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Thread: Fuel pump failure?

  1. #11
    Senior Member
    Join Date:  May 2011

    Location:  Norton, MA

    Posts:    825

    My VIN:    767 (3.0L EFI/EDIS)

    Purchased in August 2013, but the it was only used for 5-10 hours of engine testing until January of this year, when it was finally back on the road. Since then I've put around 2000 miles on it, but I don't know for sure -- my car breaks angle drives within 5 miles, even though testing individual components and combinations of components along the speedometer chain all work perfectly. I have the hardware for a hall sensor based speedometer installed, but I need to build a UI for it still.

    Point is, not too many miles on the pump, but it's six years old, and DMCH may have made improvements since then. In another thread it's claimed there's a 1% to 2% failure rate. I've also had to replace the water pump (which was new when I installed it four or five years ago, and has only 2000 miles on it) and alternator (ok, that one was used) recently as well, so who knows.

    -- Joe

  2. #12
    Administrator Ron's Avatar
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    Location:  North GA

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    Ya never know, when one sits for years; Ds particularly. They punish you if you don't drive them every day.

    6 months is a long time for a fuel pump to sit with fuel in it.
    (Same for a, however slightly, used WP ;-)

    With all you have done, it sounds like you are rounding 3rd base.

  3. #13
    Senior Member
    Join Date:  May 2011

    Location:  Norton, MA

    Posts:    825

    My VIN:    767 (3.0L EFI/EDIS)

    I replaced the pump with a $50 one from Herko that is an exact physical match (as mentioned here: http://dmctalk.org/archive/index.php/t-3824.html ). It was a huge pain to get the plastic hose on and I had to resort to a hose clamp after applying too much heat to one end, but I finally got it, reassembled the unit, connected it and... nothing. Just a soft click. Damn it.

    I went to OíReillyís and picked up a Ď98 Tahoe pump for $140, which Josh said he used in the other thread. Plugged it in and it runs just fine. I have some questions about it, though:

    The sender arm rises higher than the DMCH one does, which means the tank wonít read full. Iím guessing I can bend the arm to fix that until itís range of motion matches the old pump? Or just not care that the gauge never reads full.

    I also have to figure out how to orient the pump so that the sender arm sits in the tank properly, since it points in a different direction than the DMCH one, so Iíll have to reroute the lines a little.

    The base of the pump is taller. I still need to make sure it actually fits in the tank, but since it worked for Josh Iím guessing it will be fine.

    I want to take the car somewhere tomorrow, so hopefully I can get this installed today.

    ó Joe

  4. #14
    Senior Member Bitsyncmaster's Avatar
    Join Date:  May 2011

    Location:  Leonardtown, MD

    Posts:    7,491

    My VIN:    03572

    I run the Tahoe pump and the sender almost gives you the normal 240 ohms at full but I think the DMCH ECU unit is set up to read the 240 ohms at empty. Not sure but that is what I remember when designing my fuel gauge circuit.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  5. #15
    Senior Member
    Join Date:  May 2011

    Location:  Norton, MA

    Posts:    825

    My VIN:    767 (3.0L EFI/EDIS)

    I'll eventually do a digital dash and have the sender go into an Arduino.

    But in the meantime, I did a test and I'm seeing exactly as you described -- ~40 ohms when full on the DMCH sender, but ~240 on the Tahoe sender. I guess I'll have a backwards sender until I get around to doing my dash.

    Thanks for the info -- that would have thrown me off for a bit.

    How did you orient your unit in the tank so that the float sits properly? To match the DMCH setup I'd have to have the fuel line connections point at the back of the car, which is probably fine (the lines would run between the body and the tank), but I'm wondering if there's a better angle.

    Thanks!

    -- Joe

  6. #16
    Senior Member
    Join Date:  May 2011

    Location:  Norton, MA

    Posts:    825

    My VIN:    767 (3.0L EFI/EDIS)

    Silly question: can I simply swap the wires on the sender to get it to read the other way? My knowledge of variable resistor is JUST enough to both say that it should work and say that it shouldn't work.

    -- Joe

  7. #17
    Senior Member
    Join Date:  May 2011

    Location:  Norton, MA

    Posts:    825

    My VIN:    767 (3.0L EFI/EDIS)

    I came up with a solution. The Tahoe variable resistor rotates from left to right. I was able to flip the float arm so that the sensor now rotates right to left. That should make the gauge read correctly. Still have to actually put it in the car and try it out.

    -- Joe

  8. #18
    Senior Member Bitsyncmaster's Avatar
    Join Date:  May 2011

    Location:  Leonardtown, MD

    Posts:    7,491

    My VIN:    03572

    Quote Originally Posted by jangell View Post
    I came up with a solution. The Tahoe variable resistor rotates from left to right. I was able to flip the float arm so that the sensor now rotates right to left. That should make the gauge read correctly. Still have to actually put it in the car and try it out.

    -- Joe
    That should work.

    I took my pump apart to make the unit sit centered under the mounting hole (rotate it into other holes). It would have worked I think with the offset pump (Tahoe unit) but another user suggested to do that. Doing that I had to pull a hose and re clamp it. The float arm has to go to the back of the tank to give it room to move.
    Attached Images
    Last edited by Bitsyncmaster; 08-01-2019 at 02:19 PM.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  9. #19
    Senior Member
    Join Date:  May 2011

    Location:  Norton, MA

    Posts:    825

    My VIN:    767 (3.0L EFI/EDIS)

    Looks like we have slightly different pumps ó mine is plastic, more like DMCH, but otherwise I expect theyíre the same.

    Pointing the sender arm towards the back ignore the car works well for me, since Iíve flipped the arm. The fuel connections now point towards the passenger side of the car, and I was able to slip the hoses between the tank and the floor of the trunk. Not that I really expect to be able to get the access cover back on over it...

    I was going to disassemble my assembly, but I found that the three rods had been widened at the end so that it wouldnít easily come apart, so I decided to stick with the stock alignment.

    My current problem is getting the clamp in to hold the pump to the tank. Itís lije it doesnít want to seat quite far enough down, or the rubber gasket is keeping it from pushing down far enough.

    Thanks again

    ó Joe

  10. #20
    Senior Member
    Join Date:  May 2011

    Location:  Norton, MA

    Posts:    825

    My VIN:    767 (3.0L EFI/EDIS)

    Hereís a picture of the pump as I try to get the clamp seated.


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