OK, I'm not really familiar with this engine class, and it's peculiarities, so I'm hunting some advice. '85 F250, 460/c6, 4X4, for info purposes. Bought the truck, and when I got it home, it seemed to run ok. After about 10 months of fixing wiring problems (and running the engine regularly during testing), I decided it was time to "get it on the road". So I did an oil change, and spark plugs, and thought I was ready. On the initial road test, I only went about 10 miles, and it seemed to "drink" about a 1/4 tank of gas. On the second trip, the engine died, and upon restart, I had no oil pressure. Checked oil, showed full, no detectable gas odor in oil. Also checked plugs, #8 was BLACK soot fouled.
Any hints about it before I start tearing it apart?
Sorry for the rambling, but I wanted to get in as much info as I could on the first go-round, and thanks in advance for any help.

Doug

 

Have you checked all of the cylinders psi with a gauge ?

 

Sorry about the delay in replying. Was forced to take a "vacation" under the control of the medical profession. Feeling better though....
No, I haven't done a compression check, or a leak-down check, partly because of the above, and partly because I don't have the equipment.
I suppose the main worry that I have, is the sudden loss of oil pressure. Seeing as how there is a oil pressure control switch for the fuel pumps, I'm hoping I haven't "tanked" the engine, but I will have to see when it comes out.

 

thoughts about #8

A) 7 & 8 fire one after the other, bad wires can lead to spark induction and misfire if they are routed together.
B) Is your PCV connected to the brake booster port in that runner?

What carb do you have?
A blown powervalve in a Holley can suck a lot of fuel and cause sooty plugs + popping/backfire on the overrun.

 

Answers for ArdWrknTrk;

A) Possible. New wires, so it "shouldn't", but....
B) PCV is connected to port on throttle plate.

C) Holley, whatever is stock for this year engine (4180?)
Been a while, forgot about power valve. Thanks. Will check as soon as I am able to.

 

Well, that narrows it down.

Yes. It is a 4180 Holley made for Motorcraft.

About your oil pressure.
Is it showing 0?
Are you sure the wire hasn't come loose from the sender behind the EGR valve?
Or maybe an open circuit?
Without oil pressure the fuel pump won't work, saving the engine from damage. (if you have electric pumps)
Try jumping the sender wire directly to the block.
It should read full scale and the pump should run.

Or you may have other fuel wiring problems.
I have a schematic from 'subford' for an '86 that is the same as my '87, not sure it is the same for an '85.

 

On this motor, the sending unit for the oil pressure gauge is separate from the fuel pump switch.
When I attempted to restart the motor, it fired up for all of 30 seconds, started knocking, and died again. At this time I was watching the gauges on the dash, and the oil pressure never came off of "0".
I then called the local hook truck, and when I got it back home, I immediately checked the oil level, and pulled the plugs for inspection.
I also checked the fuel pump operation, and "jumpering" the safety switch caused them to operate properly.
Since I do not know the previous history of this truck (~80,000 on the clock, unknown if a "1" belongs in front), I'm thinking that the oil pump, or the drive rod may be the problem. (had a similar problem in a Dodge motor) Won't know for sure until I tear it down, but with a back injury, that may be a while.
Originally, was just trying to see if there was anything about this motor that was "peculiar" to it in any way.
P.S. I have a complete wiring schematic for the whole truck, but thanks for offering.

 

Ok, So it IS knocking.

My '87 made it past 315,000 before it spun a bearing. And I had low oil pressure for over a year before that.

I can tell you this.
If the valve seals get brittle and fall apart they WILL find their way to the pan and clog the screen.
(That could also cause you to burn oil even with a good compression test.)

Same with the nylon teeth on the OEM cam sprocket...

I have also seen where the dipstick tube was bent and the dipstick itself wore through the rear sump pickup extension. (if you overfilled that motor it would have oil pressure)

 

Sounds like it's time for a rebuild. Was afraid of that.
Didn't think about a clogged screen. Will watch for that as well.
I checked the odometer, and it reads 72764, but like I said earlier, I have no idea if it's that, or 172,000, or even 272,000.
Either way, looks like I'm going to have to scrape up my loose change for a while.