mixed koolaid

I just recently bought a 99 civic that had a d16y7 in it I swapped it with a d16y8 and kept the y7 harness and it was running and driving. I swapped a y8 harness into it for the vtec plugs and now the fuel pump won’t prime. The only way for me to get it to prime is if I ground pin 8 on the main relay and then it will start but run bad because the pump is constantly priming when doing this. Any ideas on what the issue could be? I also have the ob2 p2p ecu connected to the harness. Also even when I am not grounding pin 8 on the relay to get the fuel pump to prime the relay clicks but the fuel pump doesn’t prime #d16y8swap #fuelpump

JRCivic1

Do you have a '99-00 EX (Y8) engine harness ? If you are unsure, the way to know is by identifying the ECU plugs. Comparing OBD-2A ('96-98) and OBD-2B ('99-00) manual engine harnesses, the 2A will have three ECU plugs and the 2B will only have two ECU plugs (the 3rd one is part of the dash/chassis harness instead). The dead give-away would be that you have an ECU plug not connected. Where things get really confusing is that the automatic engine harnesses have one additional plug, meaning that the OBD-2A auto engine harness will have four plugs and the OBD-2B auto engine harness will have three plugs. When all ECU (and under-dash) plugs are installed on a manual chassis, positions A,C, and D are connected on the OBD-2A chassis and positions A,B, and C are connected. The automatic plug position on the 2A ECU is the "B" plug and the 2B ECU utilizes the "D" plug. A visual inspection of the ECU will show which plug positions have pins and which are empty. Obviously, plugging in an engine harness ECU plug into a bare plug doesn't work.

Simply, it just doesn't make sense that your chassis functioned perfectly (fuel pump primed) before you changed engine harnesses and now it doesn't... and this ISN'T related to the new engine harness. The possibility of another wiring problem occurring coincidentally is HIGHLY UNLIKELY.

mixed koolaid

Thank you for the response the harness is from a 96 civic that had a y8 in it all the plugs plug right into my engine. The harness itself has 3 plugs. I will upload a picture of what it my current situation looks like


this is a picture I found online because I am not home currently but just imagine where the harness plugs r going is just straight into an p2p ecu
you can see how there is that extra plug and I am wondering if that could be my issue. It couldn’t be my main relay because before swapping the engine harness and ecu the car ran and drove fine just idled a little weird and had no vtec
edit: also all of my plugs are going into the ecu where there are pins

vrbiss

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JRCivic1

Go away troll !!! MODS, please remove this user.

The '96-98 OBD-2A style engine harness, regardless of whether it is a non-VTEC (Y7) or VTEC (Y8) style, DOES NOT WORK in your '99-00 Chassis. The reason is the extra plug in the photo that you have stated still exists, unplugged, under your dash near your ECU.

You will need a '99-00 Civic EX (Y8) engine harness, or modify your original Y7 engine harness by adding the VTEC plugs and moving around the various plugs to match the replacement Y8 engine.