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Thread: burning through fuel pumps like crazy

  1. #1
    Senior Member smallclone's Avatar
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    Location:  FL

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    burning through fuel pumps like crazy

    OK so i live in FL, it gets fairly warm here.

    i drove the car 3 hours last weekend and started hearing the fuel pump struggling till then it wouldnt start. i had to push the car into the garage.

    replaced the pump this morning and the car was running like a champ... till this fuel pump started making noise and starting sputtering. got the car into the garage this time.

    im stumped.

    ive read our cars are notorious for killing pumps due to heat and also low voltage to the pumps themselves.


    can anyone suggest a way to test voltage going into the pump? (im a dummy)

    i took out the baffle too and found the strainer/filter was barely held in place by the hose and it fell apart in my hands.

  2. #2
    Senior Member Bitsyncmaster's Avatar
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    You want to check the pump voltage right across the two pump terminals. You will get a little voltage drop on each terminal due to wire resistance. What your checking is to see if the drop is more due to bad connections. Mine had a 1 volt drop due to bad connections in the two pin connector right at the pump. Of course you need to check that voltage with the engine running or the RPM relay jumpered.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  3. #3
    Senior Member
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    That sounds to me like you're starving the pump on the suction side. Either the pick-up hose is collapsing or something about the assembly in the bottom of the tank is blocking off the fuel from getting to the pump.

    Nice video here explaining how that assembly is supposed to be.



    Sept. 81, auto, black interior

  4. #4
    Senior Member DMC-81's Avatar
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    Iím all for originality, but unless you have a museum car, I strongly recommend upgrading to the all in one fuel pump module from DMC. I have had one in my car since I purchased it in 2013. I live in Florida too, and it has never missed a beat since then, even in 100+ degrees weather.

    Whether you have the new module or the old style, checking the condition of the electrical supply (both positive and negative) and the condition of the fuel tank and lines is of paramount importance.

    It looks like you have received great tips so far. Iíll add that I try to keep as full a tank as possible. I think this mitigates the characteristic fuel heating problem.
    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)

  5. #5
    Delorean Guru
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    A very good video. A couple of things to add. If the pick-up hose is soft and swollen it is prone to collapse under the vacuum the pump can make. I stick a long spring inside to hold it open. Use a spring they sell in hardware stores to close a screen door. The right length and diameter. Study ST-30-12/81 for the assembly too. If you remove the fuel sender unit you can see a little better inside the tank. Try to do this with the fuel removed and if there is any dirt or sludge remove it with Acetone where you have plenty of ventilation. If you are not up for "building a ship in a bottle" DMCH sells a pump/sender assembly that pops right in and doesn't require any assembly inside the tank. The main thing with the OEM set-up with the pick-up hose is that it CANNOT kink or collapse. If it does the fuel pump gets starved of fuel. Not only will that stop the motor, it damages the pump. The pump needs the fuel to cool it and lubricate it. Once it starts to make noise it is on it's way out. There should never be fuel inside the pump boot. If there is, the boot must be replaced or the leaking fitting fixed. The video did not show the cover boot installed. It should be installed and you have to thread the hoses through it. The baffle does not sit straight back centered in the bottom of the tank. As explained in the video there are two bumps that the tongue fits in between to position the baffle assembly correctly. Do not overtighten the stud in the bottom of the tank. It is possible to rip it loose. If you do you can attempt to re-install it by getting it VERY hot and placing it back into the tank being careful not to push it through the bottom. Just melt it into the plastic a little. Very important to get the fuel tank clean. If you see dirt or sludge in it you can figure it is throughout the fuel system. Once you are done make sure there are no leaks or you will get fumes inside the passenger compartment. As bad as this job looks it doesn't get any better removing the tank so just do it "in situ". Climb into the trunk (bonnet).
    David Teitelbaum

  6. #6
    EFI'd dn010's Avatar
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    I'd like to mention I've been here in Florida for 9 years, still using the original style pump and setup (the pump is $40 on ebay). I installed the 'hardened' pick up hose probably 15+ years ago so there is no collapsing. I do carry a spare pump but have never needed it. I've only been through 2 pumps in my 17 years of ownership, and one time wasn't even the car's fault - I took the pump out and used it to move a Volvo 780 around with bad gas thus damaging the pump. That pump still works and is the spare I carry.
    -----Dan B.

  7. #7
    Senior Member Christian Dietrich's Avatar
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    Quote Originally Posted by DMC-81 View Post
    Iím all for originality, but unless you have a museum car, I strongly recommend upgrading to the all in one fuel pump module from DMC. I have had one in my car since I purchased it in 2013. I live in Florida too, and it has never missed a beat since then, even in 100+ degrees weather.

    Whether you have the new module or the old style, checking the condition of the electrical supply (both positive and negative) and the condition of the fuel tank and lines is of paramount importance.

    It looks like you have received great tips so far. Iíll add that I try to keep as full a tank as possible. I think this mitigates the characteristic fuel heating problem.
    If its a bad connection and originality ain't important then cut out all the exterior connectors that are outside the car for the fuel pump and wire in weather pack connectors. When I bought my car I had a lot of bad connections just from slight oxidation and I cut everything out and soldered in weather pack connectors. Even on the connections for my cooling fans from DPI, all have a weather pack connector. My parking lights connector aswell! Better to be safe than sorry and the fact that I use my car as a daily driver I want to make sure that it was not going to have future problems

    Sent from my SM-N920P using Tapatalk
    Vin 11035 wide stripe, flat hood, 5 speed, Spec 1 exhaust, custom grey/black interior, custom lighting, custom stereo and custom alot of stuff!

  8. #8
    Senior Member smallclone's Avatar
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    heres what ive found.

    my car didnt have an inertia switch (lovely) and saw the pump and ground was just spliced together. i took those two connections and made a solid ground to a body bolt.

    i installed the hervey hot air damn and drove the car a bit.

    same issue.


    i think i know what it is, the butterfly part of the throttle body had bad springs and had a high idle because of it. i removed the springs and closed them off.

    the idle is now around 600 or so and purrs nicely but i think the low idle is too much on the pump.

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