i have a 1989 f250 4x4 lwb 7.5 460 with rebuilt engine, rebuilt trans new suspension. my money pit. the problem i am chasing is it will not start fuel pump buzzes, have newer in tank pump, new rail hi pressure pump,new pressure regulator, new fuel pump relay, replaced relay and engine started that eve but same problem next day.ignition switch in column is sticky in start position but isnt that old either. new ecm also i am losing hair trying to figure this one out!

 

Welcome to the site..

The three basics, one or more may be missing, or intermittent.

Is there spec fuel pressure and volume at the rail when a no start? Tested values are?
Is there a 'quality spark' delivered by the coil, on out to the plugs. Modules and pick ups were common offenders. Ocassionally a coil or harness issues.
Is there a fuel injector pulse at the injector connectors?. May help prove our engine management concerns or drop outs. CEL illuminated, and codes? Prior to the build? or after if run long enough.

Probably can rule out comp issues since it's a rebuilt, has run, and basic power plant.

Cranks fine, just no start, correct? Will it fire with a short shot of ether? If so, tends to rule out ignition issues. Sometimes on a head scratcher, you have to figure out what's right, rather than what's wrong in a diagnostic direction..

 

I think I have found the problem, the electrical part of the ignition switch seems to be the culprit. The problem is getting the switch calibrated, the wire had fallen off during shipping and I installed it any way. Now the truck starts and runs as long as I hold the key so all that is left hopefully is to drop the column once again and readjust it a little bit. Man I hate being old and bending and standing on my head!