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Main Fuel Pump Will NOT Run..........(ECU Failure???) 700 1989

posted by  Franzen on  Sun Jan 13 16:59 CST 2002
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The main fuel pump on my 1989 740 GL will not run. The car was running fine until yesterday, when I shut it off for about 5 minutes to drop off some packages at the Post Office. When I tried to restart it, I got nothing but the starter motor trying its best to turn the engine over.

Having owned many older 240 models in the past, I knew the fuel pump relay can be troublesome and therefore keep a spare in my glovebox, but it was of no use. I even jumpered the 30 and 87/2 pins in the relay board and the pump still will not run. So I replaced the pump with a working spare I had and still nothing.
Does anyone know if the car's computer plays any role in controlling main fuel pump operation? It won't even activate when my key has been turned to the number II position on the ignition switch, allowing the pump to turn on for a few seconds and go into its little self-priming mode.

Any help with this problem will be greatly appreciated and thanks in advance!!!








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    Main Fuel Pump Will NOT Run..........(ECU Failure???) 700 1989

    posted by  someone claiming to be stevek on  Sun Jan 27 16:45 CST 2002 [RELATED]

    If I'm not too late with this suggestion, check for spark. I recently had the hall effect (engine speed) sensor fail in my '86 740GLE. This left me with no start and no fuel pump operation no matter what I tried to jumper. After a few hours of frustration, I decided to go all the way back to the beginning of basic diagnostics and found the problem within 20 minutes. Brace yourself, parts in this group are spendy.








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    Main Fuel Pump Will NOT Run..........(ECU Failure???) 700 1989

    posted by  rhaire on  Mon Jan 14 03:33 CST 2002
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    last visit: Mon Aug 4 10:16 CST 2014
    [RELATED]

    Chris is right. You have the worst ECU from Volvo, the trouble-prone 561 (or 951) used in the non-turbo cars from 89-on. It is a possibility, whereas an 89 turbo ECU, no way it is failing. In my opinion you need to have a spare ECU on hand, spare AMM and a couple of relays. It is crazy not to and to be stuck with a high repair estimate. The good news is market on a 951 or rebuilt 561 is $150 or so on Ebay. Brian Leppin guarantees them for 6 months. Whether your is the cause or not, given the history of that ECU, I would (and do) always have a spare.








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    Main Fuel Pump Will NOT Run..........(ECU Failure???) 700 1989

    posted by  MKovic on  Mon Jan 14 01:49 CST 2002
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    last visit: Tue Nov 10 08:16 CST 2009
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    Try jumping number 1 fuse to number 11. This should make the pump run in any case, provided that the pump it self if good.








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    Main Fuel Pump Will NOT Run..........(ECU Failure???) 700 1989

    posted by  chris herbst on  Sun Jan 13 17:16 CST 2002
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    last visit: Mon Oct 20 20:32 CST 2014
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    You can always hardwire the fuel pump to get the car running to see whether or not it's something else.

    The computer in your car is more prone to failure. I think that there is an EPROM upgrade for that computer as it is a typical failure mode not to have a fuel pump.

    The computer does control the fuel pump in the manner you described. It is a likely failure.
    --
    Chris Herbst, near Chicago, IL. 93 940, 91 240, 90 240, 88 740, 87 240








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    Main Fuel Pump Will NOT Run..........(ECU Failure???) 700 1989

    posted by  Rtilghman on  Sun Jan 13 17:08 CST 2002
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    Not sure if the ECU plays a role, but IMHO this sounds more like a straight electrical failure. Do you have a bad ignition switch (perform the jiggle test on the keys, does the dash ever fail when you turn the car on?)? Have you check the wiring to and from the primary pump? Checked the ground?

    No activity at all despite replacing the unit and replacing the relay leads me to think its a basic problem... like no juice at all. Also, did you pull the relay board and check teh wiring underneath to make sure all the wires are cinched up tight to the board? Did you check the fuse?

    BTW, sounds like you carry an amazinbg number of "spares"... paranoid or just experienced? ;)

    -Rick








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      Main Fuel Pump Will NOT Run..........(ECU Failure???) 700 1989

      posted by  Vroom on  Mon Jan 14 01:19 CST 2002
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      He mentions carrying A(one) spare relay, that's smart. You call that an amazing number? and use the word paranoid????
      --
      88 765 w/2stage boost & G-valve @ 14 psi








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        Main Fuel Pump Will NOT Run..........(ECU Failure???) 700 1989

        posted by  Rtilghman on  Mon Jan 14 06:31 CST 2002
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        No, he mentions carrying a spare fuel relay and a spare fuel pump. I don't know many people that drive around with a spare pump in the boot, but that sounds a little hardcore.

        Of course, I also winked at the end of my message. Maybe you missed that or don't know what it means? A wink means teasing/playing. A short list of the car parts in my car, including various relays, fuses, fluids, and assorted parts would run to about 30 or 40.

        -Rick








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          Main Fuel Pump Will NOT Run..........(ECU Failure???) 700 1989

          posted by  someone claiming to be Pihl on  Mon Jan 14 09:48 CST 2002 [RELATED]

          I have a rear axle as a spare in my trunk!







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