John Parodi

Hello. I recently purchased a 1970 base model with a matching # rebuilt engine (300hp) and new gas tank. Quadrajet, fuel pump, fuel filter, distributor, coil and most other parts have been replaced. It ran fine the first couple of times I drove it. Now, it will idle, but cuts out when I am driving it. When I step on the gas, it will stall and I have to start it back up. It seems like it isn't getting fuel?? This happened on a 90 degree day and a 65 degree day. I haven't had the car that long and have only put 1 tank of gas in it.

Any thoughts? I want to get it over to my mechanic to take a look without flat bedding it.

John

Peterbuilt

You might need a new accelerator pump.
Remove the air cleaner and while the car is at idle blip the throttle linkage and look for two streams of fuel being shot into the carb.
NAPA has a good pump, #2-4055

cv67

ditto on the accelerator pump. When right the Qjets are great carbs.

v2racing

If the carb was replaced with one from a commercial rebuilder, that could be your problem. Ask Lars about this, he is the resident Quadrajet expert here.

Mike

7T1vette

My guess is a kinked rubber section of fuel line ("S" line from steel line to fuel pump?), a cracked rubber fuel line (at tank or before pump) which is sucking air, or a clogged up carb fuel filter.

sambrand

agree with op, acc pump, fuel filter, or a crimped fuel line.

stingr69

Changed fuel filter? The factory one inside the carb inlet or an external in-line filter? The one inside the carb inlet is suspect if you have not checked that one already.

crf311

John Parodi

7T1vette

Is it a problem that the new filter does not have a check valve? Only if you have difficulty starting the car after the change. The tank is "gravity feed" to the fuel pump; then the fuel is 'pumped' up to the carb and into the fuel bowl. When the engine (and fuel pump) are turned off, the elevated fuel in the carb might back-flow to the pump by siphon action, leaving the fuel bowl empty. This would require you to crank the engine (and pump) long enough to refill the carb before the engine would fire. Again, I say that might happen. If it does, you should find a replacement fuel filter WITH the check valve and install it with the check valve on the outboard end of the filter (rather than placed down inside the inlet).

I believe that you have found the root cause of your hesitation problem. But the 'solution' could cause a secondary issue. But you know how to fix that, as well. Good luck.

CanadaGrant

Those fuel filters with a check valve were/are sold by Napa and are a huge problem. With my 69 427 which is a bit of a fuel pig, if I stepped on it I could get through first and half way through second gear then ran out of gas. The only reason I found it was because it was ok before I replaced the filter with the junk pictured below. The jacket around the ball and spring is swollen out and it prevents movement plus the ball creates a big obstruction even if it was free to move. That filter is below and has the check valve removed for the pic. There is less than 100 miles on it....
Also, as 7T1 says above, make sure the filter is installed with the opening or inlet hole facing out of the carb towards the fuel line as that will make it even worse if reversed.