Fuel pressure

Tiny
JJT317
  • MEMBER
  • 2003 FORD F-150
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 100,000 MILES
What should the fuel pressure be?
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Wednesday, April 22nd, 2009 AT 3:25 AM

24 Replies

Tiny
DAVE H
  • MEMBER
Fuel pressure ...4.2L & 4.6L.......Psi 30-45 ....Kpa(207-310) here is a guide to elp you test it.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Please let us know if you need anything else to get the problem fixed.
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Wednesday, April 22nd, 2009 AT 5:34 AM
Tiny
KADUH
  • MEMBER
  • 1996 FORD F-150
  • V8
  • 2WD
  • AUTOMATIC
  • 212,000 MILES
I'm having a problem with my truck maintaining fuel pressure. It has 32psi at the rail when I start it, but it soon drops, causing the truck to sputter when you try to accellerate. I have taken the pressure regulator off and attached a hand vacuum pump and it holds steady at 40psi. I have good vacuum on the line that plugs on to the Regulator with no gas smell. I have also changed the rear tank pump and I am getting no pressure when I switch to the rear. I can hear it run, so I am a little confused. I have replaced the plugs, cap, rotor, wires, fuel filter and TPS sensor. I am at a loss on this drop in fuel pressure. Any help will be appreciated.
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Thursday, March 21st, 2019 AT 7:04 PM (Merged)
Tiny
JACK42
  • MEMBER
Probably by-passing the pressure into the front tank. Those trucks had issues with erear tank fillin gup thefront tank. There was a inline check valve that was used for awhile, but I didnt hav eany luck finding one last time I tried. Try switching to the front tank, checking the fuel level. Then run the rear tank and see if it is filling it up. If it is equipped with a fuel switching valve instead of just pumps, the switching valve is probably bad
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Thursday, March 21st, 2019 AT 7:04 PM (Merged)
Tiny
KADUH
  • MEMBER
I got under the truck yesterday because I kept reading about a fuel selector switch and wanted to see if there was one on mine that may be bad. The only thing I can find is an aluminum manifold where both the front and rear fuel supply lines tie in to that has one main supply line going forward to the engine from that point. I understand what you are saying, because I had to replace the front pump seven years ago because of the same issue you described, but this time I am stumped.
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Thursday, March 21st, 2019 AT 7:04 PM (Merged)
Tiny
JACK42
  • MEMBER
If you had to replace your front pump for that issue then you dont have a selector valve, the check valves in the pump do the same thing. You neeed to be sure the fuel pump is still getting power when it loses pressure. Did thefuel pump for that come as an entire tank unit or just a pump that you replcae on the sending unit? Ifit was just the pump, was there anything between the pump and the sender other than just a piece of high pressure hose? If so it may have a bad pulse dampener in there that is allowing the fuel pressure to bypass right back into the tank. They wil lmake pressure against a closed system, but when you start bleeding off pressure (running engine) they lose pressure. If you suspect that pressure is being lost outside tank, remove fuel pressure line at junction and install pressure gauge there to see if it making it to junction, but being lost in it
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Thursday, March 21st, 2019 AT 7:04 PM (Merged)
Tiny
KADUH
  • MEMBER
I believe it's still getting power because I can hear it, and the engine stays running. It just wants to stall when you try to give it gas. I think they just replaced the pump itself, which just slides off of the sending unit with a solid aluminum pipes that go into it. The only high pressure flex line is on the outside of the tank that goes to the junction manifold. I guess I need to go ahead and replace the front pump and see if that helps. I can order one online for $50, so it's not that bad, it's just a pain to drop the tank!
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Thursday, March 21st, 2019 AT 7:04 PM (Merged)
Tiny
JACK42
  • MEMBER
Its easier on some trucks to unbolt the bed and get a friend to help you lift it and slide it back, then the top of the tank is right there.I would double check with a pressure gauge before I replaced anything, so you dont waste time /money in the wrong direction
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Thursday, March 21st, 2019 AT 7:04 PM (Merged)
Tiny
EUGENE TANNER
  • MEMBER
  • 2005 FORD F-150
  • V8
  • 2WD
  • AUTOMATIC
  • 150,000 MILES
What is fuel pressure settings.
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Thursday, March 21st, 2019 AT 7:04 PM (Merged)
Tiny
DOCFIXIT
  • EXPERT
55 to 60 psi
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Thursday, March 21st, 2019 AT 7:04 PM (Merged)
Tiny
EUGENE TANNER
  • MEMBER
We change the spark plugs, ran ok for two days, then the same problem came back it started to shake, and you could hear a taping noise, so we check the fuel pressure, it came out to 32 psi, so we change the fuel pump, so we started again, now the tapping noise is still there, but when it warms up, it just shuts down, right before it shuts down, the oil pressure gauge shows nothan. But when it cools down it starts right up, until you put it in gear to move it, it shuts down,

do you thing its the oil pump?
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Thursday, March 21st, 2019 AT 7:04 PM (Merged)
Tiny
ED4EDWAEDS
  • MEMBER
  • 2001 FORD F-150
2001 Ford F150 V8 Two Wheel Drive Automatic

What should the fuel pressure be on a 4.6L engine?
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Thursday, March 21st, 2019 AT 7:04 PM (Merged)
Tiny
RASMATAZ
  • MEMBER
2001 Ford Truck F 150 2WD Pickup V8-4.6L SOHC VIN W
Fuel Pressure
Key on, engine off 240-310 kPa (35-45 psi)
Engine running 193-345 kPa (28-50 psi)
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Thursday, March 21st, 2019 AT 7:04 PM (Merged)
Tiny
ED4EDWAEDS
  • MEMBER
New to forum. That is a good quick answer. Thanks again
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Thursday, March 21st, 2019 AT 7:04 PM (Merged)
Tiny
SGARBEL
  • MEMBER
  • 1997 FORD F-150
  • V8
  • 4WD
  • AUTOMATIC
  • 147,000 MILES
Can anyone tell what the fuel pressure should be on my pickup.

My Haynes repair manual says the OK pressure for 5.4L in on position should be 55psi and running is 55psi.

I called autozone and they said it should be 30 to 45psi. I have tried researching on line to determine what the correct pressure should be. No luck.
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Thursday, March 21st, 2019 AT 7:04 PM (Merged)
Tiny
WRENCHTECH
  • MEMBER
Here are the official specs

FUEL PRESSURE
Key On, Engine Off (KOEO) 30-45 psi
Key On, Engine Running (KOER) 27-42 psi

This is tested at the service port without blocking the return line.
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Thursday, March 21st, 2019 AT 7:04 PM (Merged)
Tiny
MARKBETZ
  • MEMBER
  • 2004 FORD F-150
2004 Ford F150 4 cyl Two Wheel Drive

What is the fuel pressure for a ford f150 4.6 liter engine?
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Thursday, March 21st, 2019 AT 7:04 PM (Merged)
Tiny
DAVE H
  • MEMBER
FUEL PRESSURE SPECIFICATIONS
Application.(1) psi.(KPa)
4.6L & 5.4L.40-70 (275-485)
(1)With key on and engine off and fuel pump running.
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Thursday, March 21st, 2019 AT 7:04 PM (Merged)
Tiny
JBLCO
  • MEMBER
  • 1988 FORD F-150
  • 6 CYL
  • 2WD
  • MANUAL
  • 190,000 MILES
Hi,

engine is stalling, apparently due to low fuel pressure. Guage reads 45 -60 psi when first started, then as engine runs pressure gets lower until engine stalls from lack of pressure. (About 20 psi or so.) After a 30 second wait, pressure comes up and starts again.

With ground leads from rear fuel pumps disconnected from battery, there is no pressure or fuel. When connected, pressure comes up - I disconnected the ground lead from the h.P. Pump (so I can hear) and I do hear the pump in the tank whirring. Seems like a fuel volume issue. This truck has twin tanks - could the selector valve between the tanks be the culprit?

Other causes for low fuel volume to the high pressure pump?

No apparent kinks or restrictions in the fuel lines, new fuel filter, new h.P. Pump (was making bearing noises with erratic fluctuations in pressure - sounded like it was on a failure path). Rear tank pumps replaced about 1.5 years ago.

Need to get running as is a work truck and I am losing money by the hour.

Thanks.
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Wednesday, May 1st, 2019 AT 7:15 PM (Merged)
Tiny
MERLIN2021
  • EXPERT
If pressure drops that fast then either the filter is almost completely clogged, or the pumps need to be replaced, also there is a new switching valve for EFI type systems.


http://www.2carpros.com/forum/automotive_pictures/62217_F150_1.jpg

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Wednesday, May 1st, 2019 AT 7:15 PM (Merged)
Tiny
JBLCO
  • MEMBER
Since the only two components up stream of the high pressure pump are the switch and the pump, how can I eliminate one or the other?

Fuel filter is downstream of the h.P. Pump and is brand new, so filter clog is low on my list (though not completely ruled out as if there is a lot of crap in the fuel, I can see where a new filter would clog up fast.)

also parked truck on incline of about 15 degrees (front end up). Starts, runs about 30 sec and dies (pressure drops from 55-60 psi to less than 30 psi and stalls from lack of fuel).

I don't mind spending money on the system to get it going again, but dollars are tight and I don't want to keep playing this game of replacing everything and hope I got the bad part in the process.

Any test to rule out the switch, since it appears to be the easier of the two to replace?

Thanks
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Wednesday, May 1st, 2019 AT 7:15 PM (Merged)

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