My D-jet fuel injection has been working well since I got the car, likely because I had the injectors cleaned and went through all the other parts to make sure it all works well.
However there is one oddity that it has always done. There are two conditions were the engine will momentarily 'die'. After it is first started and it's still at high idle after about a minute it acts like the ignition is cut for 0.1 seconds. It's not long enough for the engine to die, it simply turns off, then catches again and goes back to high idle. This will happen a few times, maybe 20 seconds apart.
I wonder if D-jet is like L-jet, and when the TPS gives the 'idle' signal (throttle closed) it shuts off the injectors at ~1500 rpm. The high idle when cold is quite high, so if D-jet has this function this may be what is happening.

The other times it happens is when I am very easy on the gas (usually when the engine is still cold) it feels like the engine has shut off. I usually just give it more gas and it reacts normally and accelerates smoothly.

Any ideas? BTW, definitely not the ECU, unless I have 2 with exactly the same fault :-)
Thanks,

__________________
Csaba
1972 280SEL 4.5, silver

have you cleaned and adjusted TPS on throttle body?

__________________
Ron
2015 Porsche Cayman - Elizabeth
2011 Porsche Cayman - Bond,James Bond
Sadly MERCEDESLESS - ALways LOOKING !
99 E320 THE Queen Mary - SOLD
62 220b - Dolly - Finally my Finny! Sadly SOLD
72 450SL, Pearl-SOLD
16 F350 6.7 Diesel -THOR
19 BMW X5 - Heaven on Wheels
14 38HP John Deere 3038E Tractor -Mean Green
84 300SD, Benjamin -SOLD
71 220 - W115-Libby ( my first love) -SOLD
73 280 - W114 "Organspende" Rest in Peace
81 380 SL - Rest in Peace

It sounds like you are describing the "Surge" and there are a few scenarios where the "Surge" will occur. Usually when not in gear.

If your idle is too high, once you get to 1500 RPM, the injectors are shut off until 1200 RPMs, if memory serves. This is the "Coast" position on DJET where if you're, say, going down a hill and let your foot 100% off the gas, it will shut off the injectors for engine braking (And perhaps an early fuel-saving measure, no idea if that was an intended benefit from the early designers) - I think the range is 2500-1200. Your idle is too high, so it will surge as it goes in between what it believes is coast to idle mode.

You will need to lower the idle speed by turning in the idle air speed screw. Per the DJet manual, the way to adjust idle speed is using the air speed screw to get to 700-750 RPMs at idle, then use the mix knob on the ECU to get between 1.5-3.0% CO.

__________________
Current:
2021 Charger Scat Pack Widebody "Sinabee"
2018 Durango R/T

Previous:
1972 280SE 4.5
2014 Jeep Grand Cherokee Limited "Hefe", 1992 Jeep Cherokee Laredo "Jeepy", 2006 Charger R/T "Hemi"
1999 Chrysler 300M - RIP @ 221k

I think 1000 rpm is where the FI cuts back in on coast. I found this particularly annoying in parking lots and low speed driving since my car has a stick shift and the FI would cut in and out causing the car to jerk or lurch when the FI kicked back in. I am going Megasquirt when I get it back on the road.

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Tony H
W111 280SE 3.5 Coupe
Manual transmission

Past cars:
Porsche 914 2.0
'64 Jaguar XKE Roadster
'57 Oval Window VW
'71 Toyota Hilux Pickup Truck-Dad bought new
'73 Toyota Celica GT

Yes, the Djet does work that way. If you cut back on idle rpm just slightly, that cut out should go away. If you can't find a sweet spot, this could indicate that you have a vacuum leak or your AAV is not working 100%.

My 72 Djet idles at about 1200-1300rpm after a minute or so when cold.

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5

Hello Graham
Slightly Off Topic but not really
I have Followed you old Posts with great interest however never found the end of them related to using Yellow Injectors Over Blue Green Injectors . ( My Car is a 1975 Mercedes 450 SEL and runs great with the exception of the Classic Lumpy Idle . I expect I have the Bosch 0280150036 injectors (blue) )
From you old posts in part :

On my 4.5L 350SL, I have the M117 engine. This engine uses Bosch 0280150036 injectors (blue) that apparently are rated at 485 cc/min at 3bar.
********** AND >
On a 3.5L 350SL, they have the M116 engine. This engine uses Bosch 0280150034 injectors (yellow) that are rated at 317 cc/min.
**********
Now of course I don't want to Burn Valves and such But ?
I never found the end of your posts and weather you did this or not or if it worked ?
The Questions :
(1) Can this be done ?
(2) Did it work out well ?
(3) Exactly what must be done to make it work properly without damage to the running of the Car ?
(4) what are the results in Better Gas Millage and or Damage to the Motor or running of the car + or - ?

Now I understand that The mega Squirt conversion may be the way to go but never fount a simple way to convert to Mega Squirt at a low cost Method : Like for example to use a Trigger Wheel from such and such a Car and it fits right on my Front Pulley with perhaps a spot weld or two that sort of thing . a way to convert for Example for only say $500 or less ? and a link or directions of how to such .

Now lol Perhaps you abandoned the whole project and went to a diesel car I have no Idea ? or tried it and burned up your valves lol ?
Any old way if you care to reply or PM me it would be very nice of you and greatly appreciated
Regards KK

Attached Thumbnails

 

Thanks for the comments!

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Csaba
1972 280SEL 4.5, silver

Hey aluminum,
You can buy a trigger wheel made specifically to fit over your pulley inexpensively from Ebay (or at least you could a few years ago)
A few have used the existing Djet injectors and fuel rail. You can even buy a JY Ford EDIS setup inexpensively from Ebay and go distributor less.

__________________
Tony H
W111 280SE 3.5 Coupe
Manual transmission

Past cars:
Porsche 914 2.0
'64 Jaguar XKE Roadster
'57 Oval Window VW
'71 Toyota Hilux Pickup Truck-Dad bought new
'73 Toyota Celica GT

I never did try going to lower capacity injectors, but I would if a set came my way .

Reason I have not changed, is that I got my D-Jet to run perfectly well without modification.

The biggest problem most Djet owners face, is that they do not have an accurate exhaust gas analyzer. With the advent of lower cost wideband oxygen sensors, this can be overcome. I permanently installed an AEM AFR gauge on my dash and had bung welded into exhaust for wideband O2 sensor.

With this, you can adjust idle mixture using the ECU and load mixture using the MPS (They are different).

Besides mixture, everything else also needs to be as-new - A good AAV, TPS, trigger points, MPS, temperature sensors, clean tested injectors, ignition wires & plugs, no vacuum leaks etc. And timing set properly.

Sounds like a lot, but for MS you will also have to have everything as-new and on top of that pay for the MS system. And learning to run that will be another challenge! Install MS? In my opinion, only in desperation or because owners wants a project

Going to slightly lower capacity injectors could perhaps help with fuel economy (if that is important). With a dash mounted AFR, you can see mixture at all conditions and adjust by trial and error. To avoid overly lean mixtures and possible damage, you just have to make sure you are running within the range of the AFR equivalent of the %CO levels MB specified.

Have Fun

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5

Graham that is so useful, you have no idea... with the availability, low cost, and ease of getting a wideband O2 sensor and gauge to be able to do that, you probably have one of the best tuned D-Jet systems in the country.

__________________
Current:
2021 Charger Scat Pack Widebody "Sinabee"
2018 Durango R/T

Previous:
1972 280SE 4.5
2014 Jeep Grand Cherokee Limited "Hefe", 1992 Jeep Cherokee Laredo "Jeepy", 2006 Charger R/T "Hemi"
1999 Chrysler 300M - RIP @ 221k

Yes Grahams Comments as usual are very useful I agree :
He say's >
"With this, you can adjust idle mixture using the ECU and load mixture using the MPS (They are different). "

Do you think he actually" means you can adjust the MPS with the " Air fuel Ratio " Gauge then ?
As per your Comment : where is this you can get a Quality " Air fuel Ratio " Gauge ? I am seeing them at $200 + or - I may be able to get a wideband O2 sensor for little or or not to bad cost .

All in All I think Graham is on track but the Gauge I expect is costly and most likely I would not often use it .
I also Think to use yellow Injectors would definitely be a Big + I am allmost sure short of actually trying it . However this is a Side event related to different fuel millage and proformance

I am not sure why you'd want to use lower-flow injectors on a 4.5. MB designed the 4.5 system to use the higher-flow blue/green ones for a reason. It would have cost them a hell of a lot less (inventory, manufacturing differences, R&D etc) to use the yellow ones, if they would have worked right, just like using the 3.5 D-jet ECU vs the 4.5 one would have saved them a ton. I suspect the yellow injectors wouldn't flow enough fuel @ full throttle & full RPM.

It sounds like you have a major running issue you're skirting around with trying something else versus a proper fix?

As far as $200... this is literally the first one I found on eBay and it's far from $200 considering it's literally the first result for me.
APSX D2 Digital Wideband O2 Air Fuel Ratio (AFR) All-in-One Controller Gauge

__________________
Current:
2021 Charger Scat Pack Widebody "Sinabee"
2018 Durango R/T

Previous:
1972 280SE 4.5
2014 Jeep Grand Cherokee Limited "Hefe", 1992 Jeep Cherokee Laredo "Jeepy", 2006 Charger R/T "Hemi"
1999 Chrysler 300M - RIP @ 221k

Absolutely. MB provided the %CO figures at different engine loads.

%CO can be converted to AFR. You run your car at the various load conditions (need a good hill!) and then make small adjustments to MPS until you are in spec. There is quite a large range, so you can choose for yourself whether you want to be on lean or rich side. Only other way to do this, would be on a dyno.


There are several wideband packages available. There may be others, but these two have good reputation:
MTX-L Wideband O2 Digital Air/fuel Ratio Gauge
Analog Style Wideband UEGO AFR Gauge | AEM
Amazon.com: AEM (30-4110) UEGO Air/Fuel Ratio Gauge: Automotive
Auto Meter

It could cost $200-$250 by time everything is installed. Perhaps less if you weld in exhaust bung yourself or make one of these.
It's not that much if you compare with letting shops who don't understand Djets mess with your car. I use AFR gauge every day - just like the speedo, oil pressure etc Much more interesting than my fuel pressure gauge that never changes

They may make adjustment a little more precise. You would absolutely have to have an AFR meter or exhaust analyzer to readjust MPS and ECU. I would like to try them or perhaps a set out a Nissan, but don't really think there would be much difference. Our cars were designed to run with the blue injectors.

By the way, this link shows my installation:

450sl engine issue - Page 3 - Mercedes-Benz Forum

__________________
Graham
85 300D,72 350SL, 98 E320, Outback 2.5

Thanks Graham :
RE :
Quote:
Full load shifter position S 3,000 rpm = 2% - 5% (AFR 13.8-12.6)
Upper partial load position S, 2,500 rpm 300 mm Hg vacuum 0.1% - 0.5% (AFR 14.7-14.3)
Lower partial load 3rd gear shifter position S, 1,500 rpm 300 mm Hg vacuum = 0.2% - 0.5% (AFR 14.5-14.3)
Idle neutral, idle speed, oil at operating temp = 0.5% - 2.0% (AFR 14.3-13.8)
**********************************
Nice to have those Speck's to go by > Thank you
As previously stated my 450 Sedan runs just fine but could no doubt run better I expect > like the lumpy idle and such .
if I buy a AFR gauge I would for sure buy a good one not some cheap one as most of my tools i have had for many years .
Did you make or use a heat deflector for your fuel rail and such by chance?
Perhaps that's not a issue in Canada lol.
Now I expect at a smog shop you could set your AFR and MPS also but would need a dyno type smog station . my 75 is smog exempt so I might be able to get them to set mine off the DMV Computer perhaps in Las Vegas ? Most often you can get anything in Vegas .
However just having the AFR would be a big + no doubt .

We get hot summer weather, but most hot start problems seemed to occur in late Spring or Fall on warm days. At that time, we have winter fuel which is more volatile. I polished my fuel rails until they shone so as to reflect heat. I really didn't want to cover the black hoses because that is where leaks show up. I found that setting idle mixture on rich side, my hot start problems went away. But the AFR gauge does still show that mixture is very lean until fuel starts circulating. Keeping tank full in hot weather also helps.

At one time, I attempted to set mixtures using an ancient Wheatstone Bridge type CO meter. I then took car to local shop and they ran it on their Govt. smog set-up. Amazingly car passed the test (not required here either). But it was a one shot deal and I couldn't do any fine tuning. The AFR meter allows that.

__________________
Graham
85 300D,72 350SL, 98 E320, Outback 2.5