1993 940 turbo fuel injector relay issues

Discussion in 'Volvo 940' started by s m via CarKB.com, Sep 4, 2005.

  1. Hi

    My 940 Turbo (4 cyl automatic) *was* working great ... until I brought it
    home from the seller's house :)

    Apparently the car would start then when at the stop sign, it died and would
    not start again. The car turns over and I was told it is likely the fuel
    injector relay (button, switch, or whatever it is). Any ideas on how to
    replace/repair it? Where is the fuel injector relay located? Is there a fuse
    attached to it?

    All ideas welcomed

    s m via CarKB.com, Sep 4, 2005
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  2. s m via CarKB.com

    Boris Mohar Guest

    It is likely a fuel pump relay. This is a white relay behind the ashtray in
    the center console. Remove it and if you are handy open pull it out of the
    case noting the way it came out. You should resolder the circuit board that
    holds two relays and you should also clean out the relay contacts. This can
    be done by folding as sliver of fine abrasive paper so that both sides can
    work the contacts. Hold the abrasive sliver with tweezers and work it in
    between the contacts. Either that or spend $50.


    Boris Mohar

    Got Knock? - see:
    Viatrack Printed Circuit Designs (among other things) http://www.viatrack.ca
    Boris Mohar, Sep 4, 2005
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  3. s m via CarKB.com

    Randy G. Guest

    Specifically, th VO;lvo relyas seem to have a penchant for cracked
    solder joints inside of them. Remove the relay, then open the case.
    Resolder each of the solder joints even if they look OK. If you don't
    know how to solder, find a fried who does. It isn't difficult. See:

    Generally, the contact points in a relay are plated. Once they get to
    the point of needing to be sanded, they need to be replaced. What
    happens is this- the contact points should be fairly flat with a large
    contact area. Often they are nt. The electricity arcs between them,
    and usually that's OK, but eventually the arcing canwear through the
    plating, or foreign matter gets between them and becomes carbonized.
    This can weld to the surface, or cause arcing on a very small ppint
    that wears through the surfact of the opposite contact. Whatever the
    case, the surface becomes pitted and the plating is lost. Once this
    happens, sanding and burnishing can give the relay a bit more life,
    but in all but the most benign cases, teh relay will eventuially fail
    again, and at greater frequency the more it is done.

    If the contact area looks ugly, try this- take a dollar bill and cut a
    strip about 3/8" wide off one edge. wet it with WD40 and then rub in
    some flour of pumice. it is a very fine abrasive. Then place this
    between teh contacts and pull it through. Repeat until the contacts
    are smooth and shiny. Clean the contacts up with alcohol to remove all
    traces of the WD40 and pumice. But ifyou do this it would be best to
    have a spare relay on order. You will probably need it- sooner or

    Bottom line- relays are a way for a small switch that can handle only
    small electrical loads to turn on and off something that takes a high
    current load. A relay does this mechanically with an electromagnet. A
    better solution is a solid-state relay which can have a life span of
    ten-fold or more over a mechanical relay. Hmm... I have a 10 amphere
    one sitting right in front of me... Hmmm.... Off to look at the wiring
    diagram! ;-)

    __ __
    Randy & \ \/ /alerie's
    '90 245 Estate - '93 965 Estate
    "Shelby" & "Kate"
    Randy G., Sep 4, 2005
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