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Ron, ASE Certified Technician
Category: Ford
Satisfied Customers: 35843
Experience:  23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
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I have a 1990 f250 7.5L, have a code 41, can't seem to get

Customer Question

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
Side notes:
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.
Submitted: 2 years ago.
Category: Ford
Expert:  Ron replied 2 years ago.
Hello, my name is ***** ***** I am a professional here at Just Answer. I have noticed that your question was not getting a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.
The code 41 can also be set due to low vacuum to the MAP sensor, so be sure to check it as well as rechecking you ground to the PCM. See the steps to check in the link below. Copy and paste the link to your browser to open and view them.
Customer: replied 2 years ago.
I appreciate the reply. I do not understand how to perform either of those tasks you have suggested. To check frequency, what tool is used?How do I perform a voltage drop test?
Customer: replied 2 years ago.
I did see someone else online suggest to jump the orange wire to the ball/white wire, is there any chance of damaging the Pam by doing this?
Customer: replied 2 years ago.
Expert:  Ron replied 2 years ago.

You can jump is as discribed and it will not damage the PCM. I would also make sure you have a good vacuum supply to it

Customer: replied 2 years ago.
Engine vacuum off the little vacuum distributor block on firewall was 20
Expert:  Ron replied 2 years ago.

Check it at the MAP as well.

Customer: replied 2 years ago.
Ron, I jumped 46to 49... Now lean code is gone, but now I have two new codes
21 ect out if self test range
77 operator error
Expert:  Ron replied 2 years ago.

The code 21 can set due to a failing ECT or even a engine not reaching normal operating temp due to either a low coolant level and or even a stuck open thermostat. The 77 does not mean anything.

Customer: replied 2 years ago.
Ok thank you, ***** ***** supposed to cut the orange wire and jump one side to the bulk/why? If so which side? The one towards ecm or toward O2 sensor?
Customer: replied 2 years ago.
Also, map vacuum was about 12.
Am I getting charged for each reply?
Expert:  Ron replied 2 years ago.

You can cut it any place as long as you have a good ground from the engine to the PCM.

Customer: replied 2 years ago.
I'm confused, which side of wire goes to blk/wht? I believe drop box you sent said orange wire carries voltage, wouldn't grounding it out be a bad thing?
Customer: replied 2 years ago.
Will you be able to talk via telephone soon?
Expert:  Ron replied 2 years ago.

Can you explain which wire you are referring to.