No Start Issue

Mfox89 · Jun 28, 2017

Maybe someone can point me in the right direction. I have an 04 mustang gt. Has the cobra fuel tank and had the cobra duel fuel pumps. Supercharged..lots of mods including KB BAP. Well the other day i was driving and stopped in traffic and i accidently choked it down on takeoff (getting use to new clutch) well it wouldn't start back up. It would crank but not start. I ended up having it towed to my local shop. They put two new dual walbro fuel pumps in 255lph. Before that they noticed fuel pump relay would get hot and blow fuses. They tightened up lose grounds and everything and it ran good for a little while after install of pumps but ended up shutting off while driving again. And now wont crank up again. After checking the wiring and everything, the fuses do not blow anymore and the relay doesnt get hot anymore either. The fuel pumps do kick on when the key is turned to ON. Idk if this has anything to do with it but my check battery light stays on. It always has. They are going try another relay. Any suggestions? Thanks.

wmburns · Jun 28, 2017

Are you doing the work yourself or are you going to be giving the "professional" mechanic trouble shooting assistance? Are you really paying a "professional" mechanic to guess what parts your car needs?

Here is a crank with no start check list with some more information.

1996+ Crank with no start check list
http://www.allfordmustangs.com/forums/4-6l-tech/336452-1997-mustang-wont-ignite.html#2984838

Pay attention to what the theft light is doing during cranking. Pay attention to what the check engine light is doing during cranking. The exact details matter. Having a complete list of symptoms and test results matter.

Test for key on power to fuse F2.34, F2.2, and F2.8. Use a KNOWN good ground. What direction to focus upon next depends upon which fuses have power and which do not as well as the test results from the check list.

1999-2004 MY fuse panel schedule:
http://www.allfordmustangs.com/foru...r-swap-wont-fire-please-help.html#post2669271

Here's some information on how to trouble shoot the battery and alternator. Don't cut corners here.

Howto perform charging system voltage drop test
https://www.stangnet.com/mustang-fo...perform-charging-system-voltage-drop-test.56/

Note, there are relatively few no start sensors for the 4.6. There are plenty of no run sensors. Bottom line. Given the history of your car I would TRIPLE check for a possible power issue before proceeding with the trouble shooting.

The modular 4.6 no start sensors are:

CKP. The quick functional test is to confirm that the check engine light goes out during cranking.
Fuel rail pressure sensor (FRPS). In a boosted application the FRPS is bad about breaking from high fuel pressure.
MAF. a quick bypass test is to disconnect the electrical connector.
the CMP sensor is not a no start sensor for the 4.6 (it is for the V6).

In general. Think FAST. Fuel, Air, Spark, and Timing. If the motor has all in the correct amounts it will start. It may not run but it will start.

Mfox89 · Jun 28, 2017

wmburns said:
Are you doing the work yourself or are you going to be giving the "professional" mechanic trouble shooting assistance? Are you really paying a "professional" mechanic to guess what parts your car needs?

Here is a crank with no start check list with some more information.

1996+ Crank with no start check list
http://www.allfordmustangs.com/forums/4-6l-tech/336452-1997-mustang-wont-ignite.html#2984838

Pay attention to what the theft light is doing during cranking. Pay attention to what the check engine light is doing during cranking. The exact details matter. Having a complete list of symptoms and test results matter.

Test for key on power to fuse F2.34, F2.2, and F2.8. Use a KNOWN good ground. What direction to focus upon next depends upon which fuses have power and which do not as well as the test results from the check list.

1999-2004 MY fuse panel schedule:
http://www.allfordmustangs.com/foru...r-swap-wont-fire-please-help.html#post2669271

Here's some information on how to trouble shoot the battery and alternator. Don't cut corners here.

Howto perform charging system voltage drop test
https://www.stangnet.com/mustang-fo...perform-charging-system-voltage-drop-test.56/

Note, there are relatively few no start sensors for the 4.6. There are plenty of no run sensors. Bottom line. Given the history of your car I would TRIPLE check for a possible power issue before proceeding with the trouble shooting.

The modular 4.6 no start sensors are:

CKP. The quick functional test is to confirm that the check engine light goes out during cranking.

Fuel rail pressure sensor (FRPS). In a boosted application the FRPS is bad about breaking from high fuel pressure.

MAF. a quick bypass test is to disconnect the electrical connector.

the CMP sensor is not a no start sensor for the 4.6 (it is for the V6).

Thanks for the info. Im not very mechanically inclined on things like that so im letting my shop do the work. Any info i can pass along helps though. The theft light stops blinking when turning the car over. I was thinking maybe it could be something with that at first but far as i know, it couldnt make the car shutoff while driving. Thanks

wmburns · Jun 28, 2017

So if you are looking for a WAG part to change how about a ruptured FRPS diaphragm? This is causing the PCM to not get a good fuel pressure reading. This could cause the motor to shut off and could prevent restarting. As said above the FRPS is more prone to breaking on boosted applications. One quick way to test is to check the FRPS intake vacuum reference line for raw gas.

The other way to check is to monitor the fuel pressure with an ODB2 scanner. If the fuel pressure is zero or never changes when the key is cycled, then BINGO. Diagnosis is confirmed.

Mfox89 · Jun 28, 2017

wmburns said:
So if you are looking for a WAG part to change how about a ruptured FRPS diaphragm? This is causing the PCM to not get a good fuel pressure reading. This could cause the motor to shut off and could prevent restarting. As said above the FRPS is more prone to breaking on boosted applications. One quick way to test is to check the FRPS intake vacuum reference line for raw gas.

The other way to check is to monitor the fuel pressure with an ODB2 scanner. If the fuel pressure is zero or never changes when the key is cycled, then BINGO. Diagnosis is confirmed.

Thanks for all your info! It is fixed now, it was because of loose grounds and the fuel pump relay was faulty. Thanks again!

Mfox89 · Jun 28, 2017

wmburns said:
So if you are looking for a WAG part to change how about a ruptured FRPS diaphragm? This is causing the PCM to not get a good fuel pressure reading. This could cause the motor to shut off and could prevent restarting. As said above the FRPS is more prone to breaking on boosted applications. One quick way to test is to check the FRPS intake vacuum reference line for raw gas.

The other way to check is to monitor the fuel pressure with an ODB2 scanner. If the fuel pressure is zero or never changes when the key is cycled, then BINGO. Diagnosis is confirmed.

Thanks for all your info! It is fixed now, it was because of loose grounds and the fuel pump relay was faulty. Thanks again!

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