Yesterday car was running perfect. I have it tuned to 11.4-11.6 afr in boost, but today all of the sudden at 15psi at about 5500rpms it is going way lean. You can see in the data log below (the black line is afr) exactly what's happening. In the next pic I increased the fuel were it is going lean just to see if it helped, but it still goes lean. It's like the fuel pump can't keep up with the fuel demand. I'm pretty sure it's a mechanical problem. Everything else is working fine, part throttle and idle afrs are on target. It's only lean when fuel needs get high enough it can't keep up for some reason.

This exact same thing happened 6 months ago. I ended up hard wiring my fuel pump to the battery with a 30amp relay with a 30amp inline fuse and that cured the problem 100% until today when it randomly started leaning out again.

What I have done so far to try the fix the problem
-pulled fuel pump and checked fuel pump strainer and other components
-replaced fuel filter
-replaced the 30amp relay for my fuel pump
-checked all wire connections and grounds to fuel pump
-logged battery voltage and it's normal when it goes lean
-all other sensors are showing normal readings when logging
-I reloaded my tune just to make sure
-disconnected vac line to fpr and idle afr went a full point richer, pretty sure fpr is fine.


Here is a pic of a log where it goes lean. Injectors are still opening just not delivering enough fuel. Losing fuel pressure for some reason..


This is a pic of the fuel map with a retarted amount of fuel added. Still went lean when I hit these highlighted fuel cells. This seems to confirm it's a mechanical fuel issue.


A pic of the fuel pump strainer. It's dirty, but not enough to inhibit fuel flow imo.


Setup
Mostly stock ls motor
Tuned on neptune rtp by me
Walbro 255hp fuel pump hard wired to battery
600cc Bosch injectors
Stock fuel rail
Stock fpr
Very basic pieced together turbo setup
Only making a bump over 300whp is my guess.

Any help or trouble shooting ideas is very much appreciated. Thanks

 

How much fuel is in the tank ? I know in my ej coupe anything below half tank it leans...

 

Just over half tank. Just last week I was at the track with only a 1/4 tank and afrs stayed on target.

 

its been a while since I read your build, where you running stock lines and filter correct? I had similar issue I could get it to run but under boost it would lean out bad and start misfiring. Went back to tuner and pulled fuel tables, they were same but not able to keep up tried new strainer(I used the O'rilleys it took a crap on me in a couple months. It disintegrated.), new same pump, filled tank, tried to clean filters out. Ended up being injectors were clogged. After I got them back from cleaning and flow matched. Duty cycle was back to normal.

 

Walbro's go out/get weak or are DOA all the time. I hate Walbro pumps.

 

Yes stock fuel lines. It seems like to me if one or more of my injectors was clogged that my idle and part throttle afrs would be affected more were injector pulse widths are shorter.

Maybe it is my fuel pump. It's less than a year old, but I have heard of them going out quickly. It would kinda of make sense. Last time I had this problem the fuel pump had stock wiring, when i hard wired it the problem went away. Maybe the pump is slowly going bad requiring more and more amperage to maintain it's fuel flow. Does that make sense to anyone lol?

What fuel pump would you guys recommend that is not a walbro? Keep in mind I want one rated around the same flow as my fuel system is mostly stock and I run a stock fpr that I don't want to outflow.

 

On my Mustang my in tank 255 LPH Walbro was going out every 6-8 months. It was feeding a supercharged 302 making 480RWHP 520RWTQ. I added a Bosch 044 inline pump to take some load off of the Walbro and its been going for 3 years now.

 

Fuel Pump Comparison Test

I think adding a Bosch 044 inline pump would be a little over kill for my simple little setup lol. Is there another reliable option out there that is in the 255lph rating? Won't a 340lph pump outflow my stock fpr and increase my fuel pressure?

 

For me it isn't about overkill its about safety. I have an AEM 340lph in MY CRX that didn't give me any trouble but that's a small sample.

 

I was just looking at the aem 340lph intank pump. They are only about $100 witch is nice. What fpr are you running on your crx? I have a aem fpr I could install if the 340lph pump is too much flow for the stock one.

 

Stock and it works just fine @300whp

 

Thanks for the info man I appreciate it. I just ordered an aem 320lph intank fuel pump part number 50-1000. I'll let everyone know how it works out for me.

 

Find an original fuel sock and get rid of the one you have pictured. The one you have doesn't have an internal frame to keep it from collapsing on itself and becoming restrictive. Combine this phenomenon with it being a bit dirty... and you have a recipe for failure under high fuel demand.

 

Just for ***** I pulled that dirty stainer off, reinstalled the pump and did another run and it still went lean. Was this a bad idea? Probably lol but now I'm 99.9% sure it's the walbro pump. Is walbro pumps really that bad? It's less then a year old.

On a more positive note my aem 320lph pump will be here tomorrow.

 

my walbro is 5-6 years old now and still kickin lol and its had e85 for a year and had e85 sit in the tank for maybe 9 months during a rebuild

 

I had one other walbro pump go out in my turbo gsr teg while it was on the dyno getting tuned. I've had one in my Subaru wrx for a couple year now with out a problem, but on the subie the fuel pump has a duty cycle controlled by the ecu so it's only at 100% at wot unlike a honda were it's just full on all the time. Maybe that has something to do with the life of a fuel pump?

 

Is the subie returnless fuel system?

 

Well got my aem 320lph fuel pump today and got it installed. My lean problem is 100% fixed now. I'm still running the stock fpr and this pump did not out flow it or increase my fuel pressure at all. The aem pump makes about half the noise my walbro made witch is nice. As you can see in the pic it's the same size as the walbro 255 and install is exactly the same. Although I chose to drill a couple holes in my stock hanger and run the bigger wires and connector the aem pump came with. I used some grommets and sealed it up with some honda bond. I'm pretty disappointed in the walbro pump I bought as it's less then a year old. I really hope the aem pump holds up a lot longer...

 

Told you bro Walbro pumps suck!

 

Lol I now know this to be a true fact. Thanks for the help man I appreciate it!

 

I have had 2 Walbro pumps fail on me about a year ago at the same time. One was in the car for about 4 years with 93 pump gas and started acting up after it's first fuel up with E85. The other was in the car for less than a year and was on 93 pump gas, E85, and ~100 octane mixes. Both had symptoms of leaning out and erratic pressure fluctuations.

Be aware though, as the E85 AEM pump is almost 1/4" longer and can cause an issue on some hangers.

 

Where did you buy the pump from? Ht sponsor or from aem? I think i might be experiencing the same issue as you now lol

I use boost comp tuning and as i up the boost the ecu adds fuel as needed. I shouldnt need to tune past spring pressure. I keep raising boost pressure and its leaning out up top to 12.3 afr.

I been adding fuel but its not helping. I think i spoke too soon

 

I actually ordered it off amazon with prime 2 day shipping, only $100 to my door. The E85 version I think is about $40 more and like onebadturbocrv said its a little bit longer, but you still shouldn't have a problem with install as I had room to spare when I installed mine. Get that piece of **** walbro out of your car before it costs you your engine!

 

Interdesting. I was going to say probably the fuel pump. Having a fuel pressure gauge and/or regulator isnt necessary with a stock setup like yours, but I've found it helps alot with diagnosing problems. Not to mention you'd have the room to bump up the fuel pressure and squeeze more out of the injectors if you wanted to turn it up more.

I've rocked the same Walbro 255 for 3-4 years on my stock LS-T, now on a Walbro 400 E85 version going 3 years strong.

 

It took me forever to convince my brother his Walbro pump was causing his lean issues. We hooked a Fuel pressure gauge up pinched the return line closed and the pump would only build 60 psi brand new. Put in a twin turbo 300zx pump pinched the line and got over 100 psi. Problem solved. It pisses me off I still have two of them in My Lightning.