When I bought my car some years ago the metal diaphragm had completely fractured in two. I made a new diaphragm with some vinyl material, probably not a perfect solution but the car has performed well enough over this time and the fuel economy has been about normal.
@@LivingWithAClassic Relying on my memory it would be around 1mm or less, it has to be able to fit behind the circlip that holds the diaphragm to the centre boss. Another good upgrade for the XJS is fitting a T700 R4 overdrive transmission as I have recently done to mine. it reduces the RPM down to around 1700 at 100kph and It makes for an effortless cruiser with a big improvement in fuel economy.
Is that the very same part that's used on the 4-cylinder Porsche 914 1.7 and 2.0 engines? It sure looks like it. Back in 1987 or 88, I bought a refurbished manifold pressure sensor for $125.
Good thing that I found this video and could test my sensor... bad thing it could hold no vacuum at all 🤔 still the car ran before, not sure how well since it was not driveable
A service exchange from S C Parts is over £1100. 🤧 Going to test mine too, Dr. D Jet in Germany can refurb, you need to send the controller with it so he can match the refurb to it, offhand I think it’s around £250. Very reasonable.
@@LivingWithAClassic Great movie! I'm restoring a Citroen DS from 1971 also equipped with a D-Jetronic injection system. I just wanted to check if the method with the vacuum tester also works for other MAP sensor. My car is fitted with a Bosch MAP sensor with Bosch umber 02.801.000.11. It has the same working principle as the one on your Jag also consisting of 2 barometric chambers. I wanted to know if the procedure you apply could be used to detect leaks on my end as well. Could you also explain a bit more on what the experiment is based? You mention a pressure leak of 0.05 over 10 seconds. What is the reasoning behind these values? Some kind of Bosch test, experiment on the car,...? I want to know if I can do the same test or should adapt a bit as the MAP might be tuned differently as it's a 4 cylinder instead of a 12 cylinder. Thanks for your support!
Regarding the pressure drop value over time requirement: is this from some Bosch manual or based on your own experience? Thx for interesting video. I will dig up my sensor and test it before it goes back in the car
It's from an old Bosch manual for further testing some components. It mentions a "machine" that tests them and this is basically what the machine tests first.
And I even made a sepcial chapter on Jaguar XJ12: oldtimer.tips/index.php/en/d-jetronic/102-jaguar And sorry English version of my vacuum test video: oldtimer.tips/images/cars/jetronic/MAP-sensor-test.mp4
@@LivingWithAClassic I did some googling and apparently it's a variable transformer with more than just a diaphragm inside. Overly complicated German Engineering :)
No, The sensor has two coils, the primary coil inducing a signal in to the secondary coil, the signal in the secundary coil is altered by the moving core. The core is moved by two vacuum cans and a full load membrane. In a vacuum test, it is only tested whether the membrane is OK, not whether the vacuum cans are defective.
When I bought my car some years ago the metal diaphragm had completely fractured in two. I made a new diaphragm with some vinyl material, probably not a perfect solution but the car has performed well enough over this time and the fuel economy has been about normal.
That sounds really interesting! How thick was the material you used?
@@LivingWithAClassic Relying on my memory it would be around 1mm or less, it has to be able to fit behind the circlip that holds the diaphragm to the centre boss. Another good upgrade for the XJS is fitting a T700 R4 overdrive transmission as I have recently done to mine. it reduces the RPM down to around 1700 at 100kph and It makes for an effortless cruiser with a big improvement in fuel economy.
I have thought about that with my XJ12 or maybe a different rear end ratio to lower highway RPM
Thank you very much, it's help a lot,like always.
Is that the very same part that's used on the 4-cylinder Porsche 914 1.7 and 2.0 engines? It sure looks like it.
Back in 1987 or 88, I bought a refurbished manifold pressure sensor for $125.
Is there now a source for getting this part repaired?
Does having D-jetronic mean that there is no vulnerable Lucas system in the engine of an older XJS?
Now the diaphram IS availabel to allow the unit to be rebuilt. But properly adjusting the AFR is where the magic is.
Where to get the diaphragm? Thx
Good thing that I found this video and could test my sensor... bad thing it could hold no vacuum at all 🤔
still the car ran before, not sure how well since it was not driveable
The car will still run but not well at all. Hope you can find a good used one or have yours rebuilt
@@LivingWithAClassic i will find something... plenty of time b4 it goes back in the car... any year now... 😎
I have a map sensor with a small leak in either the seal or diaphragm do you rebuild them it is for a 450 sl 1973
I do not rebuild them, sorry. However Bosch rebuild them again
My MAP sensor drops to zero in 10 seconds. Arrgh! (this is a similar unit on a Volvo 140, so it might be different?)
Is it the same map sensor that is used in a xjs v12 pre-he 1975?
Yes it is
A service exchange from S C Parts is over £1100. 🤧 Going to test mine too, Dr. D Jet in Germany can refurb, you need to send the controller with it so he can match the refurb to it, offhand I think it’s around £250. Very reasonable.
I planned on sending mine to Dr. D jet too. I think it's very reasonable. I managed to find one in a parts car that's working well.
@@LivingWithAClassic Great movie! I'm restoring a Citroen DS from 1971 also equipped with a D-Jetronic injection system. I just wanted to check if the method with the vacuum tester also works for other MAP sensor. My car is fitted with a Bosch MAP sensor with Bosch umber 02.801.000.11. It has the same working principle as the one on your Jag also consisting of 2 barometric chambers. I wanted to know if the procedure you apply could be used to detect leaks on my end as well. Could you also explain a bit more on what the experiment is based? You mention a pressure leak of 0.05 over 10 seconds. What is the reasoning behind these values? Some kind of Bosch test, experiment on the car,...? I want to know if I can do the same test or should adapt a bit as the MAP might be tuned differently as it's a 4 cylinder instead of a 12 cylinder. Thanks for your support!
Do you know how to contact dr d jet in germany? I cannot log in to his homepage / forum. (Cannot activate my account)
How do I contact Dr D Jet
@@sljgroup3229 I think he has ceased trading unfortunately
Regarding the pressure drop value over time requirement: is this from some Bosch manual or based on your own experience? Thx for interesting video. I will dig up my sensor and test it before it goes back in the car
It's from an old Bosch manual for further testing some components. It mentions a "machine" that tests them and this is basically what the machine tests first.
I did this vacuum test on my 280sel MPS today. The needle is not even moving, i waited like 2 hour, it is still reading at 0.5 bar..
You're lucky! Then it should be working perfectly
I have a Mercedes 350se and it tested 99 and 376 but it holds vacuum and runs rich
And I even made a sepcial chapter on Jaguar XJ12: oldtimer.tips/index.php/en/d-jetronic/102-jaguar
And sorry English version of my vacuum test video: oldtimer.tips/images/cars/jetronic/MAP-sensor-test.mp4
Sorry about forgetting that, the link will be copied from the other videos.
Thanks again!
Hi, I have a resistance of 95 and 372. Can that already cause bad ideling when hot? I checked the water and air sensor, they both work fine.
The resistance changes over the range?
Yes they do. But if they old tight and have the correct resistance with no vacuum applied they tend to work great
@@LivingWithAClassic I did some googling and apparently it's a variable transformer with more than just a diaphragm inside. Overly complicated German Engineering :)
I still find it amazing that it works all these years later
No, The sensor has two coils, the primary coil inducing a signal in to the secondary coil, the signal in the secundary coil is altered by the moving core. The core is moved by two vacuum cans and a full load membrane. In a vacuum test, it is only tested whether the membrane is OK, not whether the vacuum cans are defective.
Sorry, that is not correct. Resistance does not change over vacuum range. Transformation changes.