Fuel pressure question ....
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Cargo Master
Joined: Sep 2015
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Fuel pressure question ....
Hey guys I just installed my fuel pressure gauge and it's reading 60 psi, but when I give it 1/2-3/4 throttle it dumps down to 50 psi. It does rebound to 60 psi when I let off the throttle. Is this normal? I checked my racor and I am getting a few super small air bubbles coming into the filter. Im going to pull what ever is left of my hair out with these damn air bubbles, Thanks for any help
Logistics Pro
Joined: Aug 2009
Posts: 3,609
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From: Arizona
Mine stays between 60-62 PSI, if I mash the pedal it will drop to 58 or 59 but only for a split second then it will rebound back to 60-62 even if my foot is still into it. So I would say no, that is not normal.
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Cargo Master
Joined: Sep 2015
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autometer installed post filter
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Cargo Master
Joined: Sep 2015
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filter is good, and I'm pretty sure the pump is original. Maybe the pump is getting weak? Or does this have anything to do with the fpr spring?
More Turbo
Joined: May 2016
Posts: 717
Likes: 9
The FPR "could be weak".
Perform an AMP Draw on the Pump. You can do this by several ways, at the Pump for a Delta, and then at the Fuse Block to monitor when putting under load.
Do the Same with a "T" and Pressure Gauge just AFTER the Pump. I use an old 10' section of Ait Line with Couplers and Bungee the Gauge to the D/S Mirror.
If both those are withing Specs. Seek a failed Check Valve in one or both Heads, or a restriction in the Fuel Lines to either Head.
Perform an AMP Draw on the Pump. You can do this by several ways, at the Pump for a Delta, and then at the Fuse Block to monitor when putting under load.
Do the Same with a "T" and Pressure Gauge just AFTER the Pump. I use an old 10' section of Ait Line with Couplers and Bungee the Gauge to the D/S Mirror.
If both those are withing Specs. Seek a failed Check Valve in one or both Heads, or a restriction in the Fuel Lines to either Head.
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Fleet Owner
Joined: Jun 2004
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From: Rio Rico, AZ.
The ONLY way you are going to eliminate any chance of air getting in the fuel is to fully pressurize the entire fuel supply line between the fuel TANK and the engine. Only way to do that is to relocate the fuel pump to inside the tank. I did that ten years ago on my 1999 F550 and it was the single most effective modification that I ever did for that truck.
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Hotshot
Joined: Jan 2011
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From: Puget Sound
I had an issue with fuel pressure loss because of air in fuel. The full Hutch mod with removal of the quick disconnects was the answer. Even then, I struggled a bit with the hoses being properly clamped, until I double-clamped.
I run at 60 PSI (with a FRx), and I have 160/100 injectors on my stock fuel pump. I can make the pressure drop to as low as 50 PSI at WOT in high RPMs, but it always snaps back to 60 PSI.
I run at 60 PSI (with a FRx), and I have 160/100 injectors on my stock fuel pump. I can make the pressure drop to as low as 50 PSI at WOT in high RPMs, but it always snaps back to 60 PSI.
Postmaster
Joined: Nov 2015
Posts: 4,807
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From: Colorado Springs
The spring does make a difference. I replaced my pump last fall because I didn't know how old it was and although there wasn't an issue it was obvious it was very tired once the new one was running.
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Cargo Master
Joined: Sep 2015
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The ONLY way you are going to eliminate any chance of air getting in the fuel is to fully pressurize the entire fuel supply line between the fuel TANK and the engine. Only way to do that is to relocate the fuel pump to inside the tank. I did that ten years ago on my 1999 F550 and it was the single most effective modification that I ever did for that truck.
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Cargo Master
Joined: Sep 2015
Posts: 2,860
Likes: 365
The FPR "could be weak".
Perform an AMP Draw on the Pump. You can do this by several ways, at the Pump for a Delta, and then at the Fuse Block to monitor when putting under load.
Do the Same with a "T" and Pressure Gauge just AFTER the Pump. I use an old 10' section of Ait Line with Couplers and Bungee the Gauge to the D/S Mirror.
If both those are withing Specs. Seek a failed Check Valve in one or both Heads, or a restriction in the Fuel Lines to either Head.
Perform an AMP Draw on the Pump. You can do this by several ways, at the Pump for a Delta, and then at the Fuse Block to monitor when putting under load.
Do the Same with a "T" and Pressure Gauge just AFTER the Pump. I use an old 10' section of Ait Line with Couplers and Bungee the Gauge to the D/S Mirror.
If both those are withing Specs. Seek a failed Check Valve in one or both Heads, or a restriction in the Fuel Lines to either Head.
Thread Starter
|
Cargo Master
Joined: Sep 2015
Posts: 2,860
Likes: 365
I had an issue with fuel pressure loss because of air in fuel. The full Hutch mod with removal of the quick disconnects was the answer. Even then, I struggled a bit with the hoses being properly clamped, until I double-clamped.
I run at 60 PSI (with a FRx), and I have 160/100 injectors on my stock fuel pump. I can make the pressure drop to as low as 50 PSI at WOT in high RPMs, but it always snaps back to 60 PSI.
I run at 60 PSI (with a FRx), and I have 160/100 injectors on my stock fuel pump. I can make the pressure drop to as low as 50 PSI at WOT in high RPMs, but it always snaps back to 60 PSI.
More Turbo
Joined: May 2016
Posts: 717
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All following test pressures relate to that pressure [Delta] to determine where an obstruction is or perhaps a failing pump.
As for the FPR Spring - Not always the case. Eventually, the spring (all springs) will loose their ability to hold closed the Pressure Disc. The pressure at the FPR should be essentially the same as what's occurring in the Bowl for Supply. The Spring collapses until the pressure is near equal.
Some of these tests will point you in the right direction.
As for the falling pressure, is it the Feed or Return Side. You need to figure that out as well. Essentially, the pressure should maintain for a period of time as any other Fuel Injected System. These are Low Pressure Supply Systems as they are actuated by the High Pressure Oil on the Head.
How long? I don't have that answer. But, I will seek it out this weekend for you.