Injectors are NOT firing
Thread Starter
Joined: Jan 2007
Posts: 976
Likes: 4
From: Newfoundland, Canada
Car: 1991 Pontiac Trans Am GTA
Engine: V8 305
Transmission: Automatic Transmission
Injectors are NOT firing
I just installed a set of injectors from South Bay as one of the stock ones were leaking fuel. Now the Injectors are NOT firing.. the mechanic thinks it maybe electrical... thoughts?
Joined: Mar 2017
Posts: 4,255
Likes: 427
From: Portland, OR
Car: 86 Imponte Ruiner 450GT, 91 Formula
Engine: 350 Vortec, FIRST TPI, 325 RWHP
Transmission: 700R4 3000 stall.
Axle/Gears: 9 Bolt Torsen 3.70
Re: Injectors are NOT firing
He "thinks"?!? Get a new mechanic. This should be easy to track down. Check for power to the injectors. Check for injector pulse from the ECM. If you get nothing there check that the ECM is getting a distributor reference pulse. If it is then check for power supply and ground to the ECM. If you have all that the ECM is bad.
GD
GD
Thread Starter
Joined: Jan 2007
Posts: 976
Likes: 4
From: Newfoundland, Canada
Car: 1991 Pontiac Trans Am GTA
Engine: V8 305
Transmission: Automatic Transmission
Joined: Dec 2004
Posts: 16,734
Likes: 993
From: Mile High Country !!!
Car: 1967 Camaro, 91 z28
Engine: Lb9
Transmission: M20
Axle/Gears: J65 pbr on stock posi 10bolt
Re: Injectors are NOT firing
A bad key reader would cause vats to act up.
to test I’m assuming this is a 1227730 ecm. There is a blue wire in cavity f10.
you can turn the key to the accessory position. If it’s working correctly you will have 2.5v on this blue wire.
https://tpiparts.net/1227730_pinout_diagram
if you have loss of spark as well it’s more than likely the icm or pickup coil. Could be a wiring issue heat can cause damage to the four wires that connect to the icm that run to the ecm.
to test I’m assuming this is a 1227730 ecm. There is a blue wire in cavity f10.
you can turn the key to the accessory position. If it’s working correctly you will have 2.5v on this blue wire.
https://tpiparts.net/1227730_pinout_diagram
if you have loss of spark as well it’s more than likely the icm or pickup coil. Could be a wiring issue heat can cause damage to the four wires that connect to the icm that run to the ecm.
Joined: Mar 2017
Posts: 4,255
Likes: 427
From: Portland, OR
Car: 86 Imponte Ruiner 450GT, 91 Formula
Engine: 350 Vortec, FIRST TPI, 325 RWHP
Transmission: 700R4 3000 stall.
Axle/Gears: 9 Bolt Torsen 3.70
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Thread Starter
Joined: Jan 2007
Posts: 976
Likes: 4
From: Newfoundland, Canada
Car: 1991 Pontiac Trans Am GTA
Engine: V8 305
Transmission: Automatic Transmission
Re: Injectors are NOT firing
fuses are good... there IS power goin to the injectors.. but the pulse that tells the injectors to fire is NOT working...
Supreme Member

Joined: Jun 2002
Posts: 2,227
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From: North East GA
Car: 1989 Firebird
Engine: 5.7 LS1
Transmission: T56
Re: Injectors are NOT firing
Did you verify no pulse with noid lights? Do you have spark? If they were firing before replacing I would suspect a connection was missed or one or more injector could be bad (even with quality parts it can happen). I would ohm each in injector.
The wiring is pretty simple I would ohm each wire back to the ECU connection as my first step of the injectors ohm out correctly. Then test the icm and also make sure the rotor is turning in the distributor if no spark.
The wiring is pretty simple I would ohm each wire back to the ECU connection as my first step of the injectors ohm out correctly. Then test the icm and also make sure the rotor is turning in the distributor if no spark.
Thread Starter
Joined: Jan 2007
Posts: 976
Likes: 4
From: Newfoundland, Canada
Car: 1991 Pontiac Trans Am GTA
Engine: V8 305
Transmission: Automatic Transmission
Re: Injectors are NOT firing
yeah the mechanic has a the light to check so I'm assuming he will do that this week. I think hes gonna concentrate on the ECM first as its a simpler process.
Joined: Mar 2017
Posts: 4,255
Likes: 427
From: Portland, OR
Car: 86 Imponte Ruiner 450GT, 91 Formula
Engine: 350 Vortec, FIRST TPI, 325 RWHP
Transmission: 700R4 3000 stall.
Axle/Gears: 9 Bolt Torsen 3.70
Re: Injectors are NOT firing
Calling out an ECM is NOT a simple process. It requires a lot of testing and verification.
GD
Supreme Member

Joined: Jun 2002
Posts: 2,227
Likes: 46
From: North East GA
Car: 1989 Firebird
Engine: 5.7 LS1
Transmission: T56
Re: Injectors are NOT firing
yea... I hate to say it but I would be finding a new mechanic, the ECU was working before the new injectors so unless he hooked the battery up backwards or did something else that he thinks fried the ECU there is no real reason to suspect it.
Supreme Member

Joined: Jun 2002
Posts: 2,227
Likes: 46
From: North East GA
Car: 1989 Firebird
Engine: 5.7 LS1
Transmission: T56
Re: Injectors are NOT firing
Do verify VATS.
Someyear cars have an inline ECU fuse beside the battery, and a wiring block behind it. If the mechanic fully removed the battery this could be effected.
My gut says he missed a connection or one went bad after unplugging.
Have you verified fuel pressure?
Someyear cars have an inline ECU fuse beside the battery, and a wiring block behind it. If the mechanic fully removed the battery this could be effected.
My gut says he missed a connection or one went bad after unplugging.
Have you verified fuel pressure?
Thread Starter
Joined: Jan 2007
Posts: 976
Likes: 4
From: Newfoundland, Canada
Car: 1991 Pontiac Trans Am GTA
Engine: V8 305
Transmission: Automatic Transmission
Re: Injectors are NOT firing
Car has been repaired.. thanks for all the help guys.. the ECM was the issue.. bought a reman acdelco from rockauto.com and the injectors now fire correctly... i seem to have lost a vacuum hose and im not sure where it went, wat hose it was or where it goes but i assume its the reason for the rough idle and SES light.
pics of what im talking about
I think you need a new mechanic. Chances are that swapping the ECM is not going to solve the issue. He needs to check reference pulse and power/ground to the ECM before he determines it's bad.
Calling out an ECM is NOT a simple process. It requires a lot of testing and verification.
GD
Calling out an ECM is NOT a simple process. It requires a lot of testing and verification.
GD
it was indeed the ECM..thanks to all that helped.
Last edited by goalieforlife; Nov 20, 2019 at 12:51 AM.
Thread Starter
Joined: Jan 2007
Posts: 976
Likes: 4
From: Newfoundland, Canada
Car: 1991 Pontiac Trans Am GTA
Engine: V8 305
Transmission: Automatic Transmission
Re: Injectors are NOT firing
I think you need a new mechanic. Chances are that swapping the ECM is not going to solve the issue. He needs to check reference pulse and power/ground to the ECM before he determines it's bad.
Calling out an ECM is NOT a simple process. It requires a lot of testing and verification.
GD
Calling out an ECM is NOT a simple process. It requires a lot of testing and verification.
GD
it was indeed the ECM..thanks to all that helped.
Last edited by goalieforlife; Nov 20, 2019 at 12:51 AM.
Joined: Dec 2004
Posts: 16,734
Likes: 993
From: Mile High Country !!!
Car: 1967 Camaro, 91 z28
Engine: Lb9
Transmission: M20
Axle/Gears: J65 pbr on stock posi 10bolt
Re: Injectors are NOT firing
You have 3 vacuum connections
1 for the hvac, 1 for map and one for fuel pressure regulator.
looks kind the regulator one might be missing.
1 for the hvac, 1 for map and one for fuel pressure regulator.
looks kind the regulator one might be missing.
Thread Starter
Joined: Jan 2007
Posts: 976
Likes: 4
From: Newfoundland, Canada
Car: 1991 Pontiac Trans Am GTA
Engine: V8 305
Transmission: Automatic Transmission
Joined: Dec 2004
Posts: 16,734
Likes: 993
From: Mile High Country !!!
Car: 1967 Camaro, 91 z28
Engine: Lb9
Transmission: M20
Axle/Gears: J65 pbr on stock posi 10bolt
Re: Injectors are NOT firing
Iirc 5/32 vacuum hose. Goes from the vacuum nipple to the pressure regulator.
if that one is already hooked up it’s for hvac and comes from the wiring loom passengers side.
if that one is already hooked up it’s for hvac and comes from the wiring loom passengers side.
Thread Starter
Joined: Jan 2007
Posts: 976
Likes: 4
From: Newfoundland, Canada
Car: 1991 Pontiac Trans Am GTA
Engine: V8 305
Transmission: Automatic Transmission
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Nasty_Bird_'90
DFI and ECM
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Mar 2, 2003 07:22 PM











icm or could be vats 