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These are the same diagrams as in my Haynes manual. For a 1987 7.5L, figures 4 and 27 are applicable to me. The engine wiring diagram essentially just shows the ignition circuit, the chassis wiring diagram shows all the lights. I don't see the fuel system anywhere. I have 2 tanks but all the wires have been cut and I'm running an aftermarket pump on the rail using the front tank only. I'd like to get both tanks working again but most of the wires have been cut and/or spliced. Can anybody give me a diagram for the fuel system? Thanks....

 

Is this what you're looking for?

 

That's not going to work. The OP has a 1987 model year truck that uses two in-tank low pressure pumps and a single high pressure pump on the frame rail. Electrically it is very different from what you posted.

Courtesy of Subford:



OP: Please do not forget there is a Dual Function Reservoir between the tanks and the external high pressure pump.

courtesy of Steve83

 

Thanks rla! That is a huge help. I started to tackle this project when I got the truck but got sidetracked by other more pressing issues. I'm currently pulling the transmission to replacea chewed up ring gear on the flywheel. I have been hesitant to go from my current setup back to stock since the truck was originally a 5.8EFI engine, but after taking a second look at the parts, I think I can make everything work once I get some low pressure pumps in the tank.




On a side note, does anybody have a good source for the dual function reservoir? I found what I think might be the right part in the LMC catalog, but it was $250 - ouch! I'm never opposed to junk yard parts, but I like the peace of mind that new parts generally provide. Thanks again!

 

...since I'm running a carburetor, do I still need the high pressure pump after the dual function reservoir? What pressures are the low in-tank and the high frame-mounted pumps putting out?

 

The LP pumps 6-12psi and are the same pumps Ford used with engines with carburetors.
The HP pump will put out 95-100psi into a blocked head.

 

Thanks Bill!

 

Sorry if this is a dumb question....why do I need 100 psi if I'm running a carburetor? Why wouldn't the in-tank pumps be enough?

 

With a carburetor you only use the pumps in the tanks.
The frame HP pump is for fuel injectors only and it uses a regulator to regulate the fuel pressure between about 30psi and 40psi for a V-8 depending on the amount of vacuum the engine is making.

 

I missed the part you have a 460 engine...it was still carbed in 1987. My diagram is still not what you need. Sorry.

 

Here is a wiring diagram for you:


/

 

Thanks. I'm still trying to figure out why there is no wiring diagram for my truck specifically.....

I spent the weekend replacing the flywheel, clutch,steering components and fuel pump. Once I get everything buttoned back up, I'm hoping to back the truck out of the garage and use the bucket on my tractor to lift the bed off and tackle the tank issues.

 

Somewhat off topic, how difficult would it be to retrofit a mechanical fuel pump? Would it just be a matter of getting an older timing chain cover? I've been reading reviews on electric pumps and the theme seems to be either pay $50 and replace every 6 months, or pay $400 and get a longer service life. Are mechanical pumps more reliable? I know they have their issues if the truck hasn't been started in a while, but thought it was worth asking.


Edit: I'm on my third electric fuel pump this year.......