Running extremely lean
 

hello, i searched around and i am not exactly sure what the problem might be. the car is a 90 supercharged 1.6 with greddy emanage/supra 305cc inj., 190walbro. the car was in boost and all of a sudden it started cutting out. the w/d went extremely lean and the car cut out. everything seems to be connected, all plugs look the same, very white, from it leaning out. The car idles fine with a/f around 15, but as soon as the vacuum goes lower/closer towards boost the gauge goes lean. seems that not enought fuel is being delievered. im going to get a new fuel filter, but im not sure if it could cause it to run that lean. any suggestions?
thanks

make sure there's no leaks between the AFM and supercharger, check your fuel pressure and/or fuel filter.

I'd throw a fuel pressure gauge on it and see if the pressure its dropping off. if so the pump may be dead...:dunno:

Fuel Pressure -- filter or pump
Check for vac leaks, if it idles not likely....

Map sensor? If you are using a map sensor, make sure it's connected.....

Grounds -- check your grounds to the emanage, and all the other wiring -- not likely, but would be good to know for safety.

If the car bucked when it happened, now seems to go lean for no reason under load (not necessarily boost), it sounds like the pump. Happened to me on the way home from the track one day.... couldn't figure out while I kept getting a real lean on the straights.

Dave,

i check the pump as it said in the haynes manual by using the diag port. the pump makes noise, and the car idles perfect, so i dont think its the pump. also looked at the fuel filter, the thing looks brand new. im using gm mapsensor, i assume its functional there is no cels. steelrat, you think that a bad pump would idle fine, but underload it would not provide enought pressure? i dont have a fuel pressure gauge, so i have not yet tested the fuel pressure. thanks, im puzzled.

yeah, i've personally seen a car that would drive 100% out of boost, give it boost and the pump could not substain the pressure and the fell flat on its face and leaned out.

https://www.miataturbo.net/braineack...sure_gauge.jpg

this should cost you less than $15 in parts.

allrite, im about to ride my bike to autozone, hope its the fuel pump, what kind of pressure is a 190 walbro hold?

if its a HP unit, then it should be able to subtain 130psi when you clamp on the return line. standard model; 90psi.

fuel pressure was around 55-60 at idle and a bit lower when i drove. this is way to low. i pinched the fuel return line like the haynes manual said and the fuel pressure immediatly went to around 100psi. so according to the manual if pressure goes up when the return line is pinched the fpr is bad. im going to replace it tomorrow to see if thats what it actually is.

Dude your FP is way too high, not way too low.

the manual says it supposed to be at around 64-80ish, mine was below that, plus the fuelpump is not stock so i assume the fp should be higher, please explain BEN.

hook up a vac line to the FPR and blow in it. Make sure you can't force air past the diaphragm. Thats another way to check for a broken FPR

I don't know what manual you are looking at. FP should be around 35 psi at idle and 50 psi at 0 vac. The 190 lph standard or hp should not produce any more fuel pressure than the stock pump under idle and cruise conditions.

The NB runs 60-63psi static.

what kind of fuel pressure should i be getting in boost?

Pay attention to sections 2,3 & 4:
FAQ

you are right, the fp is supposed to be around 32-44, i misread the spes. in the haynes manual. however it says if fp is too high, and the return line has no obstuctions, then the fpr is bad. what do you think is the problem BEN? would a bad fpr make fp high, yet make the car run very lean under load?

sounds like the fpr is bad or there is no vac signal connected to the fpr

is this a JR supercharge kit with an FMU? The top adjustment screw is probably clamped down.

squeeze the return line off with FP and GND jumped in the diagnositics box with the ignition set to ON. the pump should be able to reach 85-130psi.

sounds like the oem FPR is not seeing vacuum or failed, or the FMU is to blame.

no fmu, there is emanage and stock fp, i just hooked up another gauge i bought and all seems well, fp idle is around 30, and full wot is 40, the car runs fine, with a/f of 12 at full throttle. i think the stock fpr had a hick up, since the car runs fine now.

well if it decides to hiccup again at wot full boost your ringlands might all decide to hiccup too.