Forgive if im posting in the wrong spot im new to the site but here goes thanks in advance for any and all help. Car cranked, started, and ran fine. Pulled the distributor to install a pro billet msd unit car then cranked fired up ran a few seconds and died and would not start back up just cranked away. So i put the old distributor back in and nothing just cranks. So i have another 5.0 so i tried both the new msd unit and original unit i pulled out of the other car in my second Foxbody both worked without issue and ran my second fox just fine. I have checked with a spark tester , i have spark i have checked for fuel i have fuel i have did a noid light test i have pulse i have checked the brand new coil it is good i have tried to fire it with starting fluid nothing it just cranks i have checked compression i got 165 across the board. i replaced the ignition switch with a new one nothing just cranks. I have tried the computer in my other fox it works fine. I have swapped the fuel relay out from my other fox nothing just cranks. The fuel pump is brand new has 15 miles on it a 190 walbro also it does turn on and prime i have checked using the manual over ride test port under the hood it works. This car just got a fresh motor put in it top to bottom new everything it has been drivin and broken in about 30 miles and has never gave me a issue. BUT never gave me a issue other then this exact same situation from day one when the new motor was getting fired for the first time. It did this same crap. I checked and checked and checked and finally i took the brand new msd distributor out and threw the original back in and well well well it fired up right came to life and never gave me another issue. So i figured the msd distributor was broken day one out of the box. I sent it back to msd and got a replacement and here we are again with the second brand new msd pro billet. I took my perfectly running car swapped out the original factory ford distributor out to put the brand new msd in and now the damn thing wont start and on top of that i throw the original back in and It didnt make any difference neither will run in the car but yet they run in my other car no problems. And yes i have the distributor in correctly and its not 180 out. The only thing i can think of is its a wiring issue because i did nothing but unplug the tfi harness from the distributor and swapped the darn distributors out. Day one and this time both got me the same results. Just cranks away. I tested the number 4 wire on the tfi harness i have 12 volts with key on so the computer is sending signal correct. And i tested the number 6 pin on the tfi harness and got 12 volts so ive got ground. Ive read over and over and followed the cranks but wont start checklist its not seeming to help my situation. The motor ran awesome tons of power all day long with not one issue other than this same issue im having during it first start up and now again and both times same exact symptoms. The motor is a 302 Comp stage 3 cam Afr 165 heads 1.7 rockers Tmoss ported cobra intake Adjustable fuel regulator 70mm throttle body Full accessories Ac Smog Egr Nothing has been gutted or hacked on everything is brand new and ive checked all connections salt and pepper ect. I seem to have power everywhere i turn yet it wont run. It trys and it sputters ever so lightly. Its so very odd. I had my brother over to help me do the compression test got done after doing all cylinders said hell try it turned the key and bam it ran and stayed running for a minute i turned it off went to restart it and nothing just cranks away. I built this car im buy no means a master mechanic or a know everything guy but i built many motors and hotrods and for the life of me cannot figure this one out. Im hoping maybe someone will have some insight here because im at a lose. Just a though but this car is a 90 gt convertible. And it has a factory ford alarm system with keyless entry in it. Its always worked never gave me a issue but maybe something has crapped out on it or on the fritz. it fired ran then shut it off and wont fire up again. And it did this same crap day one when i went to fire the new motor i did nothing but pull the brand new msd distributor out threw the stocker back in and bam shes alive and never looked back or had a issue. Yet here we go again with doing nothing but touching the distributor and its dead in the water What the heck help please any advise is much appreciated. By the way i have done the cranks but wont start checklist and have gotten no results from it