Peug 406 fuel pump issue?
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  1. #1
    1000+ Posts Rod Hagen's Avatar
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    Default Peug 406 fuel pump issue?

    Ok, driving along yesterday and the 1997 406 (200,000k +) suddenly lost engine power. (Had a pretty low tank that morning before half filling)

    Won't restart, turns over fine, battery fully charged. Towed home. checked fuses and for any obvious engine wiring issues, but suspected fuel pump.

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    Waited overnight and checked for fuel pump noises on turning on the ignition. No sound. Removed back seat, removed fuel pump cover and listened again. No noise.

    Pulled electrical connector on fuel tank pump. With the ignition on the connector is delivering around 5.5 V on connections 2 and 5 when tested against the connection analagous to the one labelled 1 on the pump. The voltage on connection labelled 4 on the pump seems to vary (between about 1.5 v and 4.5 volts).

    Does this suggest a problem with the pump or a problem with some other component in the engine control system?

    Cheers

    Rod
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  2. #2
    Contented Peugeot Driver addo's Avatar
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    Check your inertia switch first, then your tachymetric relay.

  3. #3
    1000+ Posts Rod Hagen's Avatar
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    Can I test the inertia switch by simply looking for voltage across between its terminals or leads? Expect 12V+ ?
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  4. #4
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    Disconnect the lead and check for negligible resistance across the inertia switch terminals 1&3.

    Check the lead with ignition on (position immediately before starter operates) for approximately 12V at terminal 1, measured against ground.

  5. #5
    1000+ Posts Rod Hagen's Avatar
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    Ok I am only getting 0.14V on one side of the inertia switch connector (measured to earth) , and 0V on the other. I presume this means that I next head for the relay? I wonder where it is on the 406. Don't think it is tucked behind the dashboard as in the 505 sli!
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  6. #6
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    OK, looks from diagrams as if it may be over near the ECU. As soon as this bloody Melbourne rain stops again I'll go and take a look!
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    Contented Peugeot Driver addo's Avatar
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    That suggests it's either your fuses under the bonnet or the ignition switch. They feed the inertia switch and the tachymetric relay in parallel.



    Circled right, is inertia switch, left circle is positive feed from the underbonnet fusebox.

  8. #8
    1000+ Posts Rod Hagen's Avatar
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    First of all many, many thanks for your help, addo.

    I've found the tachymetric relay. With the ignition on and the wiring plug connected I tested terminal 2, which seems to be the primary feed to it (according to Haynes), and found 12 volts. Tested terminal 9 (which according to the Haynes wiring diag is the feed to the inertia switch), and found 0 volts. Does this suggest a problem with the relay itself?
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  9. #9
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    Pin 3 (centre of a five pin fuel pickup connector) should be +12V with ignition on.

    You should also have (by my diagram) perfect continuity - apparently unfused - between this Pin 3 and tachymetric relay connector pins 2,8,11,14,15. Sometimes the numbers need a magnifier to read on the connector plugs. It's my understanding they're on the infeed side of the tachymetric relay.

    One half of the tachymetric relay is activated by turning on the ignition (whether to run or crank the car) while the other half relay is activated by the ECU providing a ground via Pin 7. I'd only use a good multimeter to check that one - don't want a backfeed!

  10. #10
    1000+ Posts Rod Hagen's Avatar
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    Hi again , addo, I'll have another look in the morning.

    One thing I was thinking of doing was disconnecting the ecu and then testing the tachymetric relay by directly grounding the relevant connection (which i think is actually pin 10 rather than 7) to see if voltage then became available at pin 9 of the tachymetric(the feed to the fuel pump). If it didn't then I would assume the problem lay with the relay (given that there seems to be current where it should be on the "input side"), if it did then I'd be thinking the ecu, or something that it relies on, was responsible. Make sense?

    Pin 7 seems to actually control the injectors on the diagrams (Haynes and the one at http://peugeot.mainspot.net/wiring406/index.shtml ) I'm looking at (and on yours too).

    I'm getting worried that this may actually be an ecu issue, I'm afraid. I presume they are hideously expensive.
    Last edited by Rod Hagen; 25th November 2010 at 11:22 PM.
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  11. #11
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    Ok, with the ecu removed and ignition on I earthed pin 10 on the Tachymetric relay. Relays could heard clicking into action, and the fuel pump started running.

    Looks like either a problem with ecu or in the supply to it.
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  12. #12
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    Mmm, anyone know where I might find a means of identifying the pins on a Bosch ECU connector. Can't see any numbers on either the ecu or the connector, so where is "1", for example?
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  13. #13
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    OK, dismantling the ecu plug reveals numbering on the inside. The pin # 18 seems to be the primary ecu power supply according to the Haynes. Diagram. It is a yellow lead with markings and at present is carrying no voltage when tested with the ignition on and disconnected from the ecu.
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  14. #14
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    MMM. I obviously can't count! There actually is power at terminal 18 on the connector to the ecu (turned out to be the adjacent pin to the one I as testing). So power to the ecu, but it is not creating the necessary earth on pin 10 of the tachymetric to activate voltage on the fuel and ignition circuits on pins 9 and 1 of the Tachy.

    Apart from the ecu itself what could be involved here? Any antitheft device possibilities , I wonder.
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  15. #15
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    (Sorry about the monologue, by the way, but I thought it might be worth posting as I work my way through it for the sake of anyone else in the same situation)

    Pulled the ECU cover off. No signs of any suspicious darkening around joints etc, not that this is really much of an indication. Looks more and more like the ecu regardless. Pity I don't have a spare one to drop in to test it.

    Have to leave til Sunday, now, regardless. Any additional thoughts in the mean time would be greatly appreciated, of course!
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