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Thread: Running rich

  1. #1
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    Running rich

    Hey folks,
    I swear my disco makes problems just so i have something to do in my spare time! This time it is running way rich.

    Just in the last week or so it pops and backfires when i put the foot down a bit for hills etc, has lost power, and smells rich when driving (from a mates vehicle driving behind).

    Which sensors does the ECU derive the fuel mix from; is it only MAF and temp sensor?
    The temp gauge works fine, but i think there is a different 1-pin temp sensor for that right? Found that here: 1997 Discovery 3.9 V8 - Coolant Temp Sensor

    If it's just those two sensors, i will clean the maf out and order a new temp sensor of the net.
    Oh and it has newer yellow top injectors from a mustang. The injectors have little tiny holes instead of the one large hole of the original injectors. The new ones have been installed for ages though and it has ran really well. In fact they increased the power a little when i installed them. I originally installed them as the old injectors were suspected of being worn out and it was running rich....

    Thanks!

  2. #2
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    Running too lean will cause petrol smells just like rich running but without the black smoke. Check that your throttle position sensor is providing a smooth 0 to 5 volt output with increasing accelerator. I replaced a broken one a couple of weeks ago that had similar symptoms.

  3. #3
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    Righto, thanks.
    I presume, i turn the key on, and measure volts coming out of one of the wires (yellow perhaps) the plug on the TPS whilst i push the accelerator down?
    I hope that's not the problem - they look expensive...

    Does anyone know if i should have re-tuned the ecu when i swapped out injectors? Is the injection system that smart? I read some guy who disconnected his battery for a week to reset the ecu?!

  4. #4
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    Output wire is plain red from memory. I don't think the ECU can learn anything as it has no way of reading the mixtures. All you can do externally is play with the idle adjustment on the MAF and possibly fit an adjustable fuel pressure regulator. The only way you'll really know how the mixture is going is to fit an oxygen sensor to the exhaust and fit a suitable gauge. Also you should periodically check that the vacuum hose from the reg to the manifold is present and tight and there's no sign of fuel leakage into said hose.

  5. #5
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    Thanks. I will get a few odd jobs done on it this weekend.

    What type of adjustable fuel pressure regulator are people fitting to the rover V8's? Certain threads and range presumably?

  6. #6
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    Hello again,

    So i am doing a few jobs on the disco today and wondering what is with the timing adjustment on these rovers?
    There appears to be just one white line on the harmonic balancer and a little bit of metal that sticks out to line it up with.

    The toyotas i work on have a little scale that says the degrees "0 5 8 12" etc.
    Do you just have to eyeball it with the timing light on these rovers - put the white line at roughly 6 degrees before the metal pointer (for 6 degrees advanced)?

    I am also about to test the resistance across the coolant temp sensor, when cold then when hot to see if it's working. Don't suppose anyone knows the resistance values of a new sensor?

    Thanks

  7. #7
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    There is also a big notch/channel cut into the balancer. Is this what is meant to be used as the timing mark? Perhaps someone has just painted on the white line onto the pulley?

  8. #8
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    There should be a scale of markings on the crank pulley marked from 12 degrees "Before" to 12 degrees "After" but it is often hard to see if the pulley has become rusty. Lightly polishing the pulley with sand paper helps visibility. I usually set these engines to 8-10 degrees BTDC but factory setting is about 3 degrees. Our regular unleaded is good enough to run 10 degrees under most conditions, especially during the cooler months.

    The ECU coolant sensor should read around 280-300 ohms when hot according to what I've read.

  9. #9
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    Yep, the markings were there. Just hard to see. The timing is all set now.

    How is the fuel pump controlled to turn off when the pressure in the fuel rail is at specified pressure?
    When i turn the key on, i can here the fuel pump start up, then turn off once up to pressure. But where is the fuel pressure sender?
    Is it the little sensor in the fuel rail, or is that the fuel temperature sensor?

    There must be a sensor somewhere that tells my fuel pump to turn off once pressure is up right? I know the regulator lets out excess pressure, but my pump actually turns off once pressure is up before i start the engine...

  10. #10
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    Quote Originally Posted by Finnius View Post
    Yep, the markings were there. Just hard to see. The timing is all set now.

    How is the fuel pump controlled to turn off when the pressure in the fuel rail is at specified pressure?
    When i turn the key on, i can here the fuel pump start up, then turn off once up to pressure. But where is the fuel pressure sender?
    Is it the little sensor in the fuel rail, or is that the fuel temperature sensor?

    There must be a sensor somewhere that tells my fuel pump to turn off once pressure is up right? I know the regulator lets out excess pressure, but my pump actually turns off once pressure is up before i start the engine...
    There is no pressure sensor, just a simple timer in the ECU that shuts the pump down after about 1 second after switch on. The pump will then only run when the ignition signal is fed to the ECU. No magic sensor needed for that.

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