1987 D50 2.0 crank issues, PLEASE HELP

Evening yall, my name is zack, I'm a entry level service tech. I'm the proud owner of an 87 with a G36B, I bought the truck a few years back and has been phenomenal for me. I put her through hell and back when I was with the volunteer fire department back home in Wisconsin. She's always been there for me. But sadly the day I was getting ready to leave the shop for the night and went to warm her up, she would crank but not fire. I ran compression checks on each cylinder, 2-3 were just outside spec but have been that way since I bought it. I replaced the plugs, wires, distributor cap and rotor, I'm getting spark on all four. Still cranking with no firing. So next I think fuel, shot ether in the carb on she seemed a little happier but not by much. So I sourced a fuel pump and slapped that on, still more of the same. So the only other think I could think of that would be inhibiting detonation would be my timing being off. I just don't know why she'd fire up a couple hours earlier with not much resistance. For the record this is the first year the truck has EVER been regularly ran in the winter time and has been idling very rough until she warmed up but then she'd run like a champ. I really need some help here, I'm desperate and feel horrible that I'm leaving her outside the shop. Even worse i have to drive a Mercedes in the meantime that's all computers and bullshit. Anybody that has any ideas I'd greatly appreciate it! Thanks y'all

Definitely check the timing. Its not too awful hard to pull the front covers off and verify. These truck have a history of being off time, and jumping teeth on the belt and things of the sort. The compression issue has me puzzled but hopefully some of the more seasoned Repairmen here ont he forum will give a short talk on what to do.

when was the timing belt last changed? if it is around the time for a new 1 definitely change it. as asmyser mentioned check the timing...super easy on a G63B. my dad always said "timing is everything in life....& that's why I have 3 boys".

I back the above information concerning timing and belt replacement. Between 60K and 80K, the belts will need to be replaced or they will snap and most likely turn your timing cover inside out if they gather into a melted ball in there while on the freeway. Tooth jumping from a tensioner not adjusted to a stretching belt can cause a jump and it doesn't matter if you just got done driving it to church that day and it ran great.
Your compression test would of been probably better if you revealed the readings in your description for us. Also, be careful chasing to fix your truck with money, this rarely works out with these trucks and you'll end up kicking yourself when you find the problem. Not that your poor truck didn't need a tune up, those are the things your suppose to do when you get back from as you say, "hell and back". ;)
You have spark, you have fuel, these are the best things for combustion, though timing is everything exactly as RRTT says.

3 boys huh? Now we know what you do all winter...:thumbup:

I going to go in an opposite direction as I also have a G63B that had that issue just recently...

Check the magnetic pick up in the dizzy. they are notorious for going bad for no good reason. I changed mine twice in the last year.

Oh and if it is the magnetic pick up that is the issue. it is cheaper to just change the whole dizzy, and the MPU is more expensive by itself..

With all those y'all's , you must be from "southern" WI! I'm originally from Racine myself and still have a place in Tomahawk.

I'm guessing since the OP has gone silent this long, his issue is fixed by one of the suggestions posted above. I wish the new guys would at least tell us what worked before they disappear into the mist...