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Author Topic: Carburettors/LPG for dummies  (Read 126 times)

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Brynjaminjones

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Carburettors/LPG for dummies
« on: July 14, 2017, 07:23:46 AM »

Good morning,

Please don't disown me, but I'm a bit of an idiot when it comes to carbs and the basic LPG systems that go with them, so I'm trying to get my head around it all.

The Grand Waggy has the original Motorcraft carb with some kind of very basic LPG setup.

Question #1: Cold starting on a petrol, after a few good pumps I have to crank it a couple of times for about 10 seconds to get it to start. Once started it idles great, and it starts very quickly once warm. Is that normal, or does the carb need tinkering?

Question #2: I've not figured out how to switch to LPG. It has a three position switch (petrol, off, gas), and I've read that you should switch it to the off position for a while to drain the petrol from the carb bowl before switching to gas. I've tried this but after 30 seconds or so it was still running fine with the switch off. I tried switching over to gas which of course made it stumble like it was running very rich.
How long should it take for it to run out of petrol, or is the switch not working correctly?

Question #3: Can I start directly on LPG? We did this on the test drive when the switch wasn't connected properly, but it took forever to start. If doing this do I need to pump the throttle or does it start differently?


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wildwood

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Re: Carburettors/LPG for dummies
« Reply #1 on: July 14, 2017, 08:53:53 AM »

Motocraft carb is a goody.....
Whatever the Holly ...Edelbrock stable say....
It's the one that handles angles and inclines.....the others don't unless modded......

You should be able to go from petrol to gas on the go.....

Can't be accurate with answers to the rest as my experience was with injection system .

Good that you are already gassed up though......saves you some coin :97:
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The Recovenator

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Re: Carburettors/LPG for dummies
« Reply #2 on: July 14, 2017, 09:23:55 PM »

I would start on petrol then switch to gas, itl draw both until the petrol runs out, if you switch off then to gas it may splutter or stop until the vapour gets to the inlet manifold, is it a basic power valve setup or has it had an o2 sensor mod fitted
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5536paulj

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Re: Carburettors/LPG for dummies
« Reply #3 on: July 15, 2017, 02:07:26 PM »

Behaviour on petrol sounds about right, the fuel drains back to the tank if left for a few days and can take quite a bit of cranking to pull it through. If left for a few months I tip some fuel straight down the carb as it can take a lot of cranking and flatten battery

Can't help on lpg other than you shouldn't expect too much from it on a low compression american v8 with a carb! Not the ideal scenario but it can be made to work I'm sure.

There are lots of ways to make the amcv8 run better, start googling......

In the first instance just enjoy it, looks awesome.     :drool:
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Brynjaminjones

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Re: Carburettors/LPG for dummies
« Reply #4 on: July 16, 2017, 08:59:03 PM »

Cheers for the help guys. It does run beautifully on petrol, and feels like it's got plenty of power. It started up really quickly today after not starting for a couple of days.

It's just a basic LPG system I believe, no computers to be seen (that I've found yet). I've read a lot about backfiring etc with LPG on a carbed engine, so I've been overly cautious about playing with it until I'm more educated! I'm not expecting much from LPG, but with fuel that cheap I don't care how much it uses (our ZJ gets about 13-15mpg on gas)!

How long should it normally take for the petrol in the carb to run out?
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