I would have just deleted this post, but I couldn't find the option. So quick update;
I think the problem is that I'm out of gas. The fuel gauge actually reads full when its empty (something the PO did), it's currently reading a little less than full. When I disconnect the fuel supply line to the rail, and bypass the fuel pump relay, I think I hear it pushing air and there is no gas coming out of the line. I will add gas and get a new plastic clip for the fuel line fitting and hopefully that is the only problem.

I think I have a fuel delivery problem on a 1985 F250 302 fuel injected motor. Interesting enough, the problem came to be right after replacing the plugs and wires, after which, the truck started and ran good for about 10 seconds before sputtering and back firing and then dying. When I spray starting fluid in the throttle body, it starts every time no problem and runs long enough to burn up the ether. So, I bypassed the fuel pump relay and I can hear both the external and internal pump running. I would like to test the fuel pressure, however, there is no shrader valve on the fuel rail, and I don't yet have the special tool for disconnecting the fuel line connectors (will get one soon). I tested that the fuel injectors signal was pulsing using an oscilloscope, and I can see that while cranking the motor they are fired aprox. every 1/2 second and stay open for about 35ms, which seems reasonable. From my research it appears that there is a separate circuit for each group of 4 injectors, but I only tested a single circuit up to this point. I feel the problem is either the fuel regulator, plugged fuel filters, bad fuel pump, or tank selector valve. I would like to start by checking the fuel pressure, but not sure what would be the easiest way to do that since there is no place to attach a fuel pressure gauge to. Any suggestions on how to proceed would be greatly appreciated.

I also checked the OBD1 codes, and got 21,24 for KOEO and 18,31 for Continuous Memory codes. I think the 18,31 are from an earlier problem when I had a loss of ignition spark, which was fixed by changing the distributor (with the ignition module and PIP sensor)

 

From what I can find in my Ford Manual, the shrader valve should be on the rail, just behind the distributor.Your 85 should have 28-38 psi.You can easily check the regulator by pulling its vacuum line off and checking for the presence of gas. Replace it only if its diaphram has ruptured and leaking gas out the vacuum nipple.Those codes 21 and 24 are likely from improper checking procedures. The enginge has to be warmed up.The others could be old codes as you say and will not prevent the engine from starting.I can say from experience that ECM issues due to bad capacitors cause many fuel delivery problems on these old vehicles.. I would disconnect the battery, locate the ECM which should be behind the left kick panel.If you can remove its cover, look for bulging and leaky electrolytic capacitors.There are three and if you find issues with these, replace all three or the ECM assembly if you do not have soldering skills.

 

If as you suspect, there may be no fuel in the tank,,,, If you tap the bottom of the tank you would know right away if it is empty. Also, just put a few gallons of gas into the tank and see if you get more than the air you say is coming out. Even if you hookup a pressure gauge , you will read no pressure if there is no fuel to pump out.
These are simple basic checks and no need to get involved chasing something that may not be required.
Thee is always the possibility of a problem with the pump in the tank, but do all the basics before condemning the pump especially if you are sure it is running.

 

Thanks raski for the helpful information, good to know for sure. The 85 F250 actually doesn't have the shrader valve, so I disconnected the fuel line from the fuel rail and put the fuel line into a container and cycled the fuel pump, only heard air and no gas, after adding a few gallons to the tank, fuel would run when I would cycle the key. So, I'm pretty sure that was the only problem, but will need to get a new plastic clip to attach the line to the fuel rail before I hear it run again. I'm surprised it ran out of gas right after changing the plugs and wires, what timing! The fuel gauge is not working properly, but now I know that when it approaches the 7/8 full reading, that I'm almost out of gas.

 

Thanks hanky, good idea about knocking on the bottom of the tank, that would have given me a pretty good clue. After adding a few gallons to the tank, fuel started coming out of the line. The fuel gauge reads empty when the tank is full, and now I know it reads 7/8 full when empty. It happened to run out of fuel right after I changed the plugs and wires, what timing! Hopefully it will be running once again after getting the fuel line reattached, just need to get a new plastic clip from the parts store.

 

It's really not a big expense to obtain a retainer clip to keep the line attached,,,,,,,,,,,,,,,,,,,,,,,,unless you have to run and get another at a later date,,,,,,,,,,,,so that is why I suggest to get 2 instead of one clip. While down there since the tank ran dry, consider replacing the fuel filter. Some filters come with the extra clips, worth checking.

Also, watch out for the special little "O" rings in the fuel line that connect to the filter. If you are not aware and careful they can come out.

Last reminder,,,,always check for any leaks after installing filter,, a coupe of on/off key cycles will pressurize the line to do the check.

 

Yup, I see the clips are in stock and not expensive they come in packages of 6 so I'll have extras. Good point about the filter, I may need to put a pump inside the rear tank, since it isn't working (first need to see if it's getting power), so there will be a convenient time to take care of the filter. Thanks for the suggestions.

 

I noticed you mentioned , "the rear tank". Do you know if the sending unit part of the fuel pump module in the rear tank provides the correct fuel gauge reading?

You might have a problem obtaining a fuel pump module (pump and fuel level sending unit combined), not sure.
I ask if the rear tank unit provided a correct gauge reading because if it did than the wiring and dash gauge would be considered OK.
On those older units if there was a break in the info to the gauge it would drop to empty and if shorted to ground , it would go all the way up to full.

 

I'm not sure yet about the sending unit operation, haven't yet investigated it. I can't hear the pump inside the rear tank running when I switch to the rear tank, but I can hear the pump inside the front tank running when switched to the front tank. I haven't yet investigated it yet, it may be that it is a wiring problem and not actually the pump, I will check for power at the pump connector.

 

Don't overlook checking for good ground connections , they don't always use the vehicle for grounds,