LS swap LQ9 will not fire?

Tiny
SANCHJU1
  • MEMBER
  • 2004 CADILLAC ESCALADE EXT
  • 6.0L
  • V8
  • 2WD
  • AUTOMATIC
  • 5 MILES
Hello, seeking some advice. I ls swap lq9 6.0 in 55 Belair. Complete rebuild following 2CarPros 5.3 and ls swap YouTube series. I installed Fitech EFI system. Wired it up. Verified constant power, fuel pressure and spark. Engine will crank but won't fire. Can you help me with some troubleshooting steps I should take? Thanks for your help.
Julian
Note: pic of the engine (IG: bellaair55)
Saturday, October 28th, 2023 AT 6:56 PM

3 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
Hi,

I will forward this to Ryan for you. In the interim, I'll try to help.

If you have spark and fuel, it should run. So, if the fuel pressure is good and you confirmed it is getting spark, then we need to suspect there is no fuel getting into the engine.

Are you getting power to the fuel injectors? If so, are you getting a ground signal from the PCM? Will it fire up with starting fluid?

Let me know.

Take care,

Joe
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Saturday, October 28th, 2023 AT 10:35 PM
Tiny
SANCHJU1
  • MEMBER
  • 6 POSTS
Joe, thanks for your reply. How would I go about checking power to the fuel injectors? And ground signal. I haven't tested that, not 100% sure how.
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Saturday, October 28th, 2023 AT 10:49 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
Hi,

Okay, this is going to be difficult for me because I don't have a wiring schematic in front of me specific to what you have. However, do this.

On nearly all vehicles, there is one constant power supply to both the coils and the injectors. So, one of the wires to each fuel injector and one to each coil should be the same color. With the key in the run position, those wires should have power at all times.

Since there is power available at all times at these components, we need a ground path to complete the circuit. So, the second wire at the connectors will be different from one coil to another and one injector to another. The ground path is provided via that wire by the PCM when an ignition spark is needed and when fuel is needed for a specific cylinder.

So, first, locate the wires that have the same color. With the key in the run position, check them for battery voltage. If power is present, then connect a test light alligator clip to the battery positive and probe the wire of a different color while someone cranks the engine. If there is a ground path present, the test lamp will strobe on and off.

Let me know what you find or if you have other questions.

Take care,

Joe
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Sunday, October 29th, 2023 AT 6:32 PM

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