2004 Mach 1 crank but no start. dying inside

gavinmgrant

Member
May 23, 2022
35
3
8
26
Texas
Since the no start problem started after you drove into your garage, the cause is likely related to the work done thereafter. During the battery relocation a wire carrying 12v was possibly pierced and shorted to the 5v circuit.
Maybe this method will isolate things: Set DVOM to DC volts, put the black lead on batt (-), red lead on BRN/WHT of fuel pump connector (use hooded alligator clip for that pin, or with connector separated backprobe BRN/WHT. Get a helper to start pulling fuses until the 11.61v becomes 5v. That will identify which circuit is shorting to your BRN/WHT circuit. Things to look at are fasteners added which can pierce wires behind panels/bulkheads and pinch points on new wires ran. Let us know what you find.
I’ll let you know what I find. Thanks for the ideas. Unfortunately I got busy with work and travel so I had to step away from the car for a few days. I’ll have some updates for you over the weekend though
 
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gavinmgrant

Member
May 23, 2022
35
3
8
26
Texas
Since the no start problem started after you drove into your garage, the cause is likely related to the work done thereafter. During the battery relocation a wire carrying 12v was possibly pierced and shorted to the 5v circuit.
Maybe this method will isolate things: Set DVOM to DC volts, put the black lead on batt (-), red lead on BRN/WHT of fuel pump connector (use hooded alligator clip for that pin, or with connector separated backprobe BRN/WHT. Get a helper to start pulling fuses until the 11.61v becomes 5v. That will identify which circuit is shorting to your BRN/WHT circuit. Things to look at are fasteners added which can pierce wires behind panels/bulkheads and pinch points on new wires ran. Let us know what you find.
Unfortunately I have bad news. I was metering the wrong wire… Anyways, I’m getting 5.05v DC on BRN/WHT. My lighting in my garage is not good, dumb mistake. Still getting the 6.95v to LT BLU/ORG at the FPDM. I again shot the ground for the FPDM, shot good. 0.01 ohms. Shook the harness around, never moved from 0.01 ohms. Any more suggestions?
 

gavinmgrant

Member
May 23, 2022
35
3
8
26
Texas
Since the no start problem started after you drove into your garage, the cause is likely related to the work done thereafter. During the battery relocation a wire carrying 12v was possibly pierced and shorted to the 5v circuit.
Maybe this method will isolate things: Set DVOM to DC volts, put the black lead on batt (-), red lead on BRN/WHT of fuel pump connector (use hooded alligator clip for that pin, or with connector separated backprobe BRN/WHT. Get a helper to start pulling fuses until the 11.61v becomes 5v. That will identify which circuit is shorting to your BRN/WHT circuit. Things to look at are fasteners added which can pierce wires behind panels/bulkheads and pinch points on new wires ran. Let us know what you find.
Here is something else bizarre I found. The DK GRN/YEL wire is broken at the CCRM connector, but spliced into wire 12 RED.
 

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gavinmgrant

Member
May 23, 2022
35
3
8
26
Texas
Here is something else bizarre I found. The DK GRN/YEL wire is broken at the CCRM connector, but spliced into wire 12 RED.
UPDATE: IT IS FIXED.

I properly spliced the DRK GRN/YEL wire back together and the fuel pump primed. Started right up. I’ve never been so relieved to hear the fuel pump prime. Tapping into other 12v circuits and bypassing relays is just bad practice. What a trip this car has been. So happy it’s running again. Thank you to everyone who contributed.
 

COramprat

...I can take it. I think.
Mod Dude
Mar 2, 2003
7,791
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Sea of Tranquility
UPDATE: IT IS FIXED.

I properly spliced the DRK GRN/YEL wire back together and the fuel pump primed. Started right up. I’ve never been so relieved to hear the fuel pump prime. Tapping into other 12v circuits and bypassing relays is just bad practice. What a trip this car has been. So happy it’s running again. Thank you to everyone who contributed.
Glad you gt it figured out but you have to wonder why it was running before? Odd to say the least
 

gavinmgrant

Member
May 23, 2022
35
3
8
26
Texas
Glad you gt it figured out but you have to wonder why it was running before? Odd to say the least
I wonder the same thing. I have so many questions about this car I will never get the answer to. One of the evap lines for the EGR delete was capped with a hex screwdriver bit if that tells you anything LOL.
 
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COramprat

...I can take it. I think.
Mod Dude
Mar 2, 2003
7,791
1,165
223
Sea of Tranquility
@gavinmgrant My car had a built motor when I bought it. They spared no expense, Comp 278 cams, forged internals, dished pistons, aluminum Cobra block. I had some fuel issues after I had it about a year. When it came to connecting the wiring harness, they wire nutted the fuel pressure regulator wiring, left a bare ground that bounced around and eventually blew the PCM fuse and took two butt splices and put them on the pins for the IAC. I don't get how they spent ten grand building the engine and then BS'd the harness together.
 

gavinmgrant

Member
May 23, 2022
35
3
8
26
Texas
@gavinmgrant My car had a built motor when I bought it. They spared no expense, Comp 278 cams, forged internals, dished pistons, aluminum Cobra block. I had some fuel issues after I had it about a year. When it came to connecting the wiring harness, they wire nutted the fuel pressure regulator wiring, left a bare ground that bounced around and eventually blew the PCM fuse and took two butt splices and put them on the pins for the IAC. I don't get how they spent ten grand building the engine and then BS'd the harness together.
We will never know lol. Tonight on unsolved mysteries, mustang wiring done by the previous owner.
 
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Mach1.0

New Member
May 29, 2022
15
0
1
49
Texas
Glad you gt it figured out but you have to wonder why it was running before? Odd to say the least
UPDATE: IT IS FIXED.

I properly spliced the DRK GRN/YEL wire back together and the fuel pump primed. Started right up. I’ve never been so relieved to hear the fuel pump prime. Tapping into other 12v circuits and bypassing relays is just bad practice. What a trip this car has been. So happy it’s running again. Thank you to everyone who contributed.
Hey, glad to hear you got it fixed . Just now seeing your last posts. Miss a few days and you miss a lot . Wow, so someone bypassed the fuel pump relay in the CCRM. The bypass worked for a while then suddenly stopped working. Interesting.
Maybe the MAF or injectors which are fed by Splice 234 (Engine Control Sensor Harness behind right side of dash) developed a slightly higher voltage drop which was just enough to reduce a marginally operational current to the FPDM to the point of failure. IDK, we need Monk to figure this one out!
 

gavinmgrant

Member
May 23, 2022
35
3
8
26
Texas
Hey, glad to hear you got it fixed . Just now seeing your last posts. Miss a few days and you miss a lot . Wow, so someone bypassed the fuel pump relay in the CCRM. The bypass worked for a while then suddenly stopped working. Interesting.
Maybe the MAF or injectors which are fed by Splice 234 (Engine Control Sensor Harness behind right side of dash) developed a slightly higher voltage drop which was just enough to reduce a marginally operational current to the FPDM to the point of failure. IDK, we need Monk to figure this one out!
It is all very strange. I can’t explain how it even ran like that in the first place. I’m just glad I got it fixed. I’ll never forget this project lol