FRx spring choice
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Tuned
Joined: Oct 2009
Posts: 292
Likes: 0
From: Raleigh
FRx spring choice
Just received the new shiny FRx in the mail today...holy fast shipping Clay!...anyways, reading through the instructions I'm curious about the springs. It says the gold spring (62-65psi) is recommended out of the three. Is there any reason to not just put the black spring (67-70psi) spring in there and be done with it? I don't own a fuel pressure gauge and honestly don't have the motivation this week to hook up a gauge to see what my initial pressure is before the install of the FRx. So in summary, should I expect any issues in installing the black spring over the gold?
EDIT: In the threads i've read so far, I didn't find much info on either choice
EDIT: In the threads i've read so far, I didn't find much info on either choice
Hotshot
Joined: Jul 2008
Posts: 12,782
Likes: 2,142
From: N.GA Mountains
The spring/fuel pressure will not make any difference in the way the engine runs... 
You can test FP pretty easily using the water-drain valve. Throw a couple clamps on the rubber line at valve and attach a piece of hose to the discharge line on front of block. Put a cheap (water/air pressure) gauge on the end of hose and open valve to test pressure. Costs less than $10 and just leave the hose on discharge line so you can easily collect/inspect contents of fuel bowl in the future.
You can test FP pretty easily using the water-drain valve. Throw a couple clamps on the rubber line at valve and attach a piece of hose to the discharge line on front of block. Put a cheap (water/air pressure) gauge on the end of hose and open valve to test pressure. Costs less than $10 and just leave the hose on discharge line so you can easily collect/inspect contents of fuel bowl in the future.
Cargo Master
Joined: Oct 2011
Posts: 2,871
Likes: 767
From: SoCal/Wyoming
You won’t notice any big difference either way. Mine runs right at 65psi give or take a few. One thing you must do is check the pressure after you install the FRx. Mine was pegged at over 100psi because the spring was not centered properly so I had to take it apart and reposition the spring. You won’t know if the FP is over 100 just by the way it drives, at least I could not tell and I only found out when I installed my gauges.
Thread Starter
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Tuned
Joined: Oct 2009
Posts: 292
Likes: 0
From: Raleigh
The spring/fuel pressure will not make any difference in the way the engine runs...
You can test FP pretty easily using the water-drain valve. Throw a couple clamps on the rubber line at valve and attach a piece of hose to the discharge line on front of block. Put a cheap (water/air pressure) gauge on the end of hose and open valve to test pressure. Costs less than $10 and just leave the hose on discharge line so you can easily collect/inspect contents of fuel bowl in the future.
You can test FP pretty easily using the water-drain valve. Throw a couple clamps on the rubber line at valve and attach a piece of hose to the discharge line on front of block. Put a cheap (water/air pressure) gauge on the end of hose and open valve to test pressure. Costs less than $10 and just leave the hose on discharge line so you can easily collect/inspect contents of fuel bowl in the future.
You won’t notice any big difference either way. Mine runs right at 65psi give or take a few. One thing you must do is check the pressure after you install the FRx. Mine was pegged at over 100psi because the spring was not centered properly so I had to take it apart and reposition the spring. You won’t know if the FP is over 100 just by the way it drives, at least I could not tell and I only found out when I installed my gauges.
Thanks for the explanations so far guys, it honestly has helped. I have a bad habit of always wanting to know more
Posting Guru
Joined: Mar 2011
Posts: 1,037
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From: Florida
From what i've read so far, I agree, there won't be any difference in performance between the different springs.
Gotcha. I see the importance of checking after install now. So i guess my next question is, assuming the spring is seated properly, why bother with the lower psi springs? Please excuse my ignorance. I'm just curious and want to fully understand what's going on inside the fuel system?
Thanks for the explanations so far guys, it honestly has helped. I have a bad habit of always wanting to know more
Gotcha. I see the importance of checking after install now. So i guess my next question is, assuming the spring is seated properly, why bother with the lower psi springs? Please excuse my ignorance. I'm just curious and want to fully understand what's going on inside the fuel system?
Thanks for the explanations so far guys, it honestly has helped. I have a bad habit of always wanting to know more
I have an adjustable pressure regulator installed and have fuel pressure set to 65 psi. My truck seems to run a bit smoother (less clatter) at that pressure than it does at 75 psi and performance is the same.
Hotshot
Joined: Jan 2011
Posts: 18,849
Likes: 179
From: Puget Sound
I don't know the "why's" of the different springs, other than you have options and everybody has different goals for their truck. I know there are some dynamics to the fuel system that are misunderstood by some.
- Fuel pressure ain't what it used to be. I know the older Dodge 5.9s seek out more fuel pressure to get more power, but our injectors are more like 8 windex bottles. Releasing the handle on theWindex bottle fills a small reservoir for the next "injection event". Your fingers squeeze the handle to "inject" Windex. You can squeeze as long and as hard as you want, but there is only so much fluid in that reservoir to spray. The fuel pump's job is to fill that reservoir in time before the oil (replacement for your finger) pulls the trigger on your injector (Spray bottle head). It doesn't take long to fill the stock (or near-stock) injector with our stock pumps, and pressure is only important in that it sets how fast the resersvoir is filled. If you have 450/400 injectors running at 3300 RPM... then you have bigger issues than deciding which spring to use.
- Going the other way - flow: A pressure regulator works by allowing the pressure to build (and the pump to slow), releasing just enough fuel in the return line to build a specified pressure in the fuel supply line. More pressure means less flow out and a slower pump at low fuel demand. Higher pressure puts more wear on the pump and we folk with FRxs have warmer fuel in the return line because it has more time to warm up in the head. Warmer fuel is a good thing, so there's that. Dump the throttle and the pump now needs to speed up and the regulator is no longer doing the regualting - the injector demand is doing that job.
Posting Guru
Joined: Apr 2010
Posts: 1,164
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From: Canberra Australia
I also got my RR FRx yesterday. It took a bit longer to get to this side of the planet.
I have a fuel pressure gauge with is showing about 62psi now - it was closer to 60 before I did the Hutch mod 2 weekends back.
I will be running the Gold spring - my engine is stock.
I'm also putting in a lift pump and pre-stock pump filter-water seperator for good measure.
I have a fuel pressure gauge with is showing about 62psi now - it was closer to 60 before I did the Hutch mod 2 weekends back.
I will be running the Gold spring - my engine is stock.
I'm also putting in a lift pump and pre-stock pump filter-water seperator for good measure.
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Hotshot
Joined: May 2005
Posts: 13,484
Likes: 42
From: Stevens Point, WI
I made a FRx, used the factory spring, been driving it for over a year now and have yet to check pressure.
I do want to check the fuel pressure one day though just to know. lol
I do want to check the fuel pressure one day though just to know. lol
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Hotshot
Joined: Jul 2008
Posts: 12,782
Likes: 2,142
From: N.GA Mountains
Fwiw, I run the OE system at a stock 54psi and run my WVO system at 75psi. Each system uses an OE-style fuel pump (on F350). There is no difference in the way the engine runs AT ALL with he different pressures.
Hotshot
Joined: Jul 2008
Posts: 12,782
Likes: 2,142
From: N.GA Mountains
) The OE pump does not like any restriction in front of it. All of this just adds unnecessary complication to an otherwise more-than-adequate fuel system that is totally capable of providing looooong injector life (which is why we are filtering our fuel in the first place). For that matter, the OE fuel system as a whole works just fine as is, except for the non-serviceable in-tank strainer!!!
Posting Guru
Joined: Apr 2010
Posts: 1,164
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From: Canberra Australia
The point to make it all easy to service. With the Hutch mod the strainer is out of the tank and just ahead of it. Then a small 'Facet' lift pump pushes the fuel through a water seperator then into the stock pump, the stock pump is not made to work harder.
The idea being that if you ever get a load of bad fuel, the strainer is easy to access & clean, & spin on filter water seperator is also simple to replace - and I'll have a spare one in the vehicle.
It is a case of a problem avoided is a problem solved!
The idea being that if you ever get a load of bad fuel, the strainer is easy to access & clean, & spin on filter water seperator is also simple to replace - and I'll have a spare one in the vehicle.
It is a case of a problem avoided is a problem solved!
Hotshot
Joined: Jul 2008
Posts: 12,782
Likes: 2,142
From: N.GA Mountains
The point to make it all easy to service. With the Hutch mod the strainer is out of the tank and just ahead of it. Then a small 'Facet' lift pump pushes the fuel through a water seperator then into the stock pump, the stock pump is not made to work harder.
The idea being that if you ever get a load of bad fuel, the strainer is easy to access & clean, & spin on filter water seperator is also simple to replace - and I'll have a spare one in the vehicle.
It is a case of a problem avoided is a problem solved!
The idea being that if you ever get a load of bad fuel, the strainer is easy to access & clean, & spin on filter water seperator is also simple to replace - and I'll have a spare one in the vehicle.
It is a case of a problem avoided is a problem solved!
In 350k miles on my personal PSD's, I have yet to get a load of 'bad' fuel - but I generally choose my fuel stations carefully.
Personally, I subscribe to the K.I.S.S. method. There is no real benefit for all the added complication and potential failure points of a second pump, just to push fuel thru a redundant filter. While a spin-on filter may be a little cheaper than an OE filter - most people don't spend that much on OE filters in the first place. With a fuel pressure gauge (post filter) you can easily monitor filter life and with good fuel sources (and turnover) you can get 30-50k miles out of a filter.
Ya still prolly want a pre-filter to protect the pre-pump... Something like a WIX 33972 is ideal.
Posting Guru
Joined: Apr 2010
Posts: 1,164
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From: Canberra Australia
I'm using a 100 micron stainless fuel strainer.
It's great you've also got a good choice of fuel stations and can be choosy!
How many PSD problems have we seen on this forum where the in-tank strainer has blocked up causing loss of power & poor running, with the stealerships having no idea and replacing all and sundry at cost to the owner?
I've seen that senario enough on this forum to know that I want to take a few basic precautions to make sure if or when that happens to my truck I'll have it easily covered. I can live with the extra complications as 'insurance'. I certainly do NOT want to be cleaning a clogged strainer out on the inside my FULL 70 GALLON long-range fuel tank!
It's great you've also got a good choice of fuel stations and can be choosy!
How many PSD problems have we seen on this forum where the in-tank strainer has blocked up causing loss of power & poor running, with the stealerships having no idea and replacing all and sundry at cost to the owner?
I've seen that senario enough on this forum to know that I want to take a few basic precautions to make sure if or when that happens to my truck I'll have it easily covered. I can live with the extra complications as 'insurance'. I certainly do NOT want to be cleaning a clogged strainer out on the inside my FULL 70 GALLON long-range fuel tank!