1992 f-350 5.8l won't start

I have a 1992 f-350 with the 5.8 motor. The vehicle was parked on Friday (running fine) and refused to start on Monday (no use over the weekend). The engine will crank but it never catches. We checked fuel at the rail, checked for spark and even replaced the fuel pump - everything is good but we're not reading any codes from the computer - it's not performing the self test as it has in the past... Any ideas?
Thanks, I really need this vehicle up and running so any ideas are appreciated.

Check for compression ?

Further developments - dropped a little gas into the airbox and the motor started right up. Now starts every time no problem but still refuses to perform the koeo self test... I'm wondering if the system is running in limp mode... guess it's time for a test drive.

Anyone know what no codes sent means? Computer sends codes in engine running test
Thanks.

Computer not getting power.

Just wanted to say thanks for the replys. I took the truck around the block and it runs but really doesn't have any power like before. I'll check and see if the computer is getting power before I go out and get a new one.

See if you can borrow or rent a gauge to check the fuel pressure with. You can also fabricate one with a gauge, a few fittings and some fuel line. Pressure at idle should be around 30#, and 35 - 40 at cruise. It will run with less, but wont run properly. Just because it has fuel at the rail doesnt mean that it has enough. At idle, pinch or disconnect the vacuum line going to the fuel pressure regulator, the pressure should increase. If you have dual tanks, switch tanks and see if it does the same. I have seen the check valves in the lines at the tanks malfunction and cause low pressure. Let us know what the fuel pressure is and we`ll go from there. If the computer werent getting any power, it wouldnt run at all.

Thanks for the info. I suppose that could explain why I hear the pump running continuously? I thought it might be the computer not telling it to switch off but perhaps I've got it backwards and if there is not the correct fuel pressure the computer won't run the koeo test. When the engine is running the check engine light is on and although the motor sounds good at idle it doesn't have much response to throttle, it just limps around the block.

Hi again, I'm back again looking for a solution to the rough running old ford.

I just checked the fuel pressure and found it to be about 47psi at the rail. I'm still confused about this as I can hear the pump running continuously when the key is turned to the on position, it used to shut off after a couple of seconds but the new pump runs all the time...

The truck runs if you drop a little gas into the air box intake and continues to run untill turned off though the throttle response is lousy and it blows a lot of black smoke (which it didn't used to)

You can crank it all you want but initially it won't start without a little help from a cap of gas in the airbox intake... after it's been running a while you can cut it and re-start with just the key.

Any ideas what could cause these symptoms? The truck is barely driveable with the power it's putting out at the moment... Throttle position sensor?

I really need help with this!!!

Black smoke = too much gas, you are basically flooding the engine which is causing the loss of power. Check the engine computer for codes, will probably tell you what is wrong.

So the old Ford is still off the road with it's starting problem. I could really use some help with this one, the symptoms haven't changed since I began posting. I know someone out there has the answer!

Many thanks for any ideas,

If the computer is not passing its self test I would replace it.