Webers and fuel pressure regulators, yes or no?

[Chuck Moreland]

Are you weber boys using regulators?

Do they make a difference? Where do you set the pressure? What regulator are you using?

[ttweed]

Yup. Set at 3.5 psi. I use an in-line gauge from Summit after the regulator so that I can see the pressure is right. I use a cheap generic regulator, but Holley makes some good ones.

[gumba]

They seem to work best at 2.5-3 psi. I use a Holley.

[TimT]

yeap,

holley low pressure regulator.. with a return to the tank

[jabb]

Holley Regulator set at 3.5 lbs

[cstreit]

Holley fuel pump with regulator... 3.5 lbs, no return line though as the regulator is on the pump...

[A Quiet Boom]

For you guys running Holley regulators, be sure to tear them down yearly and clean up the crud and corrosion on the inside. If you don't they'll eventually stick in the high pressure position and flow or even hydro-lock the motor. I remember a 2 hour drive from Akron to Columbus once at high speed in which my regulator got stuck while cruising at 80+, I didn't notice it til the car stalled in traffic outside the city, I had to drive the rest of the way to my destination turning the dash mounted switch on and off LOL It turned out to be corrosion on the steel parts inside the regulator.

[Chuck Moreland]

So what benefit did you guys see with regulator vs without?

My car was originally equipped with CIS so I already have the return fuel line in place, it's plugged now. I need to check what fuel pump the car has. If it's the original CIS pump, that may be causing my problems.

I found these at Summit. They look like the ticket:

http://store.summitracing.com/partdetail.asp?part=7734

http://store.summitracing.com/partdetail.asp?part=17242
Chris, what combo pump regulator are you using? I couldn't find any Holleys like that.

[911pcars]

Chuck,
I found a low pressure pump from the local auto parts store. Mounted next to tank. No regulator needed; about $40. Line pressure is about 3 psi according to the PMO FP gauge. Make sure the required pressure is downstream of any inline filters you install (there isn't that much leeway below 3 psi).

The cheapie $20 FP regulators can't be trusted to last. As these responses indicate, the Holly is a good choice if you need one.

Sherwood Lee
http://members.rennlist.org/911pcars

Rev. 10/12: I should have used the word "upstream" or on the carb side of the filter. Sorry for the incorrect description.

[cstreit]

Actually I have two regulators...

One came with and is directly plumbed to the Holley pump. Have no idea what kind it is. That one is limited to 5 lbs. The second is in the engine compartment itself and has a hand andjustable dial, and is right next to the fuel pressure guage. This one allows me to fine tune. If you like, I can post some photo's of the setup.

I am wondering though... If you have carbs, are you using the CIS pump? THe pressure is way too high and would cause all sorts of weird problems. THese run at 40+ lbs..

If you get a pump that runs at 3 lbs, I would worry about getting proper fuel flow at higher draw levels... A basic Holley pump will work great, flow well, and any decent fuel pressure regulator such as those you mentioned should be fine...

What is your car doing that got you thinking about this?

[Chuck Moreland]

I will check the pump part number tomorrow. The car was converted to webers before I bought it.

I can't get the car to run consistantly at idle/low rpm. It will be great for awhile (minutes), then for no reason start spitting and missing badly. Then suddenly it runs great.

The problem is most severe when lifting (medium RPM, high vacum).

The car runs like all hell under load and higher RPM. It's just the trolling around town that is a problem.

I've replaced most everything in the ignition, except the distributor. And the distributor isn't very old. Centrifugal advance seems to work fine.

I've rebuilt the carbs, replaced the fuel filter and adjusted carbs till I turn blue.

So I'm scratching my head trying to figure out what would cause the changing behaviour. The carb shafts and throttle plates don't seem to be too badly worn. I can't find any vacum leaks.

So I'm suspecting fuel pressure.

[A Quiet Boom]

Chuck, check your float level! Aside from that check your needle and seats and make sure the fuel pressure is around 3.5 PSI. I'm guessing your float level is too low though. I've got mine "just right" such that on hard braking to a stop the car will almost stall as fuels spills into the cylinders but the part throttle drivability is fantastic and full throttle is an "all grins" affair. Could also be a sticking need and seat but that's harder to isolate.

[jtf914]

Have you checked the gas tank? I had a similar problem, and after weeks of Weber tuning and rebuilding, it turned out to be a rusty tank.

Justin

[Chuck Moreland]

Float level is set correctly per the guage. Needle valves replaced in the rebuild. I haven't check pressure yet. The only pressure guage I have is for injection so it's range is too high.

Could be gunk in the tank, don't know. I do have a fresh filter in place though.

[scg]

Just curious:

You guys are running between 3-4 pounds of pressure -- why does PMO suggest 4-5 pounds (engine warm) for the street and 6-7 for the track? Do PMO's require/allow slightly more pressure than "regular" webers?

Scott

[Chuck Moreland]

I picked up a guage and tested the pressure. It is reading 2 psi.

Consensus above seems to be 3.5 psi.

Now, it seems to me that too low a pressure might give me problems at WOT / high rpm. But I would not expect a problem at idle or low RPM provided the float level is correct.

Would 2 psi be causing me problems?

I've got the regulator but it seems silly to put it on with just 2 psi.

[Chuck Moreland]

New informaiton!

I think jft914 may be on the right track. I just tested the pressure upstream from the fuel filter and it read 3 psi.

That means 1 psi drop through the filter without any fuel flowing. Sounds to me like it's plugged up.

And it has maybe 300 miles on it. Time for a new filter and an autopsy. If that cures the sympton, then it's into the tank time.

[Reg]

I have a virtually new holley unit that my mechanic removed when the carbs were rebuilt and new fuel lines and pump were installed. I guess he felt it was not needed.

Anyone want it? Send me an email with an offer.

[Chuck Moreland]

The plot thickens.

It seems the fuel pump is not putting out consistent pressure. Several measurements taken with the fuel filter out of the loop showed readings ranging from 2.5 to 3.25 psi. After each reading the pump was shut down and pressure allowed to bleed down to zero. I think that is a lot of variation, too much.

I am ordering a new holley pump, this one

http://store.summitracing.com/partdetail.asp?part=876&view=1024

I will pair it with the regulator I already bought.

I cut open the fuel filter. Didn't find anything alarming. I don't think that was the problem, but obviously it is getting replaced. The good news is I probably don't have to pull the tank.

[911pcars]

Chuck,
Looking back at your symptoms, I don't think it's fuel pressure. If the pump is supplying even 2 psi pressure and some volume, then that should be enough to supply fuel for idle. When you checked the pressure did you check volume as well?

I added a fuel pump cutoff switch to the circuit as an added security device. Sometimes I forget to switch it back ON and drive away with the pump OFF. I can drive for about a block or two before the float bowls empty and the engine sputters. That's with zero psi and zero volume from the fuel pump. The engine will idle for quite awhile with the pump OFF.

I'm going to suggest you look at the idle circuits again, a possible vacuum leak and float level. Are you sure the float level isn't so high? if so, fuel will spill out of the discharge tube? Have you connected a vacuum gauge to the engine?

Sherwood Lee