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Discussion Starter · #1 ·
Hi guys,
On the top of my GQ Patrol RB30 carby LPG "mixer"(duel fuel), there's a vent that can be opened & shut from a cable attached to the dash board.

What does this do?

It obviously allows extra air into the intake, but for what reason?
When am I suppose to use it?
The LPG system has a cold start solenoid switch installed, but still needs too much cranking to start on LPG. I haven't figured out the reason yet, but suspecting a vacuum leak?!?!
I start on petrol and then switch to LPG after a minute or so.

I'm suppose to use this cable-vent thing by pulling the cable when necessary to allow extra air into the intake, but not sure what is it exactly for?

Thanks for giving me any clues.
 

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GHMBC #3
nissan patrol gq lwb,3"lift.
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the impco 300a mixer has the diaphragm lift for running on fuel- better airflow when on petrol
 

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Discussion Starter · #3 ·
the impco 300a mixer has the diaphragm lift for running on fuel- better airflow when on petrol
Does that mean I should lift the diaphragm when I start on petrol or should it be lifted all the time when the engine's on petrol?
 

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Discussion Starter · #4 ·
BTW, the engine starts on petrol, with or without the diaphragm lifted. It idles on petrol ok too. So, I'm not sure the under what conditions that I should lift the diaphragm by pulling the cable under the dashboard.
 

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nissan patrol gq lwb,3"lift.
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lifting the diaphragm should give you better economy on petrol,more air,slightly leaner mix.down and it will start on gas.it still needs to wind over to suck diaphragm down to get gas flowing,prime it and let it wind till it starts.the diaphragm itself may be old and stretched and need replacing
 

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Discussion Starter · #6 ·
lifting the diaphragm should give you better economy on petrol,more air,slightly leaner mix.down and it will start on gas.it still needs to wind over to suck diaphragm down to get gas flowing,prime it and let it wind till it starts.the diaphragm itself may be old and stretched and need replacing
Sorry mate, I used your word "diaphragm" without even understanding it.
What I see is an extra vent that opens up when the cable is pulled and I can hear the hissing and it's sucking extra air into the carby intake(obviously making the mixture slightly leaner). I didn't quite understand the "diaphragm". From what you said, I gather it's inside the "mixer" thing. There's a kinda spring mechanism that rotates a plate which causes that vent to open when the cable is pulled from the dashboard puller thing.

I had a primer(cold start solenoid switch thing) installed last year, but hasn't made much difference in terms of being able start on LPG without having to crank for half a minute.
If I understood you correctly, this "diaphragm" may be old and worn out, causing unnecessary lean on LPG starting(even though I have a primer installed), which in turn doesn't help with LPG cold starting.

Am I right?
Did I understand it correctly?

Thanks
 

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Mine always had trouble starting on gas if it sat for more than 4 or 5 hrs I use to switch it over to petrol if it was going to sit for a while only takes a couple of seconds.
 

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Discussion Starter · #8 ·
Mine always had trouble starting on gas if it sat for more than 4 or 5 hrs I use to switch it over to petrol if it was going to sit for a while only takes a couple of seconds.
Mine has been pretty much the same, until i had the primer switch installed. It's automatic type. I don't need to switch it on manually. The autogas techie wired it up.
It did work initially, though I had to pump the accelerator paddle couple of times to idel it on LPG, which I didn't mind. After couple of months, primer didn't work at all. So, I went back to the old regime of starting on petrol.
I suspected a vacuum leak somewhere for the reason of primer(cold start switch) not working, but haven't got around to find it and fix it.
As soon as I start on petrol, I can switch to LPG without causing any dramas. Doesn't even need to warm up for too long(I reckon few seconds of warming up is enough?).
Once warmed up for few minutes, the engine starts on LPG without any issues.
I would like to get the primer getting though.
One LPG expert suggested to me it's better for the engine to start on LPG, than starting
on petrol, due to petrol "wash effect".
I'm not too sure about that.
But, I would love to get the primer going again.
I would have to start looking for vacuum leaks and take it from there.
Also, it's a good tip to check the LPG mixer diaphragm thing as well.
Cheers:bananada:
 
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