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Carb in tank fuel pump???

Old 12-10-2018, 10:54 AM
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Car: 1987 Firebird Formula
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Carb in tank fuel pump???

Hi, I have the 87 formula with the CC Rochester carb on a 305 engine. Supposedly there is a low pressure pump in the fuel tank to keep the line to the engine pump pressurized to eliminate vapor lock.
I have a fuel pump relay on the firewall but don't know if I have the pump or if i its working. I cant find a bit of information on it. I have never heard it, yet the car runs perfectly.

Does anyone have any information on this mystery pump?

Thanks,

Louis

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Old 12-10-2018, 12:11 PM
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Re: Carb in tank fuel pump???

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Old 12-10-2018, 02:59 PM
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Re: Carb in tank fuel pump???

jump the hot and power to pump leads on the relay connector and you should note fuel flowing from the supply line...you can disconnect it and drop it in a container.

the car will run with a failed in-tank pump, the block pump will just have to pull through the dead one in the tank. It will be more susceptible to fuel starvation under high demand and vapor lock than a system with pick up only in the tank. best to keep it functioning.

I put a pressure gage on mine once and it didn't read much if anything, although it did flow fuel. could have been a worn pump or just the nature of things.
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Old 12-10-2018, 06:02 PM
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Re: Carb in tank fuel pump???

Thanks Drew and Naf. This is good info.

Louis
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Old 12-11-2018, 07:12 PM
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Car: 96 Impala 84 berlinetta
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Re: Carb in tank fuel pump???

vapor lock is when the carb gets too hot . I never had any vapor lock issues. fuel manual pump on the block does fail and it will reduce power. 305 CU is not a engine that requires high fuel volume . a 350CU with power up grades will .
if I had an power problem I would hook up the fuel pressure gauge .. 7 psi ish ..fuel filter dirty also ..check engine vacuum should be 17 inches and higher at 600rpm's..

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Old 12-11-2018, 09:08 PM
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Car: 1987 Z28 Camaro
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Re: Carb in tank fuel pump???

the issue isnt the carb getting hot, its the fuel lines that run next to the exhaust/headers getting hot. For the first start of the day, turn the key to run (not start) and listen, youll probably hear a whirrrr coming from the back of the car for a few seconds as it primes.

If no whirr, it either doesnt exist, or its dead. but if theres no issue with how the car is running, then theres no need worry about it. Theyre a tiny little low pressure pump, i think the one i replaced my dead one with was about 4psi from memory.
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Old 12-12-2018, 03:20 PM
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Re: Carb in tank fuel pump???

insulate the fuel lines and perhaps the headers .. see if that works do it on the cheap then use some high quality high temp insulation ..

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Old 12-27-2018, 04:45 PM
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Re: Carb in tank fuel pump???

From everything I read on the in-tank pusher pumps, they're only pushing 2-3psi tops, just enough to keep the fuel flowing "forward" and keep it circulating to help prevent the vapor lock issues when the lines are hot. When I did my original 350 swap, I got rid of it and ran a whalboro with regulator up in the engine bay.
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Old 12-29-2018, 12:35 AM
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Re: Carb in tank fuel pump???

I'm guessing this was only added to cars that were sold in hot climate areas. That being said, the fuel lines do come seriously close to the passenger side exhaust....just a bad design altogether really. When I bought Edelcrock TES headers years ago, they came with a fiberglass "wrap" to cover the fuel lines in that area, which helped. I never had vapor lock issues myself....maybe just lucky.
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