Can a stock fuel pump put out TOO much pressure?

[Kern Dog]

It looks like this:

I changed to another one that looked similar.

Delphi?

It started and ran fine…. Then started puking fuel through the inside of the ThermoQuad.

The threaded fitting on the pump that feeds the carburetor has a leak. As I tightened the line, the pump body twisted a bit.
Two pumps, same symptoms.

 

[WileE]

So...the answer to the OP's question is of course "yes" - but you won't know for fact until you put a gauge
on it.

Get a gauge on it for test so you'll know exactly what you have.

Really need a gauge on it to accurately answer your question. Otherwise you are just guessing.

Pressure gauge is probably next or your just guessing. It sure sounds like to much pressure.

^^^ First thing we did when someone came into the garage with a similar symptom. Gauge it. Confirm it, or rule it out.

 

[toolmanmike]

^^^ First thing we did when someone came into the garage with a similar symptom. Gauge it. Confirm it, or rule it out.

^^^ First thing we did when someone came into the garage with a similar symptom. Gauge it. Confirm it, or rule it out.

This guy get's it. Diagnose and repair.

 

[moparedtn]

This guy get's it. Diagnose and repair.

Yup. I always did hate guessing...

 

[lewtot184]

It looks like this:

View attachment 1693961

View attachment 1693962

View attachment 1693963

View attachment 1693964

I changed to another one that looked similar.

View attachment 1693965

Delphi?

View attachment 1693966

It started and ran fine…. Then started puking fuel through the inside of the ThermoQuad.

View attachment 1693967

View attachment 1693968

The threaded fitting on the pump that feeds the carburetor has a leak. As I tightened the line, the pump body twisted a bit.
Two pumps, same symptoms.

I'd say that's a lower pressure 2 valve pump, but a pressure gauge will tell the story.

 

[lewtot184]

I did find in a 1969 service manual where a two valve 340 pump is rated at 5-7psi. 7psi could be a border line problem.

 

[toolmanmike]

Test the pressure at the carb with a good gauge and install a regulator to reduce it to 4-5# if necessary. I have experienced a new, out of the box pump, from
Car Quest put out 10#. The application was for a 383-2 barrel so no "high performance" application. We replaced it because the old pump was putting out 7# and bleeding over both a Edelbrock and Holley carb.

 

[mopar jack]

Had a simular problem when I started my road runner after a major restoration. Had fuel flowing out of the vent bowls to 2 different carbs and found that the tank vapor return line was plugged causing the tank to build pressure.

 

[dfrazz]

It looks like this:

View attachment 1693961

View attachment 1693962

View attachment 1693963

View attachment 1693964

I changed to another one that looked similar.

View attachment 1693965

Delphi?

View attachment 1693966

It started and ran fine…. Then started puking fuel through the inside of the ThermoQuad.

View attachment 1693967

View attachment 1693968

The threaded fitting on the pump that feeds the carburetor has a leak. As I tightened the line, the pump body twisted a bit.
Two pumps, same symptoms.

You can either take the advice from several experienced people here and get a gauge on it or keep guessing and maybe you will get lucky, your choice.

 

[Kern Dog]

My whole life has been about a mix of luck and skill.
I am the guy that stumbles onto good fortune. Things often go my way. I am fortunate.

 

[Kern Dog]

This car defies my usual good fortune.
It was put together on a budget for a brother in law that had whims that changed as the wind blows. If he made friends with a guy with pink hair, in 2 weeks his would be pink too.
He glommed onto me and my interest in cars but didn’t have much money. I fronted thousands of dollars to get the car together and painted in the hopes that his interest would grow or at least maintain. They didn’t.
I bought him out of it a few years ago and have put in on the back burner. Th goal is to go through it, fix what is bad, finish the “restoration” and sell it.
The mechanical portions of the car were done in 2007-2009. It has sat relatively untouched since. It has a 1979 360 from a van. I swapped in a MP 340 cam. It actually runs pretty strong. (When it runs)
This turd is fighting me though. Read along and let me know if you’ve dealt with similar crap.
When running, it flooded the Holley.
I pulled the carb, changed the needle and seats, power valve and a few gaskets. Back on, it still floods over. I put a ThermoQuad on. It floods over too. Fuel pump? Okay… I swap in another and the flooding continues. The second pump has a twisted fitting that drips so I swap in another pump.
The ThermoQuad still floods.
Maybe it isn’t the pump then, right?
I swap in another Holley from another car. Now the car won’t start. The key gets nothing. Why?
Old wiring? I ran a jumper wire to the coil and it fired up but now there isn’t any fuel pumping to the filter. Am I out of gas? I put 2 gallons in the other day. I don’t see how I could have gone through 2 gallons just getting it to start and run.
I put the air hose to the filler neck to pressurize the tank to push gas forward. Nothing. Maybe I am out of gas. The starter was slowing down so I put the battery charger on it.
I just poured in 3 gallons. I tried pressurizing the tank again but I’m still getting nothing at the front.
I used the Hulkman to assist the battery but it was still dragging. It is a used mini starter so I’m guessing it is tired. Maybe this 3rd pump is not only dead but also blocking any and all flow forward. The engine runs with gas poured into the vent openings , at least until the gas gets used up.
I get close to figuring out one thing and another problem pops up.
It’s almost to the point where I should just go through everything.
More to come.

 

[Kern Dog]

Redemption.
I used the carburetor from this car:

Along with the fuel pump that I had in the car before:

You know, the one I first thought might put out too much pressure?
Boom. It idles great, runs great and doesn’t flood over.
The problem was not high pressure but bad floats or something in both carburetors that allowed the flooding.
Thanks for the input though. It is odd to have two parts in a row give identical symptoms.

 

[ckessel]

This car defies my usual good fortune.
It was put together on a budget for a brother in law that had whims that changed as the wind blows. If he made friends with a guy with pink hair, in 2 weeks his would be pink too.
He glommed onto me and my interest in cars but didn’t have much money. I fronted thousands of dollars to get the car together and painted in the hopes that his interest would grow or at least maintain. They didn’t.
I bought him out of it a few years ago and have put in on the back burner. Th goal is to go through it, fix what is bad, finish the “restoration” and sell it.
The mechanical portions of the car were done in 2007-2009. It has sat relatively untouched since. It has a 1979 360 from a van. I swapped in a MP 340 cam. It actually runs pretty strong. (When it runs)
This turd is fighting me though. Read along and let me know if you’ve dealt with similar crap.
When running, it flooded the Holley.
I pulled the carb, changed the needle and seats, power valve and a few gaskets. Back on, it still floods over. I put a ThermoQuad on. It floods over too. Fuel pump? Okay… I swap in another and the flooding continues. The second pump has a twisted fitting that drips so I swap in another pump.
The ThermoQuad still floods.
Maybe it isn’t the pump then, right?
I swap in another Holley from another car. Now the car won’t start. The key gets nothing. Why?
Old wiring? I ran a jumper wire to the coil and it fired up but now there isn’t any fuel pumping to the filter. Am I out of gas? I put 2 gallons in the other day. I don’t see how I could have gone through 2 gallons just getting it to start and run.
I put the air hose to the filler neck to pressurize the tank to push gas forward. Nothing. Maybe I am out of gas. The starter was slowing down so I put the battery charger on it.
I just poured in 3 gallons. I tried pressurizing the tank again but I’m still getting nothing at the front.
I used the Hulkman to assist the battery but it was still dragging. It is a used mini starter so I’m guessing it is tired. Maybe this 3rd pump is not only dead but also blocking any and all flow forward. The engine runs with gas poured into the vent openings , at least until the gas gets used up.
I get close to figuring out one thing and another problem pops up.
It’s almost to the point where I should just go through everything.
More to come.

See what happens when you put air though from the pump line to the tank. Maybe plugged from sitting? When you had the bowls off the Holley or the top off the TQ, did you see any grundge/rust etc lurking? Having debris in the system can cause the needle and seat not the seal like it should. Like a toilet flapper with flaws.

 

[Kern Dog]

When I pulled off the THIRD fuel pump, I blew air into the suction line to the tank. I could hear bubbling inside it. I then I ran the suction side line to a water bottle, then pressurized the tank with the air hose. The line flowed fine both ways. The water bottle filled with fresh gasoline.
With the pump in place, it neither pumped nor allowed flow of fuel via pressurized air.
The Bowls of the Holley did have a light amber colored film to them. I do use Sta-Bil which is red in the bottle but fades when mixed with the gas. The gas will look a very pale yellow when fresh but will get orange over time as the volatile components evaporate.
Back in 2019, my Charger sat for almost a year between fill ups. The car ran okay at idle once it warmed up but when cold, it popped and stumbled. I theorized that the older the gas got, the more the part of the gas that gives it it's punch fades away. The gas in the filter was almost orange. As the engine warmed up, it ran better. I guessed that as the gas itself got warmer, it thinned out and flowed better. My air/fuel gauge readings were all over the place. The plugs got dirty too. Old gas nowadays is not as safe to use as it used to be before all this ethanol crap.

 

[ckessel]

Pump fuel starts to separate in a week or so. It's called "Phase Separation". There are short and long term additives you can put in the fuel, Sta-Bil is one plus Joe Gibbs, Amsoil etc that prevents this for up to a year. The PS is very tough on fuel related components over time. Kills aluminum, can get the inside of the tank to rust, tough on rubber components. May be beneficial to pump/dump out what's in the tank, purge the line/lines from tank to pump with clean fuel or Acetone etc. Maybe blow through the vent lines, if any, as they can get plugged up too. If you drop the tank out, shine a light inside to see if it's clean or has issues. Your fuel sock on the pickup may need to be replaced too. If you do drop it out for inspection and flush, find a feed store that carries livestock supplies. Ask for "Cow Magnets". It's a strong magnet about the size of your ring finger. Buy a couple of those, break them in half and drop into the tank in a few places but not by the float. The magnets will keep any rust thats in the tank from getting to the carb. Rust gets by EVERY fuel filter made. But not the old magnet.

 

[Curiousyellow71]

With the quality of parts we are seeing it is possible to have multiple parts fail. Seems like I have had more issues with needles and seats the last few years as well. Especially anything w rubber like the oring on a holley's needle and seat. I have noticed fuel line isn't lasting and neither are the swivel -an fittings. We don't run ethanol in anything with a carb. I know the synthetic runner nowadays is pathetic..but can't help wonder if additives in the gas are also causing it.

 

[ckessel]

Here in the PRC, we get an extra load of goodness in the fuel courtesy of CARB. Ethanol is bad enough but the state mandated package is way worse. It's a wise idea to replace fuel hose with material thats E85 compatible. Regular hose goes to poo after awhile.