Fuel starvation problem: why do fuel pumps get noisy?

I was enjoying an early morning drive this past weekend when my car (71 911T with '83 Euro 3.0 motor) started to buck and sputter. Initially I thought I was running out of gas, but the end never came. The car would still run, but didn't generate enough power to get me home. I pulled out the sending unit, inspected the tank (still plenty of fuel, no sediment or debris in tank) and everything looked fine. The hoses looked fine, no kinks.

After sitting for a few minutes, I fired up the car -- it ran better and got me home. The fuel pump is really noisy -- which I know suggests iminent failure. (But the pump should, theoretically, be good -- I just got it from EZ two weeks ago.)

So here's the question: How do I figure out whether the pump or the in-bound fuel lines are the culprit? I don't want to get a new pump just to burn it up, if the real problem is a partially clogged fuel line. Unfortunately, I don't know what flow rate from the tank to the pump is appropriate. (THe pump is located in the rear, where the second pump is on the turbo.)

Any of your ideas would be greatly appreciated! Great forum.

Jamie

I had this problem with a rebuilt fuel pump. My problem was the screen at the fuel tank (73.5 T) was clogged with sediment. Hence, flow wasn't enough to "cool" the fuel-pump and the fuel-pump burned itself out. I went through two rebuilt pumps before I looked deeper into the fuel lines.

I would expect the fuel to flow quite fast from the tank to the fuel pump side.

Good luck.
Nick

I don't know the flow rate spec either, but you'll find it. And your fuel pump may need replacing.

On the other hand, blowing out the fuel lines is a way to avoid several expensive fuel system parts purchases over the next few years. I believe there may be a screen on or near your pump, as well as a fuel filter in the engine compartment.

This has been my experience and it has cost me multiple unnecessary purchases before I learned the trick of blowing air through fuel lines. As an experiment, just blow backwards through the line that moves gas from the front of the car to the engine compartment. I'll bet some ugly stuff will fly out. I've had the same symptoms as you, just not with 911s.

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'83 SC

after you clean out the lines, try an additive called "Marvel Mystery Topy Cylinder Lube. add a bit to the gas (don't dump it in, read the bottle) and let it work it's magic. i had similar symptoms to waht you are describing in both my 924 and my Mercedes. the noise was despite a new pump and fuel filter. the Marvel Mystery Top Cylinder lube almost acts like a lubricant for your fuel pump, and it is totally inert to gas (it won't hurt it at all).

it comes in a metal can and you should be able to find it at just about any automotive store. it's often recommended for cars that have to do their duty in cold places and other environments not frendly to gas, oil or engines in general.

good luck!

obin

Thanks for your responses. I'll blow some air through the hoses and see what happens.

Jamie