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Thread: Fuel pump failures

  1. #41
    Delorean Guru
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    Even if you use a different pump, pumping hot fuel is going to be hard on it as opposed to cool fuel. Hot fuel is easier to cause cavitation in and that leads to the noise and higher wear in the pump. The fuel lubricates and cools the fuel pump. If it pulls in air or cavitates it increases the wear on any pump. Keeping the fuel cooler is the objective, not trying to get a "better" fuel pump. Some pumps may be more forgiving of cavitation and wear but it still is not a good situation. Insulation can help reduce heat transfer from the water pipes underneath. The air dam can reduce the hot air from the radiator and finally you can wrap a coil of pipe around the A/C accumulator to remove heat from the returning fuel. Once the pump gets noisy it is only a short time till failure. It also seems to get noisy when you don't have a full tank. I think there are 2 reasons for that. One, more fuel will take more heat to get hot (more mass) and 2, the pump is submerged so the noise is muffled, the pump is cooled, and the fuel is less likely to cavitate with a little bit more pressure from the fuel above the filter. Depending on your local climate, you may have to take more steps to minimize the problem of hot fuel. On most fuel injection systems the pump in the tank doesn't work very hard. All it is supposed to do is move the fuel out of the tank to another pump which puts the fuel under high pressure. In the Bosch K-Jet system the tank pump does it all and to a very high pressure because the fuel injectors are mechanical, not electric.
    David Teitelbaum

  2. #42
    Member jorge figueroa's Avatar
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    fuel pump failures

    Quote Originally Posted by David T View Post
    Even if you use a different pump, pumping hot fuel is going to be hard on it as opposed to cool fuel. Hot fuel is easier to cause cavitation in and that leads to the noise and higher wear in the pump. The fuel lubricates and cools the fuel pump. If it pulls in air or cavitates it increases the wear on any pump. Keeping the fuel cooler is the objective, not trying to get a "better" fuel pump. Some pumps may be more forgiving of cavitation and wear but it still is not a good situation. Insulation can help reduce heat transfer from the water pipes underneath. The air dam can reduce the hot air from the radiator and finally you can wrap a coil of pipe around the A/C accumulator to remove heat from the returning fuel. Once the pump gets noisy it is only a short time till failure. It also seems to get noisy when you don't have a full tank. I think there are 2 reasons for that. One, more fuel will take more heat to get hot (more mass) and 2, the pump is submerged so the noise is muffled, the pump is cooled, and the fuel is less likely to cavitate with a little bit more pressure from the fuel above the filter. Depending on your local climate, you may have to take more steps to minimize the problem of hot fuel. On most fuel injection systems the pump in the tank doesn't work very hard. All it is supposed to do is move the fuel out of the tank to another pump which puts the fuel under high pressure. In the Bosch K-Jet system the tank pump does it all and to a very high pressure because the fuel injectors are mechanical, not electric.
    gentleman 90% of the heat comes from the cooling tubes that pass under the gas tank.
    the other 10% comes from the radiator through the electric fans that heat the front top of the tank and the fuel pump.
    With this simple thermal protection drastically reduces the heat that is transferred to the tank and gasoline.

    It is very easy to test just have to measure with a thermometer
    so they can see the different temperatures of the tank with thermal protection and without it.

    51364628_2194182390637772_8732333231971500032_n.jpg50980890_2194182357304442_3267538366345773056_n.jpg50713257_2178710612184950_943280160864468992_n.jpg50440744_2178710542184957_6044630208093356032_n.jpg

  3. #43
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by jorge figueroa View Post
    gentleman 90% of the heat comes from the cooling tubes that pass under the gas tank.
    the other 10% comes from the radiator through the electric fans that heat the front top of the tank and the fuel pump.
    With this simple thermal protection drastically reduces the heat that is transferred to the tank and gasoline.

    It is very easy to test just have to measure with a thermometer
    so they can see the different temperatures of the tank with thermal protection and without it.
    I used two thermocouples. One on the line leaving the tank and one on the line returning. With a hot engine the return line was about 1.0 degree F higher. Now depending on how much return flow you get, that would add a lot of the heating.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  4. #44
    Member dvfr750f's Avatar
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    Update

    Hi ya'll. I am glad to se this thread is still active. I just wanted to update. After I made the mod way back when, I experienced no more frequent failures. I took the car to Va and drove it there. No issues. In 2016, I drove the car from Va to NM. It performed well. After leaving Amarillo and driving to ABQ NM I experienced a fuel pump failure, but I think that was b/c the tank was more than half empty for awhile. I had a spare and changed it roadside. She has been in storage these past few years but yearly, she starts right up. I keep the battery on a tender(outside the car).
    Has anyone updated to the NEWish DMC fuel pump system? I think that is my next course of action. I will be taking the Car to SC soon.
    Cheers

  5. #45
    Senior Member hippieman9's Avatar
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    Quote Originally Posted by dvfr750f View Post
    Hi ya'll. I am glad to se this thread is still active. I just wanted to update. After I made the mod way back when, I experienced no more frequent failures. I took the car to Va and drove it there. No issues. In 2016, I drove the car from Va to NM. It performed well. After leaving Amarillo and driving to ABQ NM I experienced a fuel pump failure, but I think that was b/c the tank was more than half empty for awhile. I had a spare and changed it roadside. She has been in storage these past few years but yearly, she starts right up. I keep the battery on a tender(outside the car).
    Has anyone updated to the NEWish DMC fuel pump system? I think that is my next course of action. I will be taking the Car to SC soon.
    Cheers
    I have the DMCH fuel pump/sender combo and love it. No issues, only suggestion is ditch the rubber lines that come with the kit and install nylon. And get a 90į return line fitting for the pump, donít know why it comes with a straight one... had mine for 10 months and 5,000 or so miles, no issues. Fuel gauge is much more accurate as well.

  6. #46
    Delorean Guru
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    For a while a lot of owners had problems with the unit holding rest pressure and in some cases they replaced or added a check valve. Some experienced problems with the sender for the gauge, inaccurate, intermittent or failed. It appears that DMCH went through versions or vendors and it must be better now since there seem to be fewer complaints about the units they are shipping now. It is a nice part but it is expensive. A lot simpler to install!
    David Teitelbaum

  7. #47
    Junior Member Quinn's Avatar
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    IMG_0092.jpg

    I just got finished installing a new DMC fuel pump/sender unit yesterday. I'm disappointed to see that the fuel gauge only reads about 80% on a full tank (see picture). Otherwise, the pump seems to be working fine. Not sure if I should give them a call on Monday and see if there is anyway to calibrate the sender.

  8. #48
    Senior Member DMC-81's Avatar
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    Quote Originally Posted by Quinn View Post
    IMG_0092.jpg

    I just got finished installing a new DMC fuel pump/sender unit yesterday. I'm disappointed to see that the fuel gauge only reads about 80% on a full tank (see picture). Otherwise, the pump seems to be working fine. Not sure if I should give them a call on Monday and see if there is anyway to calibrate the sender.
    Post number 4 in this thread may help:
    http://dmctalk.org/showthread.php?17...p-Sender-Combo

    By the way, welcome to the forum. Love the avatar. I grew up laughing at Bugs Bunny's antics... and I still do.
    Last edited by DMC-81; 05-05-2019 at 08:49 PM.
    Dana

    1981 DeLorean DMC-12 (5 Speed, Gas Flap, Black Interior, Windshield Antenna, Dark Gray)
    Restored as "mostly correct, but with flaws corrected". Pictures and comments of my restoration are in the albums section on my profile.
    2006 Dodge Magnum R/T (D/D)
    2010 Camaro SS (Transformers Edition)

  9. #49
    DMC Midwest - 815.459.6439 DMCMW Dave's Avatar
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    Quote Originally Posted by DMC-81 View Post
    Post number 4 in this thread may help:
    http://dmctalk.org/showthread.php?17...p-Sender-Combo

    By the way, welcome to the forum. Love the avatar. I grew up laughing at Bugs Bunny's antics... and I still do.
    Also be sure that the anti-static wire inside the tank isn't is keeping it from coming all the way up.
    Dave S
    DMC Midwest - retired but helping
    dswingle@DeLorean.com

  10. #50
    Senior Member Parzival's Avatar
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    Location:  Florida

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    Installed mine today, I haven't filled all the way up yet, but after driving around half full, its real nice to see that needle so steady! and when I first got it all back together and put only a few gallons in there, the gas light was on, and it was so stable and constant. Really nice!

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