gatorman376

valve floated in my 90 3vze 4runner, had the heads reworked and new oem cams, new plugs wires cap and rotor timing belt. engine was at tdc on the number one cylinder when i pulled it apart, everything went back together went to turn it over, getting fuel air and fire but she just wont bust off and run.. scratching my head at a loss. tested the injectors, getting good spray, good compression timing is as close as it can be to perfect. did have a little confusion when installing the new cams but about 99% positive they are in properly. any body else have any ideas?? trying to get this thing running so i wont have to rely on the mrs to get around.
thanks

crashnburn80

Are you certain you installed the cam timing correctly? They turn at 1/2 the speed of the crank, so they can be installed 180 degrees off and everything will look right and turn over correctly but won't start. This is usually determined by verifying what valves are being engaged by the cam during installation when cylinder 1 is at TDC.

scope103

I don't think that's right. If you rotate the cam 180° (leaving the crank where it is), all you need to do is turn the crank one turn and the cam is back. If the crank was at TDC before, it will be at TDC after one turn. (On Exhaust or Compression stroke? THAT is determined by the cam; there is no difference until the cam is installed.)

If you have good compression it is not likely to be cam timing. DO make sure the distributor is not off 180° (could that be what crashburn is referring to?)

Are the plugs wet (gas) when you pull one out?

crashnburn80

Yes, I'm referring to the ignition timing and the cam being misaligned.

The assembly instructions in the FSM are based on cylinder #1 being at TDC on the compression stroke, which is specified for setting the timing. While the compression/exhaust stroke is irrelevant to the block since they are both at TDC, if the cam is set with valves open on cylinder #1 and the ignition timing procedure is followed it will set to fire cylinder #1 with the valves open resulting in a no start scenario.

A compression test will not show the cam/timing mismatch issue as the valves will close on the exhaust stroke (when they should open) and hold compression returning good numbers.