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Thread: Bypass gas temp sender?

  1. #1
    DAMINK Guest

    Bypass gas temp sender?

    I have an injected emmagas system on my 3.9 v8.

    I was wondering if there is a way to bypass the temp reader which turns the unit on?

    Basically wanting to start it on gas.

    I understand its basically illegal to run a car like this and can be dangerous. (not my intention to drive it bypassed)

    Its more for diagnosis purposes.

  2. #2
    p38arover's Avatar
    p38arover is offline Major Part of the Heart and Soul of AULRO Gold Subscriber
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    Bee Utey is your man. It should be programmable - at least it was on the LPG system I had in the P38A.

    Is it really illegal to start/run on gas? Some cars are only LPG, e.g., some factory Falcons.

    I had to do it on the P38A when the fuel pump failed in Tumbarumba and I had to get back to Albury and then home.
    Ron B.
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  3. #3
    DAMINK Guest
    Quote Originally Posted by p38arover View Post
    Bee Utey is your man. It should be programmable - at least it was on the LPG system I had in the P38A.

    Is it really illegal to start/run on gas? Some cars are only LPG, e.g., some factory Falcons.

    I had to do it on the P38A when the fuel pump failed in Tumbarumba and I had to get back to Albury and then home.

    Yep i am hoping Bee Utey can chime in here. Value his input greatly.
    The unit i have seems to be temperature related to switch over. On a warm day it will switch within a minute, on a cold day it can take 10 minutes to turn over.
    When car is warm it turns over almost instantly and at times without any throttle.
    As for illegal im not entierly sure. Just remember many years ago a sparky mate doing it to an old dunny dore i had and telling me having a duel fuel car you must start on petrol.

  4. #4
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    The main reason that LPG injection cars warm up on petrol is because the gas ECU doesn't work very well when translating petrol signals to gas while cold start petrol enrichment is engaged, LPG doesn't need the same enrichment. The secondary reason is that the LPG converter is usually too small to deliver guaranteed vapour supply until it is warm enough to vaporise enough liquid. So although there is no legal reason why you can't design a system to cold start on LPG it's simply easier to not bother. That's also because to meet emissions standards it's easier to warm the engine up instead of creating extra temp controlled conversion maps.

    Standard mixer systems can be started on LPG without petrol, it's silly to suggest otherwise. All you need is a good battery and adequate spark. Liquid injection systems can cold start on LPG as there is no need to create vapour in a converter.

    Having said that many LPG injection systems have emergency start available, simply by holding down the change over button before it lights up then cranking until it starts while still holding down the button. This should work OK so long as the engine is at around 20C or over, and you don't ask for engine power until it's a bit warmer.

    If this doesn't work on your system you might have to get the software. Jiggering the temp sender is as simple as switching an extra resistor across the sender to mimic it's hot resistance. A simple multi meter check will allow you to find a suitable resistor. That won't guarantee an instant LPG start if it isn't selected in the software. Then there's the minimum RPM set for changeover, could be anything.

  5. #5
    DAMINK Guest
    Explains why i have had issues for years trying to get the gas tuned to run just right. Good cold and good hot.
    Never could and ended up just setting it to run good when hot.
    Mind you the dealer i bought it from told me never to try run it cold. I guess it just likes to run when hot only.

    Cool i will give up on that idea.
    Paid over 80c ltr today anyway. Just about time to convert that gas tank into a good incinerator i think.
    Just threw out a non gas manifold too!! Oh well all good.

    Cheers for that Bee Utey.

  6. #6
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    Hah, my local is now at 94.9c per litre, luckily the nearest indy is still at 81.9 or I'd be thinking of switching off my gas too.

  7. #7
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    Quote Originally Posted by bee utey View Post
    Hah, my local is now at 94.9c per litre, luckily the nearest indy is still at 81.9 or I'd be thinking of switching off my gas too.
    Yes, but if ULP is 1.80 a litre ......................... it still makes sense

    it's upto 75.9 now at apco in town. They were 65.9 for a last year or so. Everyone else is at least 85.9c/l. When petrol its $1.60 a litre, gas at 80cents is still cheaper than petrol to run on ...

    seeya,
    Shane L.
    Proper cars--
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