D6 8U has fuel at injectors but no smoke - won't start

Looking for suggestions on what to could be the issue on why I have fuel at the injectors but no smoke when the D6 8U is cranking. Motor ran great last fall when I pulled it in the shop: fixed pony motor, cleaned diesel tank, new filters in fuel tower and new seals around injectors. Pony motor cranks it over but I'm not getting any smoke. I have cracked open lines at the top of pump, near injectors and bled the fuel tower and still not getting it to smoke & start. Is there something that could be limiting fuel pressure, although it will push the fuel a few inches in the air when I loosen fittings. Any tips on what to check would be much appreciated. Thanks.

No smoke at all with fuel delivery would indicate no compression. Compression is released in the start position, needs to be in run position for full compression. Apologies if this is stating the obvious, this mistake has been made before though.

I've engaged the pony with the lever in decompression and then push it in/forward to compression. Is it possible something is not correct with the internals of the decompression setup? I have a hard time believing something broke in the head with the decompression setup.

Do you notice a change in the starting engine - working harder or under more load when engage full compression? There should be a load difference noticed.

It is possible, but depends on the model. For example, on the D2, it's possible to assemble the decompressor shaft and arm 180 degrees out. I don't have familiarity with the 2U configuration but if a) it would run fine previously, and b) you haven't messed with the decompressor controls (other than just using them), then it seems less likely to be that. Still, you can check that there is a noticeable difference in effort to turn the engine over between compression on and off. Another possibility is stuck valves but that also seems less likely given how recently it ran. I suspect fuel since that's the area that you worked on. Even though it produces smoke, it can do that from fuel that's insufficient to run. So, I'd say check over your fuel system again. If you do have the injectors out to test, make sure they're misting a healthy amount - no dribble, and no weak spray. If no culprit presents itself, then start at the beginning and confirm the fuel system operation: healthy sustained flow from the tank to the transfer pump - at least 30s of solid flow, healthy output from the outlet side of the filter and well-bled, good output from the injection pump outlets, good output from the injectors

Did you check the fuel rack? it may have gotten stuck over the winter from moisture. Just one thing more to check if no smoke.

Does it fire on a misting of starting fluid? Just a quick shot to the air cleaner under compression? Don't overdue it. You said NO smoke - either no compression or not getting fuel into the cylinders.

Thanks for the suggestions. The decompression lever seems to be working because the pony slows when I engage the lever. I'll check the fuel system one more time. I've tried a little ether and it will hit but dies out. Is there a spring in the fuel tower that could possibly be plugged up with dirt and old fuel? I'll take a look at the fuel rack as well. Unfortunately the machine is over an hour away and it may be the end of the week before I make it back out there.

What he says. I have run 35 gallons of what I believe to have been fuel from about 1985 in 2014 . The latest fuel I don't think will last that long.

But twice in my 40 years of running u series D6's , after a filter change could not get it fired up until I opened the dedicated fuel bleeders behind the pumps that takes the oval wrench. Generally just grab the 3/4 open end wrench and loosen the injector lines.