87 GX, fuel pump was blown...replaced it with one I bought from a friend because I was trying to get it running fast. That pump was half the size of the OEM pump and I found it to be a problem, didn't build up pressure instantly and doesn't hold ANY fuel pressure. Now, I swapped the pump out yesterday for a 90 NA pump I had lying around...pressure built faster but still doesn't hold anything...drops right to zero. Why the hell isn't it holding pressure? The car will start with ether just about everytime..and run for like 5 minutes and will stall if I leave it unattended..it never floods..it just stalls or it doesn't start up...what the hell is the problem?