1992 bonne rebuild locked up

I recently rebuilt our 92 bonne, I started out replacing the timing chain, gears, magnet sensors and associated parts such as oil pump gears. The car has 180000 miles so by the time I tore it down I decided to do a valve job. I had the heads rebuilt like your supposed to, cleaned everything real good and put it back together. The pistons and cylinder walls looked real good, no slop no scratchs. After it started, it ran for around 1min then it died, started it back up and ran for another 30 seconds to 1 minute and it died again, it wasnt makinig any noises but wasnt running real smooth either. After it died the second time the motor locked up and now want turn over with the starter or manually. I packed the gears with petroleum jelly as the directions called for on the oil pump gears. however, there was no pressure on the gauge after starting. This is my 1st rebuild so you can imagine my disapoinment. My question is what went wrong and why. Should I just drop the oil pan 1st and if theres anything wrong with the pistons should I pull the whole motor and start over or can i just fix the piston thats causing the problem with the motor in the car. Someone told me a valve might have dropped down against the piston, would the machine shop be liable? I havent began tearing back down yet.

Signed,

Frustrated

What size engine do you have? Certain engines from Pontiac require a pressurized oiling before they are started. Even though you packed the oil pump with petroleum Jelly before starting the book indicates that every cavity must be completely filled with grease before starting or the pump will loose prime. If you missed even one cavity that could have caused the oil pressure problem. By the way, you did fill it with oil before starting? It is a good bet that you may not be able to salvage the short block. If the engine seized as you say you may have welded the rings to the cylinder walls. You can try an old mechanics trick by removing the spark plugs and squirting oil into the cylinders. This will sometimes loosen the rings so that they will free themselves. A very light penetrating oil like 3 in 1 or WD 40 is your best bet. I also doubt you dropped a valve due to the fact that you didn't hear any noises. If a valve dropped you would have heard it. My suggestion is that you pull the motor from the car and start over. The items you put on the car are still good so a short block will be sufficient to get you going again if you can't free up the old block. If you are successful, you should tear the block down and rebuild it since the rings and cylinders are probably damaged. Good Luck! I hope I am wrong about the damage.

Thanks for the help. The Engine is a 3800 non supercharged v-6, auto. trans., I packed those gears good, what about the spring and the plunger in the oil pump were thay supposed to be packed? I did put good fresh oil in, even filled the filter. Today I started tearing down again, valves all looked normal I havent pulled the heads yet. How do you pressurise the oil before starting? If I cant free up the motor how will I be able to take the bolts out of the fly wheel? Thanks,
Captbeancounter

If you packed the gears good then the problem may have been with the pump itself. The gear clearances may be incorrect or the parts store gave you the wrong gears for your engine. The non-supercharged engine does not require pressurized oiling before start-up only the supercharged engine so don't worry about that. The spring and plunger should have nothing to do with the oil pump priming itself. As far as freeing up the motor to remove the bolts from the flywheel, you will probably either need to drop the tranny or pull the engine, if you do either you should be able to get to them easily. If you can't free up the motor you are going to need to pull it anyway. Let me know what you find out when you get it torn down!

Oil pumps are very simple and very seldom fail. I never packed a pump with grease and I've never had a problem getting one to start pumping. You have a hexagon shaft that drives the oil pump. It might be possible to get that out of place when installing the oil pump drive gear. Also the holes in the main bearings must line up with the holes in the block. I dont think the pick-up screen could fall off? First thing you have to do is find out what is locking the engine up. It could be the valves hitting the piston. {If the timing chain is not timed right}. Are the torque converter bolts tight? Hopefully its not a seized bearing. Good luck and let me know if you find anything. Don't get frustrated. Everybody that works on engines goes thru this sooner or later.

Jerry