HP Fuel Pump

[junkfixr]

I'm having issues recently that seem like fuel. Replaced in-tank pump and everything was fine for about 2 weeks. Then suddenly started losing power (stalling and sputtering) under acceleration. New FPR recently, coolant temp sensor, TFI module, tune etc., etc.

I guess my question is, would the high pressure pump cause symptoms like this? It starts quickly, idles great, but when you put it in drive and put it under a load it stalls, sputters and does everything except cut off. Would a pressure test show a bad pump if there's enuogh fuel to idle but starving only under a load?

It's getting to me 'cause I don't have a code reader but can borrow a fuel pressure guage from the local parts store. I've swapped computers, same results. It doesn't seem to be a spark issue ( no backfire or popping) it just won't accelerate under a load. Any suggestions or hints would be greatly appreciated.

Could an O2 sensor cause such problems, or would it just stay open loop, run o.k. but get bad gas mileage?

 

[adsm08]

You can check fuel pressure. It should remain steady through the RPM range, if it drops as you rev the engine the HP pump is likely bad.

O2 sensors are more likely to do something somewhat opposite of what you describe. They will make it sputter at idle or cruise and run well when accelerating aggressively.

 

[truckerdawg]

I had a 4.9l in a F150 work truck that did the exact same thing-the more gas I gave it the worse it ran. Turned out to be the fuel filter.