back to the infamous rich Djet operation

[meltedpanda]

running rich and cannot get it leaned out to run properly. I have a co meter and when I test and get to 2% she runs like crap, but rich runs OK but have a terrible idle. any ideas?
Plugs are not black but not the nice tan either , so rich running it is, plus the sweet rich smell is present in the exhaust

[tgolden]

http://www.benzworld.org/forums/w116-s-se-sel-sd-class/1223523-bosch-d-jetronic-k-jetronic-troubleshooting.html

The above link has some good D-Jet troubleshooting information to include D-Jet component testing. I don't see rich mixture addressed on the link, but you may be able to solve the issue by going over each component to see what's out of spec.

I don't have a D-Jet system, so I can't give you any first hand experience type information. How old are your injectors? I've solved rich mixture problems on my K-Jet by cleaning, testing and recleaning the injectors. Injectors can wear and deliver too much fuel. I replaced the injectors that had higher volume flow (10% higher volume) when compared to the others. Even new injectors should be time-volume tested before you install them.

Regards

[alabbasi]

Ron, check your contact points, my old 280SEL 4.5 would do exactly that when the points are out of adjustment. I would then adjust them and it would run like a scalded cat.

[meltedpanda]

I have optical points, but plan to clean injector points.
I have been thinking and believe my MPS is dead or out of wack
I am running rich through all RPMS. At idle I can get the co to acceptible levels , but at 2500 -3000 rpms it jumps up significantly.
My plan is as follows, see if it will make sense
set timing
set ecu to mid point
remove TPS connection
set co at 2% with rpm at 2500 using MPS
return and set idel CO at 1.5 -2% using ecu??

right now ecu is set to almost full rich , if I move to lean she about dies. which makes no sense , but gotta try something
its burning so rich that the inside of the tail pipes are pretty black ,and if you are around the car for any period of time your clothes smell like unburned hydrocarbons
Im not allowed in the house if I am working on her while the engine is running
injectors are rebuilt and balanced, no vacuum leaks, pertronix points, fuel pressure and running vacuum at specs, so its has got to be timing /mps /ecu what do you all think

also in regards to reading timing marks looking down at engine - left of top dead center mark is considered BTDC, to the right ATDC????

[meltedpanda]

I think mt MPS is dead, anyone have a working one they would like to sell pooooor ol Ron?

[RadioTek]

Here is someone parting out a '73 after getting nailed by a red light runner.
http://www.benzworld.org/forums/r-c107-sl-slc-class/1580973-1972-350sl-part-out.html

Post your adventure, I've been having trouble passing emissions inspection.

Scott

[meltedpanda]

has anyone performed a DJET to megasquirt conversion , I have seen the KJET threads. I see a lot of talk about the DJet conversion but not the actual DJET application

[alabbasi]

Ron

Whats the part number on your MPS? I think Barri did a megasquirt conversion on a D-Jet and K-Jet. There are also lots of people doing this to Porsches and VW's which also use D-Jet. It should be simpler.

[GGR]

D-jet is easy to convert to Megasquirt. I did it and it runs well, though I couldn't test drive the car yet as I need to solve a clutch issue. I will be happy to give you info on my set-up if you need it. As said earlier Barri went that route also, though we made some different technical choices.

[Graham]

Ron,
The MPS is very sensitive. 1/8 of a turn makes a big difference. What makes you think it is bad? Have you checked it using the values given in the manual (section 7.4)?

When my car was running rich, it turned out to be worn trigger points. There have been several threads here about that. The rubbing blocks wear, then the ecu fires the injectors either too often or at the wrong time? I don't know exactly, but replacing the triggers cured the problem. Look for the thread where we discussed removing the distributor, attaching an ohm meter to each set of points and measuring the angle that the points stay closed. It should be in the 100-120 deg range (No specs that I know of). But I had one that was so worn it stayed closed for about 180deg.

Otherwise, your method of adjustment sounds about right. I wouldn't worry about the idle CO - just get it idle evenly.

BTW - If you rotate the distributor CCW timing advances. You need to be turned almost all the way to the end of the slot to get near to 30deg BTDC at 3000rpm no vac (best setting for these old cars!) At that point, tdc will be to the left. Put a paint or chalk mark at 30BTDC (clockwise from TDC) and try to adjust to it.

I just got back yesterday from a few months in SC, so am a bit rusty on this stuff. I am sure others will correct above if it is inaccurate

Hooked up the battery on the SL today and it started almost before the starter turned the engine! Went for a run and she ran beautifully.

BTW - The car does run on rich side under load. This is a post I made some time ago on BW (you may have seen it). To do teh full load test, you need to be going up a steep hill, or have your foot on the brake while maintaining 3000rpm.

The emission specs for the 117 engine according to the MB Technical Data Manual are:

Full load shifter position S 3,000 rpm = 2% - 5%
Upper partial load position S, 2,500 rpm 300 mm Hg vacuum 0.1% - 0.5%
Lower partial load 3rd gear shifter position S, 1,500 rpm 300 mm Hg vacuum = 0.2% - 0.5%
Idle neutral, idle speed, oil at operating temp = 0.5% - 2.0%

All % CO and would apply, I guess, to either dyno or road testing. I just used the idle and the full load for setting MPS & ECU.

Those are the North American specs. Euro are slightly different.

What type of meter do you have? Some of the old Wheatstone Bridge ones are apparently susceptible to moisture and kind of useless. If it is not one you can take in the car with, then you could try this:

First set timing so you have 5-8deg BTDC without vac and with A/C turned OFF. Check that you have good vacuum at idle (16-17" is normal). Also make sure your Throttle Position idle switch is functioning properly. Method is in engine manual (also HERE and in pdf attached)

- Warm the car by driving it for at least five miles.
- Disconnect the throttle position switch plug (so as to disable the idle circuit) and set the ECU knob in the middle of it's range which is 11 clicks from right or left.
- Adjust the 4mm MPS screw in VERY SMALL increments so that you get about 3.5 percent CO at 2500-3000rpm. (at least as a starting point)
- Shut engine down and reconnect throttle plug.
- Start up again and set idle speed to about 750-800 rpm's.
- Use the ECU knob to set the idle co to about 1.5- 2.5 %CO. (rev enginel in between adjustments and taking new reading)
-Take car for a drive and then recheck CO at same conditions.

On my own car, I used this procedure. At first, I had a loan of an older CO meter - But it did not give consistent results. Since then, I have purchased a wideband Air/Fuel ratio gauge. (There are a number of manufacturers - mine is an AEM and is a permanent mount. Innovation makes portable units. Cost $200-$350 and well worth it.) This allows me to monitor AFR at all times. Better than watching TV

My car currently cruises at an AFR of 13-14 and idles at about 13.5. But I can set these wherever I want. Car seems to like to run on rich side. But for economy, it could be leaned out (but not too much or you could burn valves pistons etc!) But who cares about economy on and old SL

Sorry this is so long winded. I have had my 350SL for 20 years, but with AFR gauge, have finally got somewhere this year!

[Graham]

Regarding Megasquirt

Instead of going to MS, I decided to install a wideband O2 sensor and AFR meter. (AEM and Innovate make nice ones). With display on dash, driver becomes the Megasquirt! That is, IF the D-Jet components are doing their job! If cars is running a little rich, jump out and make a slight MPS adjustment, continue driving and check again!

Megasquirt is interesting and I would like to try it. But the D-Jet system is quite sophisticated itself and can work well if set up properly.

Link to Youtube on BW

http://www.benzworld.org/forums/4215336-post25.html

http://www.youtube.com/watch?v=z4eoQUqqavc

http://www.youtube.com/watch?v=tBNjaJqggLw

http://www.youtube.com/watch?v=MLe5vI00kS4

[GGR]

The D-jest system is excellent and was quite amazing when it came out in 1969. But parts start becoming difficult to get and are crazy expensive new for some of them (contacts, MAP, 3.5 injectors).

Megasquirt brings a whole new dimension, as ignition, VE and AFR maps can be modified by the driver, or let TunerStudio do the job live.

In the end both have merits. I have a '72 pristine BMW CSI with a D-jet system and it is remaining this way as the car is all original. My W111 Coupe is a different story, with a 5.0 M117 mated to a 5 speed manual trans, the MS is just adding to the fun.

[meltedpanda]

Thanks much, wondered where you have been Graham!
So here are my current investigations, my ecu has to be turned almost to full rich to get her to idle well,and when I connect the sniffer it is as expected rich, when I rev to say 3000rpm the meter goes into the 6-7 % range . the tailpipe is black, the hydrocarbon smell is bad. She is running rich in the full range. I have not tested under load. I probably need to do that. Your thought on the trigger points makes sense so I am goign to spec those out first and let you know. I just figured MPS as I have never adjusted it and figure its time (lol) .

[meltedpanda]

been looking at the threads on testing open /close of triggers. So remove dizzy and test on bench ,but how and where does one put the ohm meter, at the electrical connection - which number?

[meltedpanda]

well I believe it is my triggers, if the 100 -120 is the magic number,
I made a jig to test roughly got the following

I have two sets, on one thay all stay open 180 +/-5
the other set 2 pair stay open 180 the other stay open 220 !!

now I need to see if I can adjust , just how, not sure .... suggestions, were you successful Graham?
perhaps the MPS is fine and all rich condition is strickly the points staying open too long

thoughts??