Holly Red Pressure test Question

Deleted the mechanical fuel pump and mounted a holly at the tank selector solenoid.
Ran that line to a Racor 500 on the passenger side, then to a Mr. Gasket 5psi deadhead regulator, then a gauge, and on to the IP.
Did a pressure test today.
With the regulator set at 1psi the gauge showed almost 3psi, and the holly never shut off.
I've never dealt with that pump before.
I know it won't pressure past 7, but assumed once it did hit that 7psi it would cycle off, and not just keep running.
Then, assuming the deadhead regulator constricted the line, the pressure in front of it would have been the full 7psi, and the set psi would only get past.
I let the pump run for about a minute after hitting the indicated pressure.
The psi stayed steady, but the pump never stopped running.
Which brings up another issue.
Have never dealt with Mr. Gasket stuff before either.
It's supposed to be a 5psi regulator.
I set it at 1psi because all I wanted to do was a low pressure initial fill, then increase incrementally while watching the gauge to verify the operation.
If I'm getting 3 psi at the 1 setting there's either a major tolerance in their accuracy, + or - 200%?, or I have a defective unit.
This is all very brand new to me, I'm used to dealing with industrial controls that have a max .05% tolerance, so this regulator is concerning.
Attached are a picture of the regulator setting and the gauge reading.

Betting the diaphragm reg is garbage.
I believe that the red has an internal bypass.
Don't quote me on that tho...

I used one of those dial regulators with a Holley red on the RV I had.

The RV lost top end power with just the pump, the IP didn't like the pressure. I ran the regulator at 3 and it did fine. Also had a racor w/s.

the way i had it:

[tanks]-[in line filters]-[fsv]-[pump]-[racor]-[regulator]-[stock fuel filter]-[IP]

I run a Holley red with no regulator. I have a turbo and I have no problems

The pump will not stop, it runs all the time. The holley red has it's own regulator built in, and when it reaches 7 psi, it internally bypasses the excess fuel back to the intake of the pump. So the pump will always run.

I do not know all the ins and outs of the ip on these trucks. But it was my impression it will not run the engine properly if it does not have a certain minimum inlet pressure at the ip. The inlet pressure is used by the mechanism in the ip pump to adjust the injection timing.

I would think about it a little bit if I was going to re-design the entire fuel system and how it works. This is in reference to the "deadhead" regulators. I would think something like that in the line would just cause a air in the fuel system situation to be worse. As in if you accidentally ran out of fuel.

Just thinking out loud here, why did they use a return system on the diesels? It's not like diesel is prone to vapor lock like gasoline is. I think the main reason is to purge the fuel system if it gets air in it. I am also thinking this happens more than you think. When the fuel tank gets low and the fuel is sloshing around in the tank, it is bound to suck a little air once in awhile going up hills and around turns. These little pockets of air would be purged through the system and sent back to the tank via the return line, and not get trapped and shoved through the ip.

franklin2 said:

why did they use a return system on the diesels?

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One reason is that the constant fuel flow keeps the IP cool.

I, too, have a deadhead regulator on my rigs. One thing I notice is when set to 5 psi, it will show 7 psi until I start the engine, then go back down to 5. Been this way for 8 years or so now. Never have had issue.

The biggest reason I ran a deadhead is I figured the return system was designed to handle the constant ip bypass and injectors dump only, and I was concerned about constricting flow with an additional flow from a bypass regulator.
Which was the core decision to use the holly due to it's relatively low max pressure, and the reason to use a deadhead reg that simply constricts the line to achieve the psi.
That said the holly still has a decent max flow rate, that little 5/16" line can't handle too much without "skin effect" potentially creating chaos with the additional fuel volume causing just enough drag to not allow proper flow.
I suppose extreme angles with a low tank could cause random air, but the sheer volume of the holly would be able to offset that, and the return at the ip would already be designed to deal with it.
It makes sense that the static pressure drops once the truck is started and a dynamic flow has begun.
I'm going to try @frankenwrench's fix, just set it at 5 see what happens.
I can always just turn off the pump if it tries to run away.

fwiw
"IF" it tries to run away
shutting off the e pump most likely will not cure the runaway...
If that is what you are saying.

Clb said:

fwiw
"IF" it tries to run away
shutting off the e pump most likely will not cure the runaway...
If that is what you are saying.

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I could see it potentially initiating a "run away", but once the fuel is shut off that would have to eventually stop the engine.
I thought it was only possible with the mechanical fuel pump in operation because there was no way to stop it.

divemaster5734 said:

I could see it potentially initiating a "run away", but once the fuel is shut off that would have to eventually stop the engine.
I thought it was only possible with the mechanical fuel pump in operation because there was no way to stop it.

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Some would say that the engine will start sucking it's own oil and running away. Which can be possible. That's why I've deleted mine a d run a rdt to an oil catch can and return it back to the intake. Still possible I assume, but less likely. Best coarse of action in my opinion, grab a pie pan to ***** the air upon initial startup. Just to he on the safe side.

frankenwrench said:

Some would say that the engine will start sucking it's own oil and running away. Which can be possible. That's why I've deleted mine a d run a rdt to an oil catch can and return it back to the intake. Still possible I assume, but less likely. Best coarse of action in my opinion, grab a pie pan to ***** the air upon initial startup. Just to he on the safe side.

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Learn something new every day.
I also deleted the CDR and put a catch can in off the valve cover.
The reg only does 5psi max, so if the static psi difference offset is linear that would mean a perfect 5psi running.
I'll be sure to have something to block off the turbo air intake handy just in case.

Some regulators won't work well under already low pressure conditions.

I tried one of the standard type of adjustable regulators on my 64 VW Bug when it had an electric pump and plastic fuel cell, and it didn't lower it at all.

The pump was running 3.5-4psi which was too high for the carburetor, and was flooding it, stalling the engine often at idle. The regulator wasn't able to lower it anymore.

Then I saw reviews from others saying that it won't work at all under those conditions. The VW carburetor expects more like 2-3 psi.

I ended up getting a stock fuel tank and a mechanical fuel pump and that solved all the fuel system problems.

divemaster5734 said:

I also deleted the CDR and put a catch can in off the valve cover.

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Early (?) ATS 085 turbo kits entirely deleted the CDR. Later (?) kits added a mounting point for the factory CDR on the lower half of the air filter box/intake tube. The 85 RV I had, lacked CDR.

I'm not sure if my current gen1 Banks has CDR either.

Holly's don't shut off