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LPG idle
« on: 27 April 2013, 07:51:34 pm »
Hello All Thanks for previous help  Misty will start on petrol and idle and can switch over to lpg  However wont idle on lpg put my foot on the accelerator and she coughs and switches to lpg But take my foot off and she cuts out Got about half a tank of lpg so not out of lpg Any ideas appreciated Thanks
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Misty 1972 88" Series 3 Station Wagon

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Re: LPG idle
« Reply #1 on: 27 April 2013, 08:04:55 pm »
Sounds like the LPG (or enough of it) isn't getting sucked into the engine

What type of switch/controls have you got on your system?

Is the engine/LPG heat exchanger/vaporiser nice and warm before switching over?

MARk
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Re: LPG idle
« Reply #2 on: 27 April 2013, 08:37:12 pm »
After mine was set up properly, the idle speed (whilst using petrol) was a quite a wee bit higher.


If set up correctly, it short start from cold unless below freezing.


Who set it up?



HHH
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Re: LPG idle
« Reply #3 on: 27 April 2013, 09:22:49 pm »
What vapourizer does it have? There are two possible adjustments:

1) adjusts the tension on the big internal diaphragm that responds to the vacum created by the engine and lets LPG pass to the mixer,
2) bleeds a small amount of LPG through at idle (when the main diaphragm is not being "sucked" as much).

If it's working ok when you give it a bootful then that suggests the diaphragm is working as it should (although it may be too "tight" and so not letting LPG through at idle - adjust to suit).  It could just be that the idle bypass screw needs opening a bit to bleed some more through so your engine keeps running when the throttle is closed.
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Re: LPG idle
« Reply #4 on: 28 April 2013, 10:20:00 am »
Hello
Thanks for the advice so far. Not sure what make the system is. Was already set up when i got Misty and drove her home 90miles on lpg. Since then only things been touched is imobilesers put on the coil and points. Two simple switches i need to flick before turning the key. A neighbour did say that the engine sounded quiet on petrol when idling. Also the petrol fuel line to carb runs through some tap type of switch which is pointing towards the fuel line in. Is the lpg idle screw a type you can turn with fingers on the side of vapouriser. I have tried it when the engine is warm too . Thanks. 
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Misty 1972 88" Series 3 Station Wagon

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Re: LPG idle
« Reply #5 on: 28 April 2013, 10:58:23 am »
Number of things it could be..
Is there a solenoid on the fuel line to shut it off when you with to gas, or is that what the tap is for?
If its struggling to idle but runs OK at higher revs on LPG, then it could be the diaphragm in the vapouriser is clogged with 'heavy ends', LPG isn't as lean as you think it might be! If you've filled from the bottom of the garages LPG tank you may have picked up a load of white which coats the back of the diaphragm and stops it working properly.
There may be a drain plug on the front of the vap to allow this out.

In my experience it's far more productive to take the truck to a garage that knows LPG systems and get hem to tune it than to play yourself. Its an iterative process with three different adjustments.
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Re: LPG idle
« Reply #6 on: 28 April 2013, 11:53:14 am »
The tap is there as part of your petrol cut off solenoid so that if your electrickery gubbins for the LPG/Petrol control fails you will not be stranded. Simply open the tap and you will run on petrol as normal.
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Re: LPG idle
« Reply #7 on: 29 April 2013, 06:37:26 pm »
Hi Folks
English weather hampered things yesterday. Tonight i adjusted the carb idle screw for petrol and got it running a bit faster I did this when the engine was nice and warm.  I switched to lpg and she coughed and spluttered whilst kicking in. Thats about normal for her. I also adjusted what i think is the lpg idle screw on the vapouriser just a quarter turn. Misty run for a good ten minutes on lpg whilst idling. Does that sound right? Will have to give her a run to test proper i think. Thanks for advice so far. More is always appreciated Andy
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Misty 1972 88" Series 3 Station Wagon

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Re: LPG idle
« Reply #8 on: 30 April 2013, 04:28:19 pm »
Hi Folks
What gap should be on my spark plugs for running on lpg. Currently they are sat .70 and are Denso ones. Wonder if this has any contribution to my poor idle on lpg Thanks
Andy
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Misty 1972 88" Series 3 Station Wagon

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Re: LPG idle
« Reply #9 on: 04 May 2013, 05:35:09 pm »
Hello All
Update on Misty Adjusted carb to run a little higher on idle whilst on petrol. Then switched to lpg and adjusted vapouriser and carb so it would idle on lpg. Did all this whilst engine was warm. Had her our for about a 20mile run got up to about 40/45mph and she seemed to be running ok.
Thanks for all advice Any more always appreciated.
Andy
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Misty 1972 88" Series 3 Station Wagon

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Re: LPG idle
« Reply #10 on: 04 May 2013, 05:58:21 pm »
Ps Even managed to start Misty on lpg.
Andy

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Re: LPG idle
« Reply #11 on: 04 May 2013, 09:19:32 pm »
Sounds good.

You will probably find the optimum timing setting is slightly more retarded for LPG compared to petrol, bit of a pain, but best to setup for the LPG, as that'll be the fuel you'll be using most.

Mark
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Re: LPG idle
« Reply #12 on: 05 May 2013, 09:47:14 am »
Hi Mark
Im not that skilled when it comes to the timing or have timing light tools. Misty is due for MOT in a couple of weeks. If still running well then will get my mechanic to check it proper.
Thanks for all advice always appreciated.
Andy.
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