VT Commodore LPG installation utilisingan LPG Memcal and Apexus Quick-kit.

Description of components and operation

LPG/Petrol Changeover switch

The LPG change-over switch is mounted inthe instrument facia to the left of theinstrument cluster and below the tripcomputer controls (Fig. 1). The switch ispush button and has a momentary action.When LPG is selected the green LPGindicator on the instrument cluster isilluminated and a green indicator lights onthe switch. If the push button switch isactivated again the LPG function is turnedoff and the vehicle reverts to petroloperation. Switching between “Petrol” and“LPG” operation can only occur while thevehicle is stationary or moving at less than3 kilometres per hour. Each time the fuel mode switch is pushed the vehicle changesfrom one fuel to the other. Even when the ignition is turned off the last fuel in use isremembered by the vehicle computer system and this is the fuel mode it uses thenext time the engine is started.

Petrol operationWhen the LPG indicator on the instrument cluster is not visible and the indicator inthe button of the fuel mode switch is “OFF” the vehicle is running on petrol. In thismode the LPG system is turned “OFF” and the vehicle functions in the same way asa vehicle not fitted with LPG. When operating on “Petrol” the fuel gauge shows theamount of petrol in the petrol tank.

LPG operationWhen the green indicator (Fig. 2) is lit themode switch has been cycled to LPGoperation. In this mode the PCM (PowerTrain Control Module) activates the LPGmixture control computer and varioussolenoid valves to allow the flow of LPG tothe engine. If the vehicle is fitted withtraction control the PCM will disable thetraction control when LPG is selected. The“TRAC OFF” traction control indicator inthe instrument cluster will light to indicatethis. In LPG mode the fuel gauge reads theamount of LPG in the LPG tank. Becausethe LPG system uses small amounts of

Fig. 1 : Apexus PS122 Gas/Petrol ModeSwitch

Fig. 2 : Dash fuel gauge used for both LPGand Petrol. LPG lamp shown illuminated

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petrol to start the engine and when running on high power, it is essential to maintainsome fuel in the petrol tank. If the petrol tank is low even in LPG mode the low lampwill light and the digital display will warn “Lo – Petrol” just after engine start.

Injector Pulse widthIn all LPG operating modes, exceptduring cranking and high poweroperation, the petrol injector pulse widthis set to zero. The PCM also injectspetrol during engine cranking to assiststarting. The amount of petrol deliveredduring the start is determined by thecoolant temperature and the crank time(Fig. 3). After cranking no further petrolis delivered to the engine unless it isneeded to cool the valves and stopvalve recession during high speed andhigh power operation.

Petrol PumpThe petrol pump relay operates thepetrol pump for about two secondswhen the ignition switch is first turnedon, and continues to operate duringcranking and then for about 5 secondsafter the engine has started (Fig. 4).During normal LPG operation the petrolpump is not running unless engaged bythe PCM during high power operation toprevent valve recession.

Spark Timing MapA special Electronic Spark Timing (EST)map which has been programmed toprovide optimum timing for LPGoperation is built into the Memcal PROM. Should the engine speed drop below 300RPM the spark plugs are prevented from firing to reduce the risk of backfire in the airintake manifold.

Trip ComputerThe PCM fuel usage output signal has a modified calibration to better suit LPG fuel.

Crank InhibitDuring starting in the LPG mode the PCM prevents the engine from cranking bydeactivating the start inhibit relay if the throttle is opened more than 7%.

2 Sec

Crank

5 Sec.

Time

Pump

Fig. 4 : Petrol Pump Operation

Ignitionon andCranking

0.4 secno start

InjectorPulse

Engine Start

Pulse time varieswith coolanttemperature

No further PetrolPulse Whenrunning On LPG

Time

Fig. 3 : Petrol Injector Pulses for LPG start sequence

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MemcalThe Memcal (Fig. 5) is a PROM(Programmable Read Only Memory).Contained within the LPG Memcal is aprogram so that the PCM can operate inone of two modes, either “Petrol” or “LPG”,ie both the petrol mode and LPG mode areprogrammed into one Memcal so that it isnot necessary to physically change theMemcal to swap from one fuel to the other.Which program mode the PCM isoperating in is determined by cycling theLPG changeover switch, the last switchposition being retained in the PCMmemory even when the ignition switch isturned off.

Kit Installation

Mechanical InstallationFit tank, LPG lines, converter, mixer, waterlines, vapour line, vapour control valve,filler system, lock-offs, intake manifoldbalance line and any other hardwarerequired for the particular installation(Fig 6.).

Electrical InstallationPreparation before fitting loom.

Remove the PCM by disconnecting thebattery, removing the left hand front sillcover using a Torx tool, (refer to Fig. 7),and removing the left hand front foot upperpanel. Remove left hand front kick panel(Fig. 8)

Fig. 7 : Undoing torx screws holdingsill trim

Fig. 8 : Undoing kick panel screw

Fig. 5 : Memcal fitted to PCM

Memcal

Fig. 6 : Vapouriser, lock-off, andApexus electronic safety cut-out (Model

CO100) which provides short circuitand overload protection, without

blowing the fuse

SafetyCut-Out

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The PCM (Fig. 9) is removed by unclippingit from the left hand front pillar.

Removal of console and facia panel iscarried out by first removing the rubber matfrom below the ash tray and then removingthe two self tapping screws located belowthe ashtray opening (Fig. 10). Next unclip,lift and remove the transmission coverpanel from the console. It may benecessary on some models to pushforward slightly on the rear of this panel toclear the electric window switches.(Fig. 11). Disconnect all wiring plugsbefore this panel can be removed. Storethe transmission cover in a safe placebeing careful not to damage the painted front surface.

Using the radio removal tool (part number AU464 - available from SpecialisedService Tools & Equipment - Phone (08) 82692588), slide the radio out (Fig. 12). Asimple radio removal tool can be made from two pieces of 1/8” welding rod, bentaround a 1¼” diameter pipe. Remove the harness and aerial plugs from the back ofthe radio unit and store the radio in a safe place. The vehicle owner will need toprovide the radio security code before it can be made operational again once it isreinstalled.

Unclip and lower the right hand lower instrument panel by pulling it down just below

Fig. 9 : PCM clipped in position

ModeRelay

Fig. 10 : Removing the transmissioncover screws

Fig. 11 : Removing the transmissioncover

Fig. 12 : Removal of radio system Fig. 13 : Remove centre consolescrews

SpecialTools

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the steering wheel to reveal the fuse and relay boxes. Lower the steering column toits lowest point.

Remove the five lower screws on theinstrument cover panel, (Fig. 13 ,14,15)remove the 2 upper screws (Fig. 16).

Carefully unclip the facia panel and unclipthe light switch harness and other sockets.Remove the facia panel past the steeringwheel and column. The facia panel mustnow be stored so as not to damage thepainted front surface.

Remove the two screws holding in theinstrument cluster (Fig. 17), slide forwardand remove the wiring plug and thenremove the instrument cluster and store ina safe place (Fig 18.).

Fig. 14 : Remove right hand sidescrews

Fig. 15 : Removing consoleretaining screw located to the left of

the steering wheel

Fig. 16 : Removing the two upperretaining screws from the console

Fig. 17 : Instrument clusterremoval (2 screws)

Fig. 18 : Removing instrumentcluster plug

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Instrument Cluster CompatibilityIn some early build vehicles the instrumentcluster may not be compatible with theLPG memcal. In some cases the fuelgauge may read empty whilst on LPG. Inthis case the instrument cluster will need tobe replaced. In other cases the fuel gaugemay function normally, but the green “LPG”lamp will not illuminate whilst on gas. Inthese cases a separate plug-in lamp isavailable to replace the existing LPG lampin the cluster. Instrument clusters inExecutive model vehicles with VINnumbers less than L326280 or Berlinamodel vehicles with VIN number less thanL322758 may fall into one of thesecategories. Replacement instrumentclusters will also need to have theodometer reading reprogrammed by aHolden dealer equipped with a Tech2diagnostic tool.

At this time it is also a good idea to checkthat there is a globe present in the LPGlamp position (Fig. 20).

Loom InstallationUsing a piece of plastic tube slid behindthe console trim over the transmissiontunnel from right hand to left hand foot-well, drag the switch part of the loom(section fitted with fuse) and the longeryellow wire from the left hand side to theright hand side of the console. Place theswitch loom in the switch area to the left ofthe steering column and route the yellowwire up to instrument plug. The fuse shouldend up behind the left hand foot well panel.On the right hand side feed the yellow wirebehind the instrument cluster area andinsert the pin fitted to the yellow wire intocavity No. 10 of the instrument clusterplug. It may be necessary to widen theopening in the white plastic insert slightly inorder to insert the pin. Ensure that the pinlocks into the socket cavity. (Fig 21).

Fig. 19 : Identifying change index(CI) on instrument cluster

Fig. 20 : Location of LPG lamp bulb

Fig. 21 : Inserting yellow wire fromLPG loom into instrument cluster plug

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Installation of the PCM wiring

On the left hand firewall above the PCM, remove the small blank rubber grommet(approximately 25mm in diameter). Feed the end of the loom with the green,green/white, grey and blue wires through the grommet hole and pass it into theengine bay. Re-fit the grommet provided on this section of the wiring loom and finallyseal the wires and grommet with silicon rubber or a similar compound where theypass through the firewall panel.

On the PCM there are three electrical plugs - the top plug has C & D rows of pins, thecentre plug (pink) has A & B rows of pins and the bottom plug (blue) has E & F rowsof pins.

Remove the lock tab on the rear of the pink plug and insert the brown wire alreadyfitted with the correct terminal into cavity A9. Replace the lock tab on this plug.

Remove the lock tab on the lower blue plug and insert the white wire already fittedwith the correct terminal into cavity E1, and insert the red wire already fitted with thecorrect terminal into cavity E11. Replace the lock tab on this plug.

PowertrainControlModule(PCM)

ModeRelay

Loom to Rearof Vehicle

Apexus SafetyCutout

Model CO100Small

FirewallGrommet

InstrumentCluster

Connection

MixtureControl

Computer

LPG/PetrolChange-over

SwitchFuse

SenderConnections Tank

SolenoidConnection

Boot

Left HandKick Panel

Instruments

Under Bonnet

Fig. 22 : Loom installation layout

PCMConnections

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Locate wire A4 (pink) on the centre (pink) PCM connector plug. Bare a small sectionand splice and solder the red wire from the harness supplied and insulate it withamalgamating tape. The red wire carries 12 volt vehicle power via a fuse and relay tothe safety cut-out, valves, LPG processor module, and indicator. On the same pinkPCM plug locate wire B11 (blue wire) and bare a small section. Splice, solder andinsulate the blue wire from the LPG harness. The blue wire carries the TPS (ThrottlePosition Sensor) information to the LPG processor module.

On the top plug locate pin D13 (grey wire) and again bare a small section, splice,solder and insulate the grey wire from the LPG harness. The grey wire carries theoxygen sensor information to the LPG processor module.

Memcal InstallationIdentify that the Memcal has the correctcode for LPG. The code should beBWLR1277 shown on the top surface (seeFig. 23).

The Memcal is most easily installed whenthe PCM is unplugged for the wiringconnections. If the PCM is still in place andconnected, first disconnect the battery fromthe vehicle then remove the left hand kickpanel. Release the PCM from its holdingclip as outlined above and then afterremoving the PCM from its carrier, undothe cover in the top right hand corner of thePCM (Fig 24). The Memcal is releasedfrom the circuit board by pulling outwardson the two locking tabs retaining theMemcal in position. In this way an LPGMemcal can be substituted for the existingpetrol Memcal in the polarised connector.After substituting the new Memcal replacethe locking tabs and cover.

Loom installation - Vehicle cabinLHSReplace the plugs to the PCM and fix thePCM to the carrier position Fix the LPG mode relay to lower left of the PCM (see Fig.9 and Fig. 22). Using the fixing screw of the relay, connect the black earth wire fromthe loom (supplied with a 6mm eyelet) to the vehicle body earth.

Fig. 23 : LPG memcal identification

Fig. 24 : Memcal location in PCM

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Loom installation - EnginecompartmentIn a previous step a section of loom waspassed from the cabin through a grommethole on the left hand side of the firewall tothe engine compartment. The green/whitewire is connected to the +12V terminal ofthe Safety Cutout as shown in theillustration (Fig. 25). The Pulse terminal onthe cutout is connected to the vehicleTacho output located on the firewall nearthe front left hand inner guard (Fig 26).

On some vehicles this tacho output is notpresent. In these cases the tacho shouldbe picked up from the plain brown wire inthe grey connector located on the firewallnext to the right hand guard in the enginecompartment (Fig. 27). The green wirefrom the safety cutout is connected to thesolenoid coil of the gas lockoff. The greenwire from the loom piggy backs onto thegreen wire from the safety cutout and isrouted in the loom to the lockoff solenoidcoil located in the LPG tank sub-compartment.

Loom installation - Rear of vehicleThe remainder of the loom is tucked underthe left hand front and rear door sill panelstravelling to the rear of the vehicle where itruns into the boot space via the centre foldseat back. Once in the boot space, theloom is fed through a 12mm hole drilled inthe floor of the boot to the outside of thecar near the vapour outlet tube (Fig. 28).When drilling the 12mm hole take extracaution to ensure that the other side of thedrill hole is clear. After the grommet isfitted, seal around the wire if necessary.The loom is fed into the vapour tube up tothe valves in the tank sub-compartmentwhere the yellow and black wires fitted withthe 6.3mm female spade connectors arepushed onto the LPG gauge senderterminals. The remaining green wire isconnected to the LPG solenoid valve. Thesecond terminal of the solenoid valve isearthed at a convenient point away fromthe vapour box on the outside under-pan ofthe vehicle.

Tidy the wire loom neatly into position andreplace left hand kick panel and sill panel.

Fig. 25 : Apexus CO100 safety cut-out terminals

Fig. 28 : Rubber grommet entry tosub-compartment

Fig. 26 : Tacho connection for safetycut-out

Fig. 27 : Alternate tacho pick uplocation

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Fitting mode switch to dashboardTaking great care to avoid damage to thepainted surface of the facia panel, fit theilluminated switch PS122 (provided with ashort loom - Fig. 29) to the facia panel atthe approximate location shown in theillustration (Fig. 30), by drilling a 10 mmhole. Carefully clean any burrs then placethe LPG label so that the writing is parallelto other text on the facia. Gently tighten thelock nut on the back of the switch. Guidethe switch loom to meet main loom atlower drop panel. Re-fit the connector tothe rear of the instrument cluster guidingthe new yellow wire behind the clusterwhere it can be taped or cable clipped inplace to avoid any rattles. Replace the twoscrews holding the instrument cluster inposition. Reconnect the plugs to faciapanel and clip and screw the facia panelinto its original position, making sure thatthe loom from the new LPG switch is clearof other components and the connectorsare accessible in the fold down fuse panelbeneath the steering wheel.

Replace the radio and centre consolepanels. Connect the switch loom wires tothe matching colours in the main loom andtidy up the wires. Clip up the lower righthand front fuse cover panel. Re-fit anyother trim panel removed for installationand ensure all connectors are re-connected.

System check and CommissionCheck that all the wiring and mechanical components are installed and connected.Reconnect the battery. Turn on the ignition and check that the LPG mode switchcycles the LPG lamp each time it is operated and that the fuel gauge cycles from onefuel to the other. Run the vehicle on petrol. Fill some LPG into the LPG tank andcheck for leaks. With the engine running on petrol and the vehicle stationary run theengine at about 2000 RPM and cycle the LPG switch so that the vehicle runs onLPG. Carry out the necessary tuning and operational checks to ensure that the LPGmixture control computer is operating in the closed loop mode.

Road test the vehicle. Leave a copy of these instructions in the glove box for futurereference during any maintenance of the system. If not already done the dashboardLPG lamp can be turned on with the Tech 2 tool used by dealers for programmingand maintenance of the vehicle computer systems.

Fig. 29 : Fuel mode switch assupplied for fitting to fascia

Fig. 30 : Drill and file hole to match fuelmode switch

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Red - Power Pickup (A4)

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