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How to check your fuel pressure

Discussion in 'Under the Hood' started by KaiserM715, November 8, 2006.

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    1. KaiserM715

      KaiserM715 Active Member

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      City, State:
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      Year and Model:
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      I needed to check my fuel pressure to help chase down possible causes for a trouble code that I had. I borrowed a fuel pressure gauge kit from a co-worker, but I have seen them new for $35 to $45 at the auto parts store.

      Here is the one that I used:
      [​IMG]

      The clear hose is connected to a relief valve to relieve the pressure in the line after testing. The brass connector on the end of the black hose connects to the fuel rail. For Fords, the small adapter shown is needed as the Schrader valve on the Ford fuel rail is smaller than other makes.

      Based on advice from the Haynes manual, I disconnected the fuel pump relay (or the inertia relay), located below the glove box in the passenger foot well area. The grey connector was disconnected.
      [​IMG]

      Then I cranked the engine over for 10-15 seconds to relieve the pressure. After the pressure is relieved, I removed the bright blue dust cap from the valve on the fuel rail. The valve is located in between the oil filler neck and the intake manifold and in front of the coil pack.
      [​IMG]

      I threaded the adapter on first and tightened it until it was snug with a wrench. Then I threaded the gauge on to the adapter.
      [​IMG]

      I reconnected the fuel pump relay and turn the key on, but I did not start the engine. The fuel pressure read to be about 62 psi (the acceptable range is from 56 psi to 72 psi).
      [​IMG]

      Then I started the engine and read the pressure to be about 66 psi.
      [​IMG]

      After I shut the engine off, I depressurized the line by depressing the black button on the relief valve. I placed the clear hose in a bucket beforehand to catch the gasoline. The pressure needs to be bled down to zero to safely disconnect the gauge.
      [​IMG]

      I stuffed a shop towel under the fuel rail fitting to soak up any gasoline that leaked out when I disconnected the gauge and the adapter. I replaced the dust cap and that was it!!

      Note: My vehicle is a '00 Ranger with the 4.0 OHV engine, so your fuel pressure specs and fuel rail valve location may differ.
       
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    3. Dylansav

      Dylansav Active Member

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      :thumbsup:

      Nice write-up! I've been wondering how the process of checking your own fuel pressure goes about. I'm going to give it a shot.
       
    4. Blacksheep Josh

      Blacksheep Josh Slinky+Escalator=Fun

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      I wonder how many pages a "Ford Explorer Write-Up" would be.

      This, like many on this sight, are a lot better then the ones even done professionally in the Haynes and Chilton's. I also like that someone actually NEEDED to do it, and didn't do it just to do. Shows it (whatever writeup) actually worked and fixed the problem.

      Was that with stock fuel pump? Sometime I feel as if my '93 Explorer fuel pump isn't working right some days...
       
    5. Maniak

      Maniak Moderator-Stock 91-94 Staff Member Moderator Elite Explorer

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      It looks like he was testing on a 2000 which runs higher pressure than the 1st gens...

      ~Mark
       
    6. KaiserM715

      KaiserM715 Active Member

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      Talk about bringing a thread back from the dead!! That is what I like to see!!

      Yes, it is the stock, original pump.

      Yep, a 2000 Ranger with the 4.0L OHV.
       
    7. javiscancino

      javiscancino New Member

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      i did a swap from a 92 4.0 ohv to 98 4.0 sohc engine,. we are using the same fuel pump the fuel pump is from a 2.9 engine, external fuel pump,. this sohc engine the ecu was reprogrammed for better performance, it worked awsome from 3000 rpms to 6500, the problem was from idle to 3000 rpms, well, i just checked the fuel pressure and at idle with the fuel pressure regulator connected was 30psi and 40psi disconnected, so, at 40psi the engine rev great from idle, that was the problem, very low pressure,

      my question is, what should be the ideal working fuel pressure for a 98 sohc engine,. it comes with a fuel pressure regulator and plastic rail,. as a matter of fact, that engine was returnless fuel rail, we put another fuel rail with the return line,.
       
    8. BlackedOut

      BlackedOut Active Member

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      Thanks for this one. Ive been wanting to check mine.
       
    9. MrShorty

      MrShorty Explorer Addict

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      For future reference, here's a thread with the fuel pressure testing specifically applied to the older "continuously circulating" fuel system used on the 1st gens. http://www.explorerforum.com/forums/showthread.php?t=142801

      It might be nice for future users if a moderator or someone could edit the titles of the two threads to make it apparent which thread applies to the newer "returnless" system and which thread applies to the older version.
       
    10. Maniak

      Maniak Moderator-Stock 91-94 Staff Member Moderator Elite Explorer

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      If you can give me the ranges that should be in the title of the two threads (years etc) I can modify them, then pull out this conversation and make sure they are in the useful thread forum too.

      ~Mark
       
    11. MrShorty

      MrShorty Explorer Addict

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      I wish I could give you definite year ranges, but I'm just not sure. I know up through ~'96 is definitely continuous circulation at 40 psi. From the information presented here, '00 4.0 is returnless/60+ psi. Part of me wants to say '98, but I really don't know what year Ford changed fuel system design, or if it makes a difference which engine (OHV or SOHC or 5.0). Hopefully somebody else can give a more definite idea of which year/engine introduced the returnless system.
       
    12. ranger7ltr

      ranger7ltr Elite Explorer

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      1999 was the first year of the returnless fuel system...

      And the operating pressures were 65-72 psi nominal...Plus there is not a vacuum operated fuel pressure regulator on the fuel rail either...The fpr is in the tank mounted on the fuel sending unit/pump mount and the device on the fuel rail is a fuel damper...And it did not matter what engine was in the truck...

      The fuel damper is there to even out the pulses of the injector opening and closing...

      Oh and the fuel pump runs constantly; it DOES NOT vary speed or pressure as the later pwm pump does...
       
    13. MrShorty

      MrShorty Explorer Addict

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      Thanks for that. That's the kind of information we're trying to pin down.
       
    14. Phreaq

      Phreaq New Member

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      I'm getting mixed information about fuel pressure ...
      I am working on a 2001 Explorer Sport-Trac 4.0 soch
      The Pressure tester manual (actron) stated 35-60psi for all 2001 explorers.
      Is there that much difference in the 2000 and 2001?
       
    15. Phreaq

      Phreaq New Member

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      Fuel Pressure for 2000 model year

      2000* Ford Explorer Fuel pump specs
      Key
      Engine, Model, Part# (9F593), Connector color, Flow rate, Fuel system (Mechanical Returnless Fuel System), Pressure

      *These specs are for the 2000 model year I did not look up 99 (sorry) and 2001 spec are not the same across all motors.
       
    16. k1k1to

      k1k1to New Member

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    17. ihatefords

      ihatefords New Member

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      Another of my bad ideas, or is it doable?

      I've been dealing with a ton of problems with my 96 Exploder, now I'm down to checking the fuel delivery components. I ordered a pressure tester, so I'm waiting for that to get here... I'm a big fan of SEAFOAM...but on injected engines, you have to dump it in the tank, and it becomes very diluted. Is it possible to maybe pull the pump fuse to relieve the pressure, modify a Schroeder valve attachment, and pump the foam directly into the rail? I know it's risky to be playing with modified valves on fuel under pressure, but I don't see any other way to use the foam instead of the fuel additive...and I really want to give a high concentration to the injectors...:smoke:
       
    18. glockman

      glockman New Member

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      Easier way to seafoam would be to pull one of the vacuum line, ie the one to the brake booster and stick it in the bottle of seafoam with the engine running. It will suck it into the intake. I don't personally use seafoam but have seen it done this way.
       
    19. keleko17

      keleko17 Member

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      I am sure I am an idiot, but I am once again bringing this thread to life.

      I have a 99 Explorer, OHV, looking for fuel pressure specs. I have tried searching, and keep coming up pretty empty, or confused. I got the loan-a-tool from Autozone to do this test. I have a few specific questions...

      1. What pressure should I have with when I turn the key to an on position?
      2. What pressure should I have running at idle?
      3. What about while under load? (Saw a Youtube video of a guy actually driving to test, I think I will just throttle up)
      4. How long should it keep pressure after turning off the engine?
      5. Can I test anywhere beside the fuel rail? Such as before the fuel filter and after, to see if the filter is a possible problem.
       
    20. 1cowboy

      1cowboy New Member

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      fuel pump 2001 ford 4.0 sport trac

      is there a fuse or relay for the fuel pump?? i disconnected fuel line at filter under drivers side floor cranked over no fuel came out? should have right??
       

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