so i bought this truck about 6 months ago from this guy for 2000$. said his neighbor had rebuilt the engine from the block up. all seemed fine with it and checked out on the obd, good fluids. ran great for 2 months except the abs dinged constantly and the guy said the oil guage was messed up so it dinged too. i replaced the sending sensor and it seemed to confirm this. well, out of the blue one day it started tapping. freaked me out but i was on my way home from work and it was friday, so i parked it. next day i changed the oil to synthetic and put some lucas stabilizer in it and a high end filter. knocked again on start up for about 30 seconds and then quieted down. I sighed relief.
. on monday i left for work and all was well. i cant remember for sure now but it may have run fine and it wasnt u til the next day on the way to work about 20 miles in, it started tapped again. i say tapping, but it felt like almost a knock. but ive had knocks and it didnt sound quite that bad. i pulled into an advance auto and tried to figure things out. a friend said a one oc the overhead spark, fuel plugs could be bad and to swap to to find out. so i did. i swapped 1 and 3, tur ing it over after to see if there was a change. no change, might have been worse so i turned it off immediately and swapped them back, then turned it over again.
I kid you not, that was the last time it ran. i tried everything diagnostic i could think of for about a week before i gave up and had it towed home and its been parked since, but i need to get it going. my brother thinks it was the oil pump all along and the guy i bought it from just screwed and knew it was about to go. any thoughtz woukd be greatly appreciated.

 

so your saying engine will crank and not fire, or engine is seized and wont rotate? Best advice is to find a large enough socket and pull bar to rotate engine at crank shaft, if rotates might be ok, if not seized, as for cranking and no fire, could be a slew of electrical mayhem some where, check for wires burnt along exhaust manifolds or even if the fuel pump is energizing

 

crank and not fire. it seemed to turn the same as it did. not like the timing belt broke or anything and not like there was alot of resistance slowing it down either. i checked for fuel and spark, it had both. it turned over sometimes like it might amost start but it never did. I eventually sprayed in some ether, granted not but a couple brief spurts, and it backfired strong enough to crack the litlle overhead cam box on top. ( not sure thats what it is. the hollow box on very top that says 3.7L or whatever on it) so it seemed to me like timing or something but i dont know how to check for that situation with these distribitor on plug wire plugs. I will say that when i went through the spark plugs one by one, the #1 plug was saturated in wet oil in comparison to the others when i pulled it and what i believe was the number 5 plug, was diveted on top like it was hitting too hard. there wasnt a hole through the top leg of the plug, just a perfect little circle dented into the metal like it was hitting it or something. I dont know if this was or might be the cause of the knocking sound. but since i bought it, this truck never failed to crank right up without hesitation until i swapped those 2 plug wires and thats when this all happened. my original concern was the knocking all of the sudden and trying to deduce its origin before I did further damage to the motor.

 

I'd say compression test next.

 

sure, but wouldnt the backfire imply that it was showing compression? i have no tool for a test, but i did at the time cover a hole upon removing a spark plug and see if it would blow it out. it did. seemed to be a descent amount of pressure but I don't have any comparison point