Fuel Pressure Regulator

[EngineerDoug]

Hello all,

I would appreciate some thoughts on where to mount a Holley fuel pressure regulator. I am running a Carter mechanical pump, followed by a vapor separator (with return line), and then a fuel filter feeding a six pack setup.

I have been having some problems with inconsistent fuel levels in the carburetors, and have decided a pressure regulator would be a good idea.

Mounting the regulator is a question - mounting it right before the carburetors makes the most sense, but it's going to be messy in terms of routing. I don't really have a place to mount the regulator on the engine so I would have to mount it to the inner apron somehow. That means more fuel lines back and forth.

So what about mounting the regulator between the pump and the vapor separator? This would be a lot less extra line, and I could put the regulator down low in the engine compartment.

I want to do the job right, but I also would prefer to plumb it so it does not look like a drag car - it's a street car and the fuel routing is really clean & direct right now. Once the fuel line enters the fuel pump the rest of the routing stays on the engine. Close to a stock look.

Your thoughts/suggestions? Thanks!

 

[Beekeeper]

I’m right with you Doug I would like to put a regulator on my hemi along with a pressure gauge
but can’t find a spot that wouldn’t look like crap.

 

[WileERobby]

Please define "inconsistent" ... Before going into "let's pick a solution", what's the issue you're having ? What pressure is your pump, that you need a regulator ?

 

[EngineerDoug]

I am running a Carter M6903, which appears to be specified between 6 and 7.5 psi. I had previously set all 3 carbs so that fuel would just trickle out the sight plug holes.

The other day I had some issues with a rough idle. I could keep it running by feathering the throttle, but something was clearly wrong. I checked sight plugs in all 3 carbs and fuel really ran out of the holes. Had this been just one fuel bowl, I might suspect some dirt on the needle & seat. But all 3 carbs were too high - probably running too rich. That would explain why I needed more throttle to keep it running. I do run a 20 micron filter just before the fuel splits to the carbs, BTW.

 

[EngineerDoug]

A little searching on the web shows there are brackets designed to mount a Holley style regulator using the carb mounting studs. This might be a way to cleanly mount the regulator just before the carb feeds. I'll see about whether I can mod this to fit a six pack setup.

 

[BSB67]

That Carter pump has been the go-to pump for thousands and thousands of applications without the use of a regulator. I doubt you have a pressure problem, but if you do, fix that, don't put a band aid on it.

 

[khryslerkid]

@EngineerDoug you might want to read this...

https://www.forbbodiesonly.com/moparforum/threads/mechanical-fuel-pump-101.194336/

 

[MelroseMopar]

I switched to an electric pump and mounted regulator to the fender out of the way. Its the long way around for you but its an option anyway.

 

[hunt2elk]

The Carter 6903's have been running way to high of pressure, like 10-11 psi for awhile now. I have had 4 of them rebuilt recently, 2 were brand new.

 

[RemCharger]

I've only played with 6 packs a little but, I believe on the outboard carbs , you should have clear sight plugs. Then set them so the level is half way up. Center carb sets like a normal 4 bbl.
I'm open to correction on this.

And needle+seats could use more changing than you'd like to think.

 

[EngineerDoug]

Hey great inputs - I appreciate it. I had also read that some 6903 Carter mech pumps may put out too much pressure. Perhaps in the past their quality control was better? I've run across a few new parts that did not pass muster, so a problem with the pump would not surprise me at all.

I already have a regulator that I had elected not to use, so once I rig that up I will see what the pressure really is. Then I can decide whether the pump needs to be corrected per the above thread.

I did pull the fuel bowls and found them to be perfectly clean, so the flooding was not due to dirty needle & seat assemblies. The entire engine build is new, with only a few hours of run time on it. BTW the outboard cards do not come with clear sight plugs - just the old fashioned brass plugs.

 

[RemCharger]

I wrote that wrong,, I meant "you should get some clear plugs"..
And needle+seats go to **** regardless of "dirt, or foreign objects".
Age, and fuel compounds can ruin them. I've seen brand new carbs that needed them.
Also the rubber o ring hardens. A lot of times guys don't think about that.