Still working on this no-start issue. I've basically ruled EVERYTHING except internal engine failure out.

I have:

Spark (from the coil and at each plug)
Fuel (not only rail pressure but I can smell gas from the throttle body while cranking)
Air (I've even propped the butterflies open to bypass the IAC)

Still no start. Every so often, I get one fart, what sounds like it wants to fire, but in the 20 or so times I've tried to start the engine, this has only happened twice.

I'm at my wits end. I decided to hook up a vacuum gauge at the intake manifold (there are a couple factory plugged ports, I used one of these). I crank the engine, and I have NO vacuum registering on the gauge. I know the gauge is working because when I manually operate it (with my lungs), I register vacuum.

I know this vacuum test isn't a real great test and a compression test would be better but it's way to cold out to be screwing around with that. I know the timing chain isn't broken because the distributor is rotating, so I have to imagine there's some other catastrophic failure somewhere in the engine, I'm just wondering if I can use this vacuum test as a clear indicator or if I'm just missing something trivial.

The only thing I haven't checked is the EEC relay. Not only can I not find it, but I have to assume the computer is working because I am getting spark and I think that the ignition module runs through the computer.

Please help!

 

Given the mileage in your profile and it's a Windsor block 5.0/5.8, I would check and see if it has jumped timing. The distributor will still turn and fuel/spark will still work fine but you might notice the engine turns over fairly easy and free........easy to check!

 

That's a good thought, I didn't think of that! I know what you mean when you say I might notice the engine will sound like it's turning over easier, but I never really paid much attention to it before this problem started.

But even if the engine jumped timing, wouldn't I still be getting vacuum on the gauge when turning the engine over? Aside from taking the timing cover off and getting the engine on TDC, there's no other sure-fire (no pun intended) way to confirm the engine jumped timing?

 

Just pop off the Distributor Cap and rotate the Engine Crankshaft back and forth a few inches by hand or a tool and see how far the Crank turns before the Dist Rotor starts to move. This will be the (play) in the Timing Chain, kinda like a sloppy Steering Wheel...LOL. I'm thinking an inch or so of free travel from left to right would be cause to dig deeper!

 

Digging deeper, Line up the Rotor with Plug Wire #1 on the Distributor Cap by turning the Crankshaft by hand, Pull the Spark Plug out on Cylinder #1 to see if the Piston is close to Top Dead Center (TDC), It should be off just a hair due to advanced timing, I use a long Screw Driver inserted into the Spark Plug hole and watch the Handle move up or down as the Crankshaft is turned. If Handle (piston) is up as far as it will go and the Rotor is still pointing at #1 on the cap and the Timing marks on the Crank Dampener are pretty close then your good! If not the Piston will still be at (TDC) and the Rotor will be pointing away from #1 by 2-3 wires and you’ve jumped timing from a sloppy Chain.........there's a few ways to do it.

 

Timing light?

If the timing chain as jumped a tooth, then the ignition and the valve timing are out of sync with the crankshaft. You might still get some vacuum but very little. Sometimes it will still fire if you advance the timing on the distributor but the valve timing is still off.
jim