Factory LPG switch + gas 'computer'

[CRCinAU]

Hi all,

I've found bugger all info on these things - so I'll ask here:

1) Where can I get a replacement Petrol / LPG switch that goes under the headlight switch on my VR? I've found tons of aftermarket - but not sure on if these will be compatible with the factory impco system. I've managed to find that one of the wires goes to the LPG solonoid, another to pin 20 on the computer - but can't find any other info on how the system is supposed to work.

2) There is an LPG 'computer' behind the glovebox that is supposed to do something when running on LPG. When I first got the car, there were two LEDs on this box - red and green - and they would flash while the LPG system was on. From what I understand, this controls something with the LPG system and allows the car to switch correctly between petrol / LPG (ie overlaps the fuels). I haven't been able to switch between fuels without stalling at idle for years. I'm trying to find the function of this box and info about it so diagnose what is going on.

3) There are 2 solenoids that are routed to the front near the air filter box that used to tap while on LPG (kinda like the injectors do for petrol) - however these no longer 'tap'. Does anyone know the function of these and what they are supposed to do? I can't find any info of this at all.

The car still runs quite well on both petrol and gas - but the changeover is horrible - even if done at non-idle RPMs.

Thoughts? Ideas? Links? Diagrams?

 

[BadDad62]

I've got the same here and know as much as you atm, going to get the system rechecked after having the mixer replaced a few weeks ago. I'll ask them and see what I can find out.

my factory switch has sunken into the dash due to the screws breaking the plastic.

I,ve looked at swapping either of the other aircon/rear window heater or hazard ones over but just need to find out if they work the same.


Indash switch/gauge VR-VS Commodore - Blue LPG Shop

http://forums.justcommodores.com.au...997/152667-vs-factory-lpg-petrol-problem.html

 

[CRCinAU]

My switch looks nothing like the ones in the Blue LPG shop... Mine is just like the hazard switch - but no light.

The controller and tappy things are exactly the same as the ones in the thread you posted to...

 

[kingswood country]

My I laws have the switch problem. I believe if I remember correctly the hazard switch is near identical, the gas switch is now obsolete.

The also have to pull over when changing from petrol to gas and swap at idle. And from memory, swap it over to petrol just to start.


Sent from my iPhone using Tapatalk

 

[Jxfwsf]

The box is just the LPG fuel mixture processor (not really a computer) essentially takes the tps and 02 sensor data and controls the solenoids.
The red and green leds will indicate rich and lean, they should be alternating at idle, what is it doing now and what led is light etc etc?

The solenoids adjust between atmosphere pressure and intake vacuum to control the diaphragms in the converter to adjust mixture (not all of them make noise but they do wear out)
Are they the solenoids with only 2 hoses going to them?
Hold onto them while it's on LPG and at idle and see if you can feel them working.
Take them off, can you blow thru them? If you can then they're worn out.

 

[CRCinAU]

Well, I pulled the glove box out today and had a look at the 'computer' down there. The green light flickers away - the red lights every now and again when I rev the engine and let it go back to idle again. I presume this is the mixture control happening in real time...

The valves at the front however seem to do nothing.

Attached some lovely photos:


The valves seem to have: FCV 940905 printed on the label. A quick google shows up nothing for this (yay!). I probed the points with a multimeter and got ~2.8vDC on them - however this could easily be an average and the valve is getting a 12 volt pulse (as you'd expect from a valve that goes 'tap tap tap tap tap').

I tried to blow or suck through the valve (without disconnecting the hose to the LPG evaporator) with no success. I can easily blow through the pushed on hose to the air intake mixer. I'm therefore wondering if the valve is just not working (seems funny that both aren't).

Any thoughts on how to test these units? Or even where to find info on them (or replacements)?

 

[CRCinAU]

Anyone? Bueller?

 

[Jxfwsf]

disconnect them and put the multimeter across the terminals on them (will see if i can find one to see what it should be) try different setting to see if they are open circuit (burnt out) or have some resistance.

you are correct that the voltage measured is a pulse so you won't see 12V normally except under whatever circumstance the processor is set to hold them open.
someone may have played with the mixture screws so the processor may not even be trying to control them.
o2 sensor could be old and worn out resulting in a similar problem.....

they may just be gummed up and stuck also, carefully they can be pulled apart with a small flat blade screwdriver unhooking the tabs on the back.

the flashing leds atleast indicated the processor is getting feedback from sensors and is somewhat working, it could be as simple as the converter and mixer are just gummed up from the years of crap.... mixer is easy, pull it off and spray carby cleaner through it from every hole... converter, bit more in depth and if you're not confident playing with the gas system here i'd say get a professional to look at that part (taking plugs out and/or disconnecting the liquid side if not resealed properly afterwards can cause a gas leak).

quick look in an impco converter (may not be the same model as yours but they're all pretty close) as can be seen there is alot of crap built up in there, can clog the seals (seals could be worn out) and basically stop it performing as it should, you can't always get these apart as over the years corrosion through the water galleries can leak past gaskets, screws seize and break while trying to get it apart etc etc.

 

[CRCinAU]

I think the thing here is that once it is running on LPG, the performance is fine. There is no rough running, no dips in power etc.

I pulled out the multimeter, measured 20 and 21 ohms across the two coils. I measured ~20ohms between one of the wires and ground (so I assume that's the proper ground) and quite a few Mohm between the other wire and ground (probably the positive).

I'm just about to wire up an LED to a resistor and put it between the two control wires and see if I get the LED pulsing. If so, then I'd say it's certainly the actual valve / solenoid things that are faulty.

 

[CRCinAU]

Ok, so I checked the signal with LED + resistor and the flashing on the LED matches the LED on the controller behind the glove box. Before I look at replacing the solenoid etc - could there be anything on the vacuum or LPG side of things that could stop the valve ticking properly?