correct placement of fuel pressure gauge

[maytag]

Hey y'all:
so, another thread here has me scratchin' my head that I might not be getting correct fuel pressure readings, and that could be part of the cause of my current carb issues.

Here's the way I've got it setup right now:


you'll note the Holley Regulator sitting between the carbs, and the gauge sitting on the other end of the inner carb. so it is "dead-headed".
There is no return line.

So the reading on the other thread suggests that a dead-head gauge will read incorrectly, and that it needs to be installed inline to be accurate.

anybody know anything for sure about this?

[vandor]

I would think it would read correctly, after all it is connected to the carb inlet, exactly where you want to know how much pressure there is. Unless there is something going on that is not obvious.

[So Cal Mark]

it's not dead headed since the needle valves are next inline. If the regulator outlets were plugged, that would be deadheaded

[maytag]

maybe I'm misunderstanding "deadhead".
the gauge is the LAST thing on the line. the fuel goes into the regulator, splits there to each carb, hits the needle valve, and then on one carb it hits a plug, and on the other carb it hits the gauge. that's it. the fuel does NOT go past the gauge to ANYTHING.

vandor: does that still qualify as a carb inlet, when it is not where the fuel enters the carb? I wouldn't think so. ??

don't get me wrong: I'd love for it to be okay the way it is. I just wanna make sure I've described it properly.

[So Cal Mark]

still, the gauge is tee'd into the whole assembly. Deadheading would be a guage at the end of the line without any other outlet for the fuel. Pressure is created by resistance, so if only the gauge is in the line, higher pressure will be shown than when the fuel is being used

[maytag]

Aha. Gotcha.
Thanks! I'm relieved!

[vandor]

> does that still qualify as a carb inlet, when it is not where the fuel enters the carb? I wouldn't think so. ??

I am pretty sure these carbs are made so it does not matter which end the fuel goes in, you can use either side as an inlet.
You just have to be careful, as a nipple designed to be an outlet may have a restrictor in it to create the fuel pressure (as Mark said the pressure is resistance to flow).

[MIGHTY 8]

That's so ironic!
I was just playing with my se-up all day today.

Can someone explain why this car has no return line and mine does? Yet they both seem to "just" work fine?

Also, I played aroundd with a brand new low pressure fuel gauge (0-6psi) and upon placing it on the outlet side in the engine compartment, it read zero?? However the car has veer set up like that for awhile??

And whereas initially, I had a dial type fuel pressure regulator on the inlet side, my other mechanic decided to put a non-adjustable diaphragm style one on the outlet side??

And it's been running great.....until it sprung a leak and I had fuel all over my engine compartment! (yes, from the same pump that my new gauge says is producing zero pressure!!!)

WHY WHY WHY WHY!!??

[vandor]

>Can someone explain why this car has no return line and mine does? Yet they both seem to "just" work fine?

All a return does is it recirculates the fuel to keep it cooler, and reduce the chance for vapor lock.

>Also, I played aroundd with a brand new low pressure fuel gauge (0-6psi) and upon placing it on the outlet side in the
>engine compartment, it read zero?? However the car has veer set up like that for awhile??

Either it is not reading the pressure correctly, or you have -JUST- enough flow to keep the carbs full.

>And whereas initially, I had a dial type fuel pressure regulator on the inlet side, my other mechanic decided to put a >non-adjustable diaphragm style one on the outlet side??

In theory a regulator on the return side is a lot more precise.

[MIGHTY 8]

The electric fuel pump is about six months old and the gauge had just come out of the box. I was startled that it read zero! I mean apart, from the fuel leak which required me to even start messing around in there, the car was running fine.

And another point, if I have a weak fuel pump (assuming the new gauge is correct) why would I need a regulator on the return side, to restrict an already weak pump?

I might need tostop by a shop and borrow another gauge, but a new broken gauge from Summit just seems unlikely.

Also need to dive under the car and get the specs from that fuel pump to know exactly what it is.

Thanks, V

[sptcoupe]

If you are running a return line and have not restricted the outlet to the returm fuel hose, you will not have much pressure if your regulator is set to regulate it to about 2.5/3.0 lbs. A .5 to 1mm opening will get you plenty of pressure which you can regulate downward with the pressure regulator

[MIGHTY 8]

Well he'll! After running with a return line for years after having swapped out the FI for Webers, i finally got frustrated and just removed the return line.
Guess what? So far the car runs fantastic!
I'll get around to placing the gauge back in soon and I suspect that having removed the return line, my pressure will be something other then zero

[sptcoupe]

i have not had a return line on 85% of my dual carbed engines and have never had an issue. I run one here in Texas to help cool the fuel during our really hot summer months.

[MIGHTY 8]

i have not had a return line on 85% of my dual carbed engines and have never had an issue. I run one here in Texas to help cool the fuel during our really hot summer months.

You know... It's just one of those things-live and learn.

If anyone cares to read my post on carb maladies which began last summer, and have brought me to a point of spending somewhere to the tune of over $3,000 in parts and labor (well, mostly labor) and a good year's worth of frustration would be as frustrated as I to know it would have most likely been resolved by removing the return line. All that was needed was a 8 inch long rubber fuel line.

Consider in my case having taken the car to four highly researched classic car mechanics in the area and not one recommended this to me.

In the end, it was this forum and the advice (free advice!) that had me driving over 150 cheek-to-cheek smile miles yesterday after a roadside repair where I just said " Hell, let me bypass this return and stick this little hose between the carbs and see what happens..."

Thank you all ladies and gentlemen. Sincerest thanks.

Mighty 8