Fuel pressure regulator?

Tiny
DILDOYLE99
  • MEMBER
  • 1999 FORD RANGER
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 132,000 MILES
I have a 99 Ford ranger xlt, 4.0, 4x4, automatic. It throws codes p0174 and I think 0173 but they say its running lean. On a full tank of gas 16.5 it gets bout 160 miles to 180 miles on a tank. Ive switched maf sensor checked intake for leaks and air box all that stuff. Still nothing. Doesnt say anything bout o2 sensors. Ive heard may fuel pressure regulator? What bout vaccum lines on the back of the motor. Looking for help
Tuesday, January 25th, 2011 AT 3:14 AM

52 Replies

Tiny
BARRY G.
  • MEMBER
  • 3 POSTS
Have a 99 ranger and millage went down the tube and finally found that the pressure regulator in the automatic trans was defective and not letting the power to go to the wheels ( 70% to wheels 30% to gas tank)
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Sunday, February 20th, 2011 AT 2:15 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,133 POSTS
If the check engine light is on, have the computer scanned. Check fuel pump pressure to make sure it is within spec. As far as the vacuum hoses beind the engine, they run to the 4wd.
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Friday, February 25th, 2011 AT 3:50 PM
Tiny
CRAIG JASTER
  • MEMBER
  • 46 POSTS
  • 1994 FORD RANGER
  • 200,000 MILES
So this is the second time I have posted on this topic. I have run through all the previously suggested tests and I'm still having the same problem. I have replaced the fuel pump, only to find that I wasted $75.00. I did come acrossed an issue that I could see would cause a fuel pressure issue. The hose that connects the pump to the sending unit was split down the side and basically shooting gasoline back down into the tank. Attached is a pic of what I removed and replaced. I'm pretty sure the pump is still good but I replaced it anyways because with the hose like that I simply dont know how long that pump has been over working itself. With the new fuel pump, I still only get 26psi running pressure, but the static pressure is holding at about 36 pis(key on engine off)
The diaphragm on the fuel pressure regulator seams to be holding a vacuum well, and isnt leaking any fuel. The injectors dont seam to be leaking off per the test I ran. I have a timing light that I'm going to hook up to it and replace the fuel filter again. Any other suggestions would be helpful.
Thanks.
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Friday, August 21st, 2020 AT 12:51 PM (Merged)
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Pinch off the return line to the tank at the pressure regulator and see what the pressure measures.

Roy
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Friday, August 21st, 2020 AT 12:51 PM (Merged)
Tiny
KHLOW2008
  • MECHANIC
  • 41,815 POSTS
Symptoms indicates the fuel pressure regulator is faulty.
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Friday, August 21st, 2020 AT 12:51 PM (Merged)
Tiny
CRAIG JASTER
  • MEMBER
  • 46 POSTS
OK, the pressure went up to about 50psi. Does that explain it?
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Friday, August 21st, 2020 AT 12:51 PM (Merged)
Tiny
KHLOW2008
  • MECHANIC
  • 41,815 POSTS
Yup, that means a bad pressure regulator.
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Friday, August 21st, 2020 AT 12:51 PM (Merged)
Tiny
CRAIG JASTER
  • MEMBER
  • 46 POSTS
Ok, I unhooked the vacuum line off the fpr and the pressure went up to normal operating pressure 35-36 psi
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Friday, August 21st, 2020 AT 12:51 PM (Merged)
Tiny
KHLOW2008
  • MECHANIC
  • 41,815 POSTS
35-36 psi is at lower edge of specs but vacuum line should be attached.
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Friday, August 21st, 2020 AT 12:51 PM (Merged)
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
That is normal. With no vacuum, the pressure should rise.
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Friday, August 21st, 2020 AT 12:51 PM (Merged)
Tiny
CRAIG JASTER
  • MEMBER
  • 46 POSTS
Put a brand new regulator on it with no change in results it seams the regulator works properly without a vacuum line hooked to it?
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Friday, August 21st, 2020 AT 12:51 PM (Merged)
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
With vacuum, it will lower the pressure. Thats normal as I said before.

What kind of pump did you use?

Roy
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Friday, August 21st, 2020 AT 12:51 PM (Merged)
Tiny
CRAIG JASTER
  • MEMBER
  • 46 POSTS
The name brand on the pump is airtek.
Now the truck is getting 26psi @ idle but if I give it a little more throttle, the pressure goes up to 36psi. Naturally a higher rpm is going to require more volume @the same pressure correct? So, does that mean the regulator is operating correctly? Maybe the old regulator was bad and I just need to take it for a spin and see what happens in stead of looking at the pressure gauge.
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Friday, August 21st, 2020 AT 12:51 PM (Merged)
Tiny
ASEMASTER6371
  • MECHANIC
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The regulator is fine. When you decrease manifold vacuum, the pressure increases.

The pressure is on the low side. I like to see around 35 at idle with the vacuum line on the regulator

Roy
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Friday, August 21st, 2020 AT 12:51 PM (Merged)
Tiny
CRAIG JASTER
  • MEMBER
  • 46 POSTS
Ok, I took it for a test drive and its still bogging down under a load, not as bad but still is. When you throttle the engine doesnt that give you more vacuum?
The pump should be more than enough to provide adequate pressure to the rail. The specs on the pump call for minimum of 80 psi and max 100 psi. Unless I got a bad pump which has happened before.
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Friday, August 21st, 2020 AT 12:51 PM (Merged)
Tiny
ASEMASTER6371
  • MECHANIC
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No, less vacuum under load. Yes, you could have a bad new pump. Airtex is a good pump but you never know.

Roy
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Friday, August 21st, 2020 AT 12:51 PM (Merged)
Tiny
CRAIG JASTER
  • MEMBER
  • 46 POSTS
Regardless of the rpms of the engine, an electronic fuel pump is going to continuously give you the same pressure, and the regulator is going to adjust the pressure into spec right?
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Friday, August 21st, 2020 AT 12:51 PM (Merged)
Tiny
CRAIG JASTER
  • MEMBER
  • 46 POSTS
The only things on the fuel system that arent new as of today are injectors, fuel rail, lines and filter. The filter is the only thing left that would cause loss of fuel pressure
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Friday, August 21st, 2020 AT 12:51 PM (Merged)
Tiny
ASEMASTER6371
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Nope, wont do it. There is a bypass if the filter gets clogged.

Roy
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Friday, August 21st, 2020 AT 12:51 PM (Merged)
Tiny
CRAIG JASTER
  • MEMBER
  • 46 POSTS
Ok, so less manifold vacuum increases the fuel pressure right, so does that mean I have too much manifold vacuum at idle?
How does manifold vacuum get too high there are any vacuum regulators anywhere, I cant find any. Could that mean I have a vacuum clogged somewhere? An open vacuum line would reduce vacuum elsewhere or could my idle be set too high? Im stumped here. Could the throttle position sensor cause this?
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Friday, August 21st, 2020 AT 12:51 PM (Merged)

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