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Rear diff Service questions

Discussion in 'Stock 1995 - 2001 Explorers' started by danno2944, November 3, 2018.

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    1. koda2000

      koda2000 Explorer Addict

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      That sucks, but I'll bet you never make that mistake again. Reminds me of when I did one of my first oil changes, forgot to put the drain plug back in and dumped 3 qts of oil into the engine before I realized it. Never made that mistake again either. We live, we learn.
       
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    3. mz35z

      mz35z Member

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      Oh man that sucks. Haha. Yeah I was in a rush won't do that again.
       
    4. imp

      imp Elite Explorer

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      @koda2000

      I have some trouble understanding......ya know I get stuck easy! If the pressure regulator is in the tank, how can it control pressure: what tells it what to do? Unless it's electrically-controlled, which seems to be a "no".

      This pressure damper as you say, it has a vacuum connection going to it? So, must have either a diaphragm acted on by the vacuum, controlling a valve, or a solenoid coil, with associated wiring, to operate a valve. I suspect it is very similar, though calibrated differently to the previous "return-type" system, was re-named "damper", which, to me, is misleading, as it in reality maintains the rail fuel pressure constant as fuel demand varies with load and speed.

      Semantics, then. @shucker1 What do you think of all this?? imp
       
    5. danno2944

      danno2944 New Member

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      Lol, I have left the filler cap off after changing oil, only lost a quart before I.noticed most of it went on the hood liner...

      It Sounds logical to me, but I'm no expert.

      I know the "pressure damper" has a vacuum line and has a diaphragm inside and it is attached to the fuel rail, that's it, no wires. The fuel pressure sensor is on the tank.
       
      Last edited: November 7, 2018 at 12:31 AM
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    6. 1998Exp

      1998Exp Active Member

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      Well, one has to wonder how those "new" (to me, owner of a 20 year old MY98) systems work. The old wisdom was to regulate the fuel pressure against the manifold pressure, because that's where the fuel is going. This required a manifold-vacuum controlled regulator. If the pressure regulation is absolute, something has to account for the manifold pressure. It's entirely possible that the pulse duration calculation takes that into account, but I wish someone in the know would chime in...
       
    7. donalds

      donalds Elite Explorer

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      The way I understand it the fpr is on the pump sending unit it allows the rail pressure no more any extra and it dumps the extra fuel back into the tank

      The damper just smooths out the pressure spikes when the injector s fire off

      If you hook up a fuel pressure gauge and look at the needle it Is almost still it moves every time a injector opens looks like a bouncing needle very little bounce
      If you unplug the damper it bounces much more
      The damper smoothed out the pulses caused by the injector s
       
    8. david4451

      david4451 Active Member

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      The fuel pressure regulator is constantly flowing the fuel back into tank, as you can imagine the fuel pump can supply much more fuel than the engine could use.

      The fuel pump works continuously and the fuel pressure regulator opens at a constant pressue between 65 to 70 plus psi on return less set up. My ST is 72 psi and stays constant.
       
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    9. J_C

      J_C Well-Known Member

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      Don't the original ball joints use plastic bearings in them? That's typical for sealed-for-life BJs. IF so, I doubt they're going to be squeaking before they've completely disintegrated the bushing inside and if that has happened you should see play with the usual prying-test.

      Anyway I would sooner suspect the sway bar bushings and would spray some soapy water on them, them immediately drive to see if the squeak goes away. If the noise is still present, next spray the control arm bushings and test drive again.

      As far as using WD-40 to test the BJs, you can get lithium spray grease in a can instead, that uses an included straw, that comes out like water and thickens as the propellant evaporates away. Rather than diluting any grease that might remain, it will replenish the BJ grease some. Very handy stuff, useful for hinges 'n latches 'n such too.
       
      Last edited: November 7, 2018 at 7:52 AM
    10. shucker1

      shucker1 Elite Explorer

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      Perfect explanation by @donalds

      During acceleration or heavy load your intake manifold pressure will change as well as the injector pulse rate (As function of speed) and injector pulse duration will change (As a function of load). The control line connected to the damper in turn changes the dampening force required.

      We have been using the same type system on the big bore units since the 70's. However we are dealing with natural gas as fuel rather than a liquid fuel.

      To reduce emissions we use a "Jet Cell" (A Pre-combustion Chamber if you will") fuel flow to the "Jet Cell" is biased off of Air Manifold Pressure.

      More Load, More Air = Higher Jet Cell Pressure.
       
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    11. koda2000

      koda2000 Explorer Addict

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      The way I understand it, In the return-less fuel system the fuel pump makes a constant pressure of around 65-70 PSI. The FPR in the tank (which is located right above the fuel pump) returns anything above that pressure right back into the fuel tank. Hence the fuel pressure at the rail remains close to a constant pressure and the PCM regulates fuel injector pulse rate and width based on feedback from various sensors (like the O2's, MAF, air temp, coolant temp). The damper on the fuel rail buffers the fuel pressure as needed based on engine vacuum.

      The FPR in the tank is strictly a mechanical device, which uses a spring to route excess pressure back to the fuel tank. The in-tank FPR is a simple, reliable device which rarely fails. If it does fail it's typically because its plastic housing cracks. Other than the fuel pump itself the most common fuel pressure problems are due to splits in the in-tank submersible fuel lines.
       
    12. shucker1

      shucker1 Elite Explorer

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      Thank you.

      Damper is needed to prevent pressure pulse spikes as the injectors open and close. (Basically Water Hammer Effect). This could upset injector closure and throw off AFR.
       
    13. imp

      imp Elite Explorer

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      @koda2000 @shucker1

      We are having a discussion here in which terminology and names for components are clouding the actual physics of it. This has left @1998Exp as confused as me!

      So, to further cloud the issue: The fuel pump is a constant-volume pump, meaning each revolution of it's guts produce the SAME amount of flow. Fuel is incompressible, so the pump is designed to deliver enough fuel when the engine is "balls-out", and at that time if it were sized with NO cushion for more, the REGULATOR in the tank would be bypassing NO FUEL back to the tank. This regulator is set to allow only a maximum pressure to exist, to protect the pump from overload. A fixed-volume pump having it's output physically blocked off, will either BREAK, burst it's connecting hose, or stall it's driving device, in our pumps, an electric motor. This is due to the incompressibility of liquid.

      The above explains in part why earlier EFI systems used lower fuel pressure, perhaps 40 psi. The newer "idea" uses about 60 psi, if i remember right, but the thing here which applies, is that to run "returnless" successfully, the pressure relief in the tank must establish the actual fuel pressure used by the injectors. Say the throttle is suddenly tromped to the floor.....INERTIA of the fuel in the line to the rail, maybe a cupful, prevents an instantaneous increased flow of fuel to the rail. It needs that added fuel BAD, and NOW, or a BOG is felt; thus a "damper" on the rail, which I stubbornly still call a "pressure regulator", since if pressure drops suddenly, that means DEMAND for fuel has jumped up, manifold vacuum drops, and the damper opens to allow more fuel flow into the rail. It's not much different than the return type system, except it works BACKWARDS: instead of closing off the return port to get more fuel, it opens the INLET line (the only line there), to admit more fuel volume until demand drops, inertia loses it's grip, more movement out of the tank happens, and this type of repeating process goes on and on.

      Apparently, something moved Ford to re-work the returnless, but not go away from it, by quitting trying to control rail fuel flow volume in this way, and rather began controlling the volume (and therefore the pressure) by controlling pump speed, I guess in 2004, maybe. Mine has it, '04. Relief valve in tank, never opens under normal circumstances. It's setting is higher, I've heard about 100 psi, again this to protect the pump, but maybe more importantly to "cover-ass" for failure of either the rail Fuel Pressure and Temperature Sensor (which "tells" the Pump Driver Module how fast to run the pump) or failure of the Module itself. Either would leave the vehicle dead in the roadway.

      So, PCM senses such failure, electrically of course, bypasses the sensor and module both, and runs the pump full-bore at 100 psi, the engine might smoke like hell, and sure pollute, but not kill the vehicle, which might be more dangerous than the Environmental Lawyers.

      Now if you guys believe this load of bullshit, I'll qualify to charge double tomorrow! imp
       
    14. donalds

      donalds Elite Explorer

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      $250 ouch:eek:

      A fuel pulsation damper is a device used to regulate the oscillation of fuel caused by the injectors opening and closing and smooth this out. Sometimes referred to as a FPD. At this time I do not have a diagram to show you, so you will need to use your imagination as I describe it the best I can. Sorry.

      The damper uses a diaphragm to absorb pulses or waves in the fuel. If you could picture what would happen if you were to have a large beach ball in a pool and "bounce" the ball half under the water, let it come up and repeat several times. Waves would form. The injectors opening and closing against the pressure sent by the pump causes the same waves in your fuel system. The damper's diaphragm is used to absorb these waves and smooth the fuel delivery.

      Many people say you do not need the pulsation damper, other will tell you that you do. The ones that say you do not need it more than likely either heard of someone or themselves had an engine fire due to the pulsation damper failing. The ones that say you do need it may have heard stories of an injector failing because there was no pulsation damper. The failure of the injector was caused by the fuel hammering the injector so hard that it failed. I have never personally seen an injector in this state (remember we se A LOT of injectors) and still feel this is an urban legend. If you happen to have an injector in this state, please let me know. I would LOVE to test and analyze it.

      If you are running an aftermarket fuel pressure regulator, more than likely there are dampening capabilities built into the regulator. I know for a fact that Aeromotive regulator use this technology but I am not sure about others. Mounting the aftermarket regulator as close to the fuel rail as possible will eliminate any need for additional dampening. The Aeromotive units will regulate the flow by creating a stable and smooth flow.

      In short, a pulsation damper does serve a purpose, but is not "nesecary". Many cars like the Mazda RX7 are equipped with a fuel pulsation damper that is prone to failing and causing an engine fire. If you plan on retaining the FPD you must keep an eye on it. Replace it BEFORE it fails and you loose your car to a fire.

      Source...Fuel Pulsation Damper

      s-l400.jpg
       
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    15. shucker1

      shucker1 Elite Explorer

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      Well as we drift further off topic I think I mentioned the same thing in Post #61?
       
    16. danno2944

      danno2944 New Member

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      Wow, thanks to everyone for all the information. I have been on many other forums where I would just be told to use the search function, lol.

      The weather is about -15 Celsius last few days and the starts have been interesting.

      Block heater was on for first start so the cold fuel pump was seemed to lack much pressure as it started right up but a low Start up rpm, with a pre prime. Normally it will start and rev to bout 1500 than go down, this was more like 1200 rpm.

      Next start after, it sat for two hours in cold, no pre prime, and I had to crank for a while which is not normal at all, but started right up again at a low rpm again though.

      I did drive about 60kilometers at about 60mph the whole way, but no bogging or loss of power. Responsiveness hasn't been the best for ages imo, so that part is tuff to tell.

      I'm thinking I should just order the Bosch...just changed my fuel filter a few thousand miles ago, would you bother with a new one again for pump install?
       
      Last edited: November 8, 2018 at 4:13 AM
    17. donalds

      donalds Elite Explorer

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      As did I in post #56 seems like there was some confusion so I posted an article ....sorry:bounce:

      I would change the filter cheap insurance
       
      Last edited: November 8, 2018 at 5:01 AM
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    18. imp

      imp Elite Explorer

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      @shucker1

      One could add that such a buffering device in hydraulics is called an "accumulator". Exactly the same as those of you having a water-well, with a pressure tank above ground. Most contain a bladder sealed around it's OD, with air pressure driven in and held on top of it. Water from the well enters from the bottom, pushes the air upwards, compressing it, pump shuts off, air press. = water press., faucet opens somewhere, air pushes water down and out, pressures drop, until pump turns on, cycle repeats. We had a 10-gallon hydraulic accumulator which operated at 3,000 psi! Interesting machine attached. Off thread. imp
       
    19. roscoe 0202

      roscoe 0202 Elite Explorer

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      I would guess imp is right with the accumulator when you push the throttle to max accumulator supplies fuel until the flow from pump catches up
      roscoe
       
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    20. imp

      imp Elite Explorer

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      @roscoe 0202

      What it does really is dump fuel volume into the system out of it's little storage area, to try to keep fuel pressure as constant as possible. Impossible, with the way some folks drive, so the thing progressed to pump speed control, in '04 I think. imp
       

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