Fuel Pressure fluctuations
12-01-2011, 01:06 PM
#1
3rd Gear Member
Thread Starter
Join Date: Jan 2007
Location: Blue Ridge Mtns, VA
Posts: 524
Fuel Pressure fluctuations
I havent made an attempt on any serious troubleshooting yet since the issue has been very intermittent but I'd like to get a feel for any suggestions.
The problem became noticeable all of the sudden a couple of weeks ago and it only happens as you go through the gears at normal acceleration but it falls flat on its face, as if you cut the ignition off for a split second, but it comes back as quickly as it happens. The problem doesnt happen during cruising speeds nor does it happen all the time during every acceleration. If you get after it hard, it doesnt happen.
The only common denominator that I've found so far when it happens is the fuel pressure on my AeroForce gauge. It typically runs a steady 40 but during these "black outs" it spikes and then plummets as you operate the gas pedal.
I'm planning to check the connections at the FPDM's but if nothing is obvious, I may just have to start replacing parts....
Your valued and experienced suggestions are welcomed.
The problem became noticeable all of the sudden a couple of weeks ago and it only happens as you go through the gears at normal acceleration but it falls flat on its face, as if you cut the ignition off for a split second, but it comes back as quickly as it happens. The problem doesnt happen during cruising speeds nor does it happen all the time during every acceleration. If you get after it hard, it doesnt happen.
The only common denominator that I've found so far when it happens is the fuel pressure on my AeroForce gauge. It typically runs a steady 40 but during these "black outs" it spikes and then plummets as you operate the gas pedal.
I'm planning to check the connections at the FPDM's but if nothing is obvious, I may just have to start replacing parts....
Your valued and experienced suggestions are welcomed.
12-03-2011, 10:52 AM
#2
6th Gear Member
Join Date: May 2006
Location: Nicely done
Posts: 11,881
i don't know.... this is a tough one.
but since you say the pressure spikes then plummets, i''m leaning
toward the Fuel Rail Pressure Temperature sensor, or an issue with
the vacuum line between it and the back of the manifold.
good luck and let us know what it turns out to be.
but since you say the pressure spikes then plummets, i''m leaning
toward the Fuel Rail Pressure Temperature sensor, or an issue with
the vacuum line between it and the back of the manifold.
good luck and let us know what it turns out to be.
12-03-2011, 12:35 PM
#3
3rd Gear Member
Thread Starter
Join Date: Jan 2007
Location: Blue Ridge Mtns, VA
Posts: 524
i don't know.... this is a tough one.
but since you say the pressure spikes then plummets, i''m leaning
toward the Fuel Rail Pressure Temperature sensor, or an issue with
the vacuum line between it and the back of the manifold.
good luck and let us know what it turns out to be.
but since you say the pressure spikes then plummets, i''m leaning
toward the Fuel Rail Pressure Temperature sensor, or an issue with
the vacuum line between it and the back of the manifold.
good luck and let us know what it turns out to be.
If I understand the sequence of operation here, the FPDM is being told to run the fuel pump based on the PCM telling it too. The PCM takes a bunch of sensors in to account and the pressure/temp sensor as well as the TPS are two of those.
Intermittent issues are a bear to fix.
12-03-2011, 01:58 PM
#4
Join Date: Nov 2011
Location: Texas
Posts: 14
I havent made an attempt on any serious troubleshooting yet since the issue has been very intermittent but I'd like to get a feel for any suggestions.
The problem became noticeable all of the sudden a couple of weeks ago and it only happens as you go through the gears at normal acceleration but it falls flat on its face, as if you cut the ignition off for a split second, but it comes back as quickly as it happens. The problem doesnt happen during cruising speeds nor does it happen all the time during every acceleration. If you get after it hard, it doesnt happen.
The only common denominator that I've found so far when it happens is the fuel pressure on my AeroForce gauge. It typically runs a steady 40 but during these "black outs" it spikes and then plummets as you operate the gas pedal.
I'm planning to check the connections at the FPDM's but if nothing is obvious, I may just have to start replacing parts....
Your valued and experienced suggestions are welcomed.
The problem became noticeable all of the sudden a couple of weeks ago and it only happens as you go through the gears at normal acceleration but it falls flat on its face, as if you cut the ignition off for a split second, but it comes back as quickly as it happens. The problem doesnt happen during cruising speeds nor does it happen all the time during every acceleration. If you get after it hard, it doesnt happen.
The only common denominator that I've found so far when it happens is the fuel pressure on my AeroForce gauge. It typically runs a steady 40 but during these "black outs" it spikes and then plummets as you operate the gas pedal.
I'm planning to check the connections at the FPDM's but if nothing is obvious, I may just have to start replacing parts....
Your valued and experienced suggestions are welcomed.
12-03-2011, 02:43 PM
#5
3rd Gear Member
Thread Starter
Join Date: Jan 2007
Location: Blue Ridge Mtns, VA
Posts: 524
I have starting issues with my 2008 Buillett Mustang.....tried starting it 16 times before it would start.....have you had problems starting your Mustang..I just replaced the fuel pump asm yesterday......I'am guessing ...it acted like it was not getting fuel when we tried to start it....
12-03-2011, 04:37 PM
#6
5th Gear Member
Join Date: Dec 2006
Location: Redding, CA
Posts: 4,552
Have you done any work to your car at all?
What are the mods?
What happens when you let off the gas and then floor it? Does it fall on it's face then? I would lean towards a vacuum leak or a dirty throttle body if you have not done anything to the car and you have a stock tune.
What are the mods?
What happens when you let off the gas and then floor it? Does it fall on it's face then? I would lean towards a vacuum leak or a dirty throttle body if you have not done anything to the car and you have a stock tune.
12-03-2011, 06:44 PM
#7
3rd Gear Member
Thread Starter
Join Date: Jan 2007
Location: Blue Ridge Mtns, VA
Posts: 524
Have you done any work to your car at all?
What are the mods?
What happens when you let off the gas and then floor it? Does it fall on it's face then? I would lean towards a vacuum leak or a dirty throttle body if you have not done anything to the car and you have a stock tune.
What are the mods?
What happens when you let off the gas and then floor it? Does it fall on it's face then? I would lean towards a vacuum leak or a dirty throttle body if you have not done anything to the car and you have a stock tune.
as of tonight, it has officially gotten worse. I was going to do a few runs as you were suggesting and at WOT the fuel pressure was no higher than 15 and the car was starving for power. I did that 2 tiimes and figure I'm pushing my luck.
It sure is acting like the 2nd FPDM or 2nd fuel pump is very inconsistent and sometime isnt even running.
I'm planning to check some wiring and look for some obvious things when it's daylight tomorrow. Any suggestions are appreciated.
12-04-2011, 07:37 PM
#8
3rd Gear Member
Thread Starter
Join Date: Jan 2007
Location: Blue Ridge Mtns, VA
Posts: 524
I looked around today for anything obvious but found nothing. Spent alot of time looking around the wiring/connectors/relay on the 2 FPDM's in the trunk and spent some time looking over the vacuum system and anything out of the ordinary on the pressure/temp sensor. Verified the 30amp fuse on the 2nd pump was okay and fondled the throttle body sensor connections. As I said, nothing at all obvious.
Before taking the car out for a test, dug out the Whipple tuner and downloaded the tune for the first time since installing the blower.
Took the car out for a few WOT throttle runs and it was a tire blistering beast. Like I said, Intermittent issues are very difficult.
Stay tuned.....
Before taking the car out for a test, dug out the Whipple tuner and downloaded the tune for the first time since installing the blower.
Took the car out for a few WOT throttle runs and it was a tire blistering beast. Like I said, Intermittent issues are very difficult.
Stay tuned.....
12-05-2011, 05:52 PM
#9
3rd Gear Member
Thread Starter
Join Date: Jan 2007
Location: Blue Ridge Mtns, VA
Posts: 524
Spoke too soon! on the way to work this morning there were seveal spits and sputters. One the way home, nothing! Stopped by the dealer and picked up a Fuel Pressure sensor, about the size of a chicken egg, 100 friggin dollars!!
stay tuned....
stay tuned....
