROLET S-10
  • 4.3L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 150,000 MILES
I just bought the vehicle listed above 4.3 TBI. When I got it it was running real rough, I have replaced all plugs and wires and I noticed one injector wasn't firing, I put a new injector plug on and it started working fine. I drove it for a bit 30 mins with no problem, then when I drove it a little while later it was running fine and all of a sudden it started running rough again. I checked it out and noticed the same injector wasn't working again. What do I need to check or what? I'm lost on this.
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Monday, December 23rd, 2019 AT 7:18 AM

37 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good morning,

Did you verify power to the injector itself when it is not working?

Also, you need a noid light to be sure the quad driver in the ECM is commanding it to allow fuel.

The other possibility is dirt in the injector.

Roy
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Monday, December 23rd, 2019 AT 8:58 AM
Tiny
LEVI1515
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I wasn't able to yesterday because I didn't have a volt meter and it was raining, is there any other way to test it without a noid light? Because when I changed the plug to begin with I wasn't getting a hot reading on either side of the the plug. But like I said it was working fine after I changed the plug and then it just quit while I was driving it. I been doing a lot of research and I been seeing where there is something in the distributor that it's suppose to read also.
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Monday, December 23rd, 2019 AT 9:07 AM
Tiny
ASEMASTER6371
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No, there is not. The distributor does send a signal to the ECM but if the other one works, that is not the case.

You can use a test light. With the connector unhooked from the injector, put one lead into one side the other lead into the other terminal and crank it and see if it flashes.

Roy
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Monday, December 23rd, 2019 AT 9:14 AM
Tiny
LEVI1515
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Okay, I will try that this evening. I just don't understand why it goes in and out, I do mechanic work but most of my experience is in diesel so I'm trying to learn this in the process. And I will say the service engine light came on a couple times and then went off. Can I retrieve a code from it, I seen another post where someone said to out a jumper wire in the obd1 plug and it will give me a code. Is that true?
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Monday, December 23rd, 2019 AT 9:18 AM
Tiny
ASEMASTER6371
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Yes, you can. You jump 2 pins on the data link connector at the top right of the connector. It will flash codes. 12 will be the first and then the actual code will flash after that.

This could be a bad ECM which was common on these old OBD1 systems.

Roy
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Monday, December 23rd, 2019 AT 9:26 AM
Tiny
LEVI1515
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That's what I'm really starting to think is it's the ECM, I really hope not but I just got to figure it out. I know it's not the injector itself cause I can swap the plug and the injector works fine.
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Monday, December 23rd, 2019 AT 9:29 AM
Tiny
ASEMASTER6371
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Okay, do the test and let me know. The ECM is cheap and is a plug and play.

Roy
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Monday, December 23rd, 2019 AT 9:35 AM
Tiny
LEVI1515
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Okay, will do. Appreciate all the help.
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Monday, December 23rd, 2019 AT 9:36 AM
Tiny
ASEMASTER6371
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You are welcome.

Always glad to help.

Roy
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Monday, December 23rd, 2019 AT 9:40 AM
Tiny
LEVI1515
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Well I tested the injector when I got to the truck and sure enough it's not getting a ground signal when trying to crank or while the truck is running, so I guess it's on to the ecm, where is it located and how can I test it to make sure before I go get one.
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Monday, December 23rd, 2019 AT 5:50 PM
Tiny
ASEMASTER6371
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Okay, It is under the right side of the dash. I attached procedure and pictures for you to view.

You cannot test it. It takes special equipment to actually test the internals.

Roy
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Monday, December 23rd, 2019 AT 5:57 PM
Tiny
LEVI1515
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Okay, I been reading some stuff about a prom what is that exactly?
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Monday, December 23rd, 2019 AT 5:59 PM
Tiny
ASEMASTER6371
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A prom is a chip with all the vehicle information. You will change that over from the old ECM to the replacement ECM.

Roy
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Monday, December 23rd, 2019 AT 6:00 PM
Tiny
LEVI1515
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Okay, will anything need to be programmed or anything or is it already programmed?
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Monday, December 23rd, 2019 AT 6:02 PM
Tiny
LEVI1515
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And is the prom inside the ECM or what? I've never messed with one before.
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Monday, December 23rd, 2019 AT 6:05 PM
Tiny
ASEMASTER6371
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There is a cover with 2, 1/4 inch bolts and the cover comes off. The prom is a circuit board that you depress the ends and it comes right up. Takes you about 5 minutes if you take your time. Just push the new one into the replacement and install the cover.

Roy
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Monday, December 23rd, 2019 AT 6:11 PM
Tiny
LEVI1515
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Okay, does a prom ever go bad? If so how can you be able to tell?
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Monday, December 23rd, 2019 AT 6:13 PM
Tiny
ASEMASTER6371
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Yes, you can tell when it does not run at all. When that happens, you replace the ECM and prom at the same time.

Roy
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Monday, December 23rd, 2019 AT 6:17 PM
Tiny
LEVI1515
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Okay, well I guess I will be getting a ECM. Thanks for all your help.
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Monday, December 23rd, 2019 AT 6:19 PM
Tiny
LEVI1515
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I pulled the ECM out this morning and under the cover I have to different do I need to reuse both or just one?
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Tuesday, December 24th, 2019 AT 6:06 AM

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