I have a 1990 f250 7.5L, have a code 41, can't seem to get rid of it.
Things I've done:
Installed new fuel pressure regulator
Changed fuel filter
Checked fuel pressure on both tanks
(32 while running, bleeds of about 2psi every five minutes when turned off)
Changed O2 sensor twice(Bosch first, then NTK)
Changed PCV valve
Smoke tested vacuum system with engine
off, slight leak coming from EGR diaphragm
The current engine came out of another truck. I believe it was a 1991 F350 7.5L.
I used the harness that came with the engine. After looking at diagrams online, I realized the newer engine harness did not have a ground for the hego, so I installed the harness from my original engine, thinking that would fix the problem, but it did not. Now I'm thinking either the PCM is not matched up or is faulty.
Also, dual tank set up. I can run front tank down, then switch to rear tank, then back to front tank and it will have fuel again which tells me the return close off valve of the front pump is probably faulty. Could this cause a lean code?
I have to smog this vehicle soon as it is my work service truck and I need it registered and working so I can make a living. I've been working on this for over a month reading forums, and any other data I can find online. I'm at my wits end. I can't afford to leave it at a shop while they get a round to it, I have to keep it in the road.