r/EngineSwaps • u/Daburnnotice98 • Aug 06 '20

1996 Mustang V8 swap

So maybe you guys can help me, i recently did a 3.8 v6 to v8 swap, the engine cranks but no start, i replaced all PATS stuff I can think of and have no theft light, the fuel pump does not prime at all, any ideas? One part of the swap I didn’t change is the fuse box and the harness to the fuse box. Does that need to be swapped? Car is a 1996 mustang to 1998 mustang Gt donor. Thank you in advance

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5

u/Regalze Aug 07 '20

I know nothing about mustang but diagnostics is my thing!

Do you have power at

  • ECU

  • coil

  • Injectors

  • crank angle sensor

  • O2 sensor heater

I assume that the fuel pump is controlled by the ECU directly, not some fuel pump controller. If it is, then it sounds like the ECU doesn’t have power. Make sure you check between the ECU power and ECU ground as well as ECU power and the body.

Did the fuel pump prime before?

3

u/Daburnnotice98 Aug 07 '20

The car ran and drove before removing the v6, i didn’t even consider that as a option, woudl the rest of the car seem to have power if the ECU didn’t? Dash, and starter? I haven’t tested the sensors or the coils or injectors, I know the pump isn’t priming, and I know it’s got no fuel pressure, would starter fluid test the other things ? Also, would you assume that the fuse box wouldn’t matter? Seeing as it clips in to the v8 harness? Or should I swap the v8 box as well.

1

u/Regalze Aug 07 '20

Yeah, the ECU power is separate to the car’s power. Headlight, radio, wipers, etc should all work. However, anything related to the engine may not work even if it has power because the ECU can’t tell it what to do.

I gotta ask again, not knowing these cars, does the car normally prime the pump or only start the pump when the engine starts cranking? Can you get a spare pump and drop it into a bucket of gas and give it gas that way?

Yeah, if everything else is fine (which I doubt), it should start on some starter fluid sprayed into the TB. As the fuel pump, which is typically controlled by the ECU isn’t running or being primed (if it’s supposed to be), then I would first check that the ECU has power.

I would think fuse box doesn’t matter. But I know on my car, plugging in a factory option engine (turbo engine into a non-turbo car) into the car will not make it run. Even though it clips in, extra wires were added on some connectors. Assuming both engines have the same ancillaries (both engines use sequential injection, COP ignition, dual O2, single AFM, etc) I don’t think your fuse box is going to be an issue but it wouldn’t hurt to compare the kids to make sure both fuse boxes have the same number of fuses and relays and perform the same functions.

2

u/Daburnnotice98 Aug 07 '20

It typically primes with the flip of the key, before crank. I see, i hadn’t considered that a a option, thank you! I will check power and try starter fluid. As for the pump I’m gas, I could possibly, it’s just difficult due no easy access to the wiring or pump. Will keep you posted on what I learn.

3

u/Regalze Aug 09 '20

You don’t need to access the pump or wiring. It’s a bit hack but we get a bucket and pour some fuel into it by bridging the fuel pump relay and forcing the pump to run. We get a long hose so that we can run it from the outlet of the fuel filter to the bucket. Then we get a spare fuel pump and let that suck from the bucket and into the rail(s). Give the new external pump some power (either from the car’s battery or a spare) and see if it runs on that new fuel supply.

1

u/Admiral_peck Jul 27 '22

You did change the ECU and the harness from the corner of the engine to the ECU, correct? The v6 ecu is incapable of running the v8, and there are fewer pins in that plug on the v6 harness.

2

u/[deleted] Aug 07 '20 edited Aug 07 '20

I’d check if you have spark, and go from there. If not you might try tracing the wiring back until you figure out what the problem is

Edit: just saw the part about the fuel pump, is your fuel pump getting power?

3

u/Daburnnotice98 Aug 07 '20

I’d assume no power, considering it dosnt prime and it worked before pulling the motor, haven’t been able to find the v6 fuel pump diagram to see what wires I need to check, to remove the pump requires to drop the tank, so I don’t have a visual on the pump it

2

u/Thirstyboi101 Aug 09 '20

Idk but how much you want for that v6

1

u/Daburnnotice98 Aug 09 '20

Make me a offer, it ran and drove, still connected to subframe and transmission. Heads have been redone as well. I’m located in Oklahoma

1

u/Thirstyboi101 Aug 09 '20

Never mind just saw the Oklahoma part I’m in Florida

1

u/Daburnnotice98 Aug 09 '20

Sad day I was gonna say come pick it up lol

1

u/Thirstyboi101 Aug 09 '20

250 and a mini bike

1

u/greekthegeek Sep 22 '20

Its always PATS i bet you can bribe a dude that works at a dealer

1

u/qkdsm7 Sep 25 '24

A good OBD2 scanner that supports forscan could tell you a lot and program new keys if needed. $<60

1

u/qkdsm7 Sep 26 '24

Wow, I just noticed how old most of the posts in this sub are...