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Thread: Fuel pump noisy when been in traffic for over an hour

  1. #1
    Member Chris_Von_Bron's Avatar
    Join Date:  May 2011

    Posts:    67

    My VIN:    05255

    Fuel pump noisy when been in traffic for over an hour

    I've a 'different' setup now so that there is no metering head and no hot unused fuel being returned the tank..... yet today after over an hour in crawling traffic, I could hear the fuel pump buzzing louder. I pulled over and opened the fuel cap and the hiss/vapour release helped (as well as a fresh top up of nice cold fuel).

    I'm sure that this never used to happen years ago to the extent it has been more recently (i.e. the same as when it was stock compared to eliminating the return of hot fuel), but on days crawling in traffic for over an hour I still ultimately hear the fuel pump buzz louder and despite the measures taken below I'm still having the following issues:

    So far I've:-


    What I've not changed
    fuel gauze on the end of the pickup hose as it seems okay, looks clean with no visible debris in the gauze, but maybe it is partially blocked and only noticeable when the tank is hotter?

    What else is there?
    • neoprene around the coolant pipes that run under the tank
    • neoprene dam to help insulate it from hot air from the radiator


    To be clear, the cooling system is running perfectly, this is purely hot tank scenario and when the noisy pump can't handle or take the amount of fuel needed, bunny hopping, stuttering and the car cutting out are what you're faced with until the tank/fuel have cooled down.

    Any thoughts/suggestions are welcome. For those of you that sit and crawl on the freeway in the hotter states like Texas etc surely must have found how to solve this?
    Last edited by Chris_Von_Bron; 03-20-2018 at 06:00 PM.

  2. #2
    Senior Member Bitsyncmaster's Avatar
    Join Date:  May 2011

    Location:  Leonardtown, MD

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    My VIN:    03572

    That is interesting that you still get pump buzz and don't have hot fuel returned to the tank. I was convinced the returned fuel was the problem (it probably is some of the problem). I made a cooler for that returned fuel.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  3. #3
    Senior Member Citizen's Avatar
    Join Date:  Jun 2011

    Location:  Houston, TX

    Posts:    720

    My VIN:    3341

    I am in Texas and when I first got the car (about 12 years ago) I had no problem in June/July/August, 98+ degrees, stop and start traffic. Then, a few years later it started doing just what you described, almost exactly. My solution was to:

    • 1- Convert to the new (at the time) DMCH integrated fuel pump
    • 2- Fabricate a hot-air dam and install it (at the time, I didn't know you could buy one from anywhere)

    I have not had a problem since. But to be fair, in the last few years, I've taken active steps to avoid stop-n-go traffic on super hot days. And in fact, I haven't put very many miles on the car since then, not on purpose, it just worked out that way.

    It's good to know removing hot fuel return didn't solve the problem. I had always suspected it was truly the hot air from the radiator causing the problem, and now with your real-world experience, I think it looks like even more that is the case.

    Thomas

    ...
    Keeper of the DeLorean Owners Directory, at www.DeloreanOwnersDirectory.net

  4. #4
    AKA "The Goat" Michael's Avatar
    Join Date:  May 2011

    Posts:    3,763

    Quote Originally Posted by Chris_Von_Bron View Post
    [*]new, higher powered Bosch fuel pump
    There you go. The new Bosch pumps are not quite the quality they were several years ago. They have been seduced by the dark side of themaking things cheaper while charging more and hoping brand loyalty and name recognition makes up the difference force.

    I had the same issue and got a new pump which fixed it. I replaced it with a Bosch and it seems to be OK but I now keep a spare in the car(generic brand) just in case.
    Last edited by Michael; 03-20-2018 at 07:14 PM.

  5. #5
    EFI'd dn010's Avatar
    Join Date:  Jul 2011

    Location:  Florida: Pinellas County

    Posts:    1,822

    My VIN:    5003

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    Explain your setup? If there is no fuel return line, you're restricting this new "high power" pump to a certain PSI with no relief. The pump will continue to pump as much as it can and have no way to send that additional pressure back into the system. For instance, if it's pumping at 100PSI and you're regulated at 60, and have no way to resolve the other 40, what do you expect? The pump will run hot if it cant efficiently push against the pressure.
    Last edited by dn010; 03-20-2018 at 08:28 PM.
    -----Dan B.

  6. #6
    Senior Member Josh's Avatar
    Join Date:  Mar 2013

    Location:  SK, Canada

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    My VIN:    11408

    Club(s):   (TXDMC)

    Following. Here is my fuel system, yours should not be any different as far as I am concerned.

    I am using a fuel pump out of a 2000 chevy tahoe, works great and cheap and easy to source. Maybe less so in the UK...
    Attached Images

  7. #7
    Tweedledumber DCUK Martin's Avatar
    Join Date:  May 2011

    Location:  DeLorean Cars, UK

    Posts:    581

    You still have a return line and it's still bringing heat back from the engine'e injector rails. Unless it's neoprene foam you've wrapped around the coolant pipes, it's likely helping the tank heat up, not hindering it. The tank sitting on top of the coolant pipes is still the dominant heating effect.

    Change the pickup filter. Filters are blocked by stuff you can't see. Just cos it looks clean does not mean it isn't restricted.
    Martin Gutkowski

    DeLorean Cars (UK)
    www.delorean.co.uk
    Twitter: @deloreancars

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

    Location:  Leonardtown, MD

    Posts:    7,492

    My VIN:    03572

    I have Hervey's "hot air dam" installed in my car before I installed my return line cooler. My pump would still buzz on a hot day.

    Here is my thread on my cooler.
    http://dmctalk.org/showthread.php?15...ht=fuel+cooler
    Last edited by Bitsyncmaster; 03-21-2018 at 06:50 AM.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  9. #9
    Delorean Guru
    Join Date:  May 2011

    Location:  Northern NJ

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    It seems once you get the pump noisy it gets noisy easily afterwards. Must be that once it gets noisy parts inside get worn and it gets easy to make the pump noisy again. The fuel can get pretty hot and if you have the original pick-up hose it softens from the heat and can easily collapse under the vacuum or kink. My answer was to put a long spring inside the pick-up hose. I got a long one that is used for a screen door. Seems to have solved the problem. The newer design that DMCH sells would be a great upgrade as long as it is more reliable but they seem to have had some problems with them. Much easier to install. The "old" design is like building a ship in a bottle! Easy to make a mistake installing it since you have to do most of it blind and with one hand.
    David Teitelbaum

  10. #10
    Senior Member
    Join Date:  May 2011

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    I have always wondered if a modern style of fuel cooler, as is fitted to most diesel common rail engines nowadays would be beneficial to cars that suffer from hot fuel return (not usually to much of an issue in the UK!) something like this as an example: https://www.ebay.co.uk/itm/Genuine-F...QAAOSw3v5YoUll
    As people may or may not know returned fuel from a common rail is very hot and these are fitted in one variation or another usually underneath the car to aid the cooling. I don't know exactly how or where it could be plumbed in but it may be an 'option'
    Chris
    Chris Williams #15768 Back on the road after 14 years. Ex#4584
    Worldwide DeLorean Owners Club: www.deloreans.co.uk Full colour DeLorean magazine shipped worldwide.
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