There's a nut that holds the solenoid coil over a brass tube, so taking that off allows the coil to be removed. Inside the brass tube is a steel plunger with a tapered end and a spring so when power is applied to the coil it moves and unplugs the hole and allows gas through. The brass tube has a hex at the base so it can be unscrewed BUT, there even with the tank solenoid closed there will be a length of pipe from the tank that is full of liquid Propane. Liquid expands by a factor of x270 when it vaporises, so 1 litre of liquid will give 270 litres of vapour. A 3m length of 8mm pipe will hold around three quarters of a litre of liquid so you'll get quite a lot of vapour and you need to slacken off the union to allow it to escape first or the brass tube will come out like a bullet.

Vacuum line off wouldn't affect changeover, just, as bpsm says, cause it to run rough..

Whatever happened to, "Download RAVE"? :-)

Sorry mate, wrong forum. Not that it would help anyway......

"Download RAVE" and "Use the Search function" can identify and fix any issue on a P38. :)

GeorgeB wrote:

Whatever happened to, "Download RAVE"? :-)

You're expected to have already done that... ;-)

Lol@download rave. Stock forum response.

Just cause you read the Hadron Collider manual, doesn't mean your able to fix it.

blueplasticsoulman wrote:

Lol@download rave. Stock forum response.

Just cause you read the Hadron Collided manual, doesn't mean your able to fix it.

Chuckles :)

I seem to have pressed on the wrong button as I meant to reply to Gilberts post not necessarily quote it all but it is very helpful and I need to ask some more. Have checked wiring and things I can get to, managed to get 12 volts to the solenoid on the reducer which sort of worked but did not seem as active as the one on the tank - it may be that the connection I was making was not very good. But what I want to ask is - does the pressure come from the simple fact that the gas in tank is under pressure and therefore makes its way to the intake manifold provided solenoids etc allow it or does the pressure get built by the reducer in addition. If the pressure is in the system all through then presumably I have a blockage or as suggested, a solenoid simply not opening ? Is it as simple as that ?

I seem to have pressed on the wrong button as I meant to reply to Gilberts post not necessarily quote it all but it is very helpful and I need to ask some more. Have checked wiring and things I can get to, managed to get 12 volts to the solenoid on the reducer which sort of worked but did not seem as active as the one on the tank - it may be that the connection I was making was not very good. But what I want to ask is - does the pressure come from the simple fact that the gas in tank is under pressure and therefore makes its way to the intake manifold provided solenoids etc allow it or does the pressure get built by the reducer in addition. If the pressure is in the system all through then presumably I have a blockage or as suggested, a solenoid simply not opening ? Is it as simple as that ?

The tank is at around 7 or 8 bar, and the reducer takes it down to a much lower pressure and larger volume. Internally they work a bit like a diving regulator - you need to "suck" on them slightly to get gas through.

Pressure is high in lines as far as through reducer solenoid valve (liquid phase). Reducer then reduces pressure to low (vapour phase) at reducer outlet then stays low pressure through vapour filter into injectors.
As Gilbertd says, could be a faulty solenoid in liquid phase, blocked filter in liquid phase, blocked filter in vapour phase, kinked pipe in vapour phase

Gilbert gave some pretty comprehensive info and I have checked what I can - managed to get 12 volts to the reducer solenoid and it seemed to work but very sluggish and no where near as noisy and active as the one on the tank. Is the pressure in the system because the gas is under pressure in the tank and allowed to find its way to the inlet manifold provided the solenoid is open and no blockage or is it dependent on getting the pressure from the reducer ? If the pressure is in the system anyway then either the solenoid and plunger are not operating correctly or there is a blockage somewhere. Is this a correct assumption ? All other pipework and wiring is as before when working ok.

Sorry - seem to have missed loads of answers which were not showing when I started this morning - Thanks for how to remove solenoid - did not want to attack it until I knew the right way and I see answer about pressure so I'm going to check solenoid and blockages !! I'm a bit of a novice at this gas thing but pretty good at the air suspension having replaced/rebuilt all of it at low cost - but then on this forum I suspect the members did that years ago with a wave of a wand ............

Replaced the filter (vapour phase) about a year ago - but not sure where the liquid phase filter is ...........

You probably missed that it had rolled over to a second page. Yes, the gas in the tank is a liquid under pressure. The solenoids open and allow it through to the reducer where it expands into vapour and the pressure is regulated down to somewhere in the region of 1.2 - 1.5 bar. That vapour at constant pressure is fed to the injectors which open to allow gas into the inlet manifold. Tank solenoid will open with a healthy clank as it is attached to a big metal tank which amplifies the noise, reducer solenoid will be quieter as you are just hearing a steel plunger moving. However, t should still make a healthy sounding click.

super4 wrote:

Replaced the filter (vapour phase) about a year ago - but not sure where the liquid phase filter is ...........

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If you have a sut off solenoid valve like this:

It's behind the big circular plate with the bolt in the middle. Make sure you get the O rings back in the right place when you put it back together though. No need to unmount whole valve from reducer to check.

DO NOT just slacken off the bolt holding the plate without releasing the gas pressure first. The plate may survive but the noise will make you think someone has just fired a shotgun at you. I did it on my first LPG car (an old Saab) and I must have jumped 2 feet in the air when the seal on the O ring let go. With the ignition switched off, slacken off the inlet union to allow the gas in the pipe to escape first so there is no pressure left in there.

One other possibility is that you've clouted the pipe between the tank and front end and squashed it flat so it restricts the amount of gas that can get through.

Well I laughed but am more frightened than ever to touch it now ! Actually - great info - have the same solenoid and filter so thanks both for pointing the way and the dangers. I have put my back out lying under the car and trying to remove front wheels by kicking from inside. They had jammed themselves on the hub (dirt and overtight nuts at last tyre place) - took an hour and WD40 galore to free them. If it was a wheel change by the roadside it would have been impossible......

By the way - to remove solenoid to get at plunger is it the little nut on the top of plate or the big one at base ? I'm plucking up courage, energy and knowledge before going up the steps to where the car is on the dirt track. If you saw my dog film on Youtube earlier post (no justification for forum but does show my two RR's for a second) you will see where I have to manage - no pit or garage and the sun is tough on cars - all the paint peels........

Sorry I missed this thread until now.

Unlikely to be a case of solenoid not opening enough to allow enough flow of liquid gas for idle but not enough flow of liquid gas for blipping the throttle or light acceleration... Unless the electrical feed to the solenoid is intermittent, in which case the solenoid might close when the throttle is blipped or in light acceleration - but unless this was due to a main power feed problem (to the LPG ECU) it would more likely be due to coincidence.

I have known plenty Zavoli reducers fail in a way where the maximum gas flow is severely restricted, in some cases the restricted gas flow has been enough to maintain vapour pressure for idle but for no greater load than idle... so blipping the throttle or light acceleration would cause pressure to fall away very quickly (can't maintain pressure of volume throughput is restricted, so pressure falls away, system senses lack of pressure and switches back to petrol). The situation described here would call for a new reducer but this may not be the case and it's worth doing other checks first.

The gas vapour temp sensor will need fixing, it's worth checking the solenoids and for issues such as bad main power feed / earth.
You could monitor voltage to the solenoid(s) while switching to gas, at idle on gas, and when you blip the throttle. The injectors pulse for longer with higher engine loads (such as when blipping the throttle) soif there's a bad main power feed to the LPG ECU the extra current drawn can cause voltage to all LPG components to lower which could cause solenoids to close or sensors (including pressure sensor) to read incorrectly.
After the system has beeped and switched itself back to petrol you could read vapour pressure on screen again, N/A (not applicable) means no pressure... If you do a pinch test on a vapour pipe (or disconnect a pipe) you'll know if this seems to be a true or false reading. False reading points to pressure sensor, voltage or ECU problem. True reading points to solenoid, voltage or reducer problem.

Another thing about Zavoli reducers is that they only really like to work at the pressure for which they were designed (1.2 or 1.5 bar depending on model). Like other reducers they have a pressure adjusting screw but on Zavoli reducers if you turn pressure down they tend not to be capable of flowing nearly as much gas (throughput) as at standard pressure.

This is all assuming the feed from the tank is good - If the tank were outputting vapour instead of liquid (on a single hole tank, particularly 30 degree tanks) if the flexible pipe that picks up liquid from the bottom of the tank has come off inside the tank the tank will output vapour. The reducer needs to be fed liquid gas but might flow enough for idle if fed vapour.

Simon

Handy hint, not LPG related, but...
Wheels stuck on hubs- loosen wheel nuts (sufficient to allow wheel to wobble on hub but not fall off). Drive car forwards and backwards a bit while turning steering from lock to lock.
Most of the time just loosening nuts and turning steering from lock to lock will do it.
Much easier on the back!

Orangebean wrote:

Handy hint, not LPG related, but...
Wheels stuck on hubs- loosen wheel nuts (sufficient to allow wheel to wobble on hub but not fall off). Drive car forwards and backwards a bit while turning steering from lock to lock.
Most of the time just loosening nuts and turning steering from lock to lock will do it.
Much easier on the back!

In my boy racer days I followed a group of lads who were in a mk1 Escort down the A1 at 100mph, they pulled up due to steering wheel wobble, turned out they'd changed a wheel earlier but can't have done the nuts up properly because 3 nuts were missing and the one remaining was nearly at the end of its threads!