I have a 2005 Avalanche . I reworked the heads put in anew cam,lifters, push rods and timing set. I have a crank and no start condition. Fuel pressure is 50psi but my compression is only 55psi. I made sure when the timing set was installed I was at tdc. My cam and crank shaft gears were at 12 and 6. Where should I start when trying to locate why my compression is so low? Thanks.
2005 Avalanche
- Thread starter rtrdad
- Start date
Well you didn't change the piston rings and these old truck do have cam and crank position sensors and if they failed they wouldn't allow you to crank to begin with so it's probably not that. If you had full compression and no start it'd probably be the sensors failing after maybe getting damaged by accident. But 55psi is low so you probably have slightly off timing but maybe not enough to upset the positioning sensors. Sure you didn't just nudge the gears when putting the chain and tensioner.
You might want to focus on fuel or spark in order to get it running, as even with low compression, the engine would still fire and run, just not well. The old '70-something shop truck I drove years ago at my job had next to zero compression (the starter spun it way faster than needed to get it running, with no resistance, and you couldn't park it on a hill unless you set the brake), but it's still fired up easily. It doesn't sound to me like compression is your problem.
Shoot some oil into the cylinders and see if compression increases. If it does, it's most likely your rings/cylinder. If compression stays the same, look toward your valves, valve timing, or head gasket.
That's the thing if he changed the rings which he didn't say he did you need to break them in to raise compression. But he didn't touch the rings which makes things weird.
On the surface.....Sounds Valve Timing related to me. Especially if it was running before the teardown.
Is it the correct cam for this engine? Also does sound like maybe the cam is out of time with the crank.
