replaced valve seals now engine wont start what should I check?

You are on the low side of you compression numbers. 8:1 compression ratio you should be 120 psi to 160 psi with no more that 5 psi difference in any of the cylinders. Although that should not cause it not to crank. Is your upper intake torqued correctly? Is all the wire harnesses plugged back in? Did you remove or move the Cam/crank position sensor? Are the plug wires back on correctly? Are you positive that the timing is lined up correctly?

all harnesses are counted for fuses checking out fine bout to change coil pack and crank angle sensor for good measure to see if that makess a differents been having spark jump on coil pack...... so thats the reason i thought of the change and timing is prefect front getting 130 arcoss the board rear 150 psi across the board getting gas sprake and compression good turn over no true leaks and only thing is electrical i think your thoughts

I think you may have the valves adjusted too tight on one side. Adjust each cylinder when piston is up and valves are closed. Snug them until there is slight play in rockers. Do this on every cylinder. This should let it start and you can adjust while running.

Tuff I believe this is a dohc 3L v6. No adjustment on rockers.

this is a mitsubishi 3000gt vr4 1992 there is no adjustments on the valves its dual overhead cams twin turbo it was running before we put the valve seals timing belt and waterpump. timing marks are in line it is getting spark and fuel but not even trying to start just turning over. plenum was removed during istallation of seals.could something electrical stop it from starting. and its the v6 3.0L twin turbo

If there is 30lbs difference in compression on one bank there is a problem on that side. Collapsed lifters, bad rockers, camshaft off 1-2 teeth, cylinders washed down on that side. Did you replace the tensioner for the timing belt? These are hydraulic and bad about letting the belt slip.

Yeah I had a brain fart dandy.

And when you reinstalled the belt did you retard the crank sprocket by three teeth so that when tensioner was drawn tight its timing mark would line up with the other four timing marks lined up too. If any one of the five timing marks is off it will probably not start.

I know its a pain in the butt but I would double check the timing marks. I have got in a hurry before and missed a mark by a tooth or two before.

Especially the left cam.

Did you remove the heads to do the valve guide seals or do them with the heads on? Oh and check the electrical connectors that are bolted to the left of the upper intake(right by your fuel pressure regulator). Have seen these lose connection due to being moved around. Mine looked normal but was actually broke and not making the connection as it should.

all timing points are on exactly. seals were installed heads on motor using compressor to hold up valves. checked wires rechecked left head pressure and reading 120 125 and 125 right head reads 150 all cylinders. wondering if cams could have been installed incorrect or any other thing after putting seals in that would make pressure low? Any advice would be helpful. engine ran before teardown. first time doing valve seals in this type engine. the 120 pressure does not leak off. Help

Bill im confused on something you said,,, you said "left head 120psi right head 150 psi " what do you mean by that,, cause you know that compression is measured per cylinder right?

yes every cyl right head 150psi cyl 3 cyl on left head is reading 120 125 and 125 all 3cyl on rght 150 psi

Does it back fire or just crank not try to start at all?

does not backfire does not try to crank at all. suggestion today was to check all spark plugs to see if all are firing and to check all cyl with air to ALL cyl at top and see if air is going out exaust or breather . WHICH WOULD indicate a open valve. really struggling any suggestions are helpful. thanks bill

You say no crank? The engine doesn't turn over with key?

yes engine turns over with key it just dosen't try to start.

Where are you checking the fuel at? Even though it has fuel pressure doesn't mean the injectors are pulsing. Spray some starting fluid in the air filter box and see if it starts.

Just a thought. Is there any chance that you got the cams mixed up? Have you tried putting a little oil in each cylinder and redoing the compression check? If psi goes up then its a ring issue and will eliminate a chance of it being a valve issue. But honestly is should still crank and run at the psi that you are getting as long as the valves are closed when the piston is on compression stroke. Does yours still have the two in one cam/crank sensor on the back bank head? If so have you tried loosening the adjustment bolt and retarding your timing in both directions? Might even try removing it and turning the piece that goes into the intake cam 180 degrees and try to start it again.

Did you find the answer to this? I have the almost identical problem with a 02 Chevy Tahoe