Hi everyone,

The Gentleman behind the counter at the local Parts store here told me that if I trade out a 1989 F-150 5.0 with a 1991 F-150 5.0 that I would have to trade out the computer also. Something about the programing of the computer to that motor. Sounds weird to me..... a motor is just a motor.... there an't no chips in it.... Can anyone give me some advice?


Also,,, After I traded the motor out the Oil Preasure, Water temp and Fuel gauges are not working..... I know you can trade out parts between a 1988 to a 1991.... so I thought everything should be the same... The way it looks, the wiring harnesses have the same connectors, Just the wires are in different ones. My Temp Sensor wire is Red with a white strip, in the 1991 it goes into the brown connector.... and on the 1989 it goes into the gray connector..... My was thinking that if I put the old wiring harness on the 1991 motor that is in the 1989 Ford it should correct all that.... Any advice would be appreciated.

Thanks

Ken

 

If you have wires going to different pins and colors I would deff. swap engine harnesses too.

 

Okay,

But is switching out the computer necessarry?

 

The computer should be fine as long as your not changing to a different trans .....Lew

 

I know this isn't the same year, but when I swapped out my dead 95 5.8 with a 94 5.8 I had to switch over the FI harness, and fuel rail. It all looked the same at first, but the only difference I could find was the 94 harness didn't have connectors for the air, it started and ran, but had a code and the diagnostic port would not read. Switched out the harnesses and the fuel rail. Ran good no codes. Apparently the 94 and 95's are different, so no reason to believe yours wouldn't be either.

Just my 2 cents

 

I would run the harness off of the original engine on the new engine - the original computer should work just fine.

 

When swapping motors the existing engine harness and computer should always be retained, the motors are identical externally except in a few rare cases so the harness will simply plug into the sensors on the repalcement motor

 

What was different about the fuel rails?

 

Both 89 and 91 are batch type speed density systems- there shouldn't be any problems with retaining the computer.
I have a pinout for eec wiring and it lists 87-95 302/351 speed density truck van and bronco in the same catagory with identical wiring to the 60 pin connector.
RSH

 

Thanks Everyone,

I left the 1989 Computer in the 1989 F-150..... I switched out the wiring harness and it works great... Engine light went off and the Temp and Oil gauge works know.... I can't believe the wires were switch around between these two trucks.

The only thing I have left to work on is the fuel gauge, tank....

On the 1989 F-150 I have a dual gas tank, When I flip the switch one tank reads past full..... the other reads past empty...

What is the best way to diagnose this problem? I know the sending unit on the rear tank of my 1991 worked so I can use it for parts.

Thanks

 

Fuel Gauge wiring:
past full = open circuit
past empty = short to ground
By opening the ground path and shorting gauge wires to ground.
No you can not, the 91 is not the same unit.

 

Okay,

I never worked on the Gas tanks or any part of it..

Let's see if I got this right,
When the Fuel Gauge shows "past full = open circuit" that means somewhere along the line their might be a break in the connection?

When the Fuel Gauge shows "past empty = short to ground" means that there is a ground issue somewhere? Or did I totally get that wrong.

I have a meter just need some wisdom on how and what to check.... My Haynes manual really doesn't help... I wish there was a how to for dummies book LOL.

Thanks
Ken

Quote:

 

You have it right.

 

Here is a diagram:


/

 

Thanks, I'll grab the meter and see what I can figure out....

Ken