Running Lean after walbro 255 install

[acemas99]

DSM Community:

I apologize if this topic has already been covered in the searches. I looked for it, but could not find a forum about this type of problem.

I recently installed an Aeromotive FPR and Walbro 255 fuel pump, and rewired it with 10 gauge wire power supply wire. I set the base fuel pressure to the stock (42.5 psi) at atmospheric air pressure. When I hooked up the vacuum lines and started her up, to my complete surprise, the car is running LEAN! The LED on my A/F ratio gauge is about half way into the red (lean) portion of the gauge for most of the RPM range.

Before I get into this, you should know that I am monitoring A/F ratio with a narrow band Autometer gauge, so already I am limited by the gauge's accuracy. You should also note that I am still running the stock injectors, and that the fuel filter was changed less than 4,000 miles ago. As for all other mods, my profile has recently been updated.


What I've tried:

Running a higher fuel pressure: I tried turning the base fuel pressure as high as 49 psi, and it seemed to have little effect on my A/F ratio. The pressure is set back to 42.5 pounds as of now.

Tuning with my S-AFC: This was also a surprise for me. I bought my car with the S-AFC installed, and until now the car had not been modded enough to require significant tuning. Watching my A/F gauge, I began to play with the low throttle, low RPM settings. Although I don't believe it was necessary, I set the low throttle position to 0% throttle to ensure the changes would effect my idle. With the S-AFC zeroed, the A/F LED was either off of the scale (to lean to read) or at the first or second position on the lean scale. After trying different levels, I finally set the 1000-3000 RPM to +17% air correction. The car seemed to run best this way, (smoother idle, more stoichiometric), but surprisingly the A/F ratio LED only moved about 2 LED positions toward stoich.

My thoughts:

Although the pressure is set to 42.5 psi (Stock), it could be different because of my Ebay fuel pressure gauge. It looks like a decent gauge, and is liquid filled, but always have my doubts about Ebay products. I don't think this is my problem, however, because as I said I tried a higher pressure (49 psi), and I don't think the gauge has an accuracy tolerance of more than 6.5 psi (49 - 42.5 = 6.5 psi).

I have thought about replacing the fuel lines also (tank to filter, filter to rail). I will do this eventually, but I don't believe it is the source of this problem because the stock fuel pump was able to deliver a better A/F ratio through these same lines.

I need to buy bigger injectors anyway, so this would be a great time to do that. (I'm thinking of 550's or probably 650's eventually for a 16g, but topic is for another time) While bigger injectors would solve the problem, I would still like to know why a much more powerful fuel pump would supply less fuel (assuming the pressures were the same). Hopefully someone out there has seen this problem before!

Thanks for your time,

Mason

 

[1992awdlaser]

Couple things.

1. Your air/fuel guage is not accurate.
2. Get a datalogger so you can watch everything like that.
3. Get an aeromotive liquid filled guage.
4. Don't drive the car until you get a logger and get it tuned.

 

[1gDSM4g63]

There are numerous things. First off, with the setup you have the 255lph and FPR is useless. If you plan to stay with the fuel system upgrade you will need bigger injectors, larger turbo and a chip or DSMLink to disable the fuel cut and a WIDEBAND.

 

[gregalmighty]

There are numerous things. First off, with the setup you have the 255lph and FPR is useless. If you plan to stay with the fuel system upgrade you will need bigger injectors, larger turbo and a chip or DSMLink to disable the fuel cut and a WIDEBAND.

Fuel system upgrades are always best to start with, they are part of supporting mods which you should always do first.

As far as the problem, check your intake for air slipping in after the MAF. Narrowband isn't the best way to watch your A/F but it does give you a general idea and it should be blinking back and forth. I agree with 1992awdlaser, get a logger and see whats actually going on. Also your stock fuel pressure is 43.5, not 42.5

 

[Stainbox12]

To begin with, this member is trying to solve a problem, not trying to buy parts. If you know you are running lean and you don´t have a logger or any other device and just a narrowband, then look at it and check your plugs. If the plugs show white then you are lean for real. If the car worked properly before, there´s no reason for it to run bad now. Check this, because it happened to me before. When you install the fuel pump, there´s a little o-ring that its pretty hard to install, most of the times it gets kinked inside, you may spill fuel inside the gas tank and you may not know. This could cause you to run lean. Is the car hard to start or its just running lean? what i did in my case, was to cut the fuel pump assambly and add a hose with clamps. Much easier than the crappy stock o-ring. The narrowband may not tell you what afr you are running, but it gives you a reading of the stock o2 sensor, and thats enough just to know if you are lean or rich.

 

[1992awdlaser]

To begin with, this member is trying to solve a problem, not trying to buy parts.

You need the right equipment in order to keep the car running right or to solve problems. You should have this equipment before problems start. Air/fuel guages are crap. A lot of times they are way off saying the car is running lean or rich and it is doing the opposite.

 

[acemas99]

Thanks for the quick replies and the $.02

Fuel system upgrades are always best to start with, they are part of supporting mods which you should always do first.

As far as the problem, check your intake for air slipping in after the MAF. Narrowband isn't the best way to watch your A/F but it does give you a general idea and it should be blinking back and forth. I agree with 1992awdlaser, get a logger and see whats actually going on. Also your stock fuel pressure is 43.5, not 42.5

A boost leak could be the problem, however that would not explain why is is suddenly lean after the pump/regulator install. Testing for boost leaks has been on my list for some time now, so this may be the motivation I needed.

To begin with, this member is trying to solve a problem, not trying to buy parts. If you know you are running lean and you don´t have a logger or any other device and just a narrowband, then look at it and check your plugs. If the plugs show white then you are lean for real. If the car worked properly before, there´s no reason for it to run bad now. Check this, because it happened to me before. When you install the fuel pump, there´s a little o-ring that its pretty hard to install, most of the times it gets kinked inside, you may spill fuel inside the gas tank and you may not know. This could cause you to run lean. Is the car hard to start or its just running lean? what i did in my case, was to cut the fuel pump assambly and add a hose with clamps. Much easier than the crappy stock o-ring. The narrowband may not tell you what afr you are running, but it gives you a reading of the stock o2 sensor, and thats enough just to know if you are lean or rich.

I can see what you mean about dumping fuel right back into the tank. I do not remember the o-ring specifically (I installed this pump a month or two ago). This could be a problem, but I do not think it is the problem because leak or no leak, I am still able to build the proper fuel pressure at the regulator. Also the car starts right up, taking no time at all to build pressure. It's useful to know about that o-ring, though.


Like Stainbox said, I am trying to solve a problem. In time, I will buy proper tuning/measuring tools, but for now I am trying to solve the problem with what I have. Right now, I am in the process of getting my motor ready for a larger turbo. Like Greg said, these are just the supporting mods. Because the car is somewhat of a DD, I am eager to get it running safely. When I have had to drive it, I have been using STP octane booster from any gas station (along with 93 octane gas), and that was good for moving the A/F LED a few notches toward stoich.

I am thinking that before this problem is solved I will end up buying injectors, probably 650's. I don't want to change the topic of this thread, but if my S-AFC has little to no effect on my stock 450's, then will I be unable to control these 650's? I know that 650 seems to be about the largest injector controllable with the S-AFC, but like I said in my earlier post I did not install the S-AFC, so I don't know if it was installed correctly. I guess my real question is are these mild tuning results with the S-AFC normal or not. I am hoping that the larger injector will give me more of a range of fuel trim with the S-AFC. Probably with the larger flow rate I will have a larger window of adjustment?..

Mason

 

[ILLiCliPSE]

it might sound like a long shot, but check to see if the pump hasnt fallen out of the pump assembly like mine did. it fell out and i was running lean and couldnt figure it out. opened the tank, and the pump was just laying in the gas tank, floating around. put it in so it wouldnt move, problem solved.

 

[bmoha2]

It should be set at with the vacuum source removed and plugged at 43.5 psi. There can be a big difference between having the vacuum source connected and plugged or not. I just put in 550 cc fic injectors and realized that my stock 450cc injectors were worn out and leaking. That is not opening and closing cleanly just opening and partway closing.