Fuel Pump?

StickyLifter · Aug 28, 2022

My truck has a 350 with a mechanical fuel pump and a quadrajet carb. It runs good, and starts good except for the first time I start it for the day. It takes some cranking before it starts the first time. Not a ton, maybe 15 seconds. I press the gas pedal down once and have confirmed the choke is closed. I'm wondering if the check valve in the fuel pump might be bad. Does this seem plausible?

Vbb199 · Aug 28, 2022

How old is the fuel filter

Turbo4whl · Aug 28, 2022

Short answer, yes. Is the pump older? The ethanol, (alcohol) or also called ethyl alcohol and grain alcohol, is added to gasoline to reduce emissions. The old rubber parts in the square's fuel system are slowly eroded by the alcohol in the fuel.

So yes, a new fuel pump may fix the problem if it has a leaking check valve.

Some quadrajets have a check valve in the carb mounted fuel filter.

fast 99 · Aug 28, 2022

Not too sure a fuel pump will cause it. Yes, there should be check valves in both the fuel filter and pump however neither could drain the float bowl. If the truck started right away, then quit I would agree with that but do check the pressure and volume anyway. Never want to say never.

Before first start in the morning check the accelerator pump for fuel. There should be enough fuel in the bowl for 3-4 or so good squirts. If only 1, the bowl is draining or leaking.

edit..... could be 2 issues, carb leak and fuel delivery. Need to check both.

potent rodent · Sep 26, 2022

u prob have well plugs going bad and then again maybe a little heat sink with todays gas

AuroraGirl · Sep 26, 2022

Fuel pump can most definitely be the cause. You buy chance have gas in your oil? Or notice you dont "burn" any off the dipstick?
If its an old original pump its probably time for that diaphram to get a new home on a shelf or in a trash can lol

Matt69olds · Sep 27, 2022

Unfortunately, that’s typical of the ethanol fuel today. Refineries don’t bother with additives to prevent fuel boiling off after a hot shutdown. It’s not needed for the 99.9 % of the cars/trucks on the road today.

Modern vehicles have closed fuel systems with electric fuel pumps that instantly prime the fuel system. It’s just not cost effective for the additives to be included.

Either live with it, or install an electric fuel pump. There are fuel pump controllers that will prime the pump for a couple seconds at key on, and then power the pump as long as it senses a tach signal. It will then shut off the fuel pump when the engine shuts off.

Ricko1966 · Nov 28, 2022

I seriously doubt the fuel pump is your problem the float bowls should still be full unless your plug wells are leaking.That being said first start in the morning first time stepping on the pedal you should have accelerator pump shot and fuel in the carb from the day before.
Editing I wish I had read all responses before throwing my 02 cents in,never even occurred to me the fuel is boiling off. Matt may very well have the answer to your problem.Even if it is leaky plug wells it won't matter if you have a primer pump. Not that I think it's Ideal to let fuel leak into the manifold. Your hard start problem would be gone. Look down the carburetor throat in the morning before you start it hold the choke open with one hand open the throttle with the other while looking for accelerator pump shot.No shot you know the carbs empty. Just to verify it is a fuel problem.

Memaloose · Feb 10, 2023

Well, it's time to replace the original fuel pump on my 1975 350, it's leaking.
Can anyone suggest the best brand/quality mechanical pump that's available? I haven't had to change a Chevy mechanical pump in decades!

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fast 99 · Feb 10, 2023

AC Delco or Delphi. Many brands do not have the return spring [pictured] inside and fail. Ask me how I know.

Memaloose · Feb 11, 2023

Thanks for the info. I'm headed into town this morning to pick up a Delphi brand one. I didn't see any AC Delco ones for sale.

fast 99 · Feb 11, 2023

They aren't available everywhere. Got 2 from Rock auto, one is a spare.

Poodlehead · Jul 12, 2023

I'm replacing my 2 line mechanical fuel pump on my 77 C10 stock truck. I'd like to use a US made AC Delco pump, but research shows they are no longer available. Would someone please tell me what the Delco P/N is in case I can find a NOS replacement? If I can't get a real Delco pump, research shows Carter brand would be a decent substitute. Would someone please confirm, recommend another mfg, and/or provide mfg part numbers?

I've owned my truck for 44 years so I'm thinking I should drop both tanks and replace the filter/sock in each tank before doing the pump. Rock Auto shows 5/16" and 3/8" size socks. Would anyone know which size filter sock I need?

I'd like to do this right the first time...
TIA,
Pat

Bextreme04 · Jul 12, 2023

Poodlehead said:
I'm replacing my 2 line mechanical fuel pump on my 77 C10 stock truck. I'd like to use a US made AC Delco pump, but research shows they are no longer available. Would someone please tell me what the Delco P/N is in case I can find a NOS replacement? If I can't get a real Delco pump, research shows Carter brand would be a decent substitute. Would someone please confirm, recommend another mfg, and/or provide mfg part numbers?

I've owned my truck for 44 years so I'm thinking I should drop both tanks and replace the filter/sock in each tank before doing the pump. Rock Auto shows 5/16" and 3/8" size socks. Would anyone know which size filter sock I need?

I'd like to do this right the first time...
TIA,
Pat

I had a Delphi pump from autozone on my 350 for several years with no issue. Then, when I rebuilt my 350 I decided to put a new carter on it. Within 500 miles the carter failed when the end of the pump arm snapped off. I replaced it with another Delphi pump from autozone and have been running around for a few years and several thousand more miles with no issues again. PN is AMF0004 for the pump with a return line and they always seem to have them in stock. 1 year warranty on them and only $25

Matt69olds · Jul 12, 2023

The problem with an American made A/C Delco pump is it will have been made long before the rubber parts were made with ethanol compatible components. Not to mention A/C Delco today is a not the same as A/C Delco of 30 years ago.

I’m a believer in keeping your “GM vehicle all GM” but it’s not the same GM.

As far as I know, Airtex and Carter are still American. Maybe I’m wrong.

Fuel Pump?

StickyLifter

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Vbb199

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Turbo4whl

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fast 99

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potent rodent

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