Ok, so nothing new for me. For some strange reason my fuel is still acting funny under boost. My car is down at TurboTrix and I'm confident they'll fix it one way or another, but I felt like starting this thread for a brainstorming session.

I have a clear mechanical problem...an on and off tapping/clicking/clacking sound from my head. I'm sure they'll have no problem finding/fixing that. Here's the kicker though.

My fuel is going bananas under boost. Basically it runs lean as hell (as high as 18.0:1) once the car reaches positive boost pressure. Now, here are the reasons this should not happen. My fuel system as it stands consists of a Walbro 255lph fuel pump, an AEM adjustable FPR (set at 40psi), and RC Engineering 440cc injectors. Fuel delivery is perfectly predictable out of boost, but once it goes positive the fuel simply can't keep up.

So far I've gotten one suggestion that may prove true. My car has a lot of electrical problems. The major problems being my broken dome light (bulb is fine, wiring is ****ed somewhere) and door locks/keyless entry. There's definitely a problem somewhere, but I don't know if it's possible that it relates to this. Now if I were to have a short in my electrical system, do you think it is likely and/or possible that it could be causing my pump or injectors to crap out under load the way it has been? How about bad grounds? I've had problems similar to this since day 1 so I'm more than open to suggestions. FMU did not work to fix the problem (it did help slightly, but I was still hitting dead lean patches, hence the 1 1/2 years of downtime.

Anyway, I'd like to hear what you guys think of that possibility, and I'd also like to hear any alternate suggestions. I can pretty much guarantee that the mechanical problem isn't causing the lean condition because this is my 2nd head on this car, and my original head had no clicking/tickin/clacking problems. So...lay it on me. Share your opinions and guesses. I'm willing to entertain them, both intelligent and otherwise.


For an up to date list of mods on my car: https://www.evolutionm.net/registry/viewride.php?vid=75

For a link to the thread since I got my car running about a week and a half ago: https://www.evolutionm.net/forums/sh...d.php?t=144673

 

Bueller? Bueller?

 

did you try another 255 pump? could be broke. just cuz it delivers well at idle doesn't mean that it'll deliver at higher IDC. i've seen a car idle fine, then when we hooked up a fuel gauge and went WOT, the pressure went down down down. bad pump.

you could try a new fuel filter. it's the whole white fuel pump assembly that is the lid on the fuel tank.

then there's the "buzz box" injector test. if the injector is stuck open/closed, or there's a short in the injector, this might tell you. there's a buzz box you hook up to an injector. hook up a fuel gauge to the rail and turn key to "on" without starting it. the rail should hold pressure. press on the buzz box and it'll let a set amount of fuel through. then check the fuel pressure and make note. then do it to the rest of the injectors to see if the pressure after a press on the buzz box is consistent.

not sure about the grounding situation, but i think the only injector related problem would be grounding from the injector to the ecu. either a short from the injector to the ecu, bad ecu, or bad grounding from the ecu to the vehicle if the injector isn't bad. you could check the positive wire to each injector to see if they're consistent to know that they're fine.

 

I'm 99.99999% sure none of the injectors are stuck because 1. They're new and more importantly 2. the flow is predictable and regular out of boost.

Keep in mind I'm using the EMS, not the stock ECU. Again, 99.99999% sure they're all firing (out of boost). That's what baffles me. If it were one of those problems it would probably present itself out of boost as well. Iono, I appreciate the input and Lord knows I trust your point of view, but all signs point to no right now.

 

lol oh yeah i'm retarded.

how about a voltage drop to the fuel pump? could the bosch relay to the fuel pump be faulty? it could be flickering when on boost due to all the voltage going to the injectors and coils and whatever other gremlins you got

 

What about your FPR? ISn't that pressure (boost) dependent? Could it be causing the problem that once you go into boost its not increasing the fuel rate? Just an idea

 

No, it's adjustable but static pressure on the FPR. With 440cc injectors and a 255lph pump there should be no need for raising fuel pressure. It's a very inefficient way of flowing additional fuel.

I think that second suggestion is more likely, rhyzin. I wish I understood a ******* thing about electricity. I'm gonna have to bring the idea up to Mark and whoever ends up working on my car.

 

Voltage loss to the fuel pump (as rhyzin mentioned) is the first thing that comes to mind. I can't find the article about it, but they tested DSMs and found that as the motor revved, the voltage to the fuel pump dropped.

Maybe test that connection?

 

I'm givin' myself another bump. Sent a PM to the guys at TTR, so hopefully they'll check on that next time they work on the car if they haven't already figured something out.

 

Let me ask you this... what boost level are you running at?? Some Miragers had problems with that AEM unit. Onee guy went through three FPRs that were failing under boost.... convinced us "big" boosters to just stick with Aeromotive. Have your explored this route?

 

The fuel cut is coming once I start making positive boost. So...1psi. Wastegate spring is either 7 or 9psi...I forget which. EBC isn't dialed in because I've never been able to run the correct amount of boost. When it's working properly I'd like to run 9psi.

 

Do you have access to any more FPRs to eliminate this possibility?

 

Stock FPR didn't work, AEM FPR doesn't work at slightly higher (2psi) fuel pressure. The more I think about it, the more likely it seems to be pump related than FPR...I don't have access to any others at the moment.

 

You stil lget your Wally whine, right? I have never heard of anyone have a Walbro fail, but I figured that they are so loud, that you can probably hear when they have failed. If you think it is the Wally, check around dsm boards and try to grab a 2G fuel pump. I had gotten wone a couple years back for 15 bucks shipped. Should be a relatively inexpensive way to double check and make sure it is not the pump.

What impedance are your injectors?

 

Yeah, it whines. I don't think it has failed. I think there's either a problem with the relay or the juice going to it under load. Iono. it whines like a **** and delivers fuel just fine until boost pressure goes positive. 16ohm 440cc