Random fuel pressure increase
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Laughing Gas
Joined: Feb 2014
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Likes: 72
From: Springfield
Random fuel pressure increase
Little backstory, I rebuilt my engine and the fuel bowl with it last march/April. I finally got around to hooking up my fuel pressure gauge again since i needed to buy a new fitting for the fuel line kit i installed and found out i had very high fuel pressure. I pulled off the FPR checked to make sure nothing was binding up put it back together with no change. I ordered the aluminum block to replace the factory piece even though I hadn’t broken the factory piece and used the middle pressure spring. Get it all together and according to my gauge i had between 75-80 psi for some reason, out of spec for the spring i installed and the fact it moved around was a little unsettling. Here in the last week or 2 I've notice the pressure going from 75 up to 90 sporadically. I’m gonna swap out the spring for the factory spec spring when I change my oil in a couple days and blow out the return line again. Anyone have an idea what could be going on that my fuel pressure is higher than it should be for the installed spring and that it fluctuates as much as it does. It does it when the cruise is set driving on relatively flat ground so no real increase in load if that would even play a role
FTE Leadership Emeritus
Joined: May 2014
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Likes: 5,946
From: Lake Hartwell, GA
What about the possibility of the sensor being damaged and reflecting incorrect readings? Shortly after I installed an electronic FP sensor and gauge, the diaphragm in the sensor was damaged and would read ~75 psi until throttle was applied. Then it would drop to ~50 psi.
The company sent me a new sensor and a snubber fitting to reduce the flow to the sensor. I have had no issues for years since then. About 2 years ago I installed the 90 degree elbow and snubber while rebuilding the bowl because I wanted the sensor in a vertical position. My FP has been steady at 62-65 psi since. I have seen where some members remotely mount a FP sensor at the end of a 18" hose or similar.
Not saying this is your problem, but it is a possibility.
The company sent me a new sensor and a snubber fitting to reduce the flow to the sensor. I have had no issues for years since then. About 2 years ago I installed the 90 degree elbow and snubber while rebuilding the bowl because I wanted the sensor in a vertical position. My FP has been steady at 62-65 psi since. I have seen where some members remotely mount a FP sensor at the end of a 18" hose or similar.
Not saying this is your problem, but it is a possibility.
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Laughing Gas
Joined: Feb 2014
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Likes: 72
From: Springfield
That may very well be the problem, i had a time or 2 where the gauge went from 75 or somewhere around there down to 25 then back up. I know the initial super high pressure was correct since the exhaust smelled rich but i cant tell now. That would be a cheap fix for sure if its the cause. By chance could the fuel pump be an issue? As far as i know its the stock one or atleast looks it. The sensor was bouncing around in the door panel of the truck then center console then i stuck it in my tool box for while. I know before i rebuilt everything my gauge held steady, Bailey moving off of the line
It is an isspro gauge from Riffraff, probably 5-6 years ago
It is an isspro gauge from Riffraff, probably 5-6 years ago
Hotshot
Joined: Jul 2008
Posts: 12,782
Likes: 2,142
From: N.GA Mountains
High fuel pressure can not ‘make the truck run rich’.... The injectors Control the amount of fuel going to the combustion chamber. Higher pressure in the rails has no effect on that.
The FPR is suspect. I would swap the OEM spring back in and inspect the plunger to insure it moves easily and is not binding up or something.
The FPR is suspect. I would swap the OEM spring back in and inspect the plunger to insure it moves easily and is not binding up or something.
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Laughing Gas
Joined: Feb 2014
Posts: 1,041
Likes: 72
From: Springfield
I understand about the injectors but when the fuel pressure was very high the exhaust smelled strong/rich, when I changed the spring and cap the smell went away. I’ll definitely double check the plunger when I change the spring in the next couple days.
FTE Leadership Emeritus
Joined: May 2014
Posts: 27,352
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From: Lake Hartwell, GA
My sensor/gauge were and still are ISSPRO as well. The link below shows the part that ISSPRO sent me along with a new sensor once the sensor went bad. I remember the tech on the phone saying something about "this was a common issue for 7.3L trucks that do not have the snubber installed". They sent everything to me free of charge, just asked that I sent the bad sensor back for analysis.
https://www.ford-trucks.com/forums/1...l#post17714316
https://www.ford-trucks.com/forums/1...l#post17714316
Hotshot
Joined: Jul 2008
Posts: 12,782
Likes: 2,142
From: N.GA Mountains
That lends itself to an internal injector issue. Maybe broken nozzle springs or damaged tips?
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Laughing Gas
Joined: Feb 2014
Posts: 1,041
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From: Springfield
Looks like I might be placing a phone call after i change the spring if it still acts weird
I thought something was wrong but since i changed the spring no more stinky exhaust, I might have changed the air filter in the there as well but cant remember at this point. Really hoping something isn’t wrong since i dont have another vehicle to down the truck for any length of time
I thought something was wrong but since i changed the spring no more stinky exhaust, I might have changed the air filter in the there as well but cant remember at this point. Really hoping something isn’t wrong since i dont have another vehicle to down the truck for any length of time
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Thread Starter
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Laughing Gas
Joined: Feb 2014
Posts: 1,041
Likes: 72
From: Springfield
Looks like I'll be calling Isspro i changed out the spring to stock pressure and the gauge still reads about the same. Plus a day or 2 ago while driving to work i watched the gauge sweep from 25-90 and settle back at 75ish
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