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My 1970 Keeps Cutting out when accelerating

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 so I'm ruling out the heat. 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

Submitted by: John Parodi


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Thanks everyone for your feedback. I so appreciate you taking the time to share your knowledge. I replaced the fuel filter in the Quadrajet and the car runs fine. The old filter had a check valve in it. The new one from NAPA Auto Parts did not have one. Things are fine now! John John Parodi on 11/15/2018 10:16:59 PM
I would change any rubber fuel lines with new pieces in case they are collapsing inside from old age, both at the pump & at the tank. Posted by Administrator on 9/18/2018 9:21:54 AM
Yea, I'd check the fuel filter...same issue with a 73 that just had all the same stuff done. But I had one that had old fuel lines sending rust to the filter every 4 days...replaced all fuel lines, case closed Posted by Administrator on 9/13/2018 12:47:46 PM
I had a 69 that also had a soft rubber fuel line from the tank and it would collapse and shut off the fuel. Steve Meillier on 9/13/2018 12:06:58 PM
1.All I read for suggestions to fix this issue are great! hook up a pressure gage to fuel pump/ line, make sure its not a bad pump. 2. My 76 Vette, I found an issue with vapor lock,... fuel line too close to block, gas vaporized before carb. I insulated gas line near block , installed in-line fuel filter now ok. #3. I think the quadra-jet carb is a POS! I tried a rebuilt, NFG too! impossible to adjust I took it off, gave it away, junk. I bought an Edelbrock 650-700?, cfm for that year Vette, installed adaptor plate , tuned it, best carb ever built no more fuel system problems, and better mileage runs great. Good luck! Thomas Barth on 9/12/2018 10:48:39 PM
all points to fuel, either pump or filter, there is one in the inlet of the carb ! Victor Bellan on 9/12/2018 8:13:53 PM
I would replace the complete fuel line from the tank to the carb. Louis Tedeschi on 9/12/2018 3:46:10 PM
Check your accelerator pump in your quadrajet . Posted by Administrator on 9/12/2018 1:14:30 PM
Sounds like you might have a fuel filter issue. Remove the filter and try it without the filter. Posted by Administrator on 9/12/2018 1:14:06 PM
Check any rubber fuel lines between the tank and the fuel pump. If it has not been replaced, the rubber line exiting the tank will be soft and can be collapsed by the vacuum created by the fuel pump. At idle, or after shutting the engine off, the vacuum will decrease enough to allow the hose to expand to what appears to be a normal diameter. I had the same thing happen to a stock 1969 Coupe. Posted by Administrator on 9/12/2018 1:13:37 PM
I once read an article where this problem was traced to a fuel line hose that had a flap of rubber inside the hose that blocked off the fuel supply under acceleration but worked fine at idle. Check your fuel line hoses. Rudy Pleskovich on 9/12/2018 11:08:02 AM
I just went through the same issue with my 72 Chevelle. At first thought it was the fuel pump. Checked all the vacuum lines and found a break in the vacuum advance. Replaced and away I went. Hope this helps. Jeff Peterson on 9/12/2018 10:47:31 AM
I had a 56 Chevy many years ago with the same problem and it was a defective Fuel Pump. Good luck. Charlie Sabo on 9/12/2018 10:13:24 AM
John, It sounds as if the carburetor isn?t receiving sufficient fuel. I?d check the fuel filter and if that?s clean consider that the fuel pump might be defective or improperly installed. These pumps are usually rebuilt and although ?new? could still be defective. If the fuel pump is working well that leaves the carburetor. Barry on 9/12/2018 9:59:03 AM

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