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Rear diff Service questions

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

^^Searches ExplorerForum.com^^
  1. 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.
     
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  3. imp

    imp Well-Known Member

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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
     
  4. 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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  5. 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?
     
  6. danno2944

    danno2944 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
  7. 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
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  8. imp

    imp Well-Known Member

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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
     
  9. 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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  10. imp

    imp Well-Known Member

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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
     
  11. danno2944

    danno2944 Member

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    Managed to change the rear diff fluid and the bearings and seals were in great shape so I didn't bother changing them. The diff was also in great shape. Found a broken diff vent tube.
    The vehicle coasts much better when I'm off the accelerator with the fresh gear oil and Hopefully my fuel economy improves a bit as well...

    Problem is the sound from the drivetrain that I concluded was a worn axle bearing was not so worn, now I have no idea where the sounds coming from.

    The sound is considerably louder while accelerating rather than decelerating particularly at moderate speeds and sounds like a rubbing,grinding noise each time whatever it is rotates a full revolution. It rubs at same place consistently at a consistent speed and the rubbing noise increases during acceleration proving it is rubbing,grinding in same place each revolution.

    Any suggestions appreciated..
     
  12. Mbrooks420

    Mbrooks420 High Voltage. Elite Explorer EF Vendor

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    Pinion bearing?
     
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  13. danno2944

    danno2944 Member

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    How do you inspect the driveshaft bearings, etc, the transfer case output to driveshaft in the rear has a fair bit of play, more than I would except.
     
  14. imp

    imp Well-Known Member

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    @danno2944
    That bearing should have no perceptible play. Are you certain you are not feeling play in the U-joints? The T-case bearing requires disassembly. Job fairly straightforward for one mechanically-inclined, even if first-time T-case mechanic. It's not very heavy, either. I hefted mine down with my two hands. imp
     
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  15. Runnin'OnEmpty

    Runnin'OnEmpty Well-Known Member

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    [QUOTE="donalds, post: 3732778, member: 288217]
    .............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.
    [/QUOTE]
    Wish I hadn't read this, won't be able to sleep tonight.....

    If the FPD fails, does 60 psi fuel spurt through the vacuum hose to the intake manifold, where it explodes, blows the hood off and immolates the driver/passengers?
     
  16. Mbrooks420

    Mbrooks420 High Voltage. Elite Explorer EF Vendor

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    I’m sure this is an extremely rare, or non-issue, or it’d be recalled like the cruise control switches
     
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  17. donalds

    donalds Elite Explorer

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    Pinion bearing preload can be fixed with a seal crush sleeve and bearing s if the barring s are even needed
     
  18. danno2944

    danno2944 Member

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    Could you explain this in more depth please.
     
  19. donalds

    donalds Elite Explorer

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  20. Mbrooks420

    Mbrooks420 High Voltage. Elite Explorer EF Vendor

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    My Mounty had a little bit of diff noise. I had a pretty badly leaking pinion seal. I kept the diff filled, and eventually replaced the crush sleeve and seal. After the seal and a refill it quieted down to the point I’m not concerned with finding a replacement axle at any point in the future.
     
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  21. danno2944

    danno2944 Member

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    Well the truck won't Wouldn't start last night, but it made it through some of of the coldest few months I have ever seen.

    Still original fuel pump 180000, was hesitating/stumbling a bit at idle a lot yesterday, and was less powerful on highway drive now that I think about it.

    Started ran for 2 seconds died. Turned over- Started ran one second died, turned over wanted to start but wouldn't.
    The pre prime on the pump from its normal whine definitely sounds different, less powerful.


    Running for rental pressure tester now.

    Quick search for Pre prime psi for the model in signature should be 40psi, is that correct?

    Any other tips appreciated, pretty sure the pumps done. Very lucky to be parked at home I reckon.

    Not really sure on testing FP on a no start, I need to still pull relay and turn over to relieve most of the pressure?

    Also Need to grab suction hose, 8ft of 3/8 is sufficient? Or if the pump still has some psi since it does actually make noise still not broken totally(in theory) could I just disconnect line and pump it out.
     
    Last edited: March 23, 2019






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