Stalling problems -- what's more likely to fail -- fuel pump relay or fuel pump

Discussion in 'General Motoring' started by byrocat, Sep 23, 2005.

  1. byrocat

    byrocat Guest

    I've been chasing this around in circles. I've replaced the cam
    position sensor on my 1993 850, and still keep stalling. Four
    non-starts after short trips plus two died-on-road.

    The last non-restart had me trying to listen for the sound of the fuel
    pump going. Ever tried that at a busy gas station and you're the only
    person in the car.

    In my attempts at the last one, I found that I got a trickle of fuel
    for some start attempts. Just enough to have the engine turn over at
    idle but it would die instantly when I touched the gas pedal. Engine
    was running just a touch ragged but not excessively so.

    The guys at the shop are talking fuel pump, but I'm thinking relay
    first because everyone here who has been having similar problems on
    their 1990's 850 and 960 cars have been commenting that the relay goes
    more than the fuel pump.

    Also, the books that I have do not show where the 850 fuel pump relay
    is located.

    Is it in the box along with the fuses but hidden up against the dash

    Thanks muchly.....
    byrocat, Sep 23, 2005
  2. byrocat

    Mike F Guest

    The trickle of fuel is a clue, if the pump is working up to spec fuel
    should shoot out.
    According to my data book, fuel pump spec is 103-160 liters/hour at 13V,
    87-145 at 12V and 70-128 at 11V.
    If your pump is nowhere near this, I'd change it first.

    The 93 is a bit of an oddball, in that it has an older fuel system than
    94 and newer. The following applies to 94 and newer, but should mostly
    apply to your '93.

    The fuel pump relay hides under the cover beside the main fuse box,
    number 103.
    There is also a main relay, mounted above the rad, beside the fan
    relay. It's usually gray, 4 round pins.

    If you want to check the relays, splice a test bulb between the
    following wires and ground:
    fuel pump relay - red wire over the cover over the fuel tank sending
    unit in the trunk
    main relay - green wire at the relay

    Mike F.
    Thornhill (near Toronto), Ont.

    Replace tt with t (twice!) and remove parentheses to email me directly.
    (But I check the newsgroup more often than this email address.)
    Mike F, Sep 23, 2005
  3. byrocat

    pepe256 Guest

    ive been having that problem with mine i drive a 86 740 gle try
    disconnecting the amm censor wires when its running and if that doesnt do
    anything you may be getting a bad connection to the amm or it could be bad
    which is not a good thing. you do have an amm dont you
    pepe256, Sep 23, 2005
  4. byrocat

    James Sweet Guest

    Usually the relay is the cause of stalling, either can be the cause of
    no-starts. Bad pump can burn out a good relay too.
    James Sweet, Sep 24, 2005
  5. byrocat

    Randy G. Guest

    The computer has a default "Limp" mode that will cause the car to run
    very rich and poorly with the AMM disconnected. You should avoid
    connecting or disconnecting anything that is part of the computerized
    system while the ignition is on.

    __ __
    Randy & \ \/ /alerie's
    '90 245 Estate - '93 965 Estate
    "Shelby" & "Kate"
    Randy G., Sep 24, 2005
  6. byrocat

    byrocat Guest

    I'm going to have to order a new relay and tell the shop "install!"
    forcefully. The tech keeps saying that he sees more fue pumps than
    relays. However, the price differential on the job (at least ten times
    the cost of the relay for the fuel pump makes me a bit suspicious....)
    byrocat, Sep 27, 2005
  7. byrocat

    James Sweet Guest

    Well it's easy enough to jumper the relay for testing purposes, if the shop
    hasn't thought to try this already then perhaps you should find another
    James Sweet, Sep 28, 2005
  8. byrocat

    z Guest

    Yeah, you got that right. The rule for repair techs is go for the most
    expensive possibility first, and if that doesn't do it, then you can
    afford to eat the cost of the cheaper fix if you have to try it next.
    All relays go bad often, although as the guy said, your seeing a
    trickle of fuel puts a different spin on things. Could be clogged fuel
    line, filter, in tank inlet filter. (Last time a mechanic got the
    (wrong) idea that my fuel problems needed a new pump, it turned out
    that the in tank inlet on the new pump was pre-collapsed from the
    factory, so he had to replace it on his own dime. haha).

    Meanwhile, I still can't figure out what's with my 240. Cranks but
    won't start; mostly when it's been standing an hour or two. Works fine
    first thing in the AM, 8 hrs later after work, or if it's only been
    standing half an hour. Starts fine if I roll down a hill and drop it
    into second, or give it a shot of starting juice. So I replaced the
    relay; and nothing changed. I can hear the pump whining when it won't
    start. ??
    z, Sep 28, 2005
  9. byrocat

    Randy G. Guest

    When it won't start:

    1) Check the battery voltage and the coil voltage when the motor is
    cranking. The fact that it can bump start but can't start when
    cranking is a clue.

    2) It could be that the starter is drawing too much current and/or the
    battery is going weak and has difficulty starting a hot motor that has
    been sitting and heat soaking.

    3) Check that the coil is getting voltage when cranking. I had a car
    that had an ignition switch go bad and would not supply voltage to the
    ignition system when the key was in the start position but did when
    the key was in the run position. Do the same with the Ignition Power
    Stage. Do the same with the fuel pump relay.

    __ __
    Randy & \ \/ /alerie's
    '90 245 Estate - '93 965 Estate
    "Shelby" & "Kate"
    Randy G., Sep 28, 2005
  10. byrocat

    z Guest

    Well, pretty close! It was a cracked distributor cap. Bleeding off
    enough juice to be iffy ignitioning when it was also cranking. Don't
    know how it relates to the half hour/1 hour/8 hour thing, but that's
    the mystery of life. Now I have a spare relay.
    z, Sep 28, 2005
  11. byrocat

    Randy G. Guest

    Aren't simple solutions great! Restates the importance of putting the
    cap and rotor on the regular maintenance list for all of us.

    __ __
    Randy & \ \/ /alerie's
    '90 245 Estate - '93 965 Estate
    "Shelby" & "Kate"
    Randy G., Sep 28, 2005
  12. byrocat

    z Guest

    The dumb part is that the only other time a car wouldn't start on me
    was ten years ago with a Civic, i kept focusing on the fuel system but
    it turned out to be...... a cracked distributor cap.
    z, Sep 30, 2005
  13. byrocat

    byrocat Guest

    I took the car into the cdealer on an unrelated problem -- the recall
    on the gas tanks for 1994 850's and others -- check the
    website for recall notices and have your VIN handy to see if you're a

    Had the shop check out the relay versus pump question, and got a third
    opinion: <quote> Technician believes that it would be the speed sensor
    over the fuel pump relay.<unquote>

    Four question marks exploded from my forehead, and I went "say what?"

    Does anyone have an idea what is being talked about.
    byrocat, Sep 30, 2005
  14. byrocat

    z Guest

    ?? Unless they mean the connection from the relay to the ignition
    system that shuts the FI down if there is no ignition pulses?
    z, Oct 1, 2005
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