Replaced fuel pressure regulator.. now engine won't crank

[smithmr]

96 GMC Sierra - 305
Replaced the fuel pressure regulator.. attempted to start upon completion, cranked engine twice with no problem, on the third attempt the motor does not turn over. Acts as though it is locked up???? Anyone ever had this issue, it has baffled me. Could it be the starter coincidently went out, or did we do something wrong in the process? Just to be clear the engine never started. Any hints/tips appreciated on this one.

 

[jagtoes]

If you put a socket on the crankshaft bolt can you turn the motor over by hand , manually. There should be no connection between the fuel pressure regulator and the motor locking up. Check that first and maybe you have the the starter pinion jammed on the flywheel. Also does the starter solenoid click when turn the key?

 

[smithmr]

If you put a socket on the crankshaft bolt can you turn the motor over by hand , manually. There should be no connection between the fuel pressure regulator and the motor locking up. Check that first and maybe you have the the starter pinion jammed on the flywheel. Also does the starter solenoid click when turn the key?

I did not see a connection either.... yes the starter actually engages, everything appears to be working normal except the motor will not crank, it literally does not turn over, it makes the effort but will not turn as if its locked up. Truck ran absolutely fine prior to putting the regulator in.

 

[jagtoes]

I did not see a connection either.... yes the starter actually engages, everything appears to be working normal except the motor will not crank, it literally does not turn over, it makes the effort but will not turn as if its locked up. Truck ran absolutely fine prior to putting the regulator in.

So can you turn the motor over manually with a socket wrench? If not then try pulling the spark plugs and then try to turn it over. Also does the starter click ? Make sure you have the transmission in neutral when you try to turn it over.

 

[smithmr]

So can you turn the motor over manually with a socket wrench? If not then try pulling the spark plugs and then try to turn it over. Also does the starter click ? Make sure you have the transmission in neutral when you try to turn it over.

Thank you jagtoes, you put me on the right path. The engine was hydrolocked. The regulator was leaking due to the small oring not seating properly and it flooded one cylinder causing the hydrolock. After removing the spark plugs and fuel pump fuse I was able to crank the fuel out of that cylinder and repair the leak in the regulator. Put it back together and it cranks and runs like a champ!
Thanks again for your help!