I recently installed a new FPR, inspected the injectors, and also took out the pump for inspection and then put it back in, and now after I shut the car off the fuel pressure drops to zero in less than a minute. It used to take a few hours. I also have a faint fuel smell on the intake manifold side, but I think only after the car is off... I have proper fuel pressure when the car is running. And I'm not seeing any leaks external leaks. Could it be a leaky injector that's stuck open? Or could it be the new FPR that's letting fuel by when there's no vacuum? Or what else could it be?

 

what fpr are you using? it is possible that once the pump shuts down the pressure between the fpr and fuel rail is bleeding back into the tank. some fpr's will only restrict pressure one way.

 

Just a stock replacement from Napa. Delphi brand, I think.

Shouldn't the fuel pump have a check valve that prevents pressure bleeding back into the tank?

 

Pulled the injectors and they're not leaking, but the pressure still drops. Pinched the return line, and the pressure still drops. Actually takes about 30 seconds for it to go to zero. I think fuel pump's check valve isn't working...

 

If you smell fuel in the engine bay, stop, and repair it immediately. Most likely candidate is the pulsation dampener. They are notorious for causing engine fires in all FI models. You can spend 100+ on a new dampener or about 8 bucks on a banjo bolt. 2nd candidate is a bad injector. I've had one that had a crack in the injector itself.

 

I've got a brand new pulsation dampener, put that in only a few months ago. Like I said, I didn't find any leaks in the rail or injector region... I pulled the rail off, secured the injectors to it, and ran the pump for a bit. Still dry.

Could this have something to do with charcoal canister and gas tank fume venting?

 

I've seen a couple pumps that have done this. Sticking check valve in the fuel pump was allowing the fuel to run back to the take. The pump would otherwose work okay, but it would take extra cranking to fire since the line would have to fill with fuel and build pressure before firing.

Easiest way to check without pulling the pump is to pull the main fuel line and connect to your fuel pressure gauge (deadhead). Run the pump and then turn off. If pressure still drops, the pump is allowing fuel to run back (assuming no leaks). If pressure holds, then check the injectors, fuel rail, etc. for leaks.

 

Ah, roger that. Will check.

 

Alright, that wasn't it. Seems like fuel pump holds pressure ok. And it's not the injectors. So I guess it's the regulator, bleeding off pressure somehow.

 

FPR could be sticking open a bit or may have a hole in the diaphram. If so, the pressure is being relieved back to the tank when the pump is off.

You could repeat the test that you just did, but on the return line instead (remove return line at firewall and install the gauge (deadhead)). If the pressure drops, you have a leak somewhere between the feed and return lines at the firewall (leaky injectors, leaking hose, etc.). If the pressure holds, that means that the FPR is letting fuel back to the tank when the pump is off.