new mazda owner needs help

i bought this truck being told it needs a head gasket. after talking to the owner the truck never overheated & there is no water in the oil. she was told by a shade tree mechanic in a bar that she needed a headgasket.
she said the truck was running fine them one day it died. a few hours later it started & she was able to make it home. that's where her mechanic comes in. after replacing just about everything he could from autozone, fuel filter, plugs, wires, belts, hoses, distibutor cap, etc... he came to the conclusion it was the head. myself, i'm not so sure. as i said the oil is fine, no water.
once i got it home i noticed the hose on the fuel fiter leaking when i tried to start it, so i fixed that. after putting it on the charger i finally got it runnning, but it's very rough & lots of black smoke. i know this is pretty vague but any help as to what i should look for or check would be greatly appreciated.

by the way, the truck is fuel injected.

black smokes means its running rich Might be the computer messing up and letting it run in a kind of limp home mode. It has problems but the one at hand does not sound like a head gasket. What codes is it giving.

I had a problem like that in my 87 B2000. It would start then after a while it would just quit, Hours later or the next day it would start. I was was thinking it was the carb so I put a Weber on and didn't fix..It turn out to be the Vacume advance. Could be something to look at. But I'm not sure, Mine was Carbed and I believe you said yours is FI..

little more info,
after it sits for a while it's hard to start. seems like it only wants to start when i put the battery charger on it.
when it does, i noticed the check engine light comes on, how do i check the codes?
also, i pulled my plugs & there was a lot of carbon build up on them. it was dry so i'm really thinking it's NOT the headgasket. if the gasket was blown shouldn't the plugs be wet?
i have a friend who's ASE mechanic coming by this weekend, hopefully! i'm just tring to figure out a few things before he gets here.
i was going to run a compresson test this afternoon & was told to do a cylinder leak test. anyone know how to do the leak test? & what should the compression be?

thanks guys, i definatly found the right place to get help with this truck.

mine did that a couple time (die out, then after a few it would crank & run again), but mine is carb'd & your is fi, but both fuel systems run off a computer & adjust by reading various sensors....here's my thought, my
pre-cat stopped up & ended up being what caused my motor to go south on me, which if the cat stops up, it will cause your exhaust temps to rise, which is also what happens if your vehicle runs too lean, if this happens, the o2 sensor (even though ours are narrow band) would throw a signal to the computer to richen the fuel mixture thus flooding the engine out......

like pont said, check to see what code it is giving you & go from there, but i'd venture to say that could be your problem, but w/o actually seeing it, that is only a guestimate at best......good luck!

how do i check the codes?

the code reader input adapter/plug is on the passenger side of the engine bay next to the firewall......autozone should have a code reader....as for the plugs being carboned up, that just one more sign of what i said above, if the exhaust stops up, it would cause that same thing.....although a compression test wouldn't hurt either, if by chance you were getting blow by from the piston rings, that could cause carbon buildup on the plugs as well....it isn't always easy to diagnose a problem, especially if there are one or more actual things causing the problem.....keep us posted

awsome, i have to run by autozone any way. hopefully i'll know something & have it running by the weekend.

also, if it did have bad rings & was getting blow by, wouldn't the plugs by wet with oil?

depends on how bad the blow buy is, if not so bad, nah, they probably wouldn't be wet with oil, but if it were some serious blow buy say with like a cracked ring then yes, they would be wet. also note if it is a multiple problem thing, say rings & exhaust stopped up, the higher temps would probably burn the wet oil off of the plugs if the blow buy isn't real bad......

well autozone wasn't any help. they said they can read imports earlier then 95. any other way? i know on some car you can jump the plug with a paperclip & the check engine light will blink the code. which plug is it?