Does this sound like my IDI is missing?

[Old Goat]

Update: don't use those o-rings from Harbor Freight. The one I used failed after about 2 hrs of run time.

Those HF O Rings might be good for some things, not with
Diesel as you discovered.
Use the Viton O Rings like I posted above.

Pull off all 4 on the one side, remove the old rings,, grease up the top of the Injector and the ring. Slip on the first one, then slide the 2nd one over the first one. this way removes the possibility of cutting/nicking it.

Once they are all on put the caps on as an assembly, and snapp them down. Just be sure to use some grease so the caps slide over the rings.

Goat