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Author
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Topic: HELP! Engine/Tranny Swap 99 4.6 SOHC auto to 03 4.6 DOHC manual
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99Flyer
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Member # 1528
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posted
 
 
If you know of a link for this swap please post!
OK here's the prestory. Old 4.6 engine blew up in 2004. Bought 03 Mach1 DOHC and 04 5spd Tranny. Dropped in the DOHC engine and tranny/pedal assembly and that's as far as I got in 2005 when I sold the car unfinished to a buddy. I got $2000 of the $10,000 promised at the time(I still held title). Fast forward to 2011 when I reposessed the car from a storage unit(day before lien sale)where my ex-buddy had it. Now I want to start the car so I changed the oil and tried cranking it over. No Start. Sprayed starting fluid and it starts for about 20 seconds and dies. I don't hear the fuel pump so I check for voltage at inertia switch (has power after switch). I check for fuel pressure at rail and theres nothing. I noticed that the Mach1 harness does not completely match all pins up to the loom to the computer.
Question 1: Am I dealing with a major wiring issue that affects the fuel pump control module and other unseen things?
Question 2: Should I pull off the Mach1 harness and put on the old GT Harness to the DOHC motor?(I read this somewhere)
Question 3: Will I need to upgrade anything else? Example:Will SOHC GT fuel pump keep up with the DOHC Motor?
Thanks in Advance!
Carlo- 98cobra.com guy here that's been out of it for a while!
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2021 Bronco Black Diamond Sasquatch
1971 Camaro 350 SC
1977 GMC Kingsley Class A
Posts: 415 | From: San Francisco | Registered: Jul 2002
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99Flyer
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Member # 1528
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posted
Here a couple pics to give y'all a visual.
[ May 10, 2011, 10:49 PM: Message edited by: 99FLYER ]
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2021 Bronco Black Diamond Sasquatch
1971 Camaro 350 SC
1977 GMC Kingsley Class A
Posts: 415 | From: San Francisco | Registered: Jul 2002
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93coupessp
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Member # 8418
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posted
i would just check the wiring diagrams to the fuel pump control module thing. check your plug on the harness and check the pin configurations. obviously ur not getting fuel to the rails. so its a pump issue. u can get rid of the module and go to a return style system with a new pump and reg and delete the module with a tuner
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89 gt project
09 f250 diesel 605hp
14 cts-v
13 harley fxdb 103ci
Posts: 1919 | From: Hell | Registered: May 2008
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Blind
2.3L
CAFords OG
Member # 3052
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posted
so you have a `99 GT with a `03 mach1 engine and wiring harness in it, but the GT computer?
You really need to outline the exact parts that were swapped.
for my 4v engine swap, I retained the GT wiring harness and computer, and just extended a few wires that didn't reach with the new engine.
The car ran and drove perfectly fine, but did pick up power when I had it dyno tuned (probably due to the 24lb injectors).
If you don't have the mach1 computer/PATS ring/key cylinder, you'll want to keep the GT computer setup and re-install the GT engine harness.
the fuel pump should be fine to start it up and drive around, it may not keep up at WOT over 6500, but a dyno tune will show that.
but if you arent getting any fuel pressure despite voltage going out of the inertia switch, I would suggest making sure there is gas in the tank, then I'd change the fuel filter and see if gas comes out, and finally replace the fuel pump.
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89 LX Notchback ex 4cyl, 14psi
02 Harley F150, 15psi
Posts: 8521 | From: Fairfield | Registered: Jul 2003
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99Flyer
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Member # 1528
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posted
quote:
Originally posted by Blind:
so you have a `99 GT with a `03 mach1 engine and wiring harness in it, but the GT computer?
YES
You really need to outline the exact parts that were swapped.
Swapped was Engine to 03Mach1 from oilpan on up, AODE swapped for a T45, swapped pedal assembly, has GT computer
for my 4v engine swap, I retained the GT wiring harness and computer, and just extended a few wires that didn't reach with the new engine.
The car ran and drove perfectly fine, but did pick up power when I had it dyno tuned (probably due to the 24lb injectors).
If you don't have the mach1 computer/PATS ring/key cylinder, you'll want to keep the GT computer setup and re-install the GT engine harness.
great info because i have the mach1 computer but not the PATS/key cylinder
the fuel pump should be fine to start it up and drive around, it may not keep up at WOT over 6500, but a dyno tune will show that.
but if you arent getting any fuel pressure despite voltage going out of the inertia switch, I would suggest making sure there is gas in the tank, then I'd change the fuel filter and see if gas comes out, and finally replace the fuel pump.
Thanks Blind this was the response I was hoping for ![[patriot]](graemlins/patriot.gif) I originally bought the setup in 04 thinking that I would keep the Mach1 harness and computer. I swapped to the MAch1 computer but It wouldnt crank/start(probably due to the GT pats/keyring) When I got the car back last week, the GT computer was back in and it would crank but not start. Today I will follow what youve done and go with the GT harness, it looks like a pretty good fit and hopefully shouldnt take very long. It feels good to be completing a dream that I started in 04!
[ May 11, 2011, 02:00 PM: Message edited by: 99FLYER ]
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2021 Bronco Black Diamond Sasquatch
1971 Camaro 350 SC
1977 GMC Kingsley Class A
Posts: 415 | From: San Francisco | Registered: Jul 2002
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Blind
2.3L
CAFords OG
Member # 3052
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posted
I think you'll be fine once you swap the GT harness back in, unless they messed up something else.
iirc the plug wires I had to extend were the coolant temp sensors on the crossover, the TPS, and the EGR sensor (EVDM?) It really wasn't that many wires, but my car has coil packs, you may need to extend the COP plugs for a couple since they sit a little further out than on a 2v.
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89 LX Notchback ex 4cyl, 14psi
02 Harley F150, 15psi
Posts: 8521 | From: Fairfield | Registered: Jul 2003
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99Flyer
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Member # 1528
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posted
Okay as i started to remove the harness this afternoon I realized that the GT harness had already been installed and the appropriate wire extentions completed, so i reconnected and double checked everything.
I was able to get ahold of my old buddy who said that he did the wiring and it ran like shit barely drivable when he parked it. He never got the GT computer flashed however.
So this leaves me to look back at the fuel pump again. I put 4 gallons of fresh supreme in the tank but still no fuel pump priming, and no fuel pressure. I put my ear to the tank and hear a slight constant hummmmm but nothing like the 3 second priming on the 06 stang.
Now I'll have to figure out if its the fuel pump control module or the pump itself.
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2021 Bronco Black Diamond Sasquatch
1971 Camaro 350 SC
1977 GMC Kingsley Class A
Posts: 415 | From: San Francisco | Registered: Jul 2002
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Blind
2.3L
CAFords OG
Member # 3052
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posted
if it's humming then the pump might just be stuck?
I haven't had to troubleshoot the fuel pump on a newer stang, but first thing I would try is running a hot wire from a 12v source to the fuel pump power lead, probably easiest to get to that from the inertia switch in the trunk.
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89 LX Notchback ex 4cyl, 14psi
02 Harley F150, 15psi
Posts: 8521 | From: Fairfield | Registered: Jul 2003
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99Flyer
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Member # 1528
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posted
Yeah I tried powering it up at the inertia switch manually buT still nothing. I'm still reading up on the fuel pump control module to see what troubleshooting I can do. I really don't want to pull the tank and buy a pump if that's not what the problem is.
Posts: 415 | From: San Francisco | Registered: Jul 2002
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