fuel line problem

[emf1367]

My car runs fine at idle and up to 70 mph (didnt try faster) without any problems if you slowly depress the gas pedal. However if you press too fast it goes for a moment and then cuts out. It will die if you dont back off the gas.

A service tech said it was a fuel starvation problem, maybe a pinched line or something. I checked the fuel pressure and it is good so it'e either a fuel pump (which is brand new) or something in the line.

My idea is to install a temporary fuel hose running directly out of the fuel filler tube to the fuel pump. If the problem disappears then I've isolated it to the fuel pick up line.

The thing I discovered is there are two lines fed to the pump from the tank. I thought the smaller one was a vent line, however when I unhooked it fuel poured out of it. So I guess one of the lines is the return line and the other is the feed line.

If I bypass the main feed line (the larger diameter one) and run from the filler tube to the pump will the system still work?

And help would be appreciated.

 

[Artsvette73]

You are right the small line is the return. If you still have the quadrajet check the fuel filter in the carb. And it could be the accelerator pump is on it's way out.

 

[LVMYVT76]

If your car has rubber lines from the fuel pump to the fuel steel lines, make sure these are the molded style. I replaced these with regular fuel hose one time, they get warm and pinch off the fuel going through. Replaced the fuel pump and fuel filter, which did not help until I put the correct hoses on.

 

[6880 Mike]

You may be doing work you don't have to do. Sounds like carburetor to me, not the fuel pump. When was the last time the Q-Jet was rebuilt?

 

[Phill]

You may be doing work you don't have to do. Sounds like carburetor to me, not the fuel pump. When was the last time the Q-Jet was rebuilt?

Thats what i was thinking to. the moulded fuel lines and in line fuel filter are available from most on line venders.

 

[TJay]

Your problem may not only be a starvation issue, it may also be a flooding problem, look inside your carb, get someone to step on the gas than off. Look to see if the fuel continues to pour into the carb when they step off the gas pedal. if so you may have a dirty needle valve. Or pull a spark plug and see if it's wet, to much fuel will also cause the motor to cut out.

All the above are good suggestions to look at also.
Good Luck

 

[minifridge1138]

Your problem is the accelerator pump in the carb.
I had the same problem (but i have an aftermarket holley).

It is a fuel starvation problem.
Your throttle plates open BEFORE your accelerator pump kicks in.
That leaves you way too lean.

Assuming that the accelerator pump is not broken, you need to adjust WHEN the accelerator pump begins to operate.
If it is very late, the car can stall.
As you get closer, and closer to correct, you will no longer stall, but there will be a delay between the time you floor the pedal and the time the car accelerates. Keep adjusting the timing until there is no delay, but don't advance it too much. Then you'll be using the accelerator pump even for light acceleration.

I'm not sure how to adjust this on a Quadra-Jet, but i'm sure someone on here does. Or you can look for a service manual or search the net for Q-Jet tuning tips.

Good Luck!

 

[wishuwerehere82]

Look down the carb throat to see if the accelerator pump is squirting gas in the venturi when you open the throttle plates. If not, the pump is bad.
There are several holes in the end of the pump arm to adjust how much gas is pumped in. The inside one squirts more, and the outer one squirts less. You can move the linkage to adjust what you want, but the pump has to be working first. Usually, the factory-set one is correct for the carb.
If you haven't changed the inline filter, do it first to see if it will get you some more flow.

 

[emf1367]

It was the sock over the pick-up tube in the tank!

Thanks to everyone for your advice and suggestions. I traced the problem all the way back to the tank. I dreaded it when I realized I had to remove the fuel tank. Once I did I opened it up and discovered that the sock at the end of the pick-up tube had collapsed and somehow bunched itself up between the bottom of the tube and the bottom of the tank. It allowed fuel to be pulled up the tube but only at a slow rate, thus the problem of fuel starvation under quick acceleration.

Of course I had the carbeurator rebuilt and the fuel pump tested before discovering the problem. I'm not sure why they put a sock over the tube in the first place since 75 was the first year for the rubber bladder/liner insode the tank.

At any rate she's running like a top now!

 

[petes74ttop]

Good for you, EMf1367, we all give the best suggestions we can think of, you went a step further and found the real problem and that helps the rest of us. well done, PG