Mobeck Tekniske has developed a “plug & play” Bolt-on EFI kit for the Jaguar V12.

After one and a half year of designing and testing it is finally ready. The problem solver for all Jaguar V12 engines.  If you have any of the phenomenons mentioned below on your 1975 to 1988 V12 you shold keep reading.

Do your V12 have:

  • High fuel consumption
  • Low idle when it should be high
  • High idle when it should be low
  • Fouling at Idle
  • Lacking power
  • Variable reliability
  • A lot of smoke behind at startup and idle

Have you tryed this:

  • Overhauled all injectors
  • bought a new ignition amplifier
  • Boght any new vacum solenoids
  • Fully understood the vacuum system
  • Exchanged the thermoswitch at the rear of the right cylinderhead
  • Bougth a new Idle valve 
  • Syncronised the throttles
  • And so on…

Well, if you haven’t started on it, you will learn it, and if you have you are probably nodding approvingly.

So, after many years of dealing with Jaguars and it’s great V12 engine I have seen the need of a complete problem-fix kit.

Throw away this

If you start in one end and try to completely understand the vacuum systems for the ignition advance. Then hunt down the solenoids and buy them, and then find a coulpe of injectors fail, and the amplifier is broken and so on. You normally end up spending a good driving season and lots of money. If you are good and manage to fix it you still end up with 40 year old technology.

So here are a few pictures of the new Bolt on kit

Design of the ECU casing
New engine harness
ECU with fuses and relay
Ethanol aproved fuel lines
New injectors with mounting brackets
Injectors in place
Remove old IAC valve, mount blanking plate and new ECU contolled active valve

You can make a V12 run in a day, but to make it run as intended from the factory takes some effort. And I dont want (preferably not) to take my customers money to make it as a mint 40 year old system anymore . The most recognitionable signs of the need of this kit is, high fuel consumption, wrong idle level and smoke at startup. So I have developed this system that bolts on and looks very originlal with harness and everything, and if makes the V12 run correct.

The kit is delivered with these parts:

  • New Air and Coolant temp sensor
  • New terminated harness with connectors, fuses and main relay
  • 12 new Bosch injectors with 10 Degree spary cone
  • Ethanol aproved rubber hoses with mounting clips
  • Injetor brackets, laser cut stainless steel
  • new electronic controlled idle valve
  • Blanking plate for the old Idle air valve
  • Coil driver with heatsink
  • Coil
  • Control wires for Fuel relay and fan relay
  • New MAP sensor
  • New modern ECU delivered with a map for a std engine
  • Optional wideband Lambda sensor.
  • Installation manual.

The great thing about this kit is that you dont need to install and calibrate a new crank trigger wheel with sensors and such, not multippel coils that look like 2020 and beyond. You dont need to g to a dyno session and make your own map. The idle and cold start system is tested from minus 15 degree celcius and up to +30 degree with a stabil idle level both in Neutral and drive. I have implemented fuel cut systems and it leans out or richens op at the correct driving modes fr better fuel effichensy.

What you need to do to install it is:

  • Before you take off anything you should check the Ignition advance acordingly to the innstallation manual. It should be std spec.
  • Remove old fuelrail and take off all injectors and old rubber hoses
  • Remove the old Idle air valve at the rear of the left head and mont the supplied blanking plate.
  • Remove the complete original injector harness.
  • Remove the ignition amplifier.
  • Remove all engine related vacuum lines. Ecept the one to the automatic transmission, brake booster and climate system.
  • Remove the original ecu in the trunk. Blank the rubber hose.
  • Install the new idle valve with the supplied hoses.
  • Adjust the throttles and tps accordingly to the installation manual.
  • Install the new injectors to the fuel rail with the hoses and clips supplied.
  • Place the new harness nicely into the engine and the ECU plug towards the Brake booster
  • Mount the fuelrail with its new injectos to the manifold with the new injector mounts supplied.
  • Mount the new air and water sensor where the old ones are at the left front of the engine.
  • Plug the harness into the distributor, idle valve, all injectors, tps sensor, coil, tacho wire, ign wire and temp sensors with the marked and terminated plugs on the harness.
  • connect the harness wire marked +12v to the battery and – engine ground to a screw on the inlet manifold.
  • Mount the new ECU on the supplied bracket that fits on the brakebooster and plug in the ECU harness connector.
  • Install the fuel pump wires on the harness to the fuel relay as describedin the installation manual.
  • Turn ignition on and check for fuel leaks when fuel pump stars for 5 sec.
  • Start up
  • Your idle should be 750-800 rpm when hot, 1100-1200 when cold.

The system has been tested for a long period both on the dyno, long trips and daily use in different conditions. the most difficoult is to calibrate the cold start systems and idle control. But Now I feel it is perfect and ready for most needs.

Dyno work with the new V12 EFI

The HP and Torque has been raised a bit and the testcar witch is a 1985 XJ12 with 100 000 km on the clock delivers 330 HP and 439 Nm on the engine with the popular Sport intake you find in the Jaguar Sport shop.
This made the car do 0-100Km/h in 6.1 sec and it has a fuel onsumption of 1.25 litres pr 10 km at variable contry road.

Find this kit with its options in the jaguar Sport shop here:
Email me if you have any questions about this please.

Best regards
Ole Martin Mobeck

    • Well, This exact kit you are looking at is not because it uses the P-Digital Lucas distributor. And its pre-programmed to the 5.3 HE.

      The 6 litre already has a pretty good system, (exept it still has that Idle air valve with the old technology).
      But since I have had many requests about doing a system for the 6 litre I am working on one now.
      It will include a new triggerwheel to mount behind the front damper where the original triggerwheel is.
      And two new coilpacks with total of 12 coils.
      But i dont know if I can make it pre-programmed as I need a car here to do it. I spend a lot of time to make the map as it is not only done on the dyno. I has to check and test the cold start systems on all temp’s from cold to hot, both air temp and egnine temp.

      But just follow this place and you will see whenthe new stuff is coming out.
      Also, by sending me an email at I can do custom systems for you.

      The system you see for sale here is for a std 5.3HE with P-Digital.

      Best regards
      Ole Mobeck

  1. Fantastic piece of work, Ole. Has the potential to add decades to the life of a classic engine. I suspect at the (quite reasonable, for the product) price point it may only appeal to the top end of town (many of the V12 cars would be worth less than the EFI!). I appreciate that it’s possibly not viable for you, but I think there might be quite a lot of interest in the replacement AAV: have you considered a ‘simple’ cut down controller that handles the cold start and hot idle only?

    • Hi Mathias Yes I understand your wish and comment, and many others also ask for spesific parts of this system to fix their problem. But After many years of trouble shooting on V12’s I have learned that the whole ignition, idle and fuel system often has several problems at the same time. When someone as if I can make their V12 run I can say, yes, it takes me 4 hours to make any V12 run. But it doesnt run nice, and then you start fixing the small things, like AAV valve, Termoswitch at the right rear, vacuum lines, some solenoids, maybe the map sensor dont sense, and then after all those things you end up cleaning and testing all those injectors, and change hoses on them, and then two are not closing, an maybe one dot open correctly, and you have to buy 3 injectors. And thy are supposed to match the other 9 old ones… And then you ended up spending 2-3 weeks chasing old parts, writing hours and end up with a 40 year old system.

      The thing is that Jaguar has been quite clever to make an ignition map on this cars that handles idle, warmup and fuel economy, and they did it with solenoids, switches, vacuumlines, thermostats and carefully adjustemnts. If you miss outy on one thing you spoil both idle and fuel consumption quality.
      So to make an standalone unit for Idle air you need to modify the ignition map witch is controlled by solenoids and, timers and temp switches, without changing the drive map. I then need to make something to controll the drive ignition map to make it as fuel effichent as it is supposed to be. I have to take avay some of the temp sensors, and solenoids but leave some in. This is not so easy, and you still end up discovering that you need to buy a couple of injectors and change the fuel lines.

      In my ECY I use both idle air and also Ignition advance wery active to make an stable idle. Both ign map and fuel map has an carefully PID controlled function. If I only used an Idle air valve I am afraid I would not be able to make an nice Idle at all temperatures. And I know my customers all over the world expect the idle to be 750 rpm, no matter what. I cannot make a idle control that is wery high at cold start for a car in Florida and almost stalls a car in northern Sweeden. And to do this I have to have full control of the whole system as the temperature rises. So.. A long answer, and not what you wanted to hear.

  2. Awesome work Ole, these charts look very promising too.

    I have a ‘83 HE which has most of AJ6’s aftermarket enhancements (larger throttle body, tuned inlet pipes, less restrictive air filter, bigger air inlets, wide bore exhaust all through and their enhanced ECU of course). Would your drop in system be compatible with that? Should it be beneficial to remap your ECU for this setup?


    • Hi Frank
      Great, yes, if you choose the EFI kit with active closed loop O2 sensor option it will absolutley adjust to the mondifications you mention. I would not need to remap it, it will aim for the optimum fuel target by itself.

  3. Hi Ole fantastic work you have done.
    Have you thought of doing a AJ6 EFI I have a 3.6 Arden xjsc with the old ecu and no trigger wheel at front.
    It’s a half v12 system if I understand it right


    • The AJ6 is not in my plans right now as I am working on the last touch of a system for the XK6 witch has more problems running nice than the AJ6.
      But I can allways make a custom sustem, but I have no AJ6 engine here to match up the heaness and calibrate the trigger system with.

  4. Hi I have a 1976 Pre HE V12 XJ-S. unfortunately I have the Borg Warner auto transmission.
    Will this kit work and what sort of performance and economy improvements could I expect? Thanks

    • I have not finished the Pre HE yet as the car is at the paint shop.
      It will need a slightly different setup regarding distributor modifications and some changes on the ignition map in general.
      But otherwise it will look the same. The performance on a Pre HE will be very similar and I expect 35 hp up like on the HE but the fuel consumption I dont know as your engine has much less compression and is not aimed towards fuel economy.
      But for the Pre HE I am working on a cam setup and also cnc ported headfs will be out soon.
      The auto trans is no problem, my white test car has the original 3 speed and does 0-100kmh 2 sec faster than before.

  5. What can you say about the Lambda sensor? Is this recommended to get optimum results of the installation?Where will it have to be installed?
    How can you check the original ignition advance to be standard spec?

    • Olav, yes the kit with Lambda is better, the one without Lambda has been enritchened 3-4% to avoid lean spots, but it will not adapt to other future modifications as the kit with Lambda will. It also constantly adjust to height above sealevel and weather changes.
      You drill a hole in the exhaust pipe just behind where the two downpipes meet and weld on a supplied ring with threads for the sensor. MIG weld is fine.
      Toe check the ignition you take off the vacum line to the distributor and block the end of the hose. Idle a t 750rpm and use a ignition strobe lamp under the front pulley to see if the pointer hits exactly 0 (zero) degrees. If it doesnt you adjust it with the small screww on the outside of the distributor.
      I can help and explain over the phone when you are there. Also if you have someone to help you and rev up a bit, you should see the pointer go all the way up to 18 degrees with the timing lamp. If not you should lubricate your rotor shaft in the distributor. Its quite easy and should be done anyway.

Leave a Reply

Your email address will not be published. Required fields are marked *