Have a new 502 long block basically built to stock merc specs cam etc,
installed a 1999 454 mag efi system
had the ecu redone by az speed for 502 fuel map
won't start, doesn't cough, spit, hickup, puff, nada

-has spark

-45 psi fuel at the log, measured

-put indicator light on injector its being pulsed, the fillment just pulses dull red for a frac of a second every turn of the crank

-has oil preasure after starter turns it over a few times

-double checked dist timing, not 180 degree out ( had someone else check it so I didn't make same mistake 2wice)

What else to try , any suggestions ?

Have you checked the compression? There are only three things an engine needs to run, fuel, ignition, and compression. Of course they need to happen at the proper time. Check the compression to be sure the cam is in time.

Distributor installed correctly? (It happend to me)

Take some starting fluid & spray in air intake while cranking motor. If motor starts then in fuel delievry, if it does not start for a second or 2 than it is spark related or valve timing.

I have been off big time on spark timing & at least it makes some kind of noise.

Double check distributor and firing order. Also make sure there is enough initial advance on your spark timing.

I built an engine one time that wouldn't start. Turns out I flooded the crap out of it when first trying to start it and flushed all the oil off the rings creating no compression. I could smell the fuel on the dipstick. Changed oil, squited 30 wt oil in each cylinder, turned off fuel flow and fed fuel manually (carb). Fired it up that way, fixed the over fuel problem and it ran great.

BT

Hand fill the fuel filter. The pump won't do it.

ursus....Have you put a timing light to it. Even at a slow "starter crank" you still should see the strobe hit the mark. At least you can see if you are close.

Bob

i had an engien that woudn;t start due to valve lashing problem. A buddy of mine helped me out and witeht elashing. Well he plays bass guitar so he was able to move the push rods due to the fact he plays bass all the time. As a result what he could easily spin the push rods (when nobody else coudl) and it wound up being WAY to to tight and was actually preventing the valves from closing all the way. Need less to say its wouldn't start. Once th lashing was undone it started right up.

i second the starter fluid idea. narrow down the possibilities and you wont be chasing down such a big problem.