May 13th, 15, 02:28 AM
Join Date: May 2015
1994 3.4L - Is this a timing issue?
I’m admittedly stuck on this one.
I have a 1994 base model for which I’ve just finished replacing the intake and valve cover gaskets. The vehicle just reached 100,000 miles, and has had no other major problems or repairs other than a replaced ignition module (approximately six months ago).
During that process, I noticed no anomalies other than during the task of resetting the valve lash. There were no noticeable markings anywhere to indicate crank position (although I’ve seen them on every other Camaro I’ve owned in this year range).
For this reason, rather than take an educated guess at when the number one and four cylinders were at TDC (per service manual), I manually set each valve by adjusting intake valve lash at the start of exhaust valve opening and the exhaust valve lash on the start of intake valve closing. In hindsight, I learned this method for engines utilizing solid lifters—I did not consider what effect the hydraulic lifters in this engine might have on the adjustment (if any). Upon completing the adjustment, the engine rotated without interference and all valves appeared to lift exactly when they were supposed to do so.
The vehicle now rotates but it will not start. I have verified the following:
· Adequate fuel pressure at the rail
· Proper signal at the injectors, verified with noid light, and (apparently) good injector operation (as heard using a mechanic’s stethoscope)
· Spark present at each plug boot
· Proper voltage at the battery, ECM and all applicable fuses
· Good ground connections at all required ground points
It goes without saying that there is a position signal from the crank (since the DIS requires this internally for a timing signal to trigger the coils), but this does not of course mean that the signal is triggering at the right time. In any event, since the tachometer signal is also driven by this same circuit, the presence of a valid RPM indication upon cranking further proves that the DIS is receiving at least some position signal.
Despite the fuel pressure at the rail and the evidence of injector operation, there is absolutely no indication that the engine is firing (usually, I hear something, if even a misfire). My thinking is that my valve adjustment method, while technically correct in terms of opening and closing sequence, might have resulted in improper spring preload due to the hydraulic lifters (versus the solid variety). Another possibility that I’m considering—however much of a longshot—is the actual timing chain.
Given the amount of time required to disassemble the top end (the air intake plenum blocks the valve covers, and engine accessories don’t exactly make things easy on this engine), I’d appreciate any suggestions as to other things that I can verify before getting to the point of disassembly again. If I have to get back into the valve rockers, or if I have to get into the timing chain cover, that’s fine—I just don’t want to do it unnecessarily.
A follow up question—and probably one that's much more serious—is that of any possible consequence to the valves should the problem be my adjustment method. As I previously stated, there appeared to be no interference at all when I manually rotated the crankshaft (plugs out) during adjustment, but I'm not sure what I could do to check this other than removing the heads.