Fuel system losing pressure
 

My fuel system is losing pressure. It has done it sincei got the truck. I jumpered the fuel pump so it turns on with the key in on position. I let it pump for 10-20 seconds and i am good to go to start it with ease.. I had the injectors rebuilt and had the fuel rail taken apart for that. but it still does it. I listened for the his at the regulator and it is not leaking there or the rail. So before I tear into the fuel pump, my question is is the return line to the fuel tank metal or rubber? I pretty much beleive the check valve may have failed, but i am just looknig for the cheaper fixes so i dont spend the money on a new OEM pump and then find it still does it. I havnt read anything in other posts about the possiblity to just replace check valve, so i am under the impression it is in the pump and a not repairable.

Thanks for any help.

Are you sure its not leaking at one of the injector o-rings. Mine was. You can hear it with a stethoscope. Otherwise, you wouldn't notice.

I had the stethoscope out but didnt hear any hissing on the injectors. I did find some hissing from the brake booster when i shut the motor down, but nothing else.

thanks!!

random question here but how can i check what pressure the fuel pump is pumping at?

I believe that you have to install a T into the system to hook up a gauge to. There's no easy use schrader valve anywhere in the system for testing purposes.

As to the OP you can check to see if its the return side or pump side by clamping off one of them and allowing it to sit for however long you usually do. Then, just before you start it remove the clamp. You'll know which side's leaking when it starts up like it should.

Is it a truck or 4runner? These toyotas have steal tanks. Fuel pump maybe your next step along with filter. Fuel pressure for these trucks is about 34-38.

If its a 4runner theres an acssess panel under nieth the passanger side rear seat.

I'd get a fuel pressure gauge. The better ones include an over-length "banjo bolt" so that you can stack an extra "eye bolt" that connects to the gauge (I've read where others have modified a stock banjo bolt by threading in a fuel-type Schrader valve, so they can use it with a less-expensive gauge set.) I expect you'll find that you have no pressure when you first apply power to the pump, and it comes up very slowly. That points to a weak fuel pump. Then take power from the pump; the pressure should drop slowly. If it drops really fast, I'd look at the fuel pressure regulator

As long as you know this is really dangerous; if you get in an accident that breaks a fuel line, you don't want the pump to keep running!

It is a 4runner. So the lines to and from the tank are rubber? I will popp off the cover on Sunday when i can get to it. At least now I figured out to let the truck sit for abotu 20 seconds and fully pressurize rather than crank and press on the gas pedal multiple times to get it to run.

Thanks!!

My 95 pickup 3.0 is losing pressure as well it seems , It will idle all day but will run out of gas if held at 3,000 rpms , I change fuel pump , filter twice , air idle sprayed carb cleaner on hoses to check for leaks , gonna replace regulator today and go from there , I love my 89 so bought this 95 , dumped a lot of cash into for cosmetics and now this is happening , do not plan on aborting mission , I'm just frustrated

Are you sure its the fuel pressure, and not something simple like ignition timing (or a disconnected EGR vacuum line)?

To test the fuel pressure, put a line on the fuel return port of the Fuel Pressure Regulator, and put the other end in a gas can. At all engine speeds fuel should be flowing out of the return line; if it keeps flowing at 3,000 rpm your fuel pressure is fine. (Of course, for a few more bucks you can buy a fuel pressure gauge with the banjo bolt and measure the pressure directly.)