LPG / Petrol - how can you know that you are running on Gas?

Apr 6, 2019
1,813
2,946
Eye, Peterborough, UK
Funster No
59,702
MH
C Class?
Exp
1999 Autocruise Impala, bought 2019
Hopefully not too silly a question, but my LPG guy is on holiday for a week and after being so helpful replacing a crusty 20 year old tank I am not going to disturb him (despite becoming friends and gave me his mobile).

I have a simple switch on dashboard - right for Petrol and a red LED - left for LPG and a little amber LED - the system is 20 years old.
When I first got the RV there was a blip in throttle downwards when you flicked from LPG to Petrol - understandable and fine by me as the solenoid flicks open the right valve and lets petrol in etc... especially as the RV had not been driven for about 9 months so I blew the cobwebs away with a trip from Anglesey back home to Eye.

NOW, there is no blip. So, how can I simply tell if the relevant valve etc has opened and the engine is actually using the LPG? I am yet to cinfirm if the petrol gauge has been dual wired to display LPG levels as previous owner said not to rely on the gauge - use 320 miles as a good indicator it is time to fill up with LPG again.

Images below of the engine and what i took to be the LPG atomiser in more detail. If I pull the top connector OFF and start the engine it just starts and runs regardless of Petrol / LPG switch. I wrongly? assumed this might turn off the atomiser and stop LPG being selected.
 

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Dec 2, 2019
1,126
2,529
South Lincolnshire
Funster No
67,140
MH
Rapido 7065+
Exp
Less of a newby
Hard to tell from just piccys where the vapouriser is but it looks like it's the circular thing on the bottom right so I'd check the solenoid attached to it - 12v supply when on gas.

lpg.png

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OP
Jev88
Apr 6, 2019
1,813
2,946
Eye, Peterborough, UK
Funster No
59,702
MH
C Class?
Exp
1999 Autocruise Impala, bought 2019
Hard to tell from just piccys where the vapouriser is but it looks like it's the circular thing on the bottom right so I'd check the solenoid attached to it - 12v supply when on gas.

View attachment 517487
Perhaps you didn't see the three other pictures that were close ups of the vapouriser ?
I have now sorted the problem - LPG tank valves have their own 12v feed and this fuse had blown. I get a distinctive dip in revs when switching fuels. This disappeared and so made me suspicious that something was amiss.
 
Dec 17, 2016
461
362
Malvern
Funster No
46,488
MH
Hymer B525 2006 A cl
Exp
2012
On the system I had in a car ( several years ago) the amber LED changed to green when on LPG.

Agree about range anxiety -I used to reset the trip counter on fill up as the LEDs were useless. You could get a Mopeka sensor which will work with a cylindrical tank but the big difference is that with the engine aftermarket system you will always have a big petrol tank as a back up so not so necessary.
Glad you sorted it anyway.
 
OP
Jev88
Apr 6, 2019
1,813
2,946
Eye, Peterborough, UK
Funster No
59,702
MH
C Class?
Exp
1999 Autocruise Impala, bought 2019
On the system I had in a car ( several years ago) the amber LED changed to green when on LPG.

Agree about range anxiety -I used to reset the trip counter on fill up as the LEDs were useless. You could get a Mopeka sensor which will work with a cylindrical tank but the big difference is that with the engine aftermarket system you will always have a big petrol tank as a back up so not so necessary.
Glad you sorted it anyway.
Unfortunately no colour change on these LEDs. Mopeka not much use as yet because;
1) I have three LPG tanks for the engine and two are exposed to road rash so would have to fashion an enclosure for Mopeka?
2) The 3rd tank is under the bed and now know it actually has a gauge! But will also investigate the 3rd tank and see if Mopeka could slide underneath - not sure how much use this would be as the three tanks all feed through a manifold, so would the reading on one slightly raised tank give an approximation to all three tanks contents? I am having to assume the tanks all empty under pressure at the same rate and equalise between them?

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Dec 17, 2016
461
362
Malvern
Funster No
46,488
MH
Hymer B525 2006 A cl
Exp
2012
I see your problem! If they do all equalise the one Mopeka sensor might work. This would need protection from road dirt in something that you could access to change the battery on the sensor.
 
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