jgracing9

i have a 91 z28 305 that the fuel pump was whineing really loud on, so i got a new acdelco fuel pump,strainer and fuel filter. after installing 2 days later the new pump is whining even louder and the car wanted to stall out. checked the evap system and its fine. the car has a vented gas cap which i thought they didnt come with? i blew air into the return line to see if its clogged but it wasnt. the fuel line to the engine throws fuel but its not a full blast steady flow.

ws6transam

What sort of condition would cause a brand new pump to fail like that? About the only things I can think of would be if the pump has a bad power or ground wire, causing low current delivery to the pump. That would make it pump erratically and provide substandard fuel pressure. The only other two things I can think of are a tank full of sand to clog the new pump filter, or else a bad pump straight out of the box.

However if your new pump is acting just like the old pump, I suggest looking at your fuel pressure to see if it's too high or too low.

If the pressure is dropping too low, I would suspect the power leads to the pump as part of the problem. They are important. When I retrofitted my '84 with a new high pressure fuel pump, I braised a new ground fitting onto the pump pickup assembly, strapped it into the body with new braided copper strap, and ran 10 gauge power wire from the relay in the engine compartment straight to the pump. Since you have a harness already, re-check to make sure the connector is super clean, and if at all in doubt, re-do the wire connector.

That pump likely draws eight to ten amps, which means it only takes a fraction of an ohm of resistance at the connector to drop your delivered current by 20 or 25%. Ohms law says: 12 volts divided by 8 amps = 1.5 ohms total resistance. Add only half an ohm of resistance at the ground wire and half an ohm at a dirty connector, and viola! 12 volts divided by 2.5 ohms = 4.8 amps, a 40% loss of power.

Don't know what to say about the whine - Maybe it's working too hard against a clogged fuel return line or a clogged fuel rail at the regulator. About the only thing I can think of is a bad fuel pressure regulator that doesn't enable the fuel to return to the pump. If it's stuck and dead-heading, you should measure about 60 psi or so at the fuel rail, and this will eventually overheat your pump and cause it's premature failure. So check your fuel pressure. It should be between 35 and 41 psi. If you don't have a fuel pressure gauge, by all means, order one from Summit Racing equipment and install it on the schrader valve to see what's going on.

jgracing9

the tank was spotless one of the cleanest i have ever seen. i noticed the acdelco pump was slightly smaller and thinner then the factory pump, i match up an airtek pump from advance to my factory pump and its the same size and width. maybe somebody put the wrong pump in the acdelco box? well i'll drop the tank and try to get an exchange for the airtek one to see what happens

ws6transam

Before dropping the tank and swapping out the pump, try getting yourself a fuel pressure gauge to see what the fuel rail pressure is doing. That will be the defining standard of whether or not the pump is the problem. If you power up the car, the pump should pressurize the fuel rail into the 30-something psi range, and when it starts, the pump should hold pressure to that level, minus the plenum pressure. in other words, at standard atmospheric pressure, the fuel rail should hold at 38 psi (or so), then with 12 lb/square inch of vacuum, fuel pressure should show 38-12psi = 26 psi, and at wide-open throttle, fuel pressure rises back to 38 psi. (if 38psi is what your regulator is set at). Of course, you can't visually measure WOT fuel pressure unless you are holding on really, really tight for dear life.

Here's the fuel pressure gage. It takes a 1/8 " NPT fitting, which means you need to create a little U adapter from the -AN Schrader valve to the the pressure gage. If you don't have those parts handy, Earls likely stocks something to fit. That will plug onto the fuel rail and tell you exactly what is what. I personally use a short little nitrous line from my Schrader valve into a little fuel block onto which my fuel gage is attached, but it's likely overkill.

http://www.jegs.com/i/Auto+Meter/105/2173/10002/-1

jgracing9

i have one its about 25 years old and hooked it up and the before i did anything a line blew on it lol i gotta get a replacement hose for it to check it.