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Premium Member
1999 500SL, 1988 SEC
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Discussion Starter · #1 ·
If you read H.D.s threads over time you would see one where he developed a diagnostic tool to read various engine functions while driving. I mentioned that I thought that would be valuable information along with the readings of duty cycle, fd fuel pressures, and fuel relay voltage etc would be a great add to data On the cars operation. At that time I had the intention of making my own device just a little different from what H.D. Showed. Well I am partly there and am starting this thread to keep all of you informed. It has taken me so long just because I had to have someone cut the aluminum plate for the gauges to go in and other things had to be taken care of first. Right now all I have left to do is wire the thing to the proper places in the car which is still a big deal. I did install a new bung in the exhaust (other side from the one the car uses) and mounted a wide band oxygen sensor to it and ran the wires to this data reader inside the car so I could read the afu mixtures at different driving conditions. The other gauges as mentioned above are for electrical levels of varios things and the indicator lights are simply to let me know if things are getting power. This unit will not stay in the car but will have a plug where I can remove it when not being used. So far I think I have about $30 in this. This does not count the afu meter though. For the most part I assume I wont need it but if things seem wonky with the engine I can simply plug it in and have some information that should help me diagnose the problem. As I get going I will keep you posted of this progress.
 

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Outstanding Contributor
1989 560SEC, 1989 560SEL, 1995 E420
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I'm at a similar point as you. Gauges are mounted and I 'just' have to wire it into the car. What are your ideas for making the connections? I haven't come up with anything I like yet.
 

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1999 500SL, 1988 SEC
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1,747 Posts
Discussion Starter · #3 ·
Well here is my thoughts. First it depends on if this is a one car device or are you going to use it to see what is not correct on other cars you might work on. For me its a one car thing so….. First the wide bang 02 sensor. Since it has its own harness with a plug I simply installed the sensor in the new bung and ran the wire through a new hole I drilled right next to the other 02 sensor. Its on the passenger side under the carpet on the tunnel. I ran that wire so the plug is easily accessible just under the dash. For the rest of the wires I plan to connect them under the hood on the correct place and using a 14 or so paired cable run that wire to the passenger side, under the dash. I will terminate it into a 14 or so pin plug. On the data logger I plan to connect the gauges using the same type of paired cable to the other plug. In this way I simply unplug the unit when not in use. Under the hood though I purchased a small fuse box where I will fuse everything.

I think I can do the underwood connections without splicing by finding a termination point and simply piggy backing there.
 

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Outstanding Contributor
1989 560SEC, 1989 560SEL, 1995 E420
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5,171 Posts
I'm using a 9-pin printer cable. I'll cut it somewhere at one end which will be terminated at my gauge cluster. The other end will go to the engine bay to each signal source. What I'm struggling with is how to tap into each item. Like, how would you physically tap into the fuel pump relay? Or the X11? Or the O2 sensor? I think H.D. recommended ring fasteners to slip onto the FPR but I didn't feel like that was a very secure connection. I may have to be more careful filing the I.D. of the ring.

Your suggestions?
 

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Premium Member
1999 500SL, 1988 SEC
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1,747 Posts
Discussion Starter · #5 ·
Luckymike, they make these little things that I think will work so as not to screw up the wire. There is a pin in the middle and as you tighten the cap it pushes the pin into the wire. These came with something else I am working on but I bet you can find them on Amazon. Onsome things though I will go another route like on the diagnostic port I might solder the wire to the terminal underneath. H.D. told me all the gauges and lights could use a common ground, which there are a number of points under the console. That makes things somewhat easier.
 

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Outstanding Contributor
1989 560SEC, 1989 560SEL, 1995 E420
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I've never seen those before. Does it wind up making kind of a 'T' connection?
 

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1999 500SL, 1988 SEC
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1,747 Posts
Discussion Starter · #8 ·
I moved along a little this weekend. I connected all the wires in the data logger to the 8 wire cable, and connected the wide band O2 sensor as well. I am showing you a picture of the fuse box and not really sure where to mount that. Ideally it would be under the hood but space is at a minimum. Other best place is under the dash but then who will ever find blown fuses??? and second if I put it there, you have unfused wires going from its point of connection to the fuse box. The longer that is the more chance you take.

So, from what you see I need to do a couple of things. First I need to get an 8 pin male and female plug so I can disconnect the data logger when not in use. One of the plugs I would neatly tuck up under the dash. The other on the pigtail of the data logger

luckymike, you might find what you are doing a little easier than what I am. I say that since I added a wide band O2 sensor and that requires two cables to use. One goes to the O2 sensor and the other power for the O2 sensor. So I have two more cables than you would have.

One of the next steps also will be to make the connections under the hood. I have all the places noted I am supposed to get connected to but its not going to be easy. I think one of two things at a time will be great. I suspect this will be a 6-9 month process so don't hold your breath. I will however document what I do.

Right now its a Wide band O2 sensor, 4 voltage meters (digital) and 4 green indicator lights, all stuffed into a box.
 

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Outstanding Contributor
1989 560SEC, 1989 560SEL, 1995 E420
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Sounding good. You might consider a 9-pin printer cable like this:

2699188
 

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Outstanding Contributor
1989 560SEC, 1989 560SEL, 1995 E420
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5,171 Posts
My thinking was to snake that one cable around the engine bay, branching off each of the nine wires as necessary at each needed location. And the plug allows removal of the device. It's only about 1/4" diameter cable.
 

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Premium Member
1999 500SL, 1988 SEC
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Discussion Starter · #12 ·
My thoughts too as to snaking the wire around the engine bay, but I also need to find a place for the fuse box. This weekend I should be able to test the O2 sensor while driving. Its going to be interesting to see what it is compared to the duty cycle readings I have tested before. One might assume correct duty cycle, correct AFU ration on the wide band O2 sensor.
 

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Premium Member
1999 500SL, 1988 SEC
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1,747 Posts
Discussion Starter · #13 ·
My cable is 11 mm diameter with 8 conductors. I am looking at the aviation type of but end connector. Can someone how to order one with the correct size for the wire to fit into and clamp it. Not sure how to order the correct size. Thanks

2699814
 

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Outstanding Contributor
'17 GLS450, '14 GLK250 "Grandpa's Roadster" Project Car, 350SDL (Sold)
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I don't have an answer for you; as a former instructor in aircraft electronics, the thought of that kind of connector makes me want to run screaming out of the room.

That's similar to what we call a cannon plug, but they aren't chrome plated in the real world. They are extremely labor intensive and serious overkill for what you're doing. How about a DB9 RS232 panel mount socket and plug? You might even be able to find a nice serial cable to hack up for your cable, and avoid having to build one.
Cannon plugs.jpg
 

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'17 GLS450, '14 GLK250 "Grandpa's Roadster" Project Car, 350SDL (Sold)
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1999 500SL, 1988 SEC
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Discussion Starter · #17 ·
Couple of things today on this, I have connected one device, the AF meter. Basically there are two bundles of wires coming into the meter that needed connection. One from the wide band O2 sensor and the other a power and ground wire which the gauge needed. The bundle coming from the O2 sensor (well first, know I installed a bung on the drivers side for the sensor, about the same distance back as the MB one on the passenger side for the cars system) for this I ran the wire up the passenger side trans hump through the floor board, with a grommet, and left the plug tucked up inside the knee bolster. The other wire, which is the power and ground, I purchased a cigarette type of plug that simply plugs into the ashtray lighter and connected that wire to it. This provides my power and ground to the meter. The plug is fused, which is good. Look at the picts to see what I mean. So both can be plugged in and removed easily. As an aside when I bought this plug it came as a pack of 5 so if someone needs one or two let me know.

So it works, and the reading I find interesting and some comments about what I see. I do have the duty cycle readings to compare but they were taken a while ago, and to compare I suppose I should redo those and make the readings more recent. Also the Car's sensor is on the passenger side and the AFU meter's is on the drivers side. As such they read different cylinder banks. It should not make a difference but...... So when first starting the car, AFU readings are all over the place, kinda high during warm up. I guess one would expect that, with the readings being like 17.5. After warmup, they run all over the place depending on what you are doing with the accelerator. If you are at a steady pace, the readings are steady, like 15.5-16% which is also what is supposed to happen. At idle with it warm, its something like 16.7%. See picture. Now one might think that is rich, and it well might be, but again, I need to look at the duty cycle, some other readings and also think about whether the placement of the O2 sensors are correct. All of that has to be done, and with a conversation with the duty cycle gurus to make sure I don't touch something that should not be messed with. As and fyi both of the sensors were placed at the collectors of the TriY downpipes.

So, one item connected, 8 more to go. Many of the other items simply measure voltage and on off situations. It will take a while to do all of them but be patient with me. I have been driving it lots so no work time

The one mistake I see I made so far is that I need to make things more compact. This is a little cumbersome but it will work,
 

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Outstanding Contributor
1989 560SEC, 1989 560SEL, 1995 E420
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Looking great, Stutz. Glad you're sticking with this.

The cigarette lighter is brilliant for power and ground. Would like to take you up on your offer. Still have my address? PayPal some shipping?
 

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Premium Member
1999 500SL, 1988 SEC
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1,747 Posts
Discussion Starter · #19 ·
Sure just another in and out burger in Dec
 

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Outstanding Contributor
1989 560SEC, 1989 560SEL, 1995 E420
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5,171 Posts
Haha! No problem.
 
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