Fuel pump issues...

Discussion in 'General Motoring' started by DerrelCopeland, Nov 13, 2005.

  1. I have a 1990 240DL that has sat for a couple years. The gas turned to
    varnish so I had the tank cleaned, bought new fuel pumps, sending unit,
    gas cap and a few other small items to complete the repairs.

    My problem is that I'm not getting voltage (current) to the pumps. I
    replaced the replay a few years back and it clicks when the key it
    turned to position II. I also have an extra LH-Jet computer. The car
    has ran in the past before any of the repairs were done, and nothing
    has changed other than it sitting for so long.

    I need ideas as to what to check. I've read a lot of posts here and
    tried most of the things that applied, but haven't found a solution.

    Any help is greatly appreciated.

    Fossil Rock
     
    DerrelCopeland, Nov 13, 2005
    #1
  2. The relay can click and still not supply power. The typical problem is
    cracks in the solder connections on the circuit board inside. If you have
    good eyes and good light the cracks are visible as dark hairlines around the
    solder meniscus on the leads of components, especially the heavier ones.

    I don't know what sort of fuses your '90 has, but if it has the round fuses
    you probably should take them out and buff up the contact surfaces on the
    fuses and holders with Scotchbrite or similar. Also check over the
    connections at the battery cable - in 700 series cars a few have had a wire
    corrode completely in two and cause the fuel pump not to get power (although
    the fuel pump relay doesn't cllick under those conditions). Still, worth a
    quick peek.

    Mike
     
    Michael Pardee, Nov 13, 2005
    #2
  3. DerrelCopeland

    zencraps Guest

    How do you know you are not getting voltage to the pumps, have you
    tested with a test light or VOM?

    If so, and if it shows voltage from the positive wire, check and see if
    the black wire has a good ground; if it doesn't, check and correct the
    ground fault.
     
    zencraps, Nov 14, 2005
    #3
  4. The relay is still in new condition. I checked for bad solder joints
    but everything looks fine. My next question is; what triggers the
    replay to send current to the pumps. I crossed 30 & 87/2 and the
    voltage showed up at the pump leads. When the relay is installed and
    the key is turned to the II position the left coil energizes but the
    right one (30 & 87/2) does not.

    What energizes the other (right) coil?
     
    DerrelCopeland, Nov 14, 2005
    #4
  5. I'm using a DVOM to test with. New copper fuses, cleaned ground
    connections. I'm a little confused as to what could be preventing the
    replay from energizing the side that feeds the pumps.
     
    DerrelCopeland, Nov 14, 2005
    #5
  6. I think I may have discovered my problem.... stupidity :(

    I was using the spare LH-Jet which was not mounted to the car. I
    plugged the original back in, which is still mounted, and both sides of
    the relay are energizing now.

    Thanks for the replies and keep your fingures crossed for me.
     
    DerrelCopeland, Nov 14, 2005
    #6
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