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1995 GMC Sonoma No fuel

Tiny
JOSHUA_PARSONS
  • MEMBER
  • 1995 GMC SONOMA
Engine Mechanical problem
1995 GMC Sonoma 6 cyl Four Wheel Drive Manual

I hooked up noid lights to my 4.3 TBI injector connectors and I'm not getting anything on either one of them. I know the noid light is working because I checked it against another TBI engine. I don't understand what this means.

I'm sure that it's I'm not getting power to the injectors but I can't figure out why. I have a fuse [ECM IGN 20amp] that keeps blowing but even when the fuse isn't blown and the key is turned I'm still not getting any light.

I don't know if it makes a difference but I just replaced my fuel pump and I'm sure that it's working (i can hear it) but I can't figure out where to hook up my fuel pressure gauge to check pressure. I've heard between the inlet line and the throttle body but that would mean splicing into the metal line. As far as I can tell there are no flexible fuel hoses anywhere within the engine compartment or aft of the fuel filter.

PLEASE HELP!
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Saturday, April 25th, 2009 AT 3:19 PM

16 Replies

Tiny
BMRFIXIT
  • MECHANIC
  • 19,053 POSTS
No start condition
fuel pump was replaced
not sure if you have fuel pressure and if fuel pump working or not
no injector pulse when engine cranking
fuse keep on blowing not sure what it dose control
hope I got all
know this where we need to start is by making sure if the fuel pump working when 1st key on and or when engine cranking
if can not locate the fuel test port you can just open fuel line and have a helper turn key on for a second you should have fuel leaking and if so we know fuel pump is working
will move on to the injectors
use a test light turn key on
check for power at the injector connector
if no power check fuses and wiring
check wires coming to the TBI unit if got pinched by the air cleaner housing
if you have power
disconnect TPS on the side of the TBI unit and try starting
check TPS volts, check coolant sensor
let me know
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Sunday, April 26th, 2009 AT 10:48 AM
Tiny
JOSHUA_PARSONS
  • MEMBER
  • 7 POSTS
Fuel pump is working, fuel is getting to throttle body.

Still no injector pulse when I hook up a noid light. I used a multimeter and a wiring diagram to check for a short, found nothing. The fuse [ECM IGN] which runs from my injectors to the vehicle control module to the fuse panel is no longer blowing when I try to crank it but it still won't start.

I'm beginning to suspect something is wrong with the VCM (which powers my injectors) but I don't know how to test it. And I'm also wondering if there could be something else wrong before I spend the money to replace it.

So I have strong spark, a new fuel pump (working) and filter and still my truck isn't turning over.
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Saturday, May 2nd, 2009 AT 1:03 PM
Tiny
JOSHUA_PARSONS
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  • 7 POSTS
Changed the coolant temperature sensor and TPS. Still nothing
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Saturday, May 2nd, 2009 AT 1:06 PM
Tiny
BMRFIXIT
  • MECHANIC
  • 19,053 POSTS
Use a test light With key on do you have battery power at red wire inject #1 and also should have battery power at the white wire
let me know
dark blue wire
dark green wire
both go back to the PCM
they get grounder by the PCM causing it to pulse
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Saturday, May 2nd, 2009 AT 2:45 PM
Tiny
JOSHUA_PARSONS
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  • 7 POSTS
I clipped one end of the test light on to the postive battery terminal and the other end to each indicated wire.

I accidentally started this test with the key OFF.
I got a bright light for the red and white wires. I got a dismal light for the dark blue and dark green wires.

Now WITH the key ON I got no light on all four wires.

I only mentioned the first test in case it may be indicative of something.
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Saturday, May 2nd, 2009 AT 6:31 PM
Tiny
BMRFIXIT
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Clip the tester on battery negative
turn key on check if light come on
let me know
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Saturday, May 2nd, 2009 AT 8:17 PM
Tiny
JOSHUA_PARSONS
  • MEMBER
  • 7 POSTS
With the test light clipped on the negative terminal, key in the on position

Yellow wire= Light comes on

White wire = Light comes on

Dark Green wire= no light

Dark Blue wire= no light

I don't know if it makes a difference but I have a VCM mounted on top of the right wheel well instead of the PCM under the glovebox.
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Saturday, May 2nd, 2009 AT 10:21 PM
Tiny
BMRFIXIT
  • MECHANIC
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Test light clipped at battery positive
injector plug disconnected
have a helper crank engine for you
check dark green wire and dark blue wire
does the test light up or blink
if not suspect bad VCM (Vehicle Control Module)
need the help of a scanner
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Sunday, May 3rd, 2009 AT 6:38 AM
Tiny
SFBDBURBAN
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  • 5 POSTS
The thing that I don't like about these forums is that the original person with the problem never responds AFTER they have their problem fixed. So I'm sitting here at 3 in the morning reading about TBI injectors not firing hoping to find an answer but just more dead ends.
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Wednesday, May 27th, 2009 AT 4:52 AM
Tiny
BMRFIXIT
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We try and ask all to update the fix but as you see it does not happen very often
what is your issue with the TBI system
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Wednesday, May 27th, 2009 AT 6:01 AM
Tiny
AJ3HARTY
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  • 6 POSTS
What was the answer that fixed the problem? I am having same problem. One more thing I can add that my truck does. I can put a little fuel it TBI and sometimes when it starts it will keep running from 2 to 15 minutes. Then dies and then back to no ground signal to injectors. When the engine does start it runs nice and smooth, I can rev it up and it has great power. I once had it running long enough to drive around block. But as soon as I turned it off it would not start again until I put fuel in TBI. I check fuel pressure and it is good.
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Sunday, February 12th, 2012 AT 11:59 PM
Tiny
BMRFIXIT
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What do you have for fuel pressure
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Monday, February 13th, 2012 AT 1:37 AM
Tiny
AJ3HARTY
  • MEMBER
  • 6 POSTS
1992 GMC Sonoma 4.3l TBI
I have done all the test for fuel and it is good. It is not a fuel problem. Here is what I found but need help on what to test next. I tested injectors with noide lite. When the engine does not run I have no flashing signal from ecm. I do have 12v on other wire and is constant. The engine will start sometimes and runs great. Other times it will not start all I have to do is put some fuel down the TBI and it will start(runs great). Sometimes it will just die after burning the fuel. Sometimes it will keep running. When it does run it can run from 2 min to half hour or so. When it dies I do not have pulse signal to injectors from ecm.
No codes
always has spark
always has fuel pressure
ign coil pickup tested (824)
**problem found**
intermitent signal from ecm to injectors,
injector pulse from ecm sometimes works.
**
What would cause the ecm to not send signal pulse?
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Tuesday, February 14th, 2012 AT 6:04 AM
Tiny
RIVERMIKERAT
  • MECHANIC
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Test the fuel injector relay when the problem is occurring. It might not be closing properly, and using fuel into the tbi to 'trick' it into running allows it to warm up enough to close properly.
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Thursday, February 16th, 2012 AT 1:49 AM
Tiny
AJ3HARTY
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  • 6 POSTS
Does anyone else have possability of something. By the way there is no such thing as a fuel injector relay on this engine.
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Monday, February 20th, 2012 AT 11:52 PM
Tiny
RIVERMIKERAT
  • MECHANIC
  • 6,110 POSTS
Your truck is equipped with a fuel pump oil pressure switch. This is located near the distributor and shuts down the fuel pump when no or low oil pressure is detected.
Check the wiring and the connectors. It's starting to sound like the ECM is dying.
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Tuesday, February 21st, 2012 AT 1:06 AM

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