Lt1 swap issues - LS1LT1 Forum : LT1, LS1, Camaro, Firebird, Trans Am, Engine Tech Forums
 
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post #1 of 6 (permalink) Old 08-25-2019, 05:03 PM Thread Starter
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Lt1 swap issues

I need more brains on an issue im running into. I have swapped a 95 lt1 into a 84 camaro. Im running stock ecm. I have no fire on my fuel pump wire and no injector pulse. I have a timer bypass module for the vats system. I believe that is my issue but i cant be certain. I had 12v on the fuel pump relay wire the first time i powered up. Now i cannot get anything. I have "reset" the ecm and nothing. I do not have power to my injectors either. 12v has been present on the pink and orange wires everywhere i have checked except the injectors. She will run all day on manual added fuel. I have jumped fire to the fuel pump and still nothing. What am i missing? What is the truth on vats shutting down the fuel pump ? Should i stop until i wire up a diag port and read codes ?
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post #2 of 6 (permalink) Old 08-25-2019, 05:27 PM Thread Starter
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I know the 12v to injectors is a huge issue i will dig into tommorrow. However it doesnt explain why i had that 12v signal on the fuel pump relay wire and then disappeared. There wasnt power at the injectors then neither so i dont believe its a power issue to the ecm. Im assuming i have a bad feed to injector harness. Does the ecm or donor care supply the key on 12v to the injectors ?
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post #3 of 6 (permalink) Old 08-26-2019, 08:56 PM
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Injectors get 12 volts anytime key is on. It's the ground to injectors that pcm supplies. Did you install the aldl connecter when you did swap? If yes get an obd 1 scanner and check for codes. The 3 ignition biggies that will shut off fuel injectors, don't light the check engine light. Dtc 16- opti low res pulse missing, also shuts down fuel pump. Dtc 41, & 42, which are icm codes, just shut down injectors.

If vats security system is malfunctioning, fuel enable signal to pcm is cut off, thus killing the injectors. To help you in your search for answers, go to the following link and download the 95 service manual. It has driveability & emissions section with codes, and troubleshooting. Also wiring section with complete wiring diagrams. www.mediafire.com/?40mfgeoe4ctti

Use the 95 service manual to check fuel system wiring, starting on page 8a-21-0. There are 2 injector fuses. Injector wiring is on page 8a-21-3 Both fuse wires run through connector C100, then go though Splice S 101 & S102 before going to injectors.

Fuel pump has a relay that must be activated for pump to run. Find fuel pump wiring on page 8a-21-2 However, there is a fuel pump prime connector that will run pump if 12 volts is hooked to it. It's a gray wire that will be sitting loose and going to nothing.

Relay works like this. Points of relay gets 12 volts from pcm/ign fuse. On Pink wire @ connector C1. Other side of relay points goes to fuel pump. Other part of relay is the coil part. Connector A1 with blk/wht wire goes to ground G103. Other side of coil with connector C2 dark green/wht wire comes from PCM & supplies voltage to relay coil.

When PCM supplies voltage to relay coil, magnetic field occurs and relay points close providing 12 volts to fp. Study the diagram as there are several connectors & splices that wires go through.

Last edited by cocobolo95; 08-26-2019 at 09:17 PM.
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post #4 of 6 (permalink) Old 08-26-2019, 10:35 PM Thread Starter
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I have rebuilt another harness to double check each wire. Everything is perfect. Honestly i cannot find a single issue anyehere now. Car still only runs 2-3 seconds. Im not losing fire and injectors are not stopping fuel pressure is stable. I can run all day on spray but only 2-3 seconds on injectors. I ran the motor before the swap and no issues were present. One other thing i noted was it seems to be loading up. She will sputter and bog but i can pull my fuel relay and boom 3 second run time. Im running an external jaguar pump anf thought maybe to much pressure but the regulator should fix that i would assume
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post #5 of 6 (permalink) Old 08-26-2019, 10:56 PM Thread Starter
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Its hard to set and type everything i have done. I am a mechanic with most tools at my disposal. I feel like it could be something simple but ive not stopped looking at this car for 3 days. The only tool i dont have is a noid light but cornwell runs tommorrow lol. However my test light shows the ground pulsing. The fuel pump is singing i have a pressure gage monitoring and im not losing spark. It will run on carb cleaner so i know its fuel problem but i dont know what to do. Injectors pulse but the motor acts like it has to much fuel. It will load up if you dont pull the relay. Pump primes 2 seconds and cuts back on when cranking. Fuel rail is sitting around 45 psi constant. Sometimes the fuel pump still runs after it dies like it cant keep up pressure but the gage shows no fluctuation. I plan on wiring an obd tommorrow to check any codes but it just dont seem likely that its a code since the pump and injectors are working. I can watch the ground pulse when probed with a test light. Heres one kicker also, my injectors are pulsing even with the bypass unhooked. As far as i know this is a stock ecm. The motor had 70000 on it and only modification i seen was a msd opti. Its possible the previous owner had vats problem and tuned it out. Thats all i can think of that would explain that. But it had stock exhaust cam etc so i wouldnt think someone would spend money on tunning without a few power adders but it may have been an owner that just wanted it to run. So here i am again beating my head on the wall.
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post #6 of 6 (permalink) Old 08-27-2019, 06:38 AM
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If your maintaining 45 psi @ idle, that's too high. Idle usually has lower pressure of about mid 30's psi. Other running conditions will have at least 40 psi.

The run for 2 seconds could be because of over pressure at idle. But it's a classic sign that pcm is cutting injector operation because of codes or vats security.
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