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 Post subject: No gas pressure.
PostPosted: Sun Sep 09, 2018 1:27 pm 
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Joined: Wed May 30, 2012 8:42 am
Posts: 241
Hi all.
Iv got an emer system on an 04 impreza WRX.

It has been alarming out on me all the time.
Laptop showed that the reducer temp was going to minus 33deg. On advice off the tech suport guy at tinley tech (always forget his name) I swaped the sensor. He was right as that sorted it.

Unfortunately the cars still cutting out
I don't know if it had 2 faults or this one developed at the time I fixed the last one

The gas system will switch over every now and then. (Obviously have to turn the ignition of and on to get rid off the alarm befor it will try again.)

But it cuts out after a couple seconds.
Today I had it ticking over on gas on the drive. Whent to move the car and it switched back to petrol.

I noticed the gasses pressure had droped right off

I checked the rear solinoid but there was no voltage. 12v applied showed the valve still works. (Even if it makes a creaky noise when opening)
I could hear gas rushing in.

But the gas pressure didn't increase. I assume the front solenoid bolted to the reducer didn't open

Iv tried changing the "dedicated tank solinoid wire" tick box but that didn't make any difference.

Dose anyone have any ideas what this could be ?

Iv checked the wireing I can see but I can't see it all as it's a bit hidden. Can't see any issues with the bits I can see.


Cheers
Josh


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 Post subject: Re: No gas pressure.
PostPosted: Sun Sep 09, 2018 2:39 pm 
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Joined: Wed Sep 29, 2010 5:01 pm
Posts: 3212
Location: Yorkshire
There will be no voltage at the solenoids after the LPG system has switched back to petrol as at that point the LPG ECU will have a;ready turned off power to the solenoids... With a system which switches back to petrol (for any reason) only (say) a second after trying to run on gas you'll only get that (again) second where there will be voltage at the coil.

You've already tried connecting constant 12v directly to the tank solenoid but it's unclear if you've tried the constant feed at the same time you tried switching to LPG?

You have an AEB ECU'd system (only these have the 'dedicated tank solenoid wire' setting in software) and since it's a WRX it'll only be a 4 cylinder AEB ECU. Not all 4 cyl AEB ECU's have separate outputs for the tank solenoid / reducer solenoid but on some that don't have the separate output the option still shows in software. If you try the constant feed again (as above) it may be necessary to untick 'dedicated tank solenoid wire' or to disable on board diagnostics to prevent the system refusing to work on gas without it's tank solenoid wire connected due to the system flagging the detected disconnected tank solenoid wire as an on board diagnostic error (if your ECU is recent enough to feature on board diagnostics). Also bear in mind that on installs with dedicated tank solenoid wiring (that didn't come with Supaseal plug already fitted for reducer solenoid) installers often confuse tank solenoid wiring with reducer solenoid wiring and this can result in OBD errors pointing to the wrong solenoid being open circuit and it doesn't help that some of the wiring diagrams confuse tank/solenoid wiring colours or that some looms mix up the colours.

Creaky noise could be telling, it should just go click in normal use but you can get creaky noises the first time the tank solenoid opens if the line between the tank has been purged of gas (because you ran on gas without supply from the tank, due to tank empty or tank solenoid not open). In which case creaky noise can be normal, as in the sound of liquid gas coming out the tank and evaporating in the line until the line has reached full pressure and is eventually full of liquid gas again.

Simon

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 Post subject: Re: No gas pressure.
PostPosted: Sun Sep 09, 2018 7:44 pm 
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Joined: Wed May 30, 2012 8:42 am
Posts: 241
So I do normaly just get the cariteristic "ting" when the solenoid engages. I get the creaking when the line is empty after I run it completely dry. Although recently I've noticed it making the noise when it was half full. I assume due to the lines being dryed out.

Iv got open in advanced enabled so the valves normaly come on once the conditions are met and will come on 5 seconds or so before. The lights are flashing like it's waiting to change over. They't seem to be opening though.

I haven't been able to do a test with it hotwired. As I don't have any way to connect to the super seal on the tank. I just pressed some wires onto it. The one at the front is next to the gearbox so hard to get to even with it jacked up.


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 Post subject: Re: No gas pressure.
PostPosted: Sun Sep 09, 2018 9:33 pm 
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Joined: Mon Jan 23, 2012 12:21 pm
Posts: 1058
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Location: Milton Keynes
If it isn't the solenoids are you sure you haven't caught the pipework somewhere under the car (either by jacking up or debris on it). If its copper rather than poly its likely to kink if so, the creaking you describe is what i'd expect if you had a restriction in the pipe as the pressure after it will be minimal. Assuming the line should be full at that point, if it was an empty tank situation I'd expect it.

It might be an idea to try and verify what pressure your actually getting on the output side - any significant pressure should be able to be felt through the flexible pipes (harder to squeeze).

Equally a gummed up solenoid could cause it, though I'd verify your happy with the coils first (resistance check with a multimeter should help doing this provided you can get to the front one as well)


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 Post subject: Re: No gas pressure.
PostPosted: Mon Sep 10, 2018 8:13 am 
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Joined: Wed Sep 29, 2010 5:01 pm
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Location: Yorkshire
5 Seconds should be enough to see voltage at the supaseal plug? To 'hotwire' you could just cut the wires to the supaseal and connect a battery to it, can always put wiring back as it was afterwards. But to check if the solenoid is the problem there's no need to do any of this, instead you could remove the plunger from the tank solenoid making the solenoid always open... To do this turn off the manual/service tap on the multivalve, remove the solenoid coil, remove the solenoid post, remove the plunger from the post, refit the post, turn the manual service tap back on, tank now supplies constant feed..

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 Post subject: Re: No gas pressure.
PostPosted: Mon Sep 10, 2018 2:13 pm 
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Joined: Mon Jan 23, 2012 12:21 pm
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A further thought - If you have a single hole tank check the valve is actually fully open before you do the above. If its partly/mostly closed that would explain the lack of pressure as well but can allow a small amount through.


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