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No fuel at boost

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CleanPalms

Probationary Member
24
0
Aug 11, 2011
Baltimore, Maryland
I recently purchased my first DSM with the issue thats present in the subject line. All my mods as accurate as I can name them are in my profile. Using an AFC NEO to tune fuel/air I have an issue building boost. Any boost. I have several questions regarding the subject. I most definitely have spent 3 days searching this issue out and if there is already a post on this, I apologize I missed it. Let me begin by stating that I thank and appreciate every and all bits of information given to me by the members of this site. Onto the issue:

  1. Using NEO to tune, is seems + numbers need to be in large amounts in order to even begin richening out the fuel:air. The wideband I'm using takes 2-3 seconds at a constant throttle position/speed in order to accurately display the AFRs. And it ALWAYS shows super lean (---) or (17.0-18.0) initially, regardless of NEO setting, is this normal?
  2. Idling with no neo correction makes the car stall out so I know the neo is working somewhat, but the numbers required to idle or operate the car correctly are outrageous in my opinion. Ex. +30 at Ne1 (1000rpm) and more at each Ne point, is this normal?
  3. The car runs normally at low throttle and while slowly increasing RPM, WOT makes the car spit and sputter, like it can't adjust fast enough. And even low throttle but attempting to build boost (any at all) makes the car spit and sputter like crazy! In it's simplest form, it is impossible for my car to build boost.
Some other things that are possibly worth mentioning:
  • 1. Car was originally an automatic, and I've been told the ECU is still the automatic one.
  • 2. MBC has been set both ways (all the way open, all the way closed) no change.
  • 3. I've read many neo usage posts and articles so I'm pretty sure I'm utilizing it correctly. + Numbers = more fuel = richening out. - Numbers = less fuel = leaning out. Unless I'm confusing the two. But I've tried it both ways and have gotten no change anyway so that doesnt matter.

I just purchased EvoScan so I can now start logging, but don't know what it is that I should be looking for. So if someone wants me to provide a log or something, I could probably do that if you tell me which options to select. Thanks again!
 
Ok so someone tell me if I'm wrong but the ECU should not matter. Also maybe the wide band is in a spot that is not optimal. So that could be why it reads lean and it takes longer. SOMEONE CORRECT ME AND HELP THIS GUY
 
Is your fuel pressure regulator connected properly? At a minimum it should be connected to manifold pressure. Normally the fuel pressure solenoid is in between that connection however. I.e. vacuum line from manifold to bottom of fps, then side port of fps to the fpr.

If the fpr is disconnected this can cause the fuel issue you're seeing. I know as a shop left my disconnected and I experienced it myself. Someone I realized exactly what it was and was able to fix it quickly.
 
I would certainly always match my ECU with my build. The Auto ECU is going to want to compensate differently considering that it is based on load/throttle/RPMS/Etc to help with shift points and boost. It assists the TCU through all of this. So I would assume. ECU's are cheap. Pick one up.

As far as it running lean and taking seconds for it to calculate and read correctly for you, it sounds like you have one or more of the following issues which need to be corrected.

A : Exhaust leak before the Wideband sensor - This will cause a delay in the reading as well as display leaner readings because most of the fuel-enriched exhaust has escaped through splits in the exhaust. By the time the wideband picks anything up it's lean air.

B : Wideband is not calibrated properly - If your wideband is not properly calibrated it will NEVER display the correct AFR's. You should follow the step by step instructions provided by the wideband manufacturer.

C : Wideband failure - If your wideband is bad.. then.. well, nothing is going to be correct. ;)

D : AFPR/FPR - Make sure this is not malfunctioning. If it is stuck or not connected to your manifold properly then you will not increase fuel pressure as you enter boost thus resulting in a lean condition that will destroy your engine.
 
Is your fuel pressure regulator connected properly? At a minimum it should be connected to manifold pressure. Normally the fuel pressure solenoid is in between that connection however. I.e. vacuum line from manifold to bottom of fps, then side port of fps to the fpr.

From what I can tell, it's connected properly. It is bypassing the fuel pressure solenoid though. This is okay right? The solenoid is still connected electrically though, is this an issue?

D : AFPR/FPR - Make sure this is not malfunctioning. If it is stuck or not connected to your manifold properly then you will not increase fuel pressure as you enter boost thus resulting in a lean condition that will destroy your engine.

I read on a Cadillac site that to check the FPR I should turn the engine on and remove the vacuum line with the engine running and check to see if it's spitting/leaking fuel. If it is, the diaphragm is busted. Is this an accurate test for 2g as well? I also read that a busted diaphragm would cause it to be rich, while my AEM is reading lean.
 
It's ok to not have the FPS connected in respect to this issue.

I personally never disassembled my stock fpr so I don't know how it's constructed but I believe you have it backwards as far as interpreting any leaking fluid out the vacuum/pressure line to the fpr. If you had a leak there then your fuel pressure would not rise in a 1:1 ratio like it should with the boost pressure and so you'd get less fuel than expected by the engine as its calibrated expecting a given pressure, given injectors, and given flow to those injectors. I.e. you'd run lean.

Have you ever confirmed that wideband is working and accurate?
 
It's ok to not have the FPS connected in respect to this issue.

I personally never disassembled my stock fpr so I don't know how it's constructed but I believe you have it backwards as far as interpreting any leaking fluid out the vacuum/pressure line to the fpr. If you had a leak there then your fuel pressure would not rise in a 1:1 ratio like it should with the boost pressure and so you'd get less fuel than expected by the engine as its calibrated expecting a given pressure, given injectors, and given flow to those injectors. I.e. you'd run lean.

Have you ever confirmed that wideband is working and accurate?

Right, if the vacuum line TO the FPR was messed up. But from the stuff I read the FPR is there because without it, the fuel pump would pump too much fuel into the fuel rail and thus too much to the injectors and too much into the cylinders causing it to run too rich.

Now if I had a vacuum leak to the FPR or the pump or anywhere in between then the rail wouldn't get enough fuel either way, and with my changing of the neo trying to force it to get richer by adding a retarded amount of fuel that has probably allowed me to just be able to run it decently, but only at low throttle.

Can I get confirmation on this? When I get back I'll be trying to search/sort for a vaccum leak between the pump and the regulator. Now knowing that if the diaphragm was busted, I'd be running rich, which obviously I'm not.
 
The FPR increases fuel flow by increasing fuel pressure so that more fuel will go out the injectors. If it's not restricting flow out of the fuel rail you get less fuel (than you would if it was working) into your cylinders, not more. You've got it completely backwards.
 
Last edited:
Yes. That isn't a vacuum line under boost. It's a pressurized line that puts pressure on the FPR diaphragm to hold more pressure in the fuel rail. ;)

Dip a straw in a glass of water and place your finger over the back. Lift the straw up. This is your Injector of 450CC's. Now, if you release your finger the water simply falls out. Now try it again, this time using your tongue to plug the hole to keep the water in. Blow slightly and remove your tongue. The water pours out faster. Same scenario. Under boost, the FPR draws closed tighter so it takes more fuel pressure to push past it and return to the tank. The amount of pressure in the fuel rail dictates how much fuel passes through the injector with each spray.
 
Ok so the diaphragm could still be the issue then? Is the method asked above a good way of testing to see if the FPR is functioning correctly or should I test this another way? I've been on several different websites stating that if the FPR is jacked up, it would cause the AFRs to be rich. The opposite of what I'm experiencing.

From http://www.howstuffinmycarworks.com/Fuel_pressure_regulator.html

- What are the symptoms of a bad fuel pressure regulator?
The symptoms of a bad fuel pressure regulator include:
Lack of fuel pressure, excessive fuel pressure, black smoke and rich engine running condition, instant drop of fuel pressure once the vehicle has been turned off, delay building sufficient fuel pressure.

So confused...LOL. Lack of fuel = lean and Too much fuel = rich. Do I at least have that right?

Also, all of these answers are all AWESOME, i am easily learning a lot. I appreciate everyones comments and for your continued help to get me through this issue and get my first DSM running like a beauty!
 
I have diagnosed a bad FPR by removing the vacuum line. remember to put your finger over the hose so that the engine continue to idle properly. You should hear a small change in the engine idle as well. If any fluid drips from the fpr's stem, then it is bad.

Also you have the correct idea. Too much fuel = Rich. Not enough fuel = Lean

10.5 AFR is Richer than 16.5 AFR

This means that there are 10.5 parts air per 1 part of fuel and so on. ;)
 
I have diagnosed a bad FPR by removing the vacuum line. remember to put your finger over the hose so that the engine continue to idle properly. You should hear a small change in the engine idle as well. If any fluid drips from the fpr's stem, then it is bad.

Also you have the correct idea. Too much fuel = Rich. Not enough fuel = Lean

10.5 AFR is Richer than 16.5 AFR

This means that there are 10.5 parts air per 1 part of fuel and so on. ;)

Okay. Excellent. Well my stem is facing up. So unless its suppose to overflow And drip down, gravity will keep it in the stem. But in either case I tested it and there was no fuel dripping out. The car idled fine even when i didn't have my finger on the tube. But When I put my finger on the tube and asked my buddy to depress the throttle I felt it sucking slightly harder on my finger. That's all I can do currently until I get an air compressor to do a vacuum test. I guess I can try looking at the injectors. Anything I should look for specifically?
 
Well I've waited about 10 - 15 minutes with the vaccum hose disconnected from my FPR just to ensure that the regulator diaphrahm was not spitting fuel. Which is wasn't. So since I've been gone doing these test I've back with several things done that none of which has resolved any issues but could assist in troubleshooting

FPR -> Operating Properly (not spitting fuel)
Reconnected FPS to FPR.

  1. Noticed that the FPR vacuum line was T'd off to the boost gauge, then T'd off again to what I've been told is a MAP sensor, then to the intake manifold.
  2. Removed boost gauge.
Currently looks like this.

FPR -> MAP Sensor & FPS -> Intake Manifold

Removed MBC and hooked directly to WG pressure.
Rented fuel pressure test kit from Auto parts store. Any ideas on where the best spot to hook this up is? I'm guessing the best spot is right before the fuel rail but I have crimped fuel lines. so I'll try right after the FPR on the return line. Also what should my readings be? I've read 42 PSI for stock Fuel Pump, but mine is Wallbro 255.
 
I recently purchased my first DSM with the issue thats present in the subject line. All my mods as accurate as I can name them are in my profile. Using an AFC NEO to tune fuel/air I have an issue building boost. Any boost. I have several questions regarding the subject. I most definitely have spent 3 days searching this issue out and if there is already a post on this, I apologize I missed it. Let me begin by stating that I thank and appreciate every and all bits of information given to me by the members of this site. Onto the issue:

  1. Using NEO to tune, is seems + numbers need to be in large amounts in order to even begin richening out the fuel:air. The wideband I'm using takes 2-3 seconds at a constant throttle position/speed in order to accurately display the AFRs. And it ALWAYS shows super lean (---) or (17.0-18.0) initially, regardless of NEO setting, is this normal?
  2. Idling with no neo correction makes the car stall out so I know the neo is working somewhat, but the numbers required to idle or operate the car correctly are outrageous in my opinion. Ex. +30 at Ne1 (1000rpm) and more at each Ne point, is this normal?
  3. The car runs normally at low throttle and while slowly increasing RPM, WOT makes the car spit and sputter, like it can't adjust fast enough. And even low throttle but attempting to build boost (any at all) makes the car spit and sputter like crazy! In it's simplest form, it is impossible for my car to build boost.
Some other things that are possibly worth mentioning:
  • 1. Car was originally an automatic, and I've been told the ECU is still the automatic one.
  • 2. MBC has been set both ways (all the way open, all the way closed) no change.
  • 3. I've read many neo usage posts and articles so I'm pretty sure I'm utilizing it correctly. + Numbers = more fuel = richening out. - Numbers = less fuel = leaning out. Unless I'm confusing the two. But I've tried it both ways and have gotten no change anyway so that doesnt matter.

I just purchased EvoScan so I can now start logging, but don't know what it is that I should be looking for. So if someone wants me to provide a log or something, I could probably do that if you tell me which options to select. Thanks again!

Read my " fuel problem" posts in my profile man... I checked everything that there was to check and it ended up being my fuel pump! Same exact problem your having turns on runs but under WOT cuts off... If u check for pressure it'll be good pressure but not enough for WOT!!
 
Read my " fuel problem" posts in my profile man... I checked everything that there was to check and it ended up being my fuel pump! Same exact problem your having turns on runs but under WOT cuts off... If u check for pressure it'll be good pressure but not enough for WOT!!

You're right it sounds like we are having a similar, if not the exact same problem. Except I can't even creep into boost without it backfiring like crazy. I was told by the previous owner that the Walboro 255 was a brand new pump and just makes me feel terrible that I would even have to replace it haha. But if thats it, then that's it. I just dislike spending money on things I can't really PROVE is causing the issue.

Another thing worth noting that my friend mentioned is that the stock boost gauge on the cluster is reading 100% boost before I reach fuel cut. Which just so happens to be the reading as just entering boost on my aftermarket boost gauge. Possibly related?

You mentioned that if I perform the pressure test at idle and what not it would give accurate readings but during WOT the pump just cant handle adjusting the fuel pressure? Am I right? How could I test for this besides keeping my car in the state of "hitting the wall" (WOT) so I can read the pressure? What should my pressure be under WOT?

Also, it seems like this matters according to some posters. If I have stock injectors (which i dont), I am running the stock FPR. Per the manual, without removing the vacuum line and plugging it with my finger, I should be reading 33psi and when removing the vacuum and plugging it, between 42 and 45psi. Is this also correct?
 
What is the serial number on the back of your Neo?

EDIT: Yes, I am serious, please go look at the back of your Neo and record the numbers on it and then post it here.
 
Either which way, you need to call APEX'i and arrange for them to reflash your unit with the updated software so it has support for Mitsubishi and Toyota MAFs.
 
Either which way, you need to call APEX'i and arrange for them to reflash your unit with the updated software so it has support for Mitsubishi and Toyota MAFs.

How can i be certain the unit hasn't been reflashed already. In the help options on the APEXi I should be able to view version number somewhere i assume. What is the firmware version that supports mitsubishi MAFs?

EDIT: I doubt it has already been flashed, but just trying to rule out every possibility. I definitely appreciate your input!
 
I don't remember for sure cause it has been a few years since I dealt with the issue. However, APEX'i is easy to get a hold of on the phone and they will be able to tell you on the spot.

Here you go:

After analyzing the data I gathered from my AFC Neo and testing another Neo on a testbench, Apex has confirmed that there is a problem with the Karman (frequency-based) airflow correction feature on current-generation (firmware revision v1.103 or less) AFC Neo products. As shown in my logs, the AFC’s output is incorrect and erratic under certain conditions, most notably when the input airflow signal rises above 1000Hz. The problem does not seem to be limited to anything specific to the 3000GT/Stealth platform, and likely applies to any application using the Karman feature.
 
I don't remember for sure cause it has been a few years since I dealt with the issue. However, APEX'i is easy to get a hold of on the phone and they will be able to tell you on the spot.

Here you go:

Well again I definitely appreciate it but it may not be the solution to my overall issue. It seems i need this insane fuel correction on the current apexi firmware version for the car to run, if i turn off hi and lo throttle correction the car just stalls out. Any ideas on this?

EDIT: In addition to your previous edit. I've ran evoscan logger for 16 minutes to determine my fueltrim status and I logged the Airflow Hz. It never went above 60hz or below 45hz at idle, should this increase during increased throttle? Don't quite get his 1000hz theory. Could you elaborate?
 
That is pretty much what the issue comes down to, the fuel correction that the unit is trying to account for is out of whack.

EDIT: Are you sure of the size of injectors that are in the car?
 
That is pretty much what the issue comes down to, the fuel correction that the unit is trying to account for is out of whack.

EDIT: Are you sure of the size of injectors that are in the car?

I'm certain, they are the pink 560CCs. Pulled each one out and inspected it.

EDIT: Another issue we located today was that one of my spark plug wires seemed busted on the end.
 
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