MacMan

iTrader: (19)

I need the guru's on this one because I'm stumped.

Car is running great one day.... next day for no good reason fuel pump starts whining at idle and I can hear it cruising, which it's never done before. Pull out the laptop and check O2 sensor activity... looks good at idle, LTFT low is -1.5% but I notice it's not logging LTFT mid and it's zeroed out? Strange

Next day crank the car and let it warm up for 5 mins or so and start to work. For the first 5 minutes of my ride, when i give it a little throttle it has a hesitation "hang" almost when switching from cruising afr's to spool up like a mild fuel cut...but the car will give it the fuel it's calling for at 11.9-12.5afr's. Then after the first 10 minutes it no longer hesitates and just stops feeding the fuel the ecu is calling for. I give it throttle and I see in my logs where the ECU is calling for the fuel, but it's going the opposite way lean off the charts... like the primary fuel pump quits pumping as it should. I"m on speed density, and from 75kpa on I see short term fuel trim calling for the max fuel adder. The car cruises perfectly where it should, but the moment i give it any gas or see's any boost, it leans out off the gauge... EXCEPT for 5th gear. 5th gear will somehow still manage to get spool up afr's if i'm crusing at low rpm and give it gas. And the car has been consistently failing this exact same way for days. I've switched back to my 93oct map, still does same. Tested all injectors with Evoscan, plugs all look good. Nothing changed in the tune or hardware... it's like something just half died overnight.

I have a double pumper with 2x 255 wallys. The second pump is activated with a hobbs at 7psi which I confirmed was still happening while doing a boost leak test. 7psi on the nose hobbs hits and second pump turns on.... not the problem. It's the main pump not keeping up and has started whining after 10 mins into a ride.

I bought two new pumps and socks thinking maybe I had a dying pump. New pumps do exact same thing. No kinks in fuel lines. Replaced the fuel pump relays 1,2,and 3... still doing the same thing. I just sent my map sensor to Omni just in case it's map related but highly doubt it's the issue, it's reading kpa as it should when i give it gas... although it had started reading lower than 100kpa with the car off/key on as it always does.

Any idea's what could be the issue? I know there's stuff I'm forgetting and I'll edit OP when i remember. The fact that the car will feed the fuel it needs for 5 minutes then stops like clockwork baffles me. Any and all help appreciated.