Motor not starting up

Yea we got nothing didnt work bud the Pressure was still around 90psi or some of the cylinders was at 30psi what would be the next step?

Well we were informed that the head gasket is possibly bad how do we exactly get to this we are stuck I got the cam spocket off and the timing chain off and suspended that was a pain but how do I exactly get the top of the motor off?

Thanks man helped alot yeah I put the car in time before removing the sprockets the head is off now there is some black on the pistons like carbon built up but nothing major ummm cylinder 1 and 4 are up and 2 and 3 are down what do you take on that? Everyone keeps telling me now to check the valves how hard and pricy of a fix could this be if there is something wrong?

Ok I will be working on the valves later tonight thanks for that now mechanic said compression problems could be piston's like the piston rings are fried everyone keeps telling me I need to take the bottom half of the motor out to check them is this true? If not how can I do it with the bottom part of the motor still hooked to the tranny if its possible

Well came back the valves were fine can you give me a better detailed layout on how to take out the pistons? Wile the block is still in well the bottom part of the motor that is. Thanks

Just ignore that picture I didnt mean to put that on there

Hey im having trouble removing the oil pump to get the my 1st and 2nd cylinder I know its a 12point or star socket at least I believe so same as I use to get the piston's off but I tried a 10mm and it was too big and a 9mm is too small = so what do I use? How do I get this damn thing off. Also the piston in Cylinder 4 is basically stuck I cant get it to come out through like I did with cylinder 3 that piston just came right out in a few hits. Is there a little trick I can do to get the piston out of cylinder 4?

While car running fifteen mph engine stop, in two (2) locations turn on and stop again. We had to tow it home. When I perform TS engine cranks but will not start. All fuses are okay, No spark, fuel working.

Engine Mechanical problem
2004 Nissan Sentra 4 cyl Front Wheel Drive Automatic 120, 00 miles

I have a 2004 Nissan Sentra that has had trouble starting. If it sits for a decent amount of time (couple of hours at least) it more than likely won't start on first crank. If it does start, it putters and dies. It will eventually start and run perfectly. Well today my fiance was driving down the road and it died out of nowhere. I went to pick her up. Went home to call a towing company. I came back to the car (about 30 minutes later), turn the key 5 times to turn the power on but not start the car. Then it suddenly started when I tried to start it. Took it down to the gas station to put gas in it. I left it running in the lot for about 5 minutes and it died again and now won't start again. Any ideas what it could be?

I did hear the fuel pump running. The Check Engine light was on but we ran it and it said something about an o2 sensor. That was changed and it went off and now nothing. I haven't yet checked for spark. It's now on it's way to the shop. I'll have to go up there over the weekend and check and see if there's spark.
Apparently this is a common issue with nissan sentras and the only person i've ever found that had success in fixing it had to have his timing chain replaced. Does that sound like something that would fix this problem?