Please Help! LM7 5.3 Not Starting
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Teching In
Joined: Dec 2023
Posts: 5
Likes: 1
From: Southern California
Please Help! LM7 5.3 Not Starting Hello again. I’m hoping to get some help troubleshooting my sons 73 nova with a 5.3 LM7. The swap was done prior to us owning it. A few weeks ago, we decided to fix a few items we knew were an issue. Rear brakes and a couple of exhaust bolts broken. After we got everything buttoned up, it wouldn’t start. It turns over, but nothing else. I realized that I didn’t hear the fuel pump prime when the key was turned to the on position. I tested the fuel pump relay and it seems to be fine. I even swapped them out just in case. We looked over the fuses and nothing looked bad there. I decided to bypass the relay and jump the wires for the pump and I heard it turn on. We even tried to start it with the relay jumped but it’s still not starting up. It makes me think the ecm is not getting power, but I am unsure as to how to test it. I will say, in the time we have spent going over this motor, we now know that we will need to completely redo a lot of the wiring. It’s not pretty, and in some areas not even safe. I guess this all happened so we could see some of the hidden issues that we wouldn’t have found otherwise.
Teching In
Joined: Jan 2024
Posts: 7
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Sorry, the blue ecm connector that connects to the ecm. You could have a blue and green or a blue and red. Blue connector, PIN 19 and 75. I had the same issue you are describing and 19 and 75 were 0 when cranking. If so, you have a blown fuse.
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Thread Starter
Teching In
Joined: Dec 2023
Posts: 5
Likes: 1
From: Southern California
Well, we decided to back trace the ecm wires to see if we could find an issue. And…I forgot to connect the pcm ground to the battery.
Yeah, I cannot even believe it. The good news is, my son is finally driving his car!!! He finished his contract with the Marines in December and we’ve been working on it since then. We have a super long way to go, but we are now one step closer! Next step is he wants the terminator x max and a 4l80e. I cannot thank you all enough! If it weren’t already dark, I would upload a pic of him learning to drive a stick.
Yeah, I cannot even believe it. The good news is, my son is finally driving his car!!! He finished his contract with the Marines in December and we’ve been working on it since then. We have a super long way to go, but we are now one step closer! Next step is he wants the terminator x max and a 4l80e. I cannot thank you all enough! If it weren’t already dark, I would upload a pic of him learning to drive a stick. LS1 Tech Stories
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