Ok. Had my Fuel pump go out at 160K. Replaced Pump for 327.00. (Pricey Modular Unit) Car started after install, ran ok. After vehicle was shut off and sat for a bit, it went through a hard start before firing over again. It will do this every time except if it's shut off and restarted within a few seconds. Fuel Pressure regulator was replaced NEW, same thing. Fuel Filter is New. MAF sensor appears to be operating correctly, vacume is strong. When the valve on the fuel rail is tested after car has sat for a few minutes after shutoff, the fuel pressure is low and fuel trickles out. You have to cycle the ket atleast 3 times before the car will fire right over normally, if not, it will hard start for about 3-6 seconds before firing over. Could this be a leaky injector? I do have a check engine light for cylider #3 misfire. I have yet to pull the injectors or have them cleaned (in Car cleaning to be done soon). If I have a leak in the injector, would a cleaning possibly solve this or would I have to pull it and inspect it? I could test it for leaks by pulling the plenum and rail, letting the key cycle and pressure charge the system to see if any drips start... other than that, I do not know what to do. I am hoping that it isn't a faulty check valve in the new pump. Any additional info would be greatly appreaciated.

A quick note. I did NOT have this type of hard start issue before the pump failer. It would hard start maybe every so often, but NOT every single time as it is doing now. I have checked the fuel lines (Around fuel rail, under car and around tank) for kinks and leaks, found none. And all quick connects are connected without damage. Filler hose and vent hose are securely connected as well. Pump went back in tightly with new gasket, and snap ring applied tightly.

RECAP - Hard start issue resulting from pressure dropping in fuel rail after car sits. NEW Fuel pump, filter, and Pressure regulator.

1998 Lumina 3.1V6 160K miles.

when you check the fuel pressure did you put the cap back on? if so do you ever smell gas?

Cap went back on. Slight smell of fuel around engine area, but also could have been residual from fuel trickling out of valve.

If this helps, I do notice a rich smell to the exhaust from time to time after some starts.

OK, if the exhaust smells with fuel that means it goes there somehow.
Did you check the spark plugs after these starts? Are all of them wet?
I know it's pain in the neck to check the rear plugs but the front ones
are easily accessible.
I doubt that all 6 injectors started leaking for no reason.
Is there any DTC stored?

Haven't checked the plugs after start. They were changed a few weeks ago due to misfire code on cylinder #3. Idle and misfire got better, but code remained. The plug from #3 looked pretty fouled. Even after the change, every so often you would feel a misstep in acceleration or as the vehicle went up a hill. Most likely not all 6 are leaking, but it just might be at least one.. The injectors are all original.

The vehicle builds pressure pretty fast after the key cycles, and doesn't lose it too fast, just after it sits for a bit. Then, in order to start smoothly, you have to cycle the key a couple time again. After the start, the vehicle runs strong and smooth, even under load so the pump appears to be ok.

I have a theory that since the old pump was weak, I didn't notice the issue to much, plus installing the newer pump with fresh, near constant high pressure may have advanced the leak in the injector?

Recheck that #3 plug see how it looks.

Sorry guys, hadn't been able to do alot to the car.. It is getting busy here since it's close to the Holidays. I MAY get a chance tomorrow to pull the plug and check it out. The situation is the same so far, no worse, no better. At least the car starts and runs ok after you prime it. Just every so often when you listen to the exhaust do you hear a miss.

A small update worth mentioning, dumped some Lucas Injector cleaner in the tank (full). After about a day and a half the vehicle now fires over nearly instantly. Only a couple of times has the engine Somewhat stumbled to start, but it's Nothing like it was. Still might get the injectors cleaned and looked at down the road, but it seems that the problem was probably some buildup holding the injector(s) open some. Pressure now appears top hold up in the rail.

I have a friend that used to work at GM in the 90's. There was an update at the dealerships , involving the fuel line sitting too close to the exhaust. When the car sits, the fuel in the line heats up and turns to vaper, creating a vaper lock in the line. When it cools down, it turns back to liquid and the car starts right up. They wrapped a material around the gas line, you can buy at hot rod shops. Or you can make a heat shield, that goes between the line and the exhaust. My 96 Lumina had this problem. I made a shield out of some thin gauge aluminum and the problem went away.

Welcome to AF, good info but the age of this thread makes it somewhat mute after 8 months.