Cadillac Repair: eldorado fuel pump?, shrader valve, wireing harness

Question
I will try to shorten this as much as possible. Ok, my eldo would start just fine, but almost exactly 10 minutes after initial start it would die. This was if you were just sitting at idel or if you were driving. After a few minutes it would restart and do fine the rest of the day. But it did this every time. I installed a new fuel pump and filter, then it would not start at all. You could hear the pump pressure up and shut off, but would not start. I figured I got a bad pump so I returned it and got another one, same results. Have you run into this problem before? The car runs like new when it is right and has been a well maintained ride. Got any ideas?  Thanks,Tony
p.s. My eldo is a 1991 touring coupe with the 4.9

Answer
Hi Tony, This is the time you need to install a fuel pressue gage to the shrader valve on the fuel rail and see what the pressure is. I believe it should come up to 40 psi running. There is a safety built into the fuel pump circuit in that if the engine hasn't started after 2 seconds then the fuel pump turns off. If fuel pressure is good then you need to test for spark. If no pressure then maybe the tank has to come out again and inspect the hoses to make sure they have clamps on them and the strainer is on and new at the bottom of the pump. If spark and fuel are presant then fuel injectors need to be tested for power and spray ability. How was your engine running otherwise? If running rough then enough fuel injectors could be shorted out that the computor shuts the engine off. Also inside the distributor the cam sensor or internal wireing harness has a tendency to develope an open. When this happens the engine will quit unexpectantly and then finially refuse to start. The computor can also develope an open circuit/bad soldier joint and by tapping on it with the engine running would get the engine to quit. Reading the computor data with eithor a scan tool or through on-board diagnostics might lead you to the fix. You are beginning to see there are alot of things that can cause a no start and maybe something other than the fuel pump decided to go bad at the time the pump was replaced and is the culpret but without testing the differant systems and eliminating things one at a time you will just be shooting in the dark. It might be time to have it towed to a shop that can diagnos this problem if going back inside the tank doesn't show anything. Good luck. Bill