380SL Diesel Conversion Project - Page 17 - PeachParts Mercedes-Benz Forum

mach4 · #**241** 03-10-2012, 10:48 PM

Quote:

Originally Posted by mercmad6.3

Yes, i see that. The EGR signal is the same as you get from the amplifier and goes to W on the tacho for the 1985 and later cars. Now i understand your problem. if you look at a 300D tach (post 85) it has three pins + - and W . The SL has only two pins TD and + ,not counting the 12vlt feed for the clock. the instruments are grounded through the instrument cluster frame. From what i have seen,the 300D tacho wont physically fit in the cluster but i am sure a bit of surgery to case will make it fit.

I just went out and pulled the steering wheel and cluster on the 300D donor, and took a look at the tach connection. There are indeed 3 pins on the cluster but only two wires connected - a green/black and a black/red and the middle pin is not used.

Are you suggesting that the SL uses a "TD" signal and the 300D uses a "W" signal?

I wonder if I should just try to find a tach amplifier and go that route. It seemed so convenient to just tap into the EGR controller to grab a signal. I also thought it would be a far cleaner signal since it appears that the signal off the crank is one pulse per revolution while the one off the flywheel would be 50 pulses per revolution (or however many teeth the flywheel has)

mach4 · #**242** 03-11-2012, 07:48 PM

Got the brakes bled and the coolant installed and took it out for a quick drive...not very far, but enough to ascertain that the speedometer indeed works.

I believe that most of my cluster problems are ground related as the gauges tend to jump around in sync. I'll be spending some time tracking down that issue. Lots of other little things too like a squeaky belt, the tach issue and my shutoff. I wired the shutoff into a "run" circuit and it really needs to be wired into an always hot circuit. If one turns the key off with the engine running, the switch won't work to shut the engine off.

I also don't know if the turbo is spooling up properly. I don't get any "whine" under acceleration although it turns freely, so that will need to be investigated as well.

Another milestone reached.

ROLLGUY · #**243** 03-11-2012, 10:34 PM

Quote:

Originally Posted by mach4

Got the brakes bled and the coolant installed and took it out for a quick drive...not very far, but enough to ascertain that the speedometer indeed works.
Another milestone reached.

GREAT!! Maybe you will be able to join us on our next cruise!
M.B.E.G. SoCal Spring Coastal Cruise to the Petersen Saturday April 21st

mach4 · #**244** 03-12-2012, 04:25 PM

I pulled the tach from the 300D and hooked it up to the 380SL to see if it would work. It didn't. But I'm convinced that the tach is bad. I was hoping to just verify that the needle would operate in the right direction. The needle shows 2k rpm at rest and won't go the full sweep. When I pulled it apart it looked like it had been "worked on". So I decided to see if the tach itself out of an '84-'85 300D (and possibly an '86-'91 as well) would fit. It did.

The tach itself is definitely different. The one on the left is out of a 300SD cluster, which I originally picked up to be able to go with mechanical oil pressure and mechanical speedometer) with the same connector as the SL.

Here are pictures of the two tach assemblies. The one on the left is from the SD and the one on the right is out of the 300D. You can see that the mounting plate is identical and it turns out the height between the mounting plate and the face plate is the same, so they will interchange.

But they are definitely different units... which makes sense I think, as one is powered by a one-pulse-per-revolution VR signal coming from the crank feeding the tach amp, and the other is coming from a 50-ish pulse-per-revolution VR signal from the flywheel coming through the EGR controller. The fact that the connector on the back of the cluster is different as well, would support this theory - SD/SL on the left and 300D ('85) on the right.

Time for a JY run to snag a good tach from an appropriate vehicle.

mach4 · #**245** 03-23-2012, 12:06 AM

I've been fighting with the tach for awhile now. I did make a trip to the junkyard awhile back and picked up a unit I thought would work. It had the same connector as the 300D but wasn't from a 300D, so I decided to take a chance anyway. No go.

I was back at the junk yard today and couldn't find a vehicle with the proper tach. I did find a tach amp which I grabbed for $4 (they had no idea what it was so charged me for an oil filler cap).

So I was doing some more research today and came across a post which gave me the clue I needed for the ultimate solution.

Quote:

Originally Posted by Johnt49

FYI the [tach] meter movements are the same on all models. The only difference is the circuit board on the back & the face. It might be easier to change out the board.

So I thought that the probability of electronics going bad, compared to mechanical stuff made the odds pretty good that swapping the board to a new movement was worth a shot, particularly since the spring looked to be messed up. So I swapped the 300D board to the 380SL tach movement and it worked.... and since the tach works, that means that the EGR controller works, so I can cross that one off the list.

I can't put the dash back together yet, since I've lent my speedo face to Rahullo to use as a template for white faces.

So again, the forums come through with the data that ends up with a great solution.

Anyone need a presumably good (but untested) tach amp? Won't be needing it after all.

The other little detail item I took care of was the PCV setup. Ultimately I'll go with a catch can/separator that will drain to the oil pan (I've got the earlier pan with that fitting), but for now I've got a setup that will pass emissions inspection.

I'll probably be ready to call for an appointment with the BAR next week.

mercmad6.3 · #**246** 03-23-2012, 04:39 AM

Hi,I missed a couple of posts but it looks like you got it sorted in the end, you can see how the TD signal is marked on the older tach (pre1985 i would imagine) and the later EGR unit is marked + - and W . These W tachs can also work off a feed tapped into one of the wires in the alternator too.
Sounds like you are going ahead in leaps and bounds. I can understand your use of the SAE sized oil lines, i have been trying to source metric hose here in Australia and although we are a metric country, there is none available . A lot of older mercedes oil line fittings are reusable.

mach4 · #**247** 03-23-2012, 07:05 PM

Quote:

Originally Posted by mercmad6.3

Hi,I missed a couple of posts but it looks like you got it sorted in the end, you can see how the TD signal is marked on the older tach (pre1985 i would imagine) and the later EGR unit is marked + - and W . These W tachs can also work off a feed tapped into one of the wires in the alternator too.
Sounds like you are going ahead in leaps and bounds. I can understand your use of the SAE sized oil lines, i have been trying to source metric hose here in Australia and although we are a metric country, there is none available . A lot of older mercedes oil line fittings are reusable.

Yea, looks like my problem is solved. I almost picked up a tach at the junk yard that had the three-pin connector and was marked W, but they wanted too much for me to experiment with. I was prepared to wait for the next half-price day and maybe pick it up then.

mach4 · #**248** 03-24-2012, 12:54 AM

Well, got my appointment with the BAR (Bureau of Automotive Repair) to have the conversion inspected and (hopefully) be issued a the sticker certifying it as a diesel and in compliance with all the smog stuff. The big day is April 3. I'll be renting a vehicle trailer for the day as I really can't drive it because it isn't licensed because it isn't smogged, and I can't smog it because it's now a diesel and I couldn't register it initially because the gas engine was blown (can't smog a non-running engine you see)

No biggie, just drag it over there with the F350 and get it done.

I'm not anticipating any problems as the smog stuff is pretty simple - Trap Oxidizer (Cat Oxidizer), EGR, ARV and PCV and I've taken great pains to hook everything up as original.... but one never knows when dealing with the government.

ROLLGUY · #**249** 03-24-2012, 01:15 AM

All of us that have been following this thread wish you luck!

charmalu · #**250** 03-24-2012, 02:46 AM

OH yes the Government, it`s run by a bunch of idiots, but the best idiots money can buy. One must not cloud their judgement with a lot of Black Sooty Smoke.

I have my fingers crossed it goes well for you. this has been one incredable project you put together. You have done what many other nay sayers said couldn`t be done.

HMMM, wonder where they are now?

Charlie

mach4 · #**251** 03-24-2012, 04:29 PM

Quote:

Originally Posted by charmalu

You have done what many other nay sayers said couldn`t be done.

And what is really interesting, in the end, I believe that almost anyone could do this conversion, especially now that all the research is done and the major issues solved with nothing really major required.

This might be a good time to just summarize the technical aspects of the project.

Engine Fit - there are five things that make the engine fit properly without any major work

1. Dropping the subframe 1/2" using four easily turned aluminum spacers and four extra length bolts are all that is involved and cutting 1/2" spacer plates for the motor mounts
2. Using engine support arms from a '75-'79 300D that uses the same subframe
3. Using an upper oil pan from an '80 300SD with no ribs
4. Using an oil filter housing/lines from a W126
5. Using cast-in-place urethane inserts for motor mounts, subframe mounts and transmission mount

Fuel System - remove electrical pump and connect tank direct to feed line

Exhaust System - New flex joint, front support bracket, and a connector/adapter to the existing exhaust

Electrical system - Very straightforward, just a lot of time and tracing wires and splicing. Since my car was an '85 I had the EGR controller to contend with, but earlier cars should be considerably easier. Using manual shutoff and manual glow plugs eliminated a lot of complexity.

Gauges - Speedometer issue is solved with a fairly easy bracket for a speed sensor and welding 4 "teeth" to the drive shaft. Tach is now an easy solution. Oil pressure is solved with the SD electrical sender.

Cooling - Easy fabrication of lower radiator bracket. Top support is extremely simple - two aluminum "U's" and two slots. A little finagling with heater hoses and coolant overflow.

Oil Cooling - Modifying the oil cooler and stock hoses to take -10AN fittings and hoses is very straightforward, but not required.

Transmission/driveshaft - No changes required other than swap the yoke from the 380SL to the donor trans. Linkage, driveshaft, mount all standard. In my case I needed to modify the NSS, but any 722.3x transmission would not need a change.

Air Filter - Final solution is pending, but a temporary solution is to use a K&N style with the PCV plumbed in.

Power Steering - Bend hard lines just a bit to connect properly

Throttle Linkage - A very simple bracket mount on the firewall allows the stock 300D linkage to be used

Vacuum - Like electrical, just time consuming and tedious. One simple hookup to existing 380SL chassis vacuum system

A/C - Had to eliminate R4 compressor due to clearance issues. A new compressor, brackets and hookup will be phase II, so not sure of everything that will be involved to have A/C. Everything was left intact, so once the compressor bracket is fabbed, I'll install a new dryer, expansion valve and make up a couple of hoses and charge the system.

The things I didn't have to do are as significant as what I did have to do.

- didn't have to notch the subframe
- didn't have to remote the oil filter
- didn't have to fabricate motor mounts
- didn't have to use a hood scoop
- didn't have to shorten/lengthen the driveshaft
- didn't have to modify the engine bay

...and literally the only thing I was unable to do by myself on this entire project, was remove and install the hood.

ROLLGUY · #**252** 03-24-2012, 05:35 PM

Quote:

Originally Posted by mach4

...and literally the only thing I was unable to do by myself on this entire project, was remove and install the hood.

I don't know about the SL, but on a 123 the hood has slots that will hold the hood without bolts, and one person can install a hood by himself. If the SL is the same, then maybe you COULD have done the entire job yourself! However, it is best to be on the safe side when working with large parts like a hood, and get help so nothing is damaged.

mach4 · #**253** 03-30-2012, 07:41 PM

After re-thinking my situation with the car registration I figured out that there is really no great hurry to go get inspected by the BAR (Bureau of Automotive Repair) When I got the car, I put it on non-op status because I had no idea whether the swap would work (why pay registration if you're not going to be driving the car) So today I went down to the DMV, paid the registration, got insurance, and got my tags that are good until January. So I can drive for the rest of the year and since smog is an every 2 year proposition, I could theoretically drive for another year before getting inspected to change the title.

Assuming everything is ok as I drive and test this weekend, I'll keep my appointment next week and get that out of the way (and be completely legal)

I'm venturing out further and further from home base and so far everything major looks good. My known issues are rough idle, flaky ground in cluster, broken clock, excess play in the steering wheel and soft brake pedal (though brakes are good).

I'll definitely need to give the engine a going over; standard stuff like valve adjustment, check timing chain stretch, check injectors and so on, that haven't been done yet.

Yes it is a turbo diesel!

PhantomCadillac · #**254** 03-30-2012, 09:24 PM

Sounds like you are ready for a nice side business. How much cost do you think you have in the project? Does it have A/C and if not would that be a problem.
That SL would be great in Florida

dude99 · #**255** 03-30-2012, 09:46 PM

Fantastic job! ... now I want one...