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Now, for Big Blue: I worked on the start circuit today and would like to report that it is fixed. I sure would like to report that. But, the fact of the matter is that I don't know if it is or not. I wasn't getting juice to the connector under the hood, in the previous pic, where it comes in from the cab. That's after the clutch switch, which hasn't been working, so I looked into that. Turns out it isn't the fault of the switch - there is no switch. Just this part of a ring-tongue terminal that is shoved into the switch's connector. And, after I pulled it out and checked everything, now it all works.
Ok then, I'll just work on the fuel pump relay. Bill/85lebaront2 sent me a harness for that relay as well as a couple of other things (thanks again, Bill!), so I compared it to mine. As it turns out, since my truck also has the trailer/marker lights relays they integrated those three harnesses. Shown below is a factory weld where they fused the grounds for those three relays.
And here's a weld of the power for the fuel pump relay and one of the others. So, it won't be a plug-and-play situation.
Given that, I think my previous plan to strip red/yellow wire out of another harness I have and tie in where someone put that crimp-on butt connector that Jim spotted. I can run it out with the ignition wires and the oil pressure wire, down the valve cover as shown here:
You know Gary, if the clutch switch goes bad you can always stick a spare fuse In that connector
At least it won't be exposed and hot with the key rolled forward to 'start'
The picture I sent showing the wiring I highlighted the down the left valve cover routing.
Yep, I saw that. But was looking through the catalog for info on the fuel pump wiring harness, which I didn't find, and came across that one so posted it.
The wiring info in the catalog is a shambles. I'd like to sit down some time and find just those for our trucks, copy them to my web site, and put some organization to them.
At least you have the yellow and pink set from the starter relay to the left fender wiring. I I come across the switch and wiring I will send them too.
The wiring I sent you goes from the starter relay across the top of the radiator area, then back on the left fender to where the plugs are (right close to the DS-II box).
Yes. I laid it out today and figured that out. Unfortunately the red/yellow wire originates on the left side and only goes a few inches before coming to the single-terminal connector where the harness that goes to the oil pressure switch plugs in. So, I'm trying to salvage enough red/yellow wire from another harness to make that run. Turns out Ford used red/yellow wire for several things, but the runs aren't very long. Amazon has some red/yellow wire, but the reasonably-priced stuff won't get here for about 10 days. I may go ahead and order it and spend the time until it gets here doing other things.
One job that needs to be done is to create the manifold that will allow the oil pressure sender, oil pressure switch, and tubing to the oil pressure gauge to all connect at one time. I looked today and the original one is there, the hex-shaped one that has two ports. So I'm thinking I'll drill and tap it 1/8" pipe to take all three w/o having to add a tee since the tee would cause things to exit at strange angles.
Sounds like a good plan. Next time I am in Newport News, I think I kept both of the centrifugal pumps. An FYI, if whoever put the front tank in Big Blue used a later tank, my front pump hanger was modified by cutting the alignment tang so I could use it in the 1990 front tank until I did the remaining part of the EFI conversion. I do still have the big 11X17? wiring diagrams for Darth with all the little harnesses drawn out complete with connector PNs etc. I have no use for it any more since I pretty well went to 1996 wiring bumper to bumper.
Jim - Looking at what you posted there seems to be a bust in the URL. It was extremely long and doesn't come through on the browser.
However, Big Blue has the hex manifold shown below and I think I'll just drill it and tap it 1/8" pipe where the red is, basically to match the port on the left where the mechanical gauge tube comes off in the second pic. I may have to mill a flat on it, but I don't think so for 1/8" as it looks like there's a 1/4" on there w/o milling.
Yeah, it's funny that the c&p showed up fine in my reply but then became a huge string of a url as it was posted to the forum.
Anyway, THAT hex was a slab of hex bar stock with ports on the top three facets and a male fitting at the bottom.
Given that, your sensor and two senders would be in one plane (radially)
Thinking that arrangement might fit better up against the firewall with the air cleaner housing in place.
Got it. Thanks. But, there appears to be plenty of room for either the sending unit shown in the pic to come out to the right where the circle is, or leave it where it is and put the switch in the new spot. So, hopefully I can get to that this afternoon - but I have to got accept a cashier's check now.
Well, I think I'm making progress, but this onion has more layers than I thought.
First, I pulled the original oil pressure "manifold" out in prep for drilling and taping it for the oil pressure switch. And, here's what I found - a puddle of oil. So, now I know where at least some of the oil coming off the back of the engine is coming from. It is possible the oil was coming from the fittings for the gauges, but I suspect it is from the rear of the intake manifold. Anyway, I cleaned it up and we will see.
Then, I tested the to-be oil pressure switch. The I/P terminals are open at 0 psi and close at 3 psi. The P/S terminals are closed at 0 psi and open at 3.5 psi. Should work perfectly for powering both the fuel pressure relay and an oil pressure warning lamp. Here's a shot of the switch, which is a Standard Motor Products PS-64:
So, back to the oil "manifold", there doesn't look like there's enough meat in it to allow it to be taped, so I added a brass tee below it and put it back in. It doesn't leak and the stock and aftermarket gauges work.
However, along the way I spotted something - shown resting on the vacuum hose to the brake booster. Yup, the cab ground. I fixed it.
I wasn't getting juice to the connector under the hood, in the previous pic, where it comes in from the cab. That's after the clutch switch, which hasn't been working, so I looked into that. Turns out it isn't the fault of the switch - there is no switch. Just this part of a ring-tongue terminal that is shoved into the switch's connector. And, after I pulled it out and checked everything, now it all works. 
