Repeatedly blown fuel pump?

[rsrose]

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?

[FetchMeAPepsi]

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.

[ilvracn]

ethanol speeds up the deteriation of the diaphram. its also hard on carb parts. i try to put in non ethanol fuel when possible.

[FetchMeAPepsi]

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.

[Jim A]

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.

[FetchMeAPepsi]

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!
:helpsign:

[kknotts]

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.

[lizziemeister'sV6]

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.

[jerrspud]

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.

[Oldygoody]

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.

[Ed Snyder]

I like to rely on the original mechanical style pumps on my trucks. But I also install an electric pump inline as a backup. It saved my bacon one time in heavy interstate traffic near Seattle. When the mechanical pump failed, fortunately I had the presence of mind to reach down right away and turn the electric pump on. Nobody even honked at me during my slow-down!

[lizziemeister'sV6]

Ed, do (or did) you have your electric pump plumbed in direct series (same line from tank) with your original mechanical fuel pump or is it fitted into a by-pass line along your frame rail? Thinking - just thinking (I get into a lot of trouble over-thinking) -if you pull fuel thru both pumps constantly do you over-burden both of them? Using the electric pump for back-up is a great idea. :welldone:

[sclor]

Lizzie:
My experience when I was going through the same thing came from disassembling a pump. Found it stopped working from getting rust stuck in the reed valves in the pump. Once the rust was cleaned out, pump resumed working as normal. I ended up changing the steel fuel line from tank to carb. No longer have mechanical pump issues ( and I use ethanol).

Hope that helps.
Regards
Steve
New Orleans

[Ed Snyder]

Ed, do (or did) you have your electric pump plumbed in direct series (same line from tank) with your original mechanical fuel pump or is it fitted into a by-pass line along your frame rail? Thinking - just thinking (I get into a lot of trouble over-thinking) -if you pull fuel thru both pumps constantly do you over-burden both of them? Using the electric pump for back-up is a great idea. :welldone:

I installed the electric pump in series with the mechanical pump, and never had any issues with premature failures. That particular truck is owned by forum member Clyde in South Carolina now.

[jerrspud]

Ed, do (or did) you have your electric pump plumbed in direct series (same line from tank) with your original mechanical fuel pump or is it fitted into a by-pass line along your frame rail? Thinking - just thinking (I get into a lot of trouble over-thinking) -if you pull fuel thru both pumps constantly do you over-burden both of them? Using the electric pump for back-up is a great idea. :welldone:

mine is hooked up like that as well. electric behind the seat near the bottom of the tank.

[jbgroby]

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.


Would you have a ratio mix, how much MMO to a tank and how often? Thanks
Jake

[jbgroby]

I've went through 3 mechanical pumps in 10 years, I drive her bi-monthly normally either to a show, a cruise in or just to stretch her legs and burn a cigar. I only use Ethanol free (about $4.00 a gallon. The last time I did the swap out about 3 years back I also bought an electric pump, because when this one goes out, I'll make the switch.

[kknotts]

Lizzie meister post here reports 4 oz mmo and 4 oz of sea foam per tank. Sounds about right for ethical blends however I use non ethonal exclusively. Since I am never at or near empty I really only use a “splash” or small pour of each at each fill up. Less when driven regularly during car show season and more in off season when it’s sits and is cranked to keep battery up and fluids brought to temperature and circulated. Don’t always add at every fill up but the last time I changed over to an electric pump I also replaced entire fuel system with new parts including new tank, fuel lines, inline filter and carb kit. She’s a happy girl now!!

[James]

This is what I use: https://www.holley.com/products/fuel_systems/fuel_pumps_regulators_and_filters/fuel_pumps/carbureted_fuel_pumps/carbureted_electric_fuel_pumps/parts/12S?srsltid=AfmBOopbtju3Qj2SwA5r_voGYM3-aEHeygwz33an5HhmMEWTb67-AveV

[Oldygoody]

Thanks for the reply. I got a Mr. Gasket 12s before checking out the reviews which were mostly bad and am reluctant to install it. The Carter mechanical is delivering too much pressure for the Holley 2300 to handle. The float inlet valve has been adjusted to the max but still floods the bowl. Perhaps the older, original and repairable version is the answer.

[ilvracn]

all those little pumps like that mr gasket, and edelbrock are junk. find a wallbro, or get a holley red pump # 12-801-1. takes up more room and more expensive, but a much better pump. this pump runs 7psi, if the carb wants to overflow, you might have to get a regulator. but it should be fine, most needle and seats will take 7 psi with no problem.

[Oldygoody]

Installed a Carter M3955 fuel pump but had to drill out mounting flange holes for the larger bolts. Much better pump than the Carter M4548 but was a very tight fit...less than 1/4" clearance between bottom of pump and engine. Now have float level control. The M4548 pressure was over the top due to poor quality control. Next project is the fuel tank level sending unit. Only ones available fail due to ethanol corrosion on the ultra-low-quality potentiometer. Marvel Mystery oil extends the life but failure is inevitable along with suction filter disintegration. That's what you get for trading off American Made for all things made in China. No nation is sovereign when it depends on foreign made for its sustenance. Tried to tell others what a mistake it was...but the profit margin dominated the market to our never-ending woe.

[jerrspud]

Next project is the fuel tank level sending unit. Only ones available fail due to ethanol corrosion on the ultra-low-quality potentiometer. Marvel Mystery oil extends the life but failure is inevitable along with suction filter disintegration. That's what you get for trading off American Made for all things made in China. No nation is sovereign when it depends on foreign made for its sustenance. Tried to tell others what a mistake it was...but the profit margin dominated the market to our never-ending woe.

uh... those have been failing since they were new from GM regardless of the gas. no reason to make stuff up.

[Oldygoody]

The business community sold out this country's domestic production for personal profit...don't have to make 'it' up. Lack of quality control and supply chain disruption are now facts of life.