Engine 1990 LX 5.0L EFI Mustang Fuel Management Problems - HELP!
- Thread starter 5.0LXStanger
- Start date
Blown88GT
Founding Member
You don't need the T-Rex boost pump any more with the 255 lph Walbro in-tank pump. The T-Rex boost pump was only needed to supplement the 88 lph in-tank factory pump. Unless I missed it, are you still using the factory A9L ECU & MAF? Neither are calibrated for 24lb injectors.
OEM 88 Lph fuel pump = High volume, low pressure
T-Rex = Low volume High pressure (should have a feed pump by all rights)
Walbro 255Lph High pressure, in-tank pump = blows all of that garbage away
T-Rex = Low volume High pressure (should have a feed pump by all rights)
Walbro 255Lph High pressure, in-tank pump = blows all of that garbage away
Ok sorry for the delay, but she's all back together with the new Walbro 255lph fuel pump and the new fuel gauge sending unit. I started her up and she still runs rough at cold idle / warm up, but once she hunts around for about a minute she settled down and idles, eventually settling in about 750rpms. Once warm I took her for a test drive. Idle and cruising fuel pressure is now around 28-32psi. She seems to be running much better - No lean popping and lots of power. 2nd gear is like a time-warp - No problem busting the wheels loose and drifting a bit in 2nd gear around 30mph. At WOT I am now seeing between 55 to 60 psi fuel pressure. I think I have solved a major reason for my LXs poor drivability. She still wants to die when coming to a stop. I will now pull codes (again) and then follow the cold / rough idle diagnostic sequence. I have a feeling I am on the right track...
