Wednesday, 13 June 2018

Range Rover P38 second air suspension pump

2nd Air suspension (EAS) pump 

My Range Rover 38 is fitted with Arnott Gen 3 suspension air bags - these bags are considerably larger (both in length and diameter) than the standard Land Rover items, and as such, require more air to fill and extend them to their maximum height.

I think it's fair to say the standard EAS pump on a Range Rover works at the top of its operating limit, even when the system is healthy, so the fitment of these bigger bags really puts a strain on the already stretched pump.

To counteract this, I've fitted a second pump. I did consider simply removing the standard EAS pump and swopping it for a larger capacity unit, however there are space limitations, and the pump location is far from ideal.

There are issues which need to be considered when fitting a second pump, the primary one being moisture. The standard EAS system draws air in through a desiccant drier - as air is drawn in, the drier traps moisture, keeping the EAS system (especially the valve block) nice and dry.
In addition, when air is released from the system, it is passed back through the drier to atmosphere, removing built up moisture from the desiccant as it goes - the drier is only effective if this 2 way cycle is maintained.

The problem with a second pump is that if air is drawn through a different source, the drier does not contribute to the system - you have to be really careful about how air is treated as it enters or moisture may become a problem. In addition, if you use the air for other things (my system is plumbed to a tyre inflator - see separate blog) the drier may become saturated as the 2 way cyclic process is not being fully carried out.

Rather than simply adding another Dunlop pump, I've gone with a Viair unit. The standard pump is a high pressure low volume unit, whereas the Viair pump has a far better CFM flow rate - in fact the model I've gone for has almost 7 times the cubic capacity compared to the standard pump.

To add the pump, I've opted to leave the standard EAS system alone as much as possible - here's the basics


  • The 2nd pump is permanently mounted in the boot, in the spare wheel well
  • Power is supplied via a separate fused switched circuit (see separate blog) - I can choose when the pump is on or off
  • The switching of the pump is via a pressure switch (identical to the standard switch) - even if I accidentally leave it on, it should not over pressurise the system
  • The circuit is ignition controlled - I cannot accidentally drain the battery running the 2nd pump
  • The 2nd pressure switch is Tee'd into the existing valve block feed line, just adjacent to the EAS valve block
  • The feed line from the 2nd pump is direct to the tank - it does not feed directly into the EAS line(s)


The pump draws air through a filter drier mounted in the void behind the base/CD changer unit (nearside rear boot) - this seemed a reasonable inlet point - it's well out of the way of potential water and mud/dust etc. and is hidden by trim.


Note the pump on the left - the battery you can see is part of my split charge/rear winch, and does not supply the Viair pump.

The standard EAS system draws from/feeds into the air receiver at the rear of the tank. However, at the front of the tank there is another screwed plug. I removed this plug and drilled and tapped the centre 1/4 BSPT, and have used it as a second inlet point - this means the standard EAS again is un-molested.
In addition the standard system uses 6mm pipe, however I've tried to optimise the extra capacity of the Viair pump, so my 2nd feed line runs into the front of the air receiver tank via 10mm plastic hose and push-fit fittings.


New 10mm tank inlet

As a side note, for push-fit metal fittings I've found Kelm to be super reliable, and for plastic fittings, I've never been let down by John Guest fittings. I always use a blunt pencil sharpener to feather the edge of the cut pipe, and a dab a bit of Vaseline on before inserting the pipe into the fitting.

I made a simple 2 way manifold for the pressure switch, and a bracket to mount it off the cruise control assembly under the bonnet - this was the easiest and closest place for the electrical wiring - the 2 relays are under the passenger seat, with the off/on switch where the ashtray used to be.

For the 2nd pressure switch I've gone for a standard EAS unit to prevent the two systems cancelling each other out. It's important the standard pump is triggered, or the EAS ECU will throw a fault (it wont understand how the suspension can still go up but the pump has not been used) - this system triggers both pumps when the pressure is reduced, but the Viaiar is so powerful, the standard unit is only on for around 30 seconds or so - apparently that's enough to keep the EAS ECU happy.


2nd pressure switch arrangement

Although I've only recently relocated the pump to the spare wheel well, and plumbed and wired the system "properly", I've run the system jury rigged for 3 years now, and it's proved fantastic - the extra demand of the Arnott bags is never a problem, and because I use my EAS a lot, she seems to be venting often enough through the drier to keep the desiccant effective.

The EAS system remains happy, with no soft or hard faults as a result of the installation.

In the UK, everything Viair is available through Matt Savage, and the customer service support team in the USA are also pretty helpful if you need them.

Friday, 8 June 2018

Range Rover P38 tyre inflator

Tyre Inflation

It’s not uncommon to deflate tyres for extra grip in off road situations, especially on soft ground or rock crawling situations.
HoIver, as soon as the car is back on tarmac, tyres will need to be re-inflated to safe road speed pressures.

The Range Rover P38 in standard form is equipped with air suspension (EAS) and assuming the system remains in situ, there is a 9 litre air receiver situated under the drivers’ side sill (UK cars)

With this reserve of air easily available, there’s an opportunity to utilise the system for tyre inflation.

This tank contains pressurised air at betIen 115psi and 140psi (around 8 to just under 10bar) dedicated to filling the air springs as the system demands.

According to web based converters, there is approximately 28 cubic feet of air in the receiver (at atmospheric pressure) - it all depends on tyre size and type, but for most 4x4 tyres…


  • To pressurise a flat tyre from 0psi to 25psi, the tyre will actually need 9.6 cu ft of air
  • To pressurise all 4 tyres from say 10psi to 22psi you’ll need 19.2 cu ft of air


Theoretically then, even allowing for pressure balance betIen the tank and the tyre, there’s enough air available to get you out of trouble, aided of course by the fact that the tank won’t deplete as the EAS pump will kick in.

The EAS system relies on expelled air passing back through the drier to remove built up moisture from the desiccant - using the system regularly as an air source like this does pose the risk of water building up in the system, but I'll be using it just for tyres, and not regularly, so we should be OK.
Also, the EAS pump is high pressure low volume, so make sure it's healthy or it will struggle - on my car we have a second pump connected to the EAS system to cope with the Arnott Gen 3 bags, so there's a plentiful supply.

I deliberated long and hard as to the position of the tyre inflation point. Under the bonnet involves relatively simple engineering, but it’s a long way to the rear wheel, and I was not happy with the need to have the bonnet up to operate the system, and the boot has the same issue of distance to the front wheels.
Under the car was eliminated simply because of the risk of dirt ingress into the system (and who would want to crawl under the car to use it?)
In addition, I tried to imagine all situations, so ignore the sunny warm afternoon, what happens if it’s dark, cold etc.?

Eventually, I decided on a central point inside the car, and opted for underneath the cubby box in the rear passenger footwell.
There are pros and cons to all locations, but this location does have the following benefits.


  • Well lit – even at night as there is a puddle light in the rear of the cubby box
  • Clean and dry
  • Central to all wheels
  • With any of the doors open, the EAS will not adjust, but the pump will still run to fill the tank – I felt this optimised potential capacity as the EAS pump is in effect directly linked to the tyre being inflated.
  • The air line route to tank is quite a simple one, and does not pass over any hot items (such as the exhaust)

So, here is my solution – a painted stainless steel fabrication, complete with local isolator and multi-jointed swivel to the PCL receiver, meaning the hose is not straining the system when directed to any tyre.
I've added acheck wire in case the connected air line releases accidentaly, so we should have no whip damage in the car if there's an issue.
The PCL folds out of the way when not in use, and there is stainless 6mm wire a foot guard over the isolator just in case (although it’s rare the centre rear seat is used)




The fabrication is clamped in place by the cubby box securing bolts, and the hose is carried in the boot, and simply plugs in as required.
The air-line is simply tee’d into the main line at the tank, and clipped to the underside of the floor and tunnel at existing fastener points.

The system works really well, but there's already a 2 piece "MK II" version in the works that will be slimmer, so as to not protrude so far, and be easier to pipe up on assembly (and check for leaks) - I'll post a picture up when its installed.

Range Rover P38 - Split charge circuit

The charging circuit.

Grab a cuppa, this is a long blog, mainly as it’s been way more difficult than it should be.

My outline requirements were simple - charge a 2nd battery in the boot which would be running the rear winch (more on the winch fitting in a separate post later) - not hard you'd think....

Well, I had access to an ex-Police '38, and it used a Land Rover voltage sensitive switch (PRC4427) to monitor the cranking battery voltage, and when it was effectively charged, it would switch an Albright contactor to permit charge to the 2nd battery - lovely, copy that then.

Not so - the internet is so full of conflicting and confusing installations - even speaking directly to Albright themselves didn't help much.

The problem lies if you fit a winch, there’s already a front winch on this car, and I’m proposing to fit a rear, so for me, winch electrics have to be taken into consideration for this project.

When the rear winch is at stall point (so under max load) it could potentially draw up to 300Amps - the 2nd battery will deplete, so the winch will then draw from the primary vehicle battery. The same can happen in reverse with the front winch.
The split charge wiring will then have to cope with this draw, and if it’s not man enough, it will promptly melt, catch fire etc. etc.

The common solution seems to be to fit wiring that's an inch in diameter, and a split charge relay capable of coping with 300Amp or so - hardly ideal.

Fortunately, the kindly folk at Gigglepin came to the rescue, and recommended a disconnection relay - basically the relay will disconnect the split charge system when either winch is activated and isolate the 2nd battery from the car battery, and re-connect only when both winches are turned off.
Cabling can be noticeably smaller (but still needs to be generous and capable of around 150Amp) as its now only dealing with the charging circuit, although once the 2nd battery is drained, the rear winch is basically useless as it can’t draw current from anywhere else.

This suits me fine - with a '38 and its BeCM, draining the primary battery is a risky venture, and the rear winch is an occasional "get out of jail free" tool for me, so all is good.

Here’s my wiring schematic – note the two winch switches are interconnected, so both need to be in the OFF position for the split charge system to work.
The winch side of the switches operate a pair of standard 4 pin relays, which switch the control feed to the respective winch solenoids – if either relay is open, the solenoids are “dead” and the winch won’t work. This method enables winch isolation, without the need for massive current isolators – yes the positive from the battery to each winch remains live, but the winches themselves cannot be spooled via the remote or the flying lead controller.
In addition, the split charge circuit is ignition controlled, so the rear battery is isolated once the ignition is off.



There is an issue of surge if the 2nd battery is completely flat and the split charge contactor is closed – the alternator in my car is rated at 120Amp so in theory the system could see this amperage. However, the actual current is unlikely to exceed 70-80amps as the car will be simultaneously drawing current, so I have fitted a 40A MIDI fuse, which will run 80A for short periods, decent cable size (25mm² 170A) and the contactor will cope with 150A quite happily. Despite the current capacity of the system, the cable is only 9.7mm outside diameter, so is still relatively easy to route and pass through the bulkhead (firewall)

The next problem was packaging – the ’38 is a big car, but it is quite full – finding spaces for circuit components involved stripping the interior until a big enough void was found.

On the reference Police car, the Albright contactor was located next to the battery box in the engine bay – ideal for wiring, but when I sent a photo across to Albright, their tech gurus noticed it had melted its casing, and put this down to ambient temperatures being too high. I remain doubtful that was the cause, but the point being made was valid - the contactor needs to be kept cool, and even though they are available IP66 water and dust resistant, the drier the better.

Eventually, I found a perfect contactor shaped void in the passenger foot well, behind the “A” post lower trim – there is a spare threaded mounting here (used for the bonnet release on US and EU spec cars I guess?) ideal for a bracket to mount the contactor. This is a particularly good area as its pretty cold (being behind the front wheel) it’s dry (assuming the pollen filter doesn’t let in water!) and it’s very close to the point where standard wiring passes through the bulkhead. It’s also exactly on my proposed route for the wiring to the rear battery, and is covered by trim, but easy to get to.

There is a small bracket already bolted in here to mount the foot well trim, so the contactor bracket is a purpose built modification of this original.



The vertical slots in the OIS bracket replicate the Land Rover bracket, and pick up the foot well trim mounting clips – I slotted the right hand mounting hole to make fitting easier as the bolt in the foot well is quite hard to get to – I can start the bolt in the threaded hole in the car, slide the bracket on and then tighten it up – far less fiddly!
Here’s the contactor in situ….



The contactor is mounted horizontally, as recommended by Albright (vertical mounting can affect coil operation, especially if the unit is jarred or vibrated) with the connectors towards the passenger cabin – this orientation keeps the cable lugs away from metal work, and permits better wiring routes. The countersunk screw (top right) screws into a rivnut on the bracket so there’s no fiddly nuts and washers to contend with in such a tight space. The screw is M6, passing through an M8 hole in the bodywork – this size disparity permits the countersunk head to sit flush, so it does not interfere with the trim.

Land Rover use the voltage sensitive switch (VSR) to open and close relays in a number of vehicles for a number of applications, most commonly high current draw items like heated screens – here’s an example from a Range Rover Classic….



You can see the VSR in the bottom right (item 72) – when it grounds the supply to earth, the coil in the rear screen relay (item 67) is energised (85-86) and the switch is closed (30-87)
In every application, there is a diode fitted to the input on the coil of the switched relay (arrowed – top right) – therefore, I’ve replicated this circuit protection in my set up – you can see the diode the circuit diagram.
I put the VSR under the passenger seat alongside other supplementary circuits added to the car.



The charging cable route runs like this – from the front battery, through a fuse, down and along the base of the front grill framework, up to the N/S inner wing behind the air box and EAS valve block and down through the bulkhead into the contactor.

From here it drops into the sill, runs under the plastic trim along the length of the car and rises around the rear wheel arch into the void behind the sub-woofer. It then passes into the rear structure of the body shell, to emerge into the spare wheel well. After it has entered the passenger cabin at the bulkhead, the cable remains inside the vehicle for its entire length.

The whole length is covered in heat shrink, and where it passes through the engine bay and where it is inside the cavity of the body shell at the rear, it is also covered in plastic convolute sleeve. There are no joins except at the contactor and at each battery.

At each end there is a fuse to protect the circuit and contactor – here’s the front fuse assembly….



….and here’s the rear, mounted on the frame work of the rear battery - you can just see it between the battery and the rear body at the bottom of the picture.




The 2nd battery.

On a P38, finding space for a 2nd battery is challenging – I’m pretty certain in a 2.5 diesel, there’s room in the engine bay, but not so in the V8.

I have seen people cut a hole in the floor so it sits under the rear seats beside the fuel tank – a drastic but pretty neat solution. However, the spare wheel well on my car was the most obvious choice as it’s vacant – the size of tyres I’m running do not fit the spare wheel well, so it has become a store for ropes and recovery gear.

In addition to the battery, I’m also adding a 2nd air suspension (EAS) pump. The pump, a Viair unit, is needed to re-inflate tyres after off road adventures, and also to assist the original EAS pump in inflating the Arnott Gen III suspension bags, which are much larger than standard ones.
The pump runs off the primary car battery, but nonetheless it still made sense to locate the two items in the same place – there’s more on the 2nd pump in a different blog.

The battery is a normal sealed lead acid, and is as large (in height) as can realistically be fitted into the spare wheel well – the terminal layout matches the front, so it can be transferred if there’s ever an issue with the primary battery.
I made a frame to cradle the battery from 3mm mild steel – this frame sits on rubber bushes directly to the boot floor, and is stepped to follow the floor profile. The battery clamp is a proprietary off the shelf item.

I’ve added a partition to the spare wheel well, and a lid to cover the battery – this is so the battery, pump, cables and air lines are not damaged when hauling ropes out of the remaining space – currently the partition and lid are painted plywood – in due course they will be replaced by laser cut GRP items for more finesse. Despite the addition of the lid and partition, the boot floor cover still hinges and latches as Land Rover intended. When everything is shut down there’s no evidence in the boot compartment of what is going on underneath and the boot space is un-affected, so my carrying capacity remains as standard.



The battery earth goes to the body, and from the body to the chassis, offering a good clean continuous path. The rear winch is earthed directly to the battery terminal.
I’m entirely confident in the wiring routes, installation and schematic design, however time will tell if my split charging proves effective – the voltage sensitive switch will only charge the 2nd battery if it sees 13.8volts at the primary – this may be too high, and I may end up with a 2nd battery that is not being effectively charged. However, it’s not a difficult item to swop out, so we’ll see.

Range Rover P38 - Adding extra circuits

In the past, I’ve successfully (and easily) added circuits to Range Rover Classics without any real issues, however, we’re now dealing with a ’38….a whole different set of challenges.

On a Classic, during its development over the years of production, extra circuits were added by Land Rover in a rather haphazard manner, so we ended up with relays in multiple locations, fuses in multiple locations, and a wiring loom more complex than a heap of spaghetti.

The scenario is much neater in the ’38 – there are two fundamental fuse boxes, one in the engine bay and one under the drivers’ seat (the venerable BeCM) and all the relays are in the engine bay, in the associated fuse box – tracing things and replacing things is far easier – you don’t even need to remove trim.
With this in mind, I wanted to avoid the miss-mash of circuitry found in the Classic when adding circuits to the ’38.
I am proposing to add….


  • Winch switching circuits (one front, one rear)
  • Light bar circuit (probably 4 lights running as 2 pairs)
  • Beacon circuits (for recovery operations during off road marshalling duties)
  • Wiring for a Viair pump, acting as a 2nd EAS pump (to cope with the enormous Arnott Gen 3 bags)
  • Various circuitry to isolate the battery split charge system from the 2 winches


As with the split charge project, first problem is space – again finding spaces for circuit components involved stripping the interior until a big enough void was found.

The passenger seat came out, and underneath there seemed to be a large enough hole to fit in all the relays and fuses I reckoned I’d need for the project.
Here’s the available space….



….not generous, but workable I hoped.
There’s already a relay there (the timer relay for the EAS) – ignore the green relay to the left of the picture, this is a remnant of a previous mod and will come out during this project.
I was after as much future proofing as possible, so the aim was to fit a larger fuse box than initially required, and more relay bases than initially needed – hopefully this would ensure no re-work in the event on further additional circuits in the future.
I made 2 brackets up – one fits to the grp frame that contains all the ECU’s, and one is bolted to the seat base upright
Here’s the semi-finished set up in situ….



On the rear plate, I’ve mounted the relay bases as low as possible, as some of the relays fitted are not standard, and are taller than a normal switching unit - the big yellow relay on the left is a Land Rover voltage sensitive switch (PRC4427) which I’ve utilised to control the split charge system for the 2nd battery, and the tall black relay (centre left) is the TRW timer relay for the EAS, more or less in the same position as it originally was, but re-wired to a new relay base. Finally, we have 3 relays for the beacons and light bar.

On the front plate, I’ve mounted a fuse box (Land Rover Defender, also the same as a late 80’s Range Rover Classic) and the relay for the 2nd EAS pump. The 3 empty relay slots are for the future if needed. These relays sit higher (to clear the fuse box) but will still be removable with the seat in position.

On the far right of the front plate is the main input power source for the relays, which comes direct from the battery in the engine bay. This is fused in the battery box, splits, and feeds directly into the fuse box to step down the fusing for each individual circuit.
Both plates are 3mm aluminium, and are not painted, replicating the ali plates Land Rover use to support the ECUs nearby.

The switching circuits are fed from the cigarette lighter feed (fused in the original car loom at 30A) which now has a solder joint, splitting the single feed into multiples, which are then individually fused via the fuse box. I’ve tried to keep the fuse box layout so it makes some kind of sense, so fuses are in pairs for each circuit. The ‘box is laid out like this….



Here’s the wiring schematic I’ve used to create the circuits – the big vertical line denotes the bulkhead…



Note the beacon and CB radio circuit is direct from the battery so I can run them with the key out, everything else requires ignition on, just to make sure we don’t deplete the battery too much.
The seat base trim has also been adjusted – now it has a rectangular cut out in it, and a clip-on cover – removing the lid gives access to the fuses – it’s a direct replica of the drivers’ side, where a panel gives access to the BeCM fusebox. The fuse box legend above is stuck to the inside of the access cover, meaning I don’t have to try and remember what I’ve done down the line if a fuse blows!



All the wiring has been bound with loom tape, and the switch loom runs under the carpet insulation, up the side of the gearbox tunnel to emerge in front of the gear selector in the ash tray void.
I’ve disposed of the ashtray and the cigarette lighter aiming to use the space for Carling Contura II switches. In addition to the switches, there is also a double USB charge socket, so the loss of the lighter does not impact my ability to use a satnav or charge my phone. Here’s the fitted switches….



The switches also pick up the illumination circuit (from the lighter wiring) so they will light up when the side lights are on, meaning I can find them in the dark.
Unfortunately, I’ve filled this void, so any future switches will have to go somewhere else in the dash – we’ll deal with that problem when it arises, for now, I have enough!

The wiring that runs to the front passes through the bulkhead in the passenger foot well, and I’ve fitted a connection point just inside the engine bay, that way if any damage happens to the loom in the engine bay, I can carry out repairs without having to undo all the loom in the passenger cabin.

Fortunately, Land Rover have left a blanking plug in the bulkhead for the bonnet release cables on a left hand drive car – popping this blank out, and fitting a grommet instead allows cables through into the engine bay without the need for drilling – the loom emerges just under the fuel evaporation canister, adjacent to the existing loom, keeping everything nice and neat.

As you may have noticed from the schematic, I couldn’t put all the fuses in the seat base – in some instances it was important to ensure the fuse was as close to the battery as possible (to reduce the length of un-protected circuitry) Adding to the original under-bonnet fuse box was not possible, so a new sub fuse box was created in the battery compartment – it contains the primary fuses for the power distribution (MAXI fuse) and the protection for the split charge circuit (see different blog) – here’s the fuse box…



It sits under the battery box lid, so remains out of the way and protected.
There are no doubt many different ways of adding circuits, but I’m quite pleased with this project – it was a lot of work, but has ended up reasonably neat I think, future proof, and safe.

Tuesday, 17 April 2018

Range Rover P38 bonnet net

This little project came about after plenty of recovery operations, and the constant battle with loose ropes - by the time we'd fallen over them, lost them in the mud and generally got in a tangle on several occasions, it became all too clear a storage solution was in order.

The frame is fabricated from 3mm stainless steel, powder coated satin black, and is backed by satin black vinyl to protect the bonnet paintwork. The frame has retainers cut out of the edge (you can see them in detail on the home page of this blog as a close up of the unit forms the background of the page) and is bolted directly to the bonnet.
8mm elasticated cord is knitted around the retainers, making a perfectly practical front recovery gear storage point.

Some would argue the net and its black vinyl background is only fitted to hide the traditional lacquer peel and paint fade that some '38's suffer from - well, to prove a point, here it is in use....



Range Rover P38 fuel pump access

On a Range Rover Classic, and on a Range Rover L322, fuel pump access is a relatively simple task.

Not so on the venerable P38 – for some un-fathomable reason, Land Rover “forgot” to provide us with access.
This means if there are any issues with the pump, or even if access is required just to test circuits etc. the tank has to come out.
The tank is a heavy awkward cumbersome affair, and removal involves the wheel arch liner, filler tube, fuel pipes, vent pipes etc.
There’s no drain to empty it, so syphoning is the only real alternative – not ideal.

I dropped the tank on my project car to change a failed pump, and vowed never to do it again!

So, here’s my solution, which I fitted without the tank coming out – a simple hatch, large enough for the pump to pass through, and providing access to fuel line couplings and electrical connectors.
There’s a frame around the hole permanently fitted to the car, with silicone between it and the body floor.


Onto this is fitted the removable lid, which has a neoprene gasket to ensure a tight seal.




Fasteners are via blind rivet nuts – blind rivet nuts are smooth at the end, and the screws cannot pass through them – this reduces the risk of the fastener chaffing on fuel lines etc.
The aperture cut into the body is trimmed with rubber edging, preventing any risk of injury on sharp edges when withdrawing the pump.

The whole system is covered by the original sound insulation and carpet, which itself is covered by the rear seat in its upright position – day to day, there is no evidence of the modification.

Normally here at OIS, I refrain from chopping pieces off my car, and try and design solutions with minimal impact to the shell – I’m always in mind of the difficulties of removing the modification, and putting the car back to standard, something that one day any owner may want to do.
I’m less fussy about replaceable outer panels (wings, bonnet, doors etc.) but work on the shell is difficult to undo, and so it’s treated with respect.
However, in this instance, there is no alternative to cutting a decent hole in the floor, which in my opinion is probably not reversible once done.

Another point of note is the cutting process – the fuel tank, pipes and wiring are very close to the underside of the floor surface – accidental cutting must be avoided, especially on a petrol car where the risk of spark has serious safety risks - cut with care!