Fuel pressure question ....
FTE Leadership Emeritus
Joined: May 2014
Posts: 27,350
Likes: 5,945
From: Lake Hartwell, GA
I know my fuel pressure drops quick after the pump shuts off while waiting for the glow plugs to light. I would bet it was 3 seconds or less from 65 to 0. When I began the turn the engine over though the fuel pressure shoots back up almost instantly.
Even at heavy throttle, the PSI in my truck is near 60 PSI, although I am on stock injectors unlike Rich.
Even at heavy throttle, the PSI in my truck is near 60 PSI, although I am on stock injectors unlike Rich.
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Cargo Master
Joined: Sep 2015
Posts: 2,859
Likes: 365
The Delta is merely the Pump Pressure Measured at the Pump, with Engine NOT running - "No load".
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.
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.
More Turbo
Joined: Nov 2016
Posts: 545
Likes: 2
From: SGV SoCal
Mine reads about 58 psig. I have not noticed any other reading.
If I go and turn on the ignition it jumps up to 58 and sits there. It has been sitting a week now. If I turn it on, it will still read 58 psig. I need to check it under load to see if it dips.
If I go and turn on the ignition it jumps up to 58 and sits there. It has been sitting a week now. If I turn it on, it will still read 58 psig. I need to check it under load to see if it dips.
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Cargo Master
Joined: Sep 2015
Posts: 2,859
Likes: 365
I know my fuel pressure drops quick after the pump shuts off while waiting for the glow plugs to light. I would bet it was 3 seconds or less from 65 to 0. When I began the turn the engine over though the fuel pressure shoots back up almost instantly.
Even at heavy throttle, the PSI in my truck is near 60 PSI, although I am on stock injectors unlike Rich.
Even at heavy throttle, the PSI in my truck is near 60 PSI, although I am on stock injectors unlike Rich.
Logistics Pro
Joined: May 2017
Posts: 4,667
Likes: 1,455
From: Muskogee, Ok
Mine is like Sous' My guage is measured on the post filter port, on the passenger side of the fuel bowl drain valve. Psi normally 61, wot runs will dip to 57. My filter is almost 2 years old but only has 4k miles. Still looked clean when I checked it last month. My pre filter psi stays 2 psi higher on wot runs with much quicker swings
Hotshot
Joined: Jan 2011
Posts: 18,849
Likes: 179
From: Puget Sound
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.
Perfectly normal - you can move past that.
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Cargo Master
Joined: Sep 2015
Posts: 2,859
Likes: 365
Mine is like Sous' My guage is measured on the post filter port, on the passenger side of the fuel bowl drain valve. Psi normally 61, wot runs will dip to 57. My filter is almost 2 years old but only has 4k miles. Still looked clean when I checked it last month. My pre filter psi stays 2 psi higher on wot runs with much quicker swings
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FTE Leadership Emeritus
Joined: May 2014
Posts: 27,350
Likes: 5,945
From: Lake Hartwell, GA
Let us know how it goes, and we like pictures.
More Turbo
Joined: May 2016
Posts: 717
Likes: 9
There are a lot of aftermarket pumps out there. DON'T be FOOLED by what you read! They are JUNK! I have changed more than a few that were just months old.
Get an OEM or BOSH (who makes the OEM). anything else, your playing roulette.
Get an OEM or BOSH (who makes the OEM). anything else, your playing roulette.
Lead Driver
Joined: Dec 2003
Posts: 5,250
Likes: 42
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.
Good to see you, Dan!
You are correct and the mod you did would take care of it.
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Cargo Master
Joined: Sep 2015
Posts: 2,859
Likes: 365
10-4 I got the Bosch pump and oem fpr rebuild kit. Should have it in by next weekend, can't wait to see if I get good results. My 80 horsepower daily is much more Snappy but I'm still losing 10 to 12 PSI when I punch it
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Cargo Master
Joined: Sep 2015
Posts: 2,859
Likes: 365
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.
It's a Van Gogh
Joined: Feb 2010
Posts: 7,809
Likes: 1,334
From: Elk Grove, CA
That pump is a VW unit made by Bosch. Here's Dan's original thread with PNs.
For your truck I'd swap on a new OE pump and expect to see great fuel pressure. Leave the FPR alone unless you really need to mess with it, they break easily.
For your truck I'd swap on a new OE pump and expect to see great fuel pressure. Leave the FPR alone unless you really need to mess with it, they break easily.
Thread Starter
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Cargo Master
Joined: Sep 2015
Posts: 2,859
Likes: 365
That pump is a VW unit made by Bosch. Here's Dan's original thread with PNs.
For your truck I'd swap on a new OE pump and expect to see great fuel pressure. Leave the FPR alone unless you really need to mess with it, they break easily.
For your truck I'd swap on a new OE pump and expect to see great fuel pressure. Leave the FPR alone unless you really need to mess with it, they break easily.