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GMC V6 and V12 Engines Engine repair and rebuilding

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  #1  
Old March 5th, 2025, 11:44 PM
rsrose rsrose is offline
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Default Repeatedly blown fuel pump?

Why is it that every couple of years, the mechanical fuel pump on my 305D V6 stops working? I drive the 1962 GMC on occasion. So far, every 2 years, if not sooner, the fuel pump stops pumping gas. Would the only solution, aside from tearing the engine apart to install a activator rod, be to go electric?
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  #2  
Old March 6th, 2025, 01:00 AM
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Default Re: Repeatedly blown fuel pump?

You can go electric if you want. Many have. The reason your mechanical pump quits on you is due to the membrane drying out inside. Once it cracks (because you're not driving it much) it can't pull like it did.
You should run the engine once a month to keep it in good shape and lubricate the seals. Even if just for a trip around the block.
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Some people are like slinkys. Not worth much but funny as heck when pushed down stairs.
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Old March 6th, 2025, 01:57 PM
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Default Re: Repeatedly blown fuel pump?

ethanol speeds up the deteriation of the diaphram. its also hard on carb parts. i try to put in non ethanol fuel when possible.
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Old March 6th, 2025, 07:03 PM
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Default Re: Repeatedly blown fuel pump?

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Originally Posted by ilvracn View Post
ethanol speeds up the deteriation of the diaphram. its also hard on carb parts. i try to put in non ethanol fuel when possible.
Right! I forgot about ethanol since we have a choice here and I always avoid it. If you're in an area with only ethanol, definitely go electric. If you can choose, just duck the ethanol stuff. It's bad for every engine, even those that say they're OK with it.
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Some people are like slinkys. Not worth much but funny as heck when pushed down stairs.
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Old March 7th, 2025, 05:22 PM
Jim A Jim A is offline
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Default Re: Repeatedly blown fuel pump?

I don't think there is ethanol-free fuel available near me except in hardware type stores.
Their $30 a gallon product and my 10 MPG 305A are a poor mix.
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Old March 7th, 2025, 08:08 PM
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Default Re: Repeatedly blown fuel pump?

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I don't think there is ethanol-free fuel available near me except in hardware type stores.
Their $30 a gallon product and my 10 MPG 305A are a poor mix.
You're in california, my brother. You will have to put an artificial intelligence robot in your GMC before too long if you want it to be allowed on the streets!
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Some people are like slinkys. Not worth much but funny as heck when pushed down stairs.
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Old March 7th, 2025, 11:14 PM
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Default Re: Repeatedly blown fuel pump?

Add some marvel mystery oil to the ethanol blend to tone it down and add lubricant for fuel pump and carb parts. Helps motor internals as well.
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Old March 8th, 2025, 01:39 AM
lizziemeister'sV6 lizziemeister'sV6 is offline
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Default Re: Repeatedly blown fuel pump?

Do you have an inline fuel filter before the pump or one after the pump? Have you ever looked at the pickup sock/screen in your tank? Maybe you are over working the pump. I use 4 oz of Marvel Mystery Oil + 4 oz. Sea-Foam to every tank full of gas.
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  #9  
Old March 10th, 2025, 05:20 PM
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Default Re: Repeatedly blown fuel pump?

all the new pumps for a 305 are terrible. they are all made by the same place and they fail rather quickly. I've gone through three myself in the last few years. I have an electric pump in the cab now and no longer have issues.
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Old March 24th, 2025, 08:55 AM
Oldygoody Oldygoody is offline
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Default Re: Repeatedly blown fuel pump?

What electric fuel pump was installed? Most have bad reviews and are made in china with little to no quality control. Bought a Mr. gasket micro electric 12s but reluctant to install in my '66 305e due to numerous complaints. Older mechanical pumps that can be repaired seem to be a better alternative to electric.
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