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Thread: 98 D1 V8 bad fuel economy - 43.2L per 100km - vacuum advance?

  1. #1
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    Question 98 D1 V8 bad fuel economy - 43.2L per 100km - vacuum advance?

    My father recently purchased a stock standard 98 D1 SE V8 with 115,000km on it. He has a work car for Monday to Friday so it doesn’t get used much but we’ve found the fuel economy to be ridiculously high and testing confirmed it at around 43.2L for 100km. This is an issue both expense wise but also as the tanks range is so limited.

    So far I have changed all fluids (engine oil and filter, automatic transmission filter and fluid, transfer box, front and rear diff oils), changed the spark plugs (NGK standards gapped according to Rave), the air filter and replaced two ignition leads which had damaged plug boots.

    While there I found the vacuum line to the distributors vacuum advance to have perished at the boots and the suck test indicated that the diaphragm had an issue.

    A new vacuum advance unit is on its way, would this be the sole cause for such poor fuel economy? Or is there other areas that I should check? We are aiming to get it to a more reasonable 20L per 100km range which I think is reasonable...

  2. #2
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    Possibly the amplifier as well, there is a good guide here on how to replace with a bosch item.
    MY08 TDV6 SE D3- permagrin ooh yeah
    2004 Jayco Freedom tin tent
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    When you're self diagnosing like this(which many of us do) it's best to do change things one at a time and test.

    Everything you've done so far seems well thought out too.

    The other thing to check for once the vac advance is fitted, will be the air flow meter/sensor.

    On all the injected Rover(SD1) vehicles I've had they were all playing up. Damned expensive things to change back then too!
    Other thing to be mindful of are the injectors themselves, they get dirty/worn and the spray pattern is fubar.
    Arthur.

    '99 D1 300Tdi Auto
    '03 D2 Td5 Auto

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    Quote Originally Posted by AK83 View Post
    The other thing to check for once the vac advance is fitted, will be the air flow meter/sensor.

    On all the injected Rover(SD1) vehicles I've had they were all playing up. Damned expensive things to change back then too!
    Is there a way to test them or matter of fitting another to see if there’s an improvement? Can they be cleaned first?

    Is there oxygen sensors on these?

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    Quote Originally Posted by twr7cx View Post
    Is there a way to test them or matter of fitting another to see if there’s an improvement? Can they be cleaned first?

    Is there oxygen sensors on these?
    Unfortunately my only experience with injected RV8's has been with SD1's.
    (although soon will have my D2 V8 on the road too).

    As for injectors, I had a few piled up over the years, and bought some more.
    My mechanic had the tester cleaner doodad tool and due to the difficult installation(for me), I got him to test/clean them all and install the good ones.

    Do plenty of research on the topic, as I think I remember reading recently(not back then when I had my RV8s!!) that some fords used the same injector types .. so could be an alternative if prices are lower.

    Also have you checked if your dads D1 has O2 sensor(s) too?
    Arthur.

    '99 D1 300Tdi Auto
    '03 D2 Td5 Auto

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    Quote Originally Posted by loanrangie View Post
    Possibly the amplifier as well, there is a good guide here on how to replace with a bosch item.
    Thanks. I assume this is what you refer to Lucas ignition amplifier replacement by Bosch 024 ?

    Is there any way to test the current one? We don’t seem to be having the back firing etc issues that others mention in that thread.

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    Could be the cold start sensor is stuffed. ETC8496. There are 2 similar sensors that are screwed into the intake manifold, so you need to check the correct one. Depending how it may have failed, it will cause high fuel consumption as the engine will be running rich all the time.

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    Is it getting hot quickly? Sounds like it is still in warm up program... thermostat needs to open quickly. At least 82degree one.

    Set timing to 10deg or even 12 if vac advance iffy. Also check that the fpr is not perforated this will draw extra fuel in to the inlet manifold.

    Jc
    The Isuzu 110. Solid and as dependable as a rock, coming soon with auto box😊
    The Range Rover L322 4.4.TTDV8 ....probably won't bother with the remap..😈

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    Cheers JC.

    Quote Originally Posted by justinc View Post
    Is it getting hot quickly? Sounds like it is still in warm up program... thermostat needs to open quickly. At least 82degree one.
    Will check. What sort of time frame should it be taking to get to normal operating temperature? Is he factory dash guage sufficient for judging this?

    Quote Originally Posted by justinc View Post
    Set timing to 10deg or even 12 if vac advance iffy.
    is that advance BTDC?

    Quote Originally Posted by justinc View Post
    Also check that the fpr is not perforated this will draw extra fuel in to the inlet manifold.
    Is it the same method as checking the condition of the diaphragm for the distributors vacuum advance module - ie connect a vacuum hose up and suck on it?

    EDIT: found V8 Fuel Pressure Regulator symptoms? which provides some related information.

  10. #10
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    From another thread:

    Quote Originally Posted by bee utey View Post
    Remember to check your vacuum and mechanical advances are working properly, loss of either will ruin your economy.
    As mentioned above I’ve checked and found the fault with the vacuum advance but how does one check the mechanical advance?

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