Show me your carb fuel pressure test setup

[Derek77]

I’m wanting to get an accurate fuel pressure reading on my recently purchased 911 with weber ida’s. I have a Holley regulator and a liquid filled JEGS pressure gauge which PO told me was a mistake to install. I’ve read engine mounted gauges won’t stay accurate for long due to vibration. Please show me your setup including fittings to quick attach and detach tester if possible

[al lkosmal]

Not carbs on this one, but I mount my pressure gauge to the regulator and mount the regulator to the body, as shown.

regards,
al

[Ayles]

Mine is a permanent install using the pmo regulator/ guage.

[Derek77]

Thanks guys.

Ayles, where did you get those cool looking fuel lines and fittings? What is the benefit of having the line that attaches both banks to each other? Do you also have a fuel return line? This is the setup I currently have which dead ends at each carb.




I found two idle jets clogged shortly after I had a shop look the car over. Are you guys running more than just the standard large fuel filter? I assume adding filters might lower delivery pressure.

Thank you

Derek

[Ayles]

I made those lines with with AN fittings and braided fuel hose the fuel bars are from PMO. When its time to replace I will go with something a little easier to build. I do have a return line. I think balance line is of debatable value...

I am using a Racor 110a fuel filter just before the regulator and had installed a brand new screen in the tank.

[obscene]

I'm similarly body mounted like the images posted above. My regulator runs a return line back to the tank. I then have individual fuel lines running to each carb with their own filters. Depending on the age of your hoses, you may also want to replace all of that too. A commonly overlooked cause of plugged pilot jets is actually deteriorating fuel hose.

[KTL]

My personal opinion is the deadhead system is a poor system layout. The pump is forced to operate in its bypass mode all the time because the pump delivery is being stonewalled by the regulator. You have to make sure the chosen pump is a low pressure pump in a deadhead system.

In a traditional supply-and-return system, the pump is "idling" and not working nearly as hard because while the fuel delivery is still being restricted by the regulator, the excess is returned back to the tank via the return line. Returning the excess also provides cooler fuel at the carbs. This is a good thing because carbs on old 911s have encountered fuel percolation if the carbs get too hot from the manifolds beneath them. The manifolds are supposed to have plastic spacers beneath them to prevent heat transfer but they can still get hot

The extra line across the carbs is debatable but the theory is that it balances the flow between the two carbs.

Dirt in the jets isn't always fuel related. The carbs of course get air via the air filters. If the filters are not well sealed, the dirt that sneaks in can get into the little ports in the air bleeds. These are the holes in the filter base plates that bleed air into the carb bodies to mix with fuel. There are very small bleed holes for the idle jets and also bleed holes for the air corrector jets.

Not trying to bury you with technical crap. But when you start working on your carbs you've got to be armed with information so you know what to look for and what to adjust.

Here's a link to another thread where I posted some cutaway drawings of how the carbs work internally. Helps you understand what those holes and fittings in the carb do and where the air and fuel goes

3.0 to 3.2ss with pics and Dyno sheets before and after

PMO and Performance Oriented have some very good information on their sites. Both guys are carburetor wizards. Performance Oriented Paul is 1QuickS here on the forums and a superhero when it comes to helping people out.

https://www.pmocarb.com/bulletins.htm
Performance Oriented

[911pcars]

PMO makes a complete bracket, gauge and manifold for the two carbs.

Notice the manifold and FP gauge assembly is mounted on the chassis, not the engine. A FP regulator is an option.

I'd suggest adding an inline filter. Webers don't like dirty fuel or high fuel pressure (5 psi max.).

AN4 braided fuel lines and hose adapters pictured.



Sherwood

[Derek77]

Kevin,

Thank you for the info and the links. I need to check which fuel pump I have. My manifolds do not have plastic spacers so I am considering installing a fuel shutoff switch as a simple solution. I cleaned the fuel strainer and replaced the engine bay fuel filter. I don't believe either of these has been done in many years. I have spent a lot of time studying Paul's website which is amazing. Right now I'm finished replacing all the gaskets on the carb's since they were seeping fuel. I'm anxious to get her running again, I'm going through withdrawals not being able to drive.

Sherwood, what fuel pressure gauge is that? Maybe I'll get a replacement for my current non working one instead of buying a tester.

Thanks guys, Derek

[911pcars]

Originally Posted by Derek77

Kevin,

Thank you for the info and the links. I need to check which fuel pump I have. My manifolds do not have plastic spacers so I am considering installing a fuel shutoff switch as a simple solution. I cleaned the fuel strainer and replaced the engine bay fuel filter. I don't believe either of these has been done in many years. I have spent a lot of time studying Paul's website which is amazing. Right now I'm finished replacing all the gaskets on the carb's since they were seeping fuel. I'm anxious to get her running again, I'm going through withdrawals not being able to drive.

Sherwood, what fuel pressure gauge is that? Maybe I'll get a replacement for my current non working one instead of buying a tester.

Thanks guys, Derek

Don't recall if the gauge was part of the PMO fuel block. However, fairly easy to source a liquid-filled gauge (e.g. eBay). Most/all gauges use NPT threads, 1/8" NPT in this case.

Inquire here: PMO High Performance Porsche 911 Carburetors & EFI & MFI Fuel Injection Kits
However, the only item currently shown is their one-piece fuel block/pressure regulator unit - handy if you have a later 911 with a fuel tank return line and your FP pressure is higher-than-needed. Early carbureted 911s only have a single fuel tank connection to the fuel system (so-called "deadhead" system), thus only requires the correct pressure to the carbs. Adding a return fuel line is a possibility, but only with a tank with a return line fitting.

A manual valve is handy for servicing system components and filter maintenance. This is a 914-six/911 front suspension with ball valve, inline filter (one of several) and a front-mount 4-5 psi pump. Soon to be relocated to the trunk for easier access/maintenance.



Sherwood

[1976 TN Porsche]

3.2, 40 IDA's, PMO Pressure Control Unit

[WMontald]

I am using one I bought trough Wish.com.
Mounted in the back (should shorten rubber tube)
Works great , engine runs smoother and no popping in exhaust anymore.