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TBI injectors not firing

Tiny
PHILL WATERS
  • MEMBER
  • 1988 CHEVROLET 3500
  • 7.4L
  • V8
  • 2WD
  • AUTOMATIC
  • 48,000 MILES
We had the vehicle shut down and would not start due to fuel filter being blocked. Replaced the filter and rebuilt the TBI but it would now start but would not run without continually pumping the gas pedal. Checked fuel pressure found it was down so replaced the fuel pump. But now there is no fuel coming from the injectors vehicle will start and run while spraying fuel down the TBI. Have had it suggested that it might be a fault in the ECM. So how do I check this or what else am I missing?

Cheers,
Phill
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Monday, May 20th, 2019 AT 11:08 PM

15 Replies

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

You need to use a noid light on the injectors to see if the ECM is commanding them on. You can rent one at a parts store.

What is the fuel pressure with the new pump?

Roy
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Tuesday, May 21st, 2019 AT 2:37 AM
Tiny
PHILL WATERS
  • MEMBER
  • 7 POSTS
Hi Roy, as I live in Australia to rent a noid light isn't possible I can purchase a kit with 10 different noid lights in it for $35.00 of eBay but do really want to do that is there another way to test them? I can see that they are not spraying any fuel out. Also the fuel pressure is about 10 psi.
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Tuesday, May 21st, 2019 AT 2:59 AM
Tiny
ASEMASTER6371
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Okay, got it.

Use a test light and insert it in both terminals. Crank the engine and see if it flashes.

Roy
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Tuesday, May 21st, 2019 AT 3:05 AM
Tiny
PHILL WATERS
  • MEMBER
  • 7 POSTS
Okay will have to do this in the morning as it is night time over here at the moment will let you know outcome.

Just a little bit more information after fitting the new fuel pump we started the engine but would not run without pumping gas pedal both injectors were spraying fuel but have since stopped and when cranking engine over they are completely dry.
Cheers
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Tuesday, May 21st, 2019 AT 3:13 AM
Tiny
ASEMASTER6371
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Make sure the new pump is working. You said 10 lbs. Is that on the new one?

Roy
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Tuesday, May 21st, 2019 AT 3:15 AM
Tiny
PHILL WATERS
  • MEMBER
  • 7 POSTS
Pump working can hear it plus disconnected inlet line on TBI and turned on ignition and had a steady flow of fuel flowing from the line. So know that pump is working.
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Tuesday, May 21st, 2019 AT 3:19 AM
Tiny
ASEMASTER6371
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Okay, do the test on the injectors.

It does sound like the quad drivers in the ECM failed.

Roy
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Tuesday, May 21st, 2019 AT 3:35 AM
Tiny
PHILL WATERS
  • MEMBER
  • 7 POSTS
Hi Roy, did as you suggested and put a test light on the lead to the injectors and cranked the engine over but did not get anything. So is it the drivers and will I have to replace the whole unit or is there something else that may need investigating?
Cheers,
Phill
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Wednesday, May 22nd, 2019 AT 12:59 AM
Tiny
ASEMASTER6371
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The ECM needs to be replaced. It is the whole unit.

Roy
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Wednesday, May 22nd, 2019 AT 2:59 AM
Tiny
PHILL WATERS
  • MEMBER
  • 7 POSTS
Hi Roy,
managed to find someone who had a noid light not the correct one but with the use of alligator clips etc, managed to jury rig a working light, on first crank over light flashed once then nothing so disconnected ECM and re-plugged it back in and again got single flash on crank over then nothing. So would that be still the ECM?
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Thursday, May 23rd, 2019 AT 4:10 AM
Tiny
ASEMASTER6371
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Yes that is correct.

Roy
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Thursday, May 23rd, 2019 AT 4:37 AM
Tiny
PHILL WATERS
  • MEMBER
  • 7 POSTS
Okay, have ordered new ECM, but it will take about 10 to 15 days to reach me. Will let you know how it goes, thanks for all your help.
Cheers,
Phill
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Thursday, May 23rd, 2019 AT 3:30 PM
Tiny
ASEMASTER6371
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You are welcome.

Always glad to help.

Roy
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Thursday, May 23rd, 2019 AT 3:32 PM
Tiny
JAY TACKETT
  • MEMBER
  • 5 POSTS
Curious to know If the ECM fixed the problem? Having similar problem myself thanks.
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Monday, December 14th, 2020 AT 9:09 PM
Tiny
ASEMASTER6371
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Usually we only hear back when it does not fix it.

If you like, start a new question and we would be happy to help you.

Roy
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Tuesday, December 15th, 2020 AT 5:21 AM

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