I have an 88 F150 with a replacement 5.8 Jasper motor with 70,000 on it.
tank pump is new, in line pump is new. Plugs, cap and rotor were changed.
relays were both changed. ICM is new.
Have not had it long or put many miles on it. It never truly seemed to run right. always seemed a bit sluggish. At times it would act like it was starved for fuel until you switched tanks. then would run ok again. Did not matter which tank, and neither were close to empty. Now it quite and when you get ti to start runs very bad. the fuel pump all test ok but will not run with out a jumper which dose nothing to get the engine to do more then a sputtering idle when playing the accelerator.
I have spark but not sure that it is as strong as it should be. dist bushing are tight and the cap bit me when I forgot to turn the key off while wiggling the rotor so the pick up coil got its signal that time.
LOL Im ready to carb it as I understand that system, but I'm also cheap!

ECM?? I'm not sure where to go next.

 

Have you changed the fuel filter? Have you tested the fuel pressure with a gauge?

 

x2 on testing fuel pressure - with a gauge.

 

Had 40psi, now no pressure with pump jumped. after testing, fuel rail is now empty. not sure if tank pumps are running. will have to test some more. For the past year fuel would return to the non selected tank, over filling it if I did not switch back and forth between tanks.

 

Oh, filter is new also. LOL Money pit!

 

After fuel injection, no way I'd go back to a carb. I have some carbed old motorcycles and they have lots of problems that FI doesn't have. I've been thinking of selling both and buying a newer FI bike.

 

Looks like you've had fuel supply/return issues...Just in case though. Did you check the inertia switch for this issue? If I remember, on the '88's it is under the dash.
Check fuses if the pumps are turning on.

 

inertia switch button is in. Duel tank fuse is good.

 

Ok well at least now you know that you have no fuel pressure so that is most likely your problem.
Generally to verify you can spray a 3 second burst of starting fluid directly into the throttle body and it will fire for a second or three. It will not hurt anything.
That will totally eliminate the timing and spark systems as the problem.
Next is individually check each pump - Are the lift pumps in the tanks pumping to the high pressure pump? Is the high pressure pump operating ?
Then you're into the whole switching valve thing - beyond my area but if you bypass it and it runs then it's very suspect.
That's the sequence I'd run through if I was trying to get it up and running before the weekend's out.

 

IT RUNS AGAIN!
After messing with every thing, I think it was the mechanical switching valve. Truck sat a lot the last few years. It was a bit sticky when I took it apart. Small "O" ring was open, but I drilled it anyway. Now I have to buy a fuel filter to get the large "O" ring to seal the cup.