No gas pressure.

Post Reply
Message
Author
joshnosh
Junior Member
Posts: 242
Joined: Wed May 30, 2012 9:42 am

No gas pressure.

#1 Post by joshnosh » Sun Sep 09, 2018 2:27 pm

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

LPGC
Installer
Posts: 3225
Joined: Wed Sep 29, 2010 6:01 pm
Location: Yorkshire
Contact:

Re: No gas pressure.

#2 Post by LPGC » Sun Sep 09, 2018 3:39 pm

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
Full time LPG installer
Servicing / Diagnostics / Repairs to all systems / DIY conversion kits supplied with thorough tech support
Mid Yorkshire
2 miles A1, 8 miles M62,
http://www.Lpgc.co.uk
Twitter https://twitter.com/AutogasSimon
07816237240

joshnosh
Junior Member
Posts: 242
Joined: Wed May 30, 2012 9:42 am

Re: No gas pressure.

#3 Post by joshnosh » Sun Sep 09, 2018 8:44 pm

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.

Brian_H
Intermediate Member
Posts: 1085
Joined: Mon Jan 23, 2012 12:21 pm
Location: Milton Keynes

Re: No gas pressure.

#4 Post by Brian_H » Sun Sep 09, 2018 10:33 pm

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)

LPGC
Installer
Posts: 3225
Joined: Wed Sep 29, 2010 6:01 pm
Location: Yorkshire
Contact:

Re: No gas pressure.

#5 Post by LPGC » Mon Sep 10, 2018 9:13 am

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..
Full time LPG installer
Servicing / Diagnostics / Repairs to all systems / DIY conversion kits supplied with thorough tech support
Mid Yorkshire
2 miles A1, 8 miles M62,
http://www.Lpgc.co.uk
Twitter https://twitter.com/AutogasSimon
07816237240

Brian_H
Intermediate Member
Posts: 1085
Joined: Mon Jan 23, 2012 12:21 pm
Location: Milton Keynes

Re: No gas pressure.

#6 Post by Brian_H » Mon Sep 10, 2018 3:13 pm

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.

joshnosh
Junior Member
Posts: 242
Joined: Wed May 30, 2012 9:42 am

Re: No gas pressure.

#7 Post by joshnosh » Sun Dec 02, 2018 10:58 pm

Right gents. About a month ago I took a look at it but haven't touched it since then.

Little odder than originally planned as all previous diagnosis was done with the car warm

Car currently running as follow.
Car starts. Valves ting. Pressure builds up. Lights flashing waiting for temperature. Threashhold reached and it switches over. Lovely.
Except it's not really running on gas it seems to switch between petrol and gas injection all the time. Light stays the same staying it's running on gas


I was accelerating and watching and the gas timings. They where roughly. 20. 0. 0. 0. 22. 21 0. 0. 18. 0.0

Running on gas about 1/4 off the time

At ideal the story is much the same but running on gas 3/4 off the time. Pressure doesn't seem to be too low. It's not bellow the change over threshold at any point.

After around 8 mins driving the car will switch back to petrol completely

Switching the car back to gas. Even after restarting the car or clearing the codes (there aren't any) dose nothing. It just waits to switch over. ECU dosent turn the valves on so no pressure and no switching over. After 10 mins or so it will try to switch over anyway but then immediately fail. And go back to petrol

Car only runs on gas again after sitting for 4 or 5 hours

LPGC
Installer
Posts: 3225
Joined: Wed Sep 29, 2010 6:01 pm
Location: Yorkshire
Contact:

Re: No gas pressure.

#8 Post by LPGC » Mon Dec 03, 2018 1:07 pm

Have a look in vehicle configuration/gas petrol. If operation an minimum / operation at high rpm with gas partialization are set to anything other than gas you could get switching back to petrol partly or fully at low rpm / when you put your foot down respectively. Also check the split fuel box, this can cause problems if ticked (particularly in combination with an engine that idles with low pinj and some of the other settings below).

Look in modify carb, some combinations of extra injection cutting / extra inj sensitivity and/or high figures in the 2 boxes below will filter short petrol injection pulses to the extent that the gas ECU effectively (for purpose of applying multiplier and correction factors to calculate gas injector pulse length) see zero petrol injector pulse length.

In modify carb, is switching back to petrol for low gas temperature selected?

Where is the system getting engine run (red and white wire) ignition on signal from?

In Changeover is the RPM wire box ticked or cleared? Is the brown RPM wire connected and if so where to?

On software screen in bottom left corner next to the icon of a petrol pump there are 4 'indicator lights', do any of these come on or flicker?

What interface cable, software version and version of Windows (and 32/64 bit) are you running? Some combinations seem more prone to occasionally showing unreal figures on screen than others.. but even with a good cable on totally compatible Windows version you sometimes get spurious readings. Spurious readings on screen are sometimes what the ECU is actually doing (so that would be bad as then the actual fuelling is affected), sometimes the ECU is working on correct readings/figures behind the scenes but just not reflecting the correct readings/figures on screen. In the latter case I've found that sometimes it's possible to lessen spurious readings (if the brown rpm wire isn't connected and 'revolution type signal' box is unticked) by temporarily ticking the revolution type signal box and changing settings in revolution type signal drop down menu and ignition type drop down menu, then unticking the revolution type signal box again. This shouldn't have any effect because when the box is unticked the other settings are greyed out and shouldn't have any bearing on anything, but sometimes this does help prevent spurious readings!
Full time LPG installer
Servicing / Diagnostics / Repairs to all systems / DIY conversion kits supplied with thorough tech support
Mid Yorkshire
2 miles A1, 8 miles M62,
http://www.Lpgc.co.uk
Twitter https://twitter.com/AutogasSimon
07816237240

4eyes
New member
Posts: 46
Joined: Fri Nov 15, 2013 4:09 pm

Re: No gas pressure.

#9 Post by 4eyes » Tue Dec 04, 2018 12:08 pm

Hi joshnosh. I've got a Subaru outback with a romano system. A few months ago it was randomly switching back to petrol, sometimes 3 or 4 times a day, then be fine for weeks. No codes, nothing wrong, solenoids, valves etc all ok. I changed the battery about 3 months ago and I haven't had the issue since. Apparently Subaru s are famous for acting wierd if the battery is not quite 100%, giving spurious codes on non lpg vehicles too It might be something you can check.

Post Reply