Need help with fuel problem.

[Stater212]

Ok quick run down I bought the car in Colorado Springs a few weeks ago and drove it 7 hrs home, ran perfect. Drove it 2 hours to my folks house then another 1&1/2 hours to Kansas City then back to my folks and back Wichita. Car has ran absolutely flawless until the drive back to Wichita today. I ran into a rain storm and problems started.

While cruising around 75mph I noticed my wideband was creeping to the lean side then all of a sudden pegged lean and stopped reading A/F. Car did not die but was struggling bad. I pulled over shut her down and waited. Fired it back up all was fine. About 5-10 miles later same thing. I figured I was getting rain through my intake messing up the AF ratio. Well long story short ended up trailering it home to risk any damage. Car did not throw any codes until we got home took it off the trailer and got it in the garage and it threw p1233 I know that code is fpdm. Now when I bought the car the guy thought the fpdm was bad so replaced it but found his fuel lines were kinked in a spot so thought the original fpdm was ok well I swapped it and the pumps didn't even prime when I put the old one on so I think it is bad. The pumps do still prime with the current fpdm. The car does have KB bap (which is set at 50? All the way rich?) not sure if that's typical.

But it need some help guys could it just be my MAF is bad and doing this? I've read it could be a whole slew of things just wanted to explain exactly what happened to me.

Thank you!!

 

[Stater212]

Oh and BAP does have upgrade wires not sure if that's useful info or not.

 

[cj428mach]

Ok quick run down I bought the car in Colorado Springs a few weeks ago and drove it 7 hrs home, ran perfect. Drove it 2 hours to my folks house then another 1&1/2 hours to Kansas City then back to my folks and back Wichita. Car has ran absolutely flawless until the drive back to Wichita today. I ran into a rain storm and problems started.

While cruising around 75mph I noticed my wideband was creeping to the lean side then all of a sudden pegged lean and stopped reading A/F. Car did not die but was struggling bad. I pulled over shut her down and waited. Fired it back up all was fine. About 5-10 miles later same thing. I figured I was getting rain through my intake messing up the AF ratio. Well long story short ended up trailering it home to risk any damage. Car did not throw any codes until we got home took it off the trailer and got it in the garage and it threw p1233 I know that code is fpdm. Now when I bought the car the guy thought the fpdm was bad so replaced it but found his fuel lines were kinked in a spot so thought the original fpdm was ok well I swapped it and the pumps didn't even prime when I put the old one on so I think it is bad. The pumps do still prime with the current fpdm. The car does have KB bap (which is set at 50? All the way rich?) not sure if that's typical.

But it need some help guys could it just be my MAF is bad and doing this? I've read it could be a whole slew of things just wanted to explain exactly what happened to me.

Thank you!!

Most recommend maxing out the BAP setting. The dial is deceiving as it really has no effect on how rich or lean the car is....well unless you're actually running out of fuel. The way the returnless system works is the ecm monitors the FRPS and fuel pump voltage to get the proper output to maintain the necessary pressure.

With the BAP there is more voltage going to the pumps so the output is higher but the ecm can still modulate the pump output by controlling the pressure. So if the BAP is maxed out the PCM just lowers voltage until it maintains the same pressure. The BAP helps when you need more fuel the PCM can tell the pumps to flow more fuel and because the voltage is higher the pumps flow more and you get more flow to maintain the pressure.

I would log your MAF, and FRPS and FPDC and see whats going on.

 

[Stater212]

Most recommend maxing out the BAP setting. The dial is deceiving as it really has no effect on how rich or lean the car is....well unless you're actually running out of fuel. The way the returnless system works is the ecm monitors the FRPS and fuel pump voltage to get the proper output to maintain the necessary pressure.

With the BAP there is more voltage going to the pumps so the output is higher but the ecm can still modulate the pump output by controlling the pressure. So if the BAP is maxed out the PCM just lowers voltage until it maintains the same pressure. The BAP helps when you need more fuel the PCM can tell the pumps to flow more fuel and because the voltage is higher the pumps flow more and you get more flow to maintain the pressure.

I would log your MAF, and FRPS and FPDC and see whats going on.

Ok when you say log, run a full data log from my sct and check those parameters? I will do that as soon as I get home.

 

[TRBO VNM]

Yes, use livelink and your flasher to log those.

MAF counts
Fuel Rail Pressure
Pressure drop across the injector is good as well
Returnless Fuel Pump Duty Cycle
RPM
short term fuel trims bank 1 and bank 2 unless it is a WOT issue, but those aren't bad to log as well

 

[Stater212]

Yes, use livelink and your flasher to log those.

MAF counts
Fuel Rail Pressure
Pressure drop across the injector is good as well
Returnless Fuel Pump Duty Cycle
RPM
short term fuel trims bank 1 and bank 2 unless it is a WOT issue, but those aren't bad to log as well

Well went out to data log the car and she won't even start now. Pumps are no longer priming prior to start up either. I cleaned my MAF prior to starting the car just to give it a little help but I think my FPDM is completely shot. I checked my fuel pump fuse and all is good there. Anything else I should check before buying a new FPDM?

 

[cj428mach]

Well went out to data log the car and she won't even start now. Pumps are no longer priming prior to start up either. I cleaned my MAF prior to starting the car just to give it a little help but I think my FPDM is completely shot. I checked my fuel pump fuse and all is good there. Anything else I should check before buying a new FPDM?

I'm pretty sure the FPDM is the same on all new edge mustangs it might even be the same as the ones on other Fords. If you're looking for one you might check the pick a part on 21st street.

The other suggestion is to go Return Fuel System, I love mine.

 

[Stater212]

I'm pretty sure the FPDM is the same on all new edge mustangs it might even be the same as the ones on other Fords. If you're looking for one you might check the pick a part on 21st street.

The other suggestion is to go Return Fuel System, I love mine.

I thought about that but not sure I want to throw that much at it right yet. We are living for the dominican republic in 3 weeks and want to save some $$$ for that. So you think I should go ahead and pick up a FPDM? Anything else I should check over? The funny thing is last night the pumps primed when turning the key over. I get off early today and they won't prime at all and it won't start. :shrug:

 

[Midnight_Cobra]

All FPDM's are the same. Just grab one from the junk yard. V6 or GT.

Can you physically hear the pumps prime? If so, are you getting fuel at the schrader valve?

I would just replace the filter and you might have a bad tank of gas...I know I've gotten "91" before and it ran like crap. Filled up again and everything was fine. Hopefully you're overthinking things.

 

[Stater212]

All FPDM's are the same. Just grab one from the junk yard. V6 or GT.

Can you physically hear the pumps prime? If so, are you getting fuel at the schrader valve?

I would just replace the filter and you might have a bad tank of gas...I know I've gotten "91" before and it ran like crap. Filled up again and everything was fine. Hopefully you're overthinking things.

No the pumps are no longer priming. They did prior to today. I had an older FPDM that I tried last night and they wouldn't prime put the newer one back in and they primed. I get off work today to data log the car and now they won't prime.

 

[MalcolmV8]

Have you checked your FPDM is getting power?

 

[Stater212]

Have you checked your FPDM is getting power?

As soon as I figure out how to do that ha ha.

 

[MalcolmV8]

lol pull the harness off and check with a meter.

 

[Stater212]

lol pull the harness off and check with a meter.

Sounds good ha ha thank you. My plan tonight is to check all fuses/relays etc. Fuses under hood, fuses for power wire to BAP under hood and in trunk, relay that the BAP is connected to in the trunk, FPDM and inertia switch most likely in that order. I bought a new meter last night. How would I check the 4 connection relay to verify its operating ok? Am I going about troubleshooting this correctly?

Thanks for your guys help. I want to be able to completely resolve this and post exactly what I found and how I fixed this issue. I have looked all over the internet and it seems quite a few people have this problem but on a lot of threads they leave them open ended. I want to complete this to help out others in the future.

 

[MG01GT]

Seems like everybody is getting **** blocked by electrical gremlins lately lol... I would check all your wiring grounds as well.

 

[Stater212]

Just checked the fuse coming off the relay to the bap and test light did not come on. Power wire from under the hood to the relay did show power. So power to the relay is good but why am I not getting power from relay to BAP, I had key on but not cranking. Coming off the relay is also a ground and green/yellow wire. What is the green and yellow wire? I've yet to hook up meter just wanted to test for power first.

 

[MalcolmV8]

Sounds like the green/yellow wire is your trigger wire to activate the relay. Might need to trace it and see why it has no power to turn on the relay to power up your BAP.

 

[cj428mach]

Sounds like the green/yellow wire is your trigger wire to activate the relay. Might need to trace it and see why it has no power to turn on the relay to power up your BAP.

Green/Yellow is supposed to be hot all the time with the key on isn't it Malcolm? Its been a long time since I've been back there but I think thats the wire people use on their return systems when wiring that hack way....lol.

Stater212 if you get in a major wiring job let me know as I have the Ford Shop Wiring Diagram Manual for 2003 Mustangs in the garage. I also have the regular shop manual but I don't know if gets into trouble shooting the FPDM.

 

[Stater212]

This is my current setUp. When I tested it last my key was off sorry. The green/yellow wire from the FPDM to the relay is hot. The power wire from front to relay is hot. The red wire from relay to BAP is not hot. Should it be or only when cranking?

 

[MalcolmV8]

The green/yellow wire from the FPDM to the relay is hot. The power wire from front to relay is hot. The red wire from relay to BAP is not hot.

OK if power to the relay is hot and the trigger is hot but the wire from relay to BAP is dead then either your ground on the relay is bad and the relay is not activating or the relay itself has died.