Can't get my new injector to pop in

[FolkertSX]

Alright so my cars been giving me trouble lately. We're pretty sure its the o ring on the fuel injector. So we replaced it with some generic orings but they ripped apart because theyre not meant for fuel injectors. They worked for one drive. Then i got a kit specifically for a 1991 240sx and the ring was too small, put it on and it still ran like crap. So yesterday i got from advanced auto parts which we think were just a little small, it ran great for a couple min, then i really stepped on the gas and it immediately started smoking again from the exhaust. We think we're smashing the o ring when we put the injector in. We put oil on the seals, but my dad still cant push it in. So we put the cap on and then just screw it down. Reason i saw i think we're breaking them is because we pulled the last one out and it was torn, not destroyed like the other ones. Anyone know how we're supposed to push them in? With the smaller o ring it went right in, but it didnt seal it. Maybe we just havent got the perfect sized o ring yet?

[locoluna825]

rub that o ring down in vaseline.

[OutToWinPAHC]

I like oil

[FolkertSX]

^we already tried that

[biggie]

Some regular grease (white lithium worked for me) and some elbow grease.

[Lonismos14]

get the orings from oriellys. They make real parts.

[Dittoz7]

Lotsa Lube.

*that's what she said*

[DeatschWerks]

Those side-feeds can be a pain sometimes. Is just one injector you are having problems with, or the whole bunch? If it is just one, is it the same port every time or has it moved every time you've taken out the injectors. How does the rail look? Any burrs or is the cup deformed?