Hi everyone,

I have a wierd problem, I pulled a motor out of a 1991 5.0 F-150 that was running sweet. I put it in a 1989 ford F-150 that had a 5.0 in it.
1) Both trucks had the AOD Transmission

One wierd thing was the trucks wiring, the harness had the same ends... however when i compared them, the wires were not in the same arrangement so I put the 1987 wiring harness on the 1991 Motor...

Everything works great (Except the fuel gauges).... Here's my problem.

Took the truck for a test drive in my subdivision (30mph speed limit) I got up to 35 and backed of the accelerator, when i step on the accelerator it gives me a shake/vibration in the truck. I can step on the gas peddle and it will take off. No warning lights. The people I bought the truck off said they were having trouble with the front fuel tank working. Before I started swapping out the fuel components I wanted to seek you'lls advise.

Thanks Ken

 

Went underneath the 1991 to pull all the pumps off and put it on the 1989 and realize there ain't one... All I saw on the 1991 was fuel lines and a filter.

The 1989 F-150 has all two types of pumps under it.

What did they do different differently to the fuel system on the later model EFI's (1990 & up)? Was there something I need to trade out that I did not do?

Second question, can I taked the fuel system out of the 1991 and put it in the 1989?

 

Ken,
1989 and earlier trucks used low pressure pumps in the tanks and a high pressure pump on the frame rail near the fuel selector under the drivers door.

1990 and later trucks used high pressure pumps in the tanks. You are straddling the dividing line.

Subford may have drawn up easy to read schematics of these systems. He might be able to help. I have all the Ford shop manual and trouble shooting manual diagrams of the 1989 truck. If you need a portion of the schematic, let me know.

 

Do you think any of the valves or sensors on the engine (1991) needs to be changed out? or would they be the same?

What do you think would cause the surging that I'm getting around 30 to 35 MPH?

Here is a dumb question

Can I take the tank and all the lines off the 1991 Ford and put it on the 1989? Just in case if it is the low pressure line.... I'm trying to find a place that has a pressure cage.

Thanks Ken

 

From the schematics an '89 appears very similar to '88, '90, and '91. I've never checked the part numbers. Some of the '87 V8s are are not EFI, some are. All the L6s are. Which computer are you using?

Absolutely, Which vss are you using.

Once again, no question is dumb.

I don't know. Hopefully someone with more knowledge will chime in.
I might have the resources to look this stuff up, if a knowledgeable person does not show up.