How much fuel should be pumping out through filter when disconnected from fuel line on a 1996 Chevy Impala?

Question

I thought I had solved the fuel supply problem a couple of months ago when I replaced the internal fuel pump. The car started right up and hadn't had a problem since. Now, after warming the car up for about 5 minutes of idling, it died and I can't get it started again. I bled the Schrader valve, and saw a fair amount of air bubbling out with the fuel. I separated the lines from both ends of the filter and cranked the engine to see what came out. Nothing came out when cranking, only when turning the key to the on position and hearing the pump humming did a little continuous dribble come out. I would think that more would flow when I turn over the engine, but that's when it stopped. Also, nothing ever came out from the input end of the line when switched on or cranking, only from the filter output side. Odd! My questions are: Should I be seeing more output flow than there is, and from either the input line end or output from the filter? Shouldn't there be flow when cranking the engine over, too? The tank is nearly full, and the car hasn't been driven enough to run out, or to need a fill up, so the pump hasn't dried out. Do you suppose the internal pump's screen/filter is clogged already and needs to be cleaned, meaning dropping the tank again, or is there some other issue I'm overlooking. I wrote earlier getting the advice to replace the pump originally, when I thought the injectors were clogged, but the engine ran perfectly after replacing pump, so I don't think the injectors are the problem. Thanks for any advice and/or suggestions. -Gary

Answer 1

If you have one or can rent one from the local auto parts store get a fuel pressure gage that hooks to the scharader valve. See what the pressure reading is. Most likely the pump filter sock is clogged or the new pump is a bad one.

Answer 2

Did you replace the pump with an ac/delco unit or some aftermarket unit.  It sounds like the pump is failing or the screen in the tank is clogging up.  You should get a decent flow for a few seconds when the key is turned to the on position no matter what side of the filter you disconnect.  Since you have nothing to lose, get a rubber tipped air nozzle and blow air back into the tank, filter removed to see if you can clear a clog.  Just a short burst should do if it will help at all.