So, I have the walbro 255 LPH pump. Stock FPR.

How can I tell if the stock FPR is failing? Can having the higher output pump ruin the stock FPR?

I have an A/F gauge, using the narrow band O2 sensor, which I know won't tell much hardly anything. But, I noticed, that when I have the throttle at just slightly pressed, and then go from there and push it down to about half really quick, the car will bog a second and then start going. I do this and watch the O2 reading, and the gauge drops to 1 bar lean and then back to 2 bars in the rich area.

I know that the narrow band O2 isn't a good tuning tool, but could this be telling me anything? Normally it just fluctuates between lean and rich, but never almost completely lean.

Thanks!

Please don't post to tell me that trying to tune using a narrow band won't work. I am not trying to tune with it, I am trying to figure out what is wrong and wondering if maybe that is a sign of something. Any other ideas would be great.

 

Why the hell have you got the huge pump on a basically stock NA? That's madness. You'll be running far too rich.

 

lean spike is basically the engine misfiring because of the Uber rich condition that exists in that situation. There is absolutely no need for a walbro unless you pport that sucker and rev it to like 12k.

dpf22

 

man a 225 is a **** pot of way too much fuel, were building a 86 base into a drag car w/ stock motor and we are only gona put 550cc injectors, adjustible FPR, PD delete (maybe), and rewire the stock fuel pump directly to the battery w/ i think 4 ga. wire and cut-off switch on the center console in it. basicly the only things we didnt upgrade were rails and pump.

 

man a 225 is a **** pot of way too much fuel, were building a 86 base into a drag car w/ stock motor and we are only gona put 550cc injectors, adjustible FPR, PD delete (maybe), and rewire the stock fuel pump directly to the battery w/ i think 4 ga. wire and cut-off switch on the center console in it. basicly the only things we didnt upgrade were rails and pump. O yeah and we are going to ground the pump in like 4 differnt places.

 

LoL. Sorry, should have specified. Old pump was on it's way out, and had the Walbro 255 laying around from an 87 626 project (turbo). It fit right in perfectly. .

So, the stock FPR is going to just let all the extra fuel flow into the injectors? I have a new adjustable FPR, but I haven't tapped the fuel rail to add it in yet. Waiting to get all my S5 manifold stuff and S5 fuel rails before I tap, and add the lines for the new FPR.

So, basically my car is running way too rich. With the stock FPR is there anyway to stop this for the time being, or just wait until i put the car up in the garage and start doing the serious work on it?

Trying to get my GF's cabriolet running to be my DD while i do some serious work to the RX.

Her cabriolet is being very retarded though. Maybe someone on here would know. Starts, dies, starts dies. After about 5-10 starts, it will idle, but as soon as I touch the gas, it dies.

Bleh. Thanks guys.

P.S. Yea, I get told all the time that the 255 is too much, but I didn't want to go fork out more cash for another pump.

 

Yep. The FPR only responds to manifold pressure. It cannot compensate for changes in upstream fuel pressure.

Why are installing an aftermarket FPR? That's totally unnecessary on an NA.

Nope.

A used stock pump would've been cheaper than the FPR and require no custom work to fit.

 

I have the FPR hoping that I can turn down the fuel pressure to stock, and hopefully not make the injectors shoot too much fuel. The FPR didn't cost me a lot.

Thanks for the info NZ.

 

It will probably be easier to put the proper pump in the car and continue to use the stock regulator. But maybe I'm just stating the obvious.

 

If I have another fuel rail laying around, is it really much more difficult to tap M14x1.5 on the S5 fuel rail, then to just go buy a new OE pump and put that in?

I am looking to tap M14x1.5 to a barb fitting.

Thanks for the info though. I hope it really isn't too difficult.