Fuel Pump That Reliably Delivers 4-4.5 PSI?

[DC67]

Does anyone recommend a mechanical pump from a brand / sources other than Carter that reliably delivers the lower 4-4.5 PSI ?

My 67 Charger is stock (see info. below) and it has never really run well. I've been chasing fuel problems and have replaced everything from the tank to the carburetor. It is fouling plugs, idles rough and I recently saw fuel varnish appearing on the sides of carburetor.

The carburetor (Carter 4326S) is completely clean with everything adjusted including the floats. The only issue is high fuel pressure: The Carter M6903 (High Performance) shows 6-6.5 PSI when running - so I installed the stock replacement pump (Carter M3672 rated at a lower 4-5.5 PSI) and it is now showing 9 PSI!

The service manual and other resources claim the Carter AFB is sensitive to fuel pressure and needs 4-4.5 PSI max. to prevent fuel from blowing past the needles.

Added Edit:
I'd like to find a pump that puts out the right pressure and avoid the modifications needed to install a fuel pressure regulator.

Any guidance appreciated!

Vehicle Background Info.:

Vehicle: 1967 Dodge Charger - 71 440ci motor
Carburetor: Stock Carter 4326S
Old Fuel Pump: Carter M6903 (Rated 6-7.5 PSI) -- Delivering 5-6.5 PSI
New Fuel Pump: Carter M3672 (Rated 4-5.5 PSI) -- Delivering 8-9 PSI
Main Fuel Line: New 3/8" Steel Line from Tank to Engine Bay (stock configuration)
Pump to Carb: New 5/16" Stainless Line (stock configuration)

 

[YY1]

Get a regulator?

 

[YY1]

What gas are you using?

 

[Bird 426]

Do not know who it is, but someone does fuel pumps. Saw it either here or on FABO. What about an over the counter pump, non Carter? Yeah, Chinizium.

 

[DC67]

What gas are you using?

Unfortunately all that's available in my area is 10% ethenol pump gas -- I'd like to avoid plumbing in a regulator if possible to avoid one more potential failure point in the fuel system however if there are no pumps out there that can deliver the lower pressure I will resort to that.

 

[Aron Gleason]

The only way to make sure your fuel pressure stays at 4-4.5 is to get a fuel pressure regulator.

 

[WileE]

Get a regulator?

The only way to make sure your fuel pressure stays at 4-4.5 is to get a fuel pressure regulator.

Prudent recommendations.

 

[DC67]

Do not know who it is, but someone does fuel pumps. Saw it either here or on FABO. What about an over the counter pump, non Carter? Yeah, Chinizium.

Yes, there is this post:
Mechanical Fuel Pump 101

And the business 'Then And Now' publishes a good video on rebuilding the Carter M6903 here:


..but hopefully there is a new pump out there by a different manufactures that meets the 4-5 PSI needed by the edelbrock / carter carburetors so commonly installed on Mopars.

 

[DC67]

The only way to make sure your fuel pressure stays at 4-4.5 is to get a fuel pressure regulator.

Thanks for the suggestion, I'm aware of that solution but I'd like to avoid the added project of fuel line modifications, adapters etc. It also adds one more part that can fail. There seems no shortage of poor quality auto parts, and that includes the regulators.

It just seems odd that pumps output more pressure than they specify - maybe it's just me getting a couple defective pumps.

If I can't find a better pump recommendation than a regulator may be my only choice.

 

[Bird 426]

Does someone know who the guy is that you can send your pump to to modify fuel pressure? I'm not qualified to use the search engine here to find him. Think he's from out east . Yeah, sucks to have to slide away from stock with a regulators. Have two cars with them, but they're not stock.

 

[toolmanmike]

My buddy's 70 Bee had a rich/rough running issue. He messed with the carb for a week and couldn't cure it. We checked the pressure and with the stock pump, he was getting 7#. He ran to Car Quest for another stock pump and it put out almost 10#. Check it or not, your choice.

 

[khryslerkid]

Do not know who it is, but someone does fuel pumps. Saw it either here or on FABO. What about an over the counter pump, non Carter? Yeah, Chinizium.

Yep, Then And Now (Its in the link im posting. The website is bad but their address and ph# is good.)

Does anyone recommend a mechanical pump from a brand / sources other than Carter that reliably delivers the lower 4-4.5 PSI ?

My 67 Charger is stock (see info. below) and it has never really run well. I've been chasing fuel problems and have replaced everything from the tank to the carburetor. It is fouling plugs, idles rough and I recently saw fuel varnish appearing on the sides of carburetor.

The carburetor (Carter 4326S) is completely clean with everything adjusted including the floats. The only issue is high fuel pressure: The Carter M6903 (High Performance) shows 6-6.5 PSI when running - so I installed the stock replacement pump (Carter M3672 rated at a lower 4-5.5 PSI) and it is now showing 9 PSI!

The service manual and other resources claim the Carter AFB is sensitive to fuel pressure and needs 4-4.5 PSI max. to prevent fuel from blowing past the needles.

Added Edit:
I'd like to find a pump that puts out the right pressure and avoid the modifications needed to install a fuel pressure regulator.

Any guidance appreciated!

Vehicle Background Info.:

Vehicle: 1967 Dodge Charger - 71 440ci motor
Carburetor: Stock Carter 4326S
Old Fuel Pump: Carter M6903 (Rated 6-7.5 PSI) -- Delivering 5-6.5 PSI
New Fuel Pump: Carter M3672 (Rated 4-5.5 PSI) -- Delivering 8-9 PSI
Main Fuel Line: New 3/8" Steel Line from Tank to Engine Bay (stock configuration)
Pump to Carb: New 5/16" Stainless Line (stock configuration)

I had the same problem. Mike at Then and Now replaced the spring with a lighter one.

Mechanical Fuel Pump 101

 

[lewtot184]

I'd try a different pressure gauge for a test. I use 6903's. They usually run around 5psi hot. If the engine is driving ok i doubt you have a pressure problem.

 

[Bird 426]

Sorry, I missed post #8! That's the guy.

 

[khryslerkid]

Does anyone recommend a mechanical pump from a brand / sources other than Carter that reliably delivers the lower 4-4.5 PSI ?

I'd send it to Mike at Then and Now for a lighter spring. He changed my m6903 and it made the difference.

Then and Now Automotive
447 Washington Street
Weymouth Ma. 02188
Ph# 781-335-8860

Mancini used to carry the Carter m6903 that only had 5.5 to 6psi. They were made for them by Carter with a lighter spring. Currently out of stock. Everything else out there is 6, 8, 9 psi or higher.

Mechanical Fuel Pumps.

 

[lewtot184]

Rock Auto hss the factory style 3-5 pound pumps. They're not good pumps but you can drive on them.

 

[DC67]

Thank you all for contributing here.

Yes, Then and Now can modify a mechanical fuel pump (the type you disassemble like the Carter M6903 not the cripped body style like the stock replacement Carter M3672) and as you can see from the video they can also restore and improve the shortcomings of these pumps as they come from the factory.

The Mancini Racing versions of the pump is an interesting option. They are all out of stock as mentioned but maybe that's something to try down the road.

As for now, I'd like to find an off-the-shelf pump that meets the 4.5-5 PSI output pressure advertised. I've listed a few pumps by different manufacturers below in case anyone has had a good experience.

Airtex - 267
Carter - M3672
Carter - M6903 (High Performance)
Delphi - MF0056
Napa - B-0002-P
Sparta - PN8031
Spectra Premium - SP1064
US Motor Works - USMP09180

The Spectra Premium is rated at 4.5-5 PSI output, and their website seems well organized so I might give that a try this week.
SP1064MP

I had a good experience installing their replacement fuel tank a few years ago.
I'll report back after installation.

 

[jimbosride]

Don't want to hijack here but my gauge on the carb jumps around. Engine runs great, fuel pump 2 years old?

Is a fluid filled gauge better or is it fuel pump issues?

 

[DC67]

Don't want to hijack here but my gauge on the carb jumps around. Engine runs great, fuel pump 2 years old?

Is a fluid filled gauge better or is it fuel pump issues?

View attachment 1956719

My understanding is mechanical fuel pumps create pressure spikes and pulsations, so liquid filled gauges are preferred to dampen those signals when installed on a motor. But yes, measuring fuel pressure could be separate thread you start.