I fitted a lambda sond on my -76 XJ12 to see how the fuel injection
was doing. I found some strange readings however.
Running in ‘‘city’’ light throttle and around 40-50km/h its running
extreamly lean, if I accelerate for a few seconds and then go back
to the same speeds its running ok.
Running in ‘‘city’’ > lite acceleration > runnig very lean
Running in ‘‘city’’ > hard acceleration > OK
Running in ‘‘city’’ > full throttle > OK
However I expected it to run rich while accelrating but its not,
seems like the acceleration enritchment is not working?
Running on highway ~90km/h > OK but can occasionaly run very lean
Running on highway > lite acceleration > very lean
Running on highway > hard acceleration > OK but no enrichment
Running on highway > full throttle > OK but no enrichment
Fuel cut of is working as it should, cuts out and back in again at
~1400rpm
Throttle switch is OK and adjusted
No vacuum leaks
Throttle valves and linkage adjusted and OK
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
In reply to a message from tobmag sent Sun 17 May 2009:
Hi, As a lmatter of interest what AFR readings are you getting?–
The original message included these comments:
Hi .
I fitted a lambda sond on my -76 XJ12 to see how the fuel injection
was doing. I found some strange readings however.
Running in ‘‘city’’ light throttle and around 40-50km/h its running
extreamly lean, if I accelerate for a few seconds and then go back
to the same speeds its running ok.
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
In reply to a message from nicktruman sent Sun 17 May 2009:
Hi.
Im using an ‘‘old’’ sond not the wide band type unfortunatly…
Running in ‘‘city’’ light throttle and around 40-50km/h its running
extreamly lean, if I accelerate for a few seconds and then go back
to the same speeds its running ok > 13,2:1
Running in ‘‘city’’ > lite acceleration > no reading on meter
Running in ‘‘city’’ > hard acceleration > 13,2:1
Running in ‘‘city’’ > full throttle > 13,2:1
However I expected it to run rich while accelrating but its not,
seems like the acceleration enritchment is not working?
Running on highway ~90km/h > 13,2:1 (but can occasionaly run very
lean > no reading
Running on highway > lite acceleration > no reading
Running on highway > hard acceleration > 13,2:1
Running on highway > full throttle > 13,2:1
Looking on this againg it seems to be running a bit fat actually.
Running 12-12,5:1 on acceleration is OK but 13,2:1 on normal
highway is too much I guess?
With no reading I mean that the gauge bottoms out on the lean side.
Seems strange with so little variation on different engine loads
otherwise.
Gauge is accurate, I had it tested at our company’s engine
development center
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
In reply to a message from tobmag sent Sun 17 May 2009:
Tobmag,
As I see it all of your readings are fat or rich most of the time.
Maybe you need new O2 sensors. Are these what you call sonds? In
fact it seems to be content with 13.2 when not on scale. You may
want to read the O2 sensor voltages directly!
Regards,
Noel
As I reread your post, what are you using to take your readings??–
The original message included these comments:
extreamly lean, if I accelerate for a few seconds and then go back
to the same speeds its running ok > 13,2:1
Running in ‘‘city’’ > hard acceleration > 13,2:1
Running in ‘‘city’’ > full throttle > 13,2:1
Running on highway ~90km/h > 13,2:1 (but can occasionaly run very
lean > no reading
Running on highway > hard acceleration > 13,2:1
Running on highway > full throttle > 13,2:1
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
In reply to a message from Jags+30jugs sent Sun 17 May 2009:
Hi.
Yes, sond is what we call the sensor in this case. Its been
calibrated in our R&D engine center and is 100% OK. (sensor and
gauge togeather)
‘’‘’
In fact it seems to be content with 13.2 when not on scale.
‘’‘’
Sorry dont really undestand what you mean!?
BR//Tobmag–
The original message included these comments:
As I see it all of your readings are fat or rich most of the time.
Maybe you need new O2 sensors. Are these what you call sonds? In
fact it seems to be content with 13.2 when not on scale. You may
want to read the O2 sensor voltages directly!
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
Noel,
There are no O2 sensors on D-Jetronic engines. He must be talking about an
instrument that is based on O2 sensors. I’ve never used one, but as I
understand it they are not very accurate.
In reply to a message from tobmag sent Sun 17 May 2009:
Tobmag,
As I see it all of your readings are fat or rich most of the time.
Maybe you need new O2 sensors. Are these what you call sonds? In
fact it seems to be content with 13.2 when not on scale. You may
want to read the O2 sensor voltages directly!
Regards,
Noel
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
In reply to a message from Ed Sowell sent Sun 17 May 2009:
Hi Ed.
Thats right, this is an instrument and of course the newer wide-
band sensors are better then the old narrow band but they are
relaible enough to tell you if you are running rich or lean.
Perhaps not the best to use when mapping a 3rd part injection
system or a carb set-up.
The wide-band will as its says give you a wider measuring range but
the accurecy isnt much better.
BR//Tobmag–
The original message included these comments:
There are no O2 sensors on D-Jetronic engines. He must be talking about an
instrument that is based on O2 sensors. I’ve never used one, but as I
understand it they are not very accurate.
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
In reply to a message from tobmag sent Mon 18 May 2009:
Hi Tobmag,
This is interesting. I have a narrowband O2 sensor on my twin turbo
V12 and I have set the AFR up to around 13.1:1 deliberately. I am
in the process of buying a Tech-edge wide band system that will
control the AFR far more accurately with the Megasquirt. Jagwit
might confirm but for a stock engine you should be running 14.7 air
to fuel so your engine is indeed running too rich–
The original message included these comments:
Thats right, this is an instrument and of course the newer wide-
band sensors are better then the old narrow band but they are
relaible enough to tell you if you are running rich or lean.
Perhaps not the best to use when mapping a 3rd part injection
system or a carb set-up.
The wide-band will as its says give you a wider measuring range but
the accurecy isnt much better.
BR//Tobmag
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
In reply to a message from nicktruman sent Mon 18 May 2009:
Hi Nick
Yes thats my thought too that its a bit rich actually, what worries
me more is when its running to lean…dont really know what to
check. Could be the ECU or the map sensor since all other
components are OK.
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
Its acceleration enrichment you are lacking isn’t it? If so, what is
triggering that?
Sorry, don’t have experience with D-jetronic, although I have a book or two
on it in my library.
This from the internet: (D-Jetronic on Porsche 914)
“Acceleration: Due to the finite response time of the pressure sensor and
the ECU, and the inertia of the air mass in the intake manifold, there is a
delay between the opening of the throttle and the response of the system to
the need for added fuel. To reduce this response time, a separate
acceleration system is required for good engine response. D-Jetronic uses a
set of contacts in the throttle position switch to provide both immediate
injection pulses and a delayed acceleration enrichment effect when the
throttle is opened.”
Other sources suggested that with the ignition on (but not running) opening
the throttle should result in the sound of the injectors firing (Brrrrrp) to
produce the enrichment effect.
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
In reply to a message from Mark Eaton sent Mon 18 May 2009:
Hi Mark.
Thats right there is a ‘‘switch’’ in the trottle switch for
enritchment and they are working OK, I have not checked that they
really reach the ECU though.
The 2nd test will not work since the injection will not work if it
doesnt get any trigger puleses and for that the engine needs to
turn…
I would summarise the problem as:
Running rich on highway and in city
Running lean in city depending on speed/throttle pos.
Running lean on lite acceleration
Running OK on hard acceleration
Running OK on full throttle
Will add a vaccum gauge as well to see what is happening when.
BR//Tobbe–
The original message included these comments:
‘‘Acceleration: Due to the finite response time of the pressure sensor and
the ECU, and the inertia of the air mass in the intake manifold, there is a
delay between the opening of the throttle and the response of the system to
the need for added fuel. To reduce this response time, a separate
acceleration system is required for good engine response. D-Jetronic uses a
set of contacts in the throttle position switch to provide both immediate
injection pulses and a delayed acceleration enrichment effect when the
throttle is opened.’’
Other sources suggested that with the ignition on (but not running) opening
the throttle should result in the sound of the injectors firing (Brrrrrp) to
produce the enrichment effect.
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
In reply to a message from tobmag sent Mon 18 May 2009:
Just a thought.
You might find that oily injector connections and brittle wires
could be a problem. I have heard of people who change their
injection looms and associated wiring and the engine starts running
as it should. I can’t imagine the fuel tables will slip, SO its
either too much or little air or too much or little fuel (or a
combination of them both).
I guess you should check manifolds for air leaks, check loom for
good connections and no breakages, check butterflies are synced and
injectors are squirting equally.
Have you put the O2 sensor in the other bank? Do you get the same
readings?–
Regards Nick - Twin turbo 5.3l V12 mid engined kit car
London, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
In reply to a message from nicktruman sent Tue 19 May 2009:
‘’‘‘You might find that oily injector connections and brittle wires
could be a problem. I have heard of people who change their
injection looms and associated wiring and the engine starts running
as it should.’’‘’
I have changed the whole wire harness to the engine using hq
cables and Canon military standard connectors, will anyway measure
everything at the ECU just to be shore.
‘’‘’
‘’‘‘I can’t imagine the fuel tables will slip, SO its
either too much or little air or too much or little fuel (or a
combination of them both).’’‘’
I agree on that.
‘’‘’
I guess you should check manifolds for air leaks, check loom for
good connections and no breakages, check butterflies are synced and
injectors are squirting equally.‘’‘’
Allready done and ok, just need to control measure at the ECU
‘’‘’
Have you put the O2 sensor in the other bank? Do you get the same
readings?‘’‘’
No I have not but since its devived in 4 injector groups by the
amplifier and they are splitted between A and B bank I dont think
there is any difference.
Found out at another hompage that a faulty map sensor can give this
type of problems even they seem OK on a vacuum test.
I will nick the one from my fathers 1972 MB350SLC just to see how
it behaves.
(((Some one in the USA that can send me a cheap wideband UEGO
meter
prices in Sweden is out of space…)))
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
<>Have you put the O2 sensor in the other bank? Do you get the same
readings?’
<><>No I have not but since its devived in 4 injector groups by the
amplifier and they are splitted between A and B bank I dont think
there is any difference.
Tobmag,
I have installed EGO sensors on both sides of my D-Jetronic V12. I have also moved the MAP sensor
about 10cm and shifted its orientation so that the hex-socket grub screw in the front end of it is
accessible. I found that the O2 readings from each bank were slightly different, despite setting up
the throttle linkages according to “The Book”. So I rigged up a U-tube manometer to check the difference
in vacuum on each side of the engine; sure enough, there was a difference of about 10 inches of water
height when the throttle was “blipped”! When the throttle linkage was adjusted to eliminate the
differences in vacuum, the EGO readings became almost identical.
So, while the D-Jetronic system is providing the same fuel to each cylinder bank, the banks may not be
getting the same quantities of air, despite the balance tube. I adjust my MAP sensor so that it’s slightly
rich on wide throttle openings, and it’s then lean at low throttle, just as you have observed.
But mine definitely goes rich when the throttle is opening, just like the accelerator pump on
carburetted systems. If yours doesn’t, maybe there is a problem switching system on the throttle pedestal.
Good luck!
Owen Holmwood
XJ-S 1978
Sydney
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
In reply to a message from owen holmwood sent Tue 19 May 2009:
Hi Owen.
Nice hearing some one thats done the same excerice.
Yes I will put in a vacuum meter and check as well.
You said you adjusted the MAP to run lean on low thtottle, mine is
running so lean its not even gives a signal on the meter,
medium, hard, full throttle will give the same value,
If you look in my posts you will se all values.
Did you suffer the same problem or why did you fit the EGO sensor
to start with?
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
In reply to a message from nicktruman sent Tue 19 May 2009:
Hi Nick, thanks for the tip, will check first in the office is
someone is going over to the states soon, just missed a guy there.
(but he is bring a lot of parts for my transmission
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
You said you adjusted the MAP to run lean on low thtottle, mine is
running so lean its not even gives a signal on the meter,
medium, hard, full throttle will give the same value,
If you look in my posts you will se all values.
Did you suffer the same problem or why did you fit the EGO sensor
to start with?
Tobmag,
I installed the EGO sensors to find out what the h*ll was going on with
the engine tuning. It was
all part of a project to get a handle on the beast’s fuel un-economy. I
installed a 16 inch electric fan,
a second alternator to drive it (!), and followed Kirby’s advice with a
separate switch to control
the AC compressor clutch. I have a bar-graph display in the driver’s ash
tray for the EGO sensors,
and a switch to hop from left to right. I think that it’s critical to
have a slightly rich mixture with wide
throttle openings, then let the D-Jetronic do the rest. At 100km/hr it
burns about 14 litres/100km.
To make yours run richer, adjust that grub-screw on the MAP sensor
anti-clockwise. Just thirty degrees
makes a big difference.
I’m working on the assumption that lean mixtures at low power outputs
won’t damage anything.
But it would be helpful to get some comments from those on this list who
could speak with more
authority on the topic.
Cheers
Owen Holmwood
1978 XJ-S
Sydney
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
In reply to a message from owen holmwood sent Tue 19 May 2009:
Owen.
Interesting, my car is actually running quite OK but have the same
problem with accesive fuel consumption which can be explained since
its running fat all the time. I have some electrical stuff to
check, vacuum etc. Ill come back with the results.
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
Hello. I see that this is an old post but I have recently discovered the same thing.
Short story long, I was having issues on my 75 XJ12C. I was losing 6 injectors after 8 minutes of running and was scratching my head for months until I found the real problem. (that is for another post coming soon)
Anyways I got it running with all 12 injectors and I had messed with the map sensor adjusting screw during trouble shooting. (I know, never touch the MAP sensor) So I want to get it tuned now that it is running semi correctly.
I am using a wideband oxygen sensor and my AF gauge is set to LAMBDA. 1=stoich, less than 1=rich, more than 1=lean.
As per tobmag’s description at the start of this post, that is the way D-jetronics run. Rich most of the time and LEAN when you think it should be rich. The ECU isn’t smart enough or fast enough (especially with no feedback from an O2 sensor) to make adjustments to correct the lean parts.
Mine idles rich, .90 lambda (as lean as I can get it)
cruises rich, .87. Most engines can cruise lean. .87-.90 is equivalent to 13.0:1 AF/ratio
part throttle-light acceleration, goes lean after going a little rich(the 10 contacts in throttle switch richen it a tad), 1.7 and more.
If the MAP sensor is too lean you will get pop-back from the intake(don’t go messing with the map sensor unless you are very sure you want to). To clarify on our map sensors with the black cap and single 4mm screw(3rd design?). Counter(anti) clockwise is richening, clockwise is leaning.
Full throttle goes really rich, .70-.80. .85 is equivalent to 12.5:1 AF/ratio
Living in the Denver area I am above 5000ft elevation. My idle screw on the ECU all the way lean.(idle adjuster on the ECU case, counterclockwise=lean, clockwise=rich. Opposite of the map sensor.
I have 2 extra good ECU’s and it runs the same with small variations ecu to ecu.
Just wanted to verify that these readings although not ideal for most newer injection systems is OK for the D-jet system. Although the car runs well I believe there is a lot left on the table with the D-jet and I will start to research for a possible replacement that will help the v12 run stronger and more efficiently.
Hope this helps.
Monte
