2001 GT no start electrical issue

Mojo6921

Member
Jun 19, 2020
5
1
13
34
Georgia
Hey all, i'm having a no start issue on this GT I bought and the problem is dodging me. I'll try to be as detailed as I can about what's going on and what I've done so far.

The car will crank but doesn't start. The PCM power wire (V) is only getting .46v. All the grounds that I've checked so far seem good and have low ohm resistance. I do have some voltage drop on some fuses with key in run, but in accessory I have no drop. Fuel pump kicks on fine and I have around 35lbs from pressure test, I have 12v on all of my sensors. When I try to start it floods the engine to the point that gas gets in the oil so PCM seems to be sending 100% to the injectors when trying to start. Spark is good, and I replaced the plugs. No vacuum leaks. The battery is toast, and wont take a full charge, so i'm having to get my references with a battery charger hooked up. Not sure if that will play a role, but I plan on replacing the battery tomorrow.

Any ideas or clues where to go next?

Parts replaced on this adventure so far
FPDM
FRPS
Cam sensor
Crank sensor
Fuel filter
spark plugs
vacuum line from throttle body
 
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08GT500

Active Member
Jul 12, 2018
799
113
53
Massachusetts
Hey all, i'm having a no start issue on this GT I bought and the problem is dodging me. I'll try to be as detailed as I can about what's going on and what I've done so far.

The car will crank but doesn't start. The PCM power wire (V) is only getting .46v. All the grounds that I've checked so far seem good and have low ohm resistance. I do have some voltage drop on some fuses with key in run, but in accessory I have no drop. Fuel pump kicks on fine and I have around 35lbs from pressure test, I have 12v on all of my sensors. When I try to start it floods the engine to the point that gas gets in the oil so PCM seems to be sending 100% to the injectors when trying to start. Spark is good, and I replaced the plugs. No vacuum leaks. The battery is toast, and wont take a full charge, so i'm having to get my references with a battery charger hooked up. Not sure if that will play a role, but I plan on replacing the battery tomorrow.

Any ideas or clues where to go next?

Parts replaced on this adventure so far
FPDM
FRPS
Cam sensor
Crank sensor
Fuel filter
spark plugs
vacuum line from throttle body
Hi!
What year, precisely?
First clue, stop throwing money at it with parts that have not been found faulty via proper troubleshooting.
You need a good battery that provides at least 12VDC to your CPU. You’re substituting an inadequate power supply for a good Battery and the surges & spikes from its imbalance may harm sensitive electronics.
Engine will not start without a solid 12VDC or greater and solid ground at the EEC.
Pull your EEC Codes, no CEL does not guarantee there aren’t any.
Minimum you’ll need the above, certainly sounds as if you may have clogged injectors that are not stopping fuel flow, a wiring issue, no ground pulse. Have a NOID light, test light should show a pulse at one side, 12VDC at the other while cranking.
Note one injector’s wiring or issue with an injector can affect them all, so label & pull all the injector wires off injectors, measure resistance across each injector, have someone Crank it while searching for the injector pulses on each injectors connector.
I’d disable the fuel pump until you have a verification of the ground pulse at the injectors before both your rings are glazed and lower bearings are destroyed.
Remove that oil & filter from the motor, save some $$ by running Dino oil in it for the moment, you’ll need change it again.
You mentioned < 1/2 DCV at the EEC? What pin # did you measure from? Check your EEC wiring, fuses and relay.
Need that 12VDC from the new battery....
Check all your main grounds & solidify, Battery to block, block to chassis, battery to EEC, Battery to chassis. Remove all, clean, add electrical conductivity paste & be sure they’re good & tight.
Battery or alternator issue prior to this, or is this a result of over cranking; depletion?
Did this occur out of the blue? What preceded the issues?
Post your results.
Good luck!
-John
 

Mojo6921

Member
Jun 19, 2020
5
1
13
34
Georgia
Hi!
What year, precisely?
First clue, stop throwing money at it with parts that have not been found faulty via proper troubleshooting.
You need a good battery that provides at least 12VDC to your CPU. You’re substituting an inadequate power supply for a good Battery and the surges & spikes from its imbalance may harm sensitive electronics.
Engine will not start without a solid 12VDC or greater and solid ground at the EEC.
Pull your EEC Codes, no CEL does not guarantee there aren’t any.
Minimum you’ll need the above, certainly sounds as if you may have clogged injectors that are not stopping fuel flow, a wiring issue, no ground pulse. Have a NOID light, test light should show a pulse at one side, 12VDC at the other while cranking.
Note one injector’s wiring or issue with an injector can affect them all, so label & pull all the injector wires off injectors, measure resistance across each injector, have someone Crank it while searching for the injector pulses on each injectors connector.
I’d disable the fuel pump until you have a verification of the ground pulse at the injectors before both your rings are glazed and lower bearings are destroyed.
Remove that oil & filter from the motor, save some $$ by running Dino oil in it for the moment, you’ll need change it again.
You mentioned < 1/2 DCV at the EEC? What pin # did you measure from? Check your EEC wiring, fuses and relay.
Need that 12VDC from the new battery....
Check all your main grounds & solidify, Battery to block, block to chassis, battery to EEC, Battery to chassis. Remove all, clean, add electrical conductivity paste & be sure they’re good & tight.
Battery or alternator issue prior to this, or is this a result of over cranking; depletion?
Did this occur out of the blue? What preceded the issues?
Post your results.
Good luck!
-John
It’s a 2001 4.6 gt. I don’t have much history on it because I bought it not running. It was running just 3 weeks prior to me purchasing it and the previous owner replaced the fuel pump suspecting that was the problem. A lot of the other things I did like vacuum lines and fuel filter needed replacing anyway so I went ahead and did it.

So I replaced the battery and unplugged the PCM. Checked all the grounds for continuity with a jumper wire going straight to the negative post of the battery getting about 5 ohms of resistance. I was getting closer to 12ohm at the ground supplied for the pcm. I cleaned those up good and it’s got a much better ground now. Will do the same to the others. I confirmed 12v (key on) coming out of the ccrm to the pcm. My obd2 has no codes at all but the evap system and catalyst system stay incomplete. I have a confirmed short to ground somewhere because when I check at my FRPS I can get a vref on either lead of the battery. What I’m not sure of is if I can get a short to ground from a failed accessory, like the ignition switch, alternator or starter or if I need to specifically look for a broken wire somewhere.
 

Mr.Electric

Member
Jun 21, 2020
6
3
13
41
California
Thats a tough issue.
Did you determine if the ecu has 12v in run position.
Does a scan tool communicate with engine ecu.
Ive heard of an engine Ecu hanging all injectors open continuously in two cases. One was an old e150 van. A main ground was left disconnected after an engine job. When they tried to start it all the starter current went through ecu grounds for some reason. Totally roasted the engine ecu. Another was an infinity that got struck by lightning.
 

Mojo6921

Member
Jun 19, 2020
5
1
13
34
Georgia
I don’t know what pin to check for power on the PCM side, but at the ccrm I have 12v (key in run position) on both PCM power wires and a solid ground. I haven’t been able to find a matching pinout diagram for the PCM. Pinout I do have could be the same but wire colors don’t match so I need to trace it on the other end to be sure. I did check if the short was still present with the PCM unplugged and it is. The scan connects good and it shows it’s getting 12v on the obd2 port. I’ll use the noid light to see if it gets any pulse at the injectors and follow up.
 
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08GT500

Active Member
Jul 12, 2018
799
113
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Massachusetts
It’s a 2001 4.6 gt. I don’t have much history on it because I bought it not running. It was running just 3 weeks prior to me purchasing it and the previous owner replaced the fuel pump suspecting that was the problem. A lot of the other things I did like vacuum lines and fuel filter needed replacing anyway so I went ahead and did it.

So I replaced the battery and unplugged the PCM. Checked all the grounds for continuity with a jumper wire going straight to the negative post of the battery getting about 5 ohms of resistance. I was getting closer to 12ohm at the ground supplied for the pcm. I cleaned those up good and it’s got a much better ground now. Will do the same to the others. I confirmed 12v (key on) coming out of the ccrm to the pcm. My obd2 has no codes at all but the evap system and catalyst system stay incomplete. I have a confirmed short to ground somewhere because when I check at my FRPS I can get a vref on either lead of the battery. What I’m not sure of is if I can get a short to ground from a failed accessory, like the ignition switch, alternator or starter or if I need to specifically look for a broken wire somewhere.
Hi,
Ok, back up a bit. Guy messed with it, no telling what else he knows. If he replaced a pump, did he use the correct type to operate off the Pulsed power sent to run it ?
Receipt, maybe ask...?
As you’re starting from square one, Try this to narrow things down...gain some ground.
Disable your pump via inertia switch..
1) Pull your air intake off.
2) Clean all your plugs.
3)Blast a 1 second pulse of starting fluid inside the (open) throttle body plates.
4)Reassemble.
5) Turn the car over, engine attempt to fire?
Did you ever get any backfires out of the motor (intake or exhaust when attempting to start?(Timing).
Check for raw fuel or strong odor of fuel coming out of the FPRS line.
Pull the MAF sensor & blast it with some CRC, need to test MAF plug voltages & grounds, have the Shop Manual? Should get one, i can post what you need.

Disable the pump via inertia switch.
Have someone Crank the engine, hang onto an injector..is it firing? Best, If you have a NOID light, test light, look for the injector pulse.
- Pump enabled, How long does a key on fuel prime bring up fuel pressure to 35lbs for, before falling to zero?
What you need to determine is if all your injectors seem to be flooding the engine, or just one or even a few that have media inside, sticking them- hanging them open. Or perhaps a failed one, check resistance across all injectors.
Start with the basics...Compression-Spark-Fuel-Air.... Ignition, Injector, Cam Timing..
The EEC provides a floating ground for running the injectors, TPS, fuel pump, other solenoids, sensors, etc. any one of them in a failed condition may pull this ground down flat so nothing operates correctly.
-Check your TPS Voltage, <1 DCV?
If you don’t have the injector pulse, pull off all the injector’s plugs. Plug in one, turn the motor over, see if it begins to pulse, then plug in another, repeat until you find your problematic injector.
FPRS & Flooding...
FPDM pin 3 and 10 do not read 12 volts as that is how the FPDM controls the FP output. If FPDM pins 3 and 10 did read 12 volts, the FP duty cycle would be 100%.
Disconnecting the FRPS vacuum line will not change the idle because of the feedback from the IAC. It will make the motor run rich at idle.
Pump primes the motor with key on, correct?...didn’t continually run until the motor was actually cranking?
Check through your harness carefully for any wiring that may be chafed on the chassis, You can have a short to ground from many sources, you’ll have to slowly look over all your wiring under-hood, to pump.
Best!
-John
 

Mr.Electric

Member
Jun 21, 2020
6
3
13
41
California
Reading 08gt500's post I see that the sn95 has a pwm controlled fuel pump.
And previous owner just changed the fuel pump.
Wild guess here but maybe previous owner was confused by computerized fuel pump control circuit and simply added a switched power to the pump. Maybe worth looking at fuel pump wires for signs of hacking, twisted wires covered in scotch tape, 5 crimp connectors in a row , coat hanger used as wire , tin foil technology etc.
 
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Mojo6921

Member
Jun 19, 2020
5
1
13
34
Georgia
Hi,
Ok, back up a bit. Guy messed with it, no telling what else he knows. If he replaced a pump, did he use the correct type to operate off the Pulsed power sent to run it ?
Receipt, maybe ask...?
As you’re starting from square one, Try this to narrow things down...gain some ground.
Disable your pump via inertia switch..
1) Pull your air intake off.
2) Clean all your plugs.
3)Blast a 1 second pulse of starting fluid inside the (open) throttle body plates.
4)Reassemble.
5) Turn the car over, engine attempt to fire?
Did you ever get any backfires out of the motor (intake or exhaust when attempting to start?(Timing).
Check for raw fuel or strong odor of fuel coming out of the FPRS line.
Pull the MAF sensor & blast it with some CRC, need to test MAF plug voltages & grounds, have the Shop Manual? Should get one, i can post what you need.

Disable the pump via inertia switch.
Have someone Crank the engine, hang onto an injector..is it firing? Best, If you have a NOID light, test light, look for the injector pulse.
- Pump enabled, How long does a key on fuel prime bring up fuel pressure to 35lbs for, before falling to zero?
What you need to determine is if all your injectors seem to be flooding the engine, or just one or even a few that have media inside, sticking them- hanging them open. Or perhaps a failed one, check resistance across all injectors.
Start with the basics...Compression-Spark-Fuel-Air.... Ignition, Injector, Cam Timing..
The EEC provides a floating ground for running the injectors, TPS, fuel pump, other solenoids, sensors, etc. any one of them in a failed condition may pull this ground down flat so nothing operates correctly.
-Check your TPS Voltage, <1 DCV?
If you don’t have the injector pulse, pull off all the injector’s plugs. Plug in one, turn the motor over, see if it begins to pulse, then plug in another, repeat until you find your problematic injector.
FPRS & Flooding...
FPDM pin 3 and 10 do not read 12 volts as that is how the FPDM controls the FP output. If FPDM pins 3 and 10 did read 12 volts, the FP duty cycle would be 100%.
Disconnecting the FRPS vacuum line will not change the idle because of the feedback from the IAC. It will make the motor run rich at idle.
Pump primes the motor with key on, correct?...didn’t continually run until the motor was actually cranking?
Check through your harness carefully for any wiring that may be chafed on the chassis, You can have a short to ground from many sources, you’ll have to slowly look over all your wiring under-hood, to pump.
Best!
-John
It’s going to be one more day before I get a chance to get in there and play because of work schedule and an extra set of hands to crank while I check the injectors but I did climb underneath when I got home and snapped a few pics of the starter. I haven’t confirmed anything with my meter but it doesn’t look that good.
 

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08GT500

Active Member
Jul 12, 2018
799
113
53
Massachusetts
It’s going to be one more day before I get a chance to get in there and play because of work schedule and an extra set of hands to crank while I check the injectors but I did climb underneath when I got home and snapped a few pics of the starter. I haven’t confirmed anything with my meter but it doesn’t look that good.
Hi!
Yes indeed, Pulse Width Modulation driven pump, frequency counter or SillyScope to view, a DVM reading will just hang there at the RMS reading, if that.
I’ve seen replacements installed using the very basic, 6th Grade electrical 12V (+), 12V (-) on/off ideation, modification, and the issues ensue. There’s many possibilities as to what could occur. Your issue with the injectors drowning the engine suggest sticky, leaking injectors. That’s why I’d asked how long the Pump prime pressurized the rail, if it drops like a rock, it may be.
No, that starter solenoid looks more like a crudely devised, key operated arc welder, the cover’s completely broken (likely moisture inside) & connectors aren’t radiused for clearance in tight spots, actually look like AC Service Entrance Panel lugs specific to Residential, Commercial, or Industrial usage than for an Automotive App.
Have a clamp on Amprobe to measure battery cable current flow.... or own a VOM you can safely install** in a series connection between the disconnected battery Cable to the Battery itself to measure the DC load to Ground?
** Internally protected for Amperage levels that may measure higher than the intended capability of your VOM, usually 10A Max., if uncertain, consult the users guide or Mfg.
If not, Resistance measurements will work just fine..
To answer your question, yes, a short to ground is possible in an Alternator, Starter, Your Solenoid pic is the poster child!:nice:.
Any 12V+ wiring that leaves the battery can become either dead shorted, (Positive directly contacting Negative) or partially shorted to ground, (Chafed wire on a sharp edge of painted Chassis, engine, exhaust where Positive & Negative are close & moisture may bridge them slightly, etc.)
Only takes one, most offer fuse protection ...some do not.
Then there’s the EEC’s floating ground for all the sensors, solenoids, injectors, etc.
One dead shorted Sensor can pull down the entire switching & communication ability of the EEC. Or worse, take out the EEC.
A dead shorted Injector, for instance, can cause all to fail, as mentioned above.
It’s great you have located that, it could cause a huge Voltage drop when the key is turned, or before depending on the specifics.
That should be your starting point, I strongly suggest acquiring a Shop Manual for your new Mustang, the diagrams alone are invaluable. A Haynes costs 20-25$.
As suspected, it seems the Seller knows more than he’s admitting. You’ll want to erase all those mistakes, and be prepared for whatever else comes down the road.
Keep posting results, good job!
Best!
-John
 

Mojo6921

Member
Jun 19, 2020
5
1
13
34
Georgia
Hey everyone quick update. I finally found the short to ground but I'm not out of the dark yet. I had to order the part and its going to take a few days to get here so I can't confirm anything until it gets here. Not to mention the potential damage done to my injectors for staying energized so long, or anything else that's not discovered yet. Here is what all I did to find the short.

I unplugged every single sensor on the car and was still getting continuity from hot to ground on sensors. I unplugged my PCM to rule out electronic failure there. I did a parasitic amp draw on my battery with everything turned off and I was pulling around 1.5 amps. I started unplugging fuses and when I unplugged (I/P fuse panel, Instrument cluster, Powertrain Control Module) fuse my amp draw went to 0. I did a voltage drop test and found fuses 2 and 8 under the dash were showing moderate voltage drop. Both of those fuses are engine controls. After testing and chasing every sensor's hot wire independently I get to the MAF sensor and its power wire had no resistance to ground as if it were a solid ground. Chased that to the CCRM. I unplugged the CCRM, and jackpot. I have no more short to ground. With CCRM unplugged I tested from CCRM to PCM to make sure the drop wasn't behind it. Tested ground to all pins in CCRM plug to make sure it wasn't crossed wires.

I don't completely understand how my CCRM is the problem based on the symptoms. It powers everything that it's supposed to and my PCM was only affecting my sensors and injectors. If this doesn't fix the problem at least it fixed a shorted circuit. Since I have no PCM power until the new CCRM comes I wont be able to do the noid light test on my injectors. If you know of anything else it could be i'm all ears.
 
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