Hello,
Before I tell you my problem, here is what I'm running. I have installed and been tuned on 1100cc injectors, Tomei fuel rail, Tomei fpr, 300L/hr fuel pump and apexi fpr gauge. I've been running this setup and tune since last summer and everything has been fine until about a month ago.

Car starts fine, idles fine, daily driving is good, and even drives fine with gradual boost build. But, everytime I wot and hold, my fpr gauge builds the proper pressure as before(when my car ran properly) but after a sec or two it drops by 0.5 bar and picks itself back up and drops again and picks itself up. As its dropping my afrs go from low 11s to 12s and fluctuates with the fuel pressure gauge. Obviously I'm losing fuel pressure at high boost and before I purchase a new fuel pump to try out I was wondering if anyone has any input. Could this also be a boost leak issue?

No misfire codes or any codes for that matter.

 

I dont think a boost leak would cause that. It could be the pump or voltage fluctuations at the pump (alternator going) but thats a stretch i think. Are the lights dimming when this happens?

What brand is the pump? Aeromotive? I dont know much about those. Usually i go for the bosch 044 pumps.

 

FPR is where i would look first, when my 044 failed it did not fluctuate it just started to gradually not keep up, if it was a voltage issue it should only fluctuate if the fuel flow at the lower voltage was not enough to keep up with the demand other wise regardless the FPR should hold it constant, i would definately check for leaks just tee in a boost gauge to the FPR reference line and see.
cant hurt to put a multi meter across the pump supply all the same

 

+1 on the FPR...

 

Getting back to figuring out this issue..Any more input at what could be the issue? I'm running a deatschwerks 300lph fuel pump. Thanks.

 

Edited

 

FYI, 20 fuel pumps go bad for every 1 fpr. Just sayin......

 

Im kind of thinking its the fuel pump too. I've tried gradually building boost without wot and it can build the fuel pressure to where it needs to be without fluctuating but as soon as I wot, after a second or two it'll start dropping and picking its selve up.

I've noticed that it would do that fluctuation a lot sooner in the pressure reading if I were to turn off my EBC and go off of my wastegate.

I've also swapped it with my stock pump and it would build about 1 bar of pressure less than what it should be and lean out much sooner. I figured the stock pump doesn't have enough juice to keep up but then I've heard people running them on in their setup.

Voltage reading seems fine and no lights dim but I haven't tried reading the voltage at the pump.

 

sounds like the fuel pump to me

 

Do the re-wire mod on the fuel pump. If that helps then you have a voltage issue to the pump and it is not delivering fuel as it should.

If it doesnt help then I would swap the pump before looking at the FPR.

 

Easy way to test the fpr of you have a spare boost gauge is just have the car at idle and use another air source , compressor with a regular is ideal but yo can use a bike pump , just make sure the fuel pressure is rising proportionally with air pressure your putting into the fpr because your only idling fuel demand is low so if the pump is dodgy it shouldn't show up so therefore if it plays up under this test it is likely the fpr

 

Thanks for the suggestions. I will do both of those after it warms up here.

 

Thanks for the suggestions. I will try these soon.

 

I had a pair of dw300's go bad on me within about 2 months of daily driving. Just a heads up..

 

In your particular case, did they go bad individually or together atthe same time as in a double pumper? What were the telltale signs in your case. Did yours too start to lean out up on top during WOT, etc?