1995 E36 328 Coupe LPG Conversion - DRAFT Disclaimer No warranty of any kind implied or given and no liability accepted for any loss, damage or injury, no matter how incurred from reading or attempting to follow this document. This is merely how I installed LPG on a car and I am not recommending this process. Revision history This document is in draft and unchecked. Safety first Work should only be undertaken by competent persons If in doubt seek expert advice or help prior to starting the job and do not attempt it. Do not place yourself or others at risk A method of safely raising and supporting the vehicle is required and is not covered in this document The suspension system will be partially dismantled and additional care must be taken to avoid inhaling or coming into contact with brake dust Do a risk assessment before starting work. If in doubt do not attempt it. It may not be advisable to work alone under a vehicle. Before working on the electrical system the battery should be safely disconnected by removing the earth lead.
Instructions on how to convert a BMW e36/E39 to LPG
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1995 E36 328 Coupe LPG Conversion - DRAFT
Disclaimer No warranty of any kind implied or given and no liability accepted for any loss, damage or injury, no
matter how incurred from reading or attempting to follow this document. This is merely how I
installed LPG on a car and I am not recommending this process.
Revision history This document is in draft and unchecked.
Safety first Work should only be undertaken by competent persons
If in doubt seek expert advice or help prior to starting the job and do not attempt it.
Do not place yourself or others at risk
A method of safely raising and supporting the vehicle is required and is not covered in this
document
The suspension system will be partially dismantled and additional care must be taken to
avoid inhaling or coming into contact with brake dust
Do a risk assessment before starting work. If in doubt do not attempt it.
It may not be advisable to work alone under a vehicle.
Before working on the electrical system the battery should be safely disconnected by
Safety first ............................................................................................................................................. 1
Parts list ................................................................................................................................................ 5
Background Modern LPG conversions are a good way to retain the performance of a large engine petrol car but
with the equivalent running costs of a diesel or small car.
The basic options are as follows:
Take the vehicle to a specialist for conversion.
o Pro – hassle free, no tools required.
o Con – requires more money, not necessarily true if you do not have the required
tools or skills.
Purchase LPG equipment and fit, setup and calibrate.
o Pro – cheapest option.
o Con – requires conventional tools, effort and experience of setting up LPG, laptop
and appropriate interface.
Purchase LPG equipment from a reseller that is prepared to brief you on the equipment and
includes returning the car to them for setup and inspection.
o Pro – Medium cost, benefit from professional inspection and setup, and receive
appropriate certificates.
o Con – requires conventional tools and more running around. No laptop or interface
required*.
Purchase a vehicle with LPG already fitted.
o Pro – Minimum effort and someone else will have borne the brunt of the costs.
o Con – LPG is relatively rare so it may be impossible to find your chosen car with it
already fitted.
This document only covers the third option.
*Note: I supplemented the third option with my own laptop and purchased an interface. I also
installed Windows Media Encoder to capture the whole setup process for reference.
Cost Benefit Analysis I chose LPG based on the following factors:
An expected reduction in fuel costs of approximately 30% - 40%
Break even on the purchase in <8 months
The logical conclusion that the cost of fuel would go up year on year
Tools These tools are required:
Comprehensive general tool collection, not limited to:
o Assorted sockets
o Assorted spanners
o Clic/Clic R hose clamp pliers
I purchased 040214231 from Machine Mart
o Large flat blade screwdriver
o Torque wrench(s)
Job specific tools, not limited to:
o Soldering iron, solder, and heat shrink
o Spring compressor
o 5mm Drill bit
o 6mm Tap
o Flexible drill drive
o Grinder
o Welder and consumables / safety equipment
o Steel / Aluminium sheet
o Rivet gun and rivets
Garage equipment for raising and supporting the car
Safety equipment, such as but not limited to:
o Eye protection
o Dust mask
o Gloves
Knowledge base:
o LPG kit parts literature
o Supplier that provides phone or email support
o I personally collected the kit so the supplier could talk me through the parts and how
they fitted together. It is surprisingly simple. As it happened he had a converted 525
on site which was nice to see
Parts list o LPG Kit
o Steel sheet and optionally Aluminium sheet
o Rivets / Screws
o General wiring consumables.
o Other – there are always a load of bits and bobs required, for example I used part of
a Vectra cooling system hose to improvise coolant pipes to the reducer / heat
exchanger.
Design decisions The pros and cons of some component selections are below. These are laid out to aid in the choices
and also to show how someone else would select different parts depending on their vehicle /
application.
Design decision 1 – Tank Option Pro Con
Cylinder in boot space
Larger capacity tank easily accommodated
Full size spare retained in original location
Increased range
Boot space compromised
Split rear seats may be obstructed
More complex mounting
More complex connections to filler
Raises centre of gravity
Toroidal in spare wheel well
More boot space available
Split rear seats still clear
Simple fitting*
Simple connections
Reduced range
No spare or reduced luggage space Note some may find a can of tyre repair an acceptable mitigation
Based on the above a toroidal tank was chosen and a compromise on boot space achieved with the
purchase of a second user 16” space saver to minimise the amount of boot space used.
*Note: Some later cars may have the fuel tank carbon canister situated under the spare wheel well
which would require re-location or a different design decision outcome.
Design decision 2 – Filler type and location Option Pro Con
Panel mounted Convenient and clean position
Unlikely to be damaged in a collision
70mm diameter hole required in panel
Black, cannot be colour coded
More complex mounting
More complex routing to tank
Battery box and exhaust back box inhibit routing to a toroidal tank if mounted in either quarter
Bumper mounted Does not require cutting an expensive panel
May be damaged in collision
Complicates bumper removal
Requires clearance behind bumper
Must comply with COP11 clearance from exhausts
Under bumper central mount
No panels are cut to enable fitting
May use a pump on either side of the car
Simple connection to tank
Less likely to be damaged in a collision
Must comply with COP11 clearance from exhausts
May be inconveniently low
Based on the above an under bumper filler was chosen
Procedure
Mount tank It should be noted that LPG is a heavy gas and does not easily disperse. The design of the toroidal
tank and its fitments are such that all the bolt holes and screw holes and cover have rubber seals to
ensure that any gas leaked or “blown off” by the pressure release valve is safely vented under the
vehicle onto the floor where it can disperse. To this end the vent tubes need to be a good fit in the
floor and protrude far enough below the vehicle.
The mount for bolting down the spare wheel would not allow the toroidal tank or its vent tube to be
easily fitted or a good seal. Therefore the sealer was removed from above the seam in the spare
wheel well and the mount twisted anti-clockwise to remove it. Two flats are provided on the
trumpet part to allow this to be easily done with a big enough spanner.
I did consider getting another spare wheel mount to modify and storing the old “colour coded” one.
However, I decided that the likelihood of removing the kit was low, that another mount could be
acquired in future if required and modifying the existing one reduced expense and effort.
The removed spare wheel mount.
Test fitting of bare tank once the spare wheel mount was removed.
Spare wheel mount modifications start here. The original mount is modified to capitalise on its easy
removal and refitting to allow the conversion to be reversed with minimum work if required.
Note: If a welder is not available a circle of 3mm or 4mm steel plate could be used for this purpose.
Pilot hole drilled and trumpet removed with a nibbler.
A grinding disk made a nice template for drawing around, the disk of steel was cut out with tin
snips....
....and then clamped in place. Note that the vent tube is fitted into notches cut in the wheel mount
and new disk that together make a hole. The position and size of which were marked from a cereal
box template of the middle of the LPG tank.
Then the middle was tack welded.
This is the mount placed on the centre of the tank to make sure all the holes are in the right places
before seam welding.
Disk seam welded into the spare wheel mount and the two reinforcing tags provided with the tank
welded to it. These tags are provided to mount the tag to a flat spare wheel well floor.
Two “generic self grip wrenches” used to twist the mount into place in the floor.
Mount in place ready for the tank.
Note: Before the tank was finally bolted down the filler mount was fitted
Tank loosely bolted into place to check fit. When the tank is properly fitted seals are used under the coach bolt heads, and O rings under the vent tube and vent tube fixing screws to ensure any gas vents under the floor and not into the spare wheel well and battery area.
And allow for adjustment of the vent tube length.
Multivalve installation into the tank Once the tank is securely bolted down the multivalve is fitted. The float is held in line with the “fill
level tube” and the flexible LPG pick up pipe is held together with them. Avoid the common error of
hooking the LPG pick up pipe over either of the other two.
The multivalve should be installed in line with the manufacturer’s instructions provided with it. The
bolts in the tank threads are discarded; they are only provided to protect the threads and are not
intended to secure the multivalve. The multivalve packaging contains more bolts. A torque wrench
may be needed here.
Mount filler If I remember rightly the COP11 regulations specify that the filler mount should be able to withstand
more than 50KG. They do not, however, specify that any panel it is connected to should.
It should also be noted there are two types of pump “nozzles”, those similar in appearance to the
traditional petrol or diesel nozzle and some where it is more like a fireman’s hose with an arm that
flips forward and hence requires more panel clearance.
The information I was given for mounting an under bumper filler was that most are mounted at the
bottom of the bumper and that there should be 6” clearance all around. As the bumper curves under
mounting it on the boot floor back edge would not provide 6” clearance all around making these
appear contradictory and exclusive instructions.
I wasted one day thinking about this and finally decided to make a mount that provided 6” clearance
all around from a couple of inches behind the gas bayonet filler and was adjustable without
removing the tank in case I made a mistake.
I purchased approximately 300mm of 50mm by 3mm wall box section.
Various cuts are made to the steel. Cutting at an angle, to make it less likely to get hooked on
anything, and then cutting a wide slot in the remainder of the bottom to allow good access to
tighten the compression joint.
The brass bayonet filler came with a steel L shaped bracket, the short side of the L to allow it to be
screwed or bolted to a suitable place was sawn off and I welded the remains to my bracket.
Shown below with the brass bayonet and plastic trim fitted.
Shown below is the same bracket with bayonet removed and holes drilled to make its positioning
adjustable,
The mounting bolts are spot welded to steel oblongs for two purposes. This spreads the load of
securing the filler bracket to the boot floor making it more secure and able to take a bigger load and
stops the bolts spinning as once the tank is in place they will not be readily accessible if the bracket
is moved.
Paint applied. You may be able to see a 5mm hole drilled in the bottom right corner of the filler
bracket.
Various articles on the web spoke of allowing a coil of pipe to allow slack in case the filler is damaged
in an accident so as to protect against damaging other components so I allowed a loop as this would
also accommodate if the filler bracket was moved fore or aft later.
The rubber sleeve is stripped from the pipe at both ends and olives used where it connects to the
multi-valve and brass filler. This is basically a compression fitting for those familiar with plumbing.
A hole was also drilled in the filler cap and two zip ties used to create a tether to stop it being lost
The finished filler and cap are shown in place. Note the lugs on the bayonet are East and West not
North and South.
Multivalve shown with the filler pipe on the left and the front to rear pipe on the right.
Note: I wasted about a half a day trying to bend these pipes to line up with the multivalve. In the
end I bought a Clarke CHT264 from Machine Mart which allowed me to get the pipes near enough to
apply some adjusting force by hand to finally fit them.
Rear to front LPG line The COP11 rules state that pipes should be secured not more than 60cm apart under the vehicle. As
I was not going to strip the whole interior out I slid some brake pipe down the drill to make sure it
went just through the bodywork without going far enough inside to cause damage to trim etc.
I removed the near side rear spring to allow access to route the front to rear pipe and make sure it
would clear the suspension throughout the full range of movement. I lost about ½ a day due to a
stripped locking wheel nut.
Heat shield mount doubled as pipe securing bolt. The front to rear pipe left the multivalve, out of
the vent tube, and up the side of the spare wheel well................
..........then around the outside of the subframe mount but above the anti-roll bar mount
.....and up the inside of the chassis box section.......
........ because I had found that when the car is on the bump stops if it was on the bottom of the box
section it would be crushed.
The pipe then has to come across to the outside to go around the petrol tank..........
...........and above the rear trailing arm. Clearance still exists with the car sitting on the bump stop
The plastic shield is removed from the corner near the tank to allow the pipe to be routed and
secured.
And trimmed..........
........and refitted.
A simple screw replaces the sheared stud and nut that fixed the shield in place.
And the pipe bender came in handy again as the LPG pipe joins the run parallel to the brake and fuel
lines.
And continues along the floor behind the fuel filter cover and up into the engine bay closely
following the line of the fuel pipes until it deviates to connect to a solenoid mounted with the
reducer.
Solenoid valve and reducer mounting I assembled the front solenoid and reducer onto a bracket and piped them together.
The complete assembly was them bolted to what would be the battery mount on a 1.8. The open
fitting on the left of the solenoid is where the front to rear LPG pipe will connect.
Injector mounting Note: these are essentially solenoid valves if my understanding is correct.
Mounting of the injector blocks depends on the type you have. The chosen location complicates
changing coils or spark plugs and is not ideal. However, the injector blocks lift away after undoing 4
nuts so it is a minor inconvenience.
A bracket location was chosen and marked on the cam cover trim.
I am not a fan of using this thin plastic as a mount so a plate was also fitted on the inside to spread
the load and ensure the mount was rigid.
A view of the inside of the cam cover trim showing the reinforcing plate.
Cam cover trim refitted to the car. This would not be the only time it was removed and refitted.
Here you see the solenoids mounted on the bracket. Note the wires for the pressure sensor near the
oil filler cap.
Each block is capable of fuelling 4 cylinders, so two are used and two solenoids will be left unused. I
must point out that various solenoids are available in singles and threes as well. However, four is
likely to be the cheapest and most readily available and I choose to see having two ”spares” built in
as a bonus
Each block is mounted on two rubber bobbin type mounts that screw into the base plate and are
then bolted to the bracket.
In this picture you can see the short length of LPG pipe and hose clips securing the two together in
series.
MAP sensor mounting With the fuse box lid removed the relay cover was lifted away and the MAP sensor mounted with a
self drilling self tapping screw. Obviously this relies on a relay location being free. However, this is a
small sensor easily mounted elsewhere.
ECU mounting The ECU provided can be mounted anywhere dry in the engine bay, preferably with the wiring
connector at the bottom. However, due to various options a good mounting space was not as easy
to find as expected so it was decided that it would be piggy backed in the standard ECU space.
Note: This space is already occupied by an ECU for the gearbox in automatic transmission models
Sound proofing is removed then 5 screws are undone to remove the cover panel to expose the
standard ECU.
With the wiring disconnected the ECU slides out.
There are a few pictures missing here but the steps are as follows:
The ECU mounting bracket was removed, to do this I had to cut a spanner in half for
clearance
Once removed the mounting bracket looks something like part 6 in this image. The top and
half the height of the nearside were removed.
An aluminium plate was cut to size and then riveted to it at half height
The LPG ECU was then screwed to it.
Part 11 in the image was trimmed to allow the wiring to exit into the heater area.
The ECU mounting bracket was refitted to the car with the LPG ECU already attached
o Note that there is a round grommet in the back of the ECU space. This was used to
pass the wiring for the LPG gauge and on / off switch into the interior of the car
entering the passenger compartment behind the glove box.
Here you can see the wiring passing through the cut out in part 11 and back in to the engine bay.