Instilling on a 2001 Chev S10 Fuel Pump on 2001 Chevrolet S10

I need some help. on instilling this pump i got the old pump out but can not get the new one back on the o ring will not go all the way up. on the pump and to lock the pump in is a C ring Grrrr. P.S i did put Lubricant on the ring so i push and push and will not go all the way down so i can lock it in

Asked by for the 2001 Chevrolet S10
see if the old pump will go in
then look whats different.

ok i will do that now and see and get back to you thank you

It work i got the new pump on i did what you said and it went on so i taken the old one off put on the new one and add lub under the new pump and it work

thank you for all your Help