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Thread: New owner with an ecu problem

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  1. #1
    Join Date
    Apr 2018
    Location
    Worcestershire
    Posts
    9

    New owner with an ecu problem

    Hi everybody
    I am new to Beat ownership having bought a type f from e-bay a couple of months ago. Since then I have been preparing it for a Mot. All was going well but now I need some help.

    I changed the battery yesterday (the one it came with was too big for the tray). Now the new battery is connected there seems to be a problem with the ecu – the fuel pump doesn’t prime and the engine will not start.
    I have checked the following:
    • The immobiliser seems to be doing what it should – it blinks the right codes etc.
    • The main relay is getting power both direct from the battery and via ‘gauges’ when the ignition is on
    • The ‘main relay’ is proving power to the ecu (the yellow and black wire) so one relay is working
    • The fuel pump relay works if provided with an earth
    • The fuel pump works
    • The ecu is getting an earth
    • The issue appears to be that the ecu is not providing an earth to the fuel pump relay
    I have searched the forum and looked at others for 1990’s Hondas - it appears that problems with the ecu and the main relay are common and there is a lot written about it. All that combined knowledge points to an ecu problem with my car but is there anything else I should check? For example does the ecu expect a certain response from any of the sensors before it primes the fuel system?
    Any suggestions will be appreciated!

    Sorry to be only posting when I need help.
    Tom

  2. #2
    Join Date
    Sep 2013
    Posts
    98
    hi tom
    did your car run ok before battery change ?
    if so I would first disconnect and reconnect all fuses in both fuse boxes 1 by battery and 1 under osf of dash then check power going in and out with voltmeter to check all fuses are ok. (I had this once and it was because car had been standing ages and corrosion on a fuse under dash )

    when you supply an earth does it start ? if so then you don't need to look any further just trace back the earth
    if not and only the pump is running you will be just borewashing the cylinders and making it more difficult to start anyway

    I would also make sure you have a spark as if not I would guess the immobiliser is the main culprit as most will cut spark and fuel so by disconnecting the battery completely you in effect turn it on

    hopefully 1 of these will give a bit of help if not let us know what you find
    mikei

  3. #3
    Join Date
    Apr 2018
    Location
    Worcestershire
    Posts
    9
    hi mikei
    Thanks for your quick reply and suggestions. It ran ok before the battery change. It did have the same symptoms when I first got it but the problem righted itself while I was checking the relay - perhaps pointing towards an intermittent poor connection somewhere. I will investigate further along the lines you suggest.
    Tom

  4. #4
    Join Date
    Nov 2008
    Location
    Canadian prairie
    Posts
    220
    Is the 7.5 Amp starter signal fuse ok?

  5. #5
    Join Date
    Apr 2018
    Location
    Worcestershire
    Posts
    9
    Still no progress. I have checked the fuses and checked the supply and earths on the ecu connectors - all appear good. The starter signal fuse looks good (though oddly the starter still works with it removed?). The engine doesn't fire even with the fuel pump running via a jump wire. Not sure what to check next. Any suggestions?

    Tom

  6. #6
    Join Date
    Sep 2013
    Posts
    98
    hi tom
    so are you saying the car cranks fine but you have no spark and no fuel pump prime ?
    if so what immobilizer is on it
    is this the blue one that was on ebay

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