My First post - Restoring a W107

[Chai]

There's no anti-pollution gear installed in the early '70s. Recall you mentioning this car is a UK import and assume it is a 3.5 litre from the 1971 manufacture. There will be anti-pollution gear if the car is a 450 USA import though.
I also can't recall you mentioning, but assume it has a D-Jet electronic ignition installed - same as my car.

If the engine runs but is not happy, think the ECU (EFI computer) is over-enriching the air-fuel mixture. Initial suspect is a leaky/porous rubber hose from the rear of the engine manifold (firewall side) to the Manifold Air Pressure (MAP) sensor. Did you replace this rubber hose? There's no clamp on the hose - just push fit. Think it's 8mm internal diameter - same as the fuel lines.

Also, visually check the electric wiring to the MAP connector. I had situation where the wire to a connector had snapped and the broken ends of the wires 'just' touched each other.

[iank]

Thanks for your comments, Chai.

All your assumptions about my engine are correct. I have replaced all the hoses recently, but I am now of the opinion that I may have a "leaky" injector. Actually, I have now done what I should have earlier - removed all injectors, and taking them in to MB Spares later this week to be checked, etc.

I am sorry I did not post this earlier. I only just found it today!! I will provide an update after I know the condition of the injectors.

Thanks again for your suggestions.

iank

[iank]

Update on previous post:

Just back from Canberra and MB Spares. Interesting results on the injectors tested. Of the 8, 4 tested OK, 2 were not working at all, and 2 were "leaky". No wonder M116 was unhappy. Now all have been tested OK.

When I have got around to re-installing the injectors, complete with new seals (and reinstalled the re-sealed steering box, and put the exhaust pipe back on), I will post a further update. Here's hoping!!

[iank]

A further Update:

350SL now has Steering Box, Injectors and Exhaust all back in the right place (I think!!) Steering Box seems good - just added fluid and bled OK but car still on blocks.

M116 started almost immediately (thank goodness) and runs pretty well, considering it hasn't done anything for about 20 years. First few short (5 min) runs,(at idle) ran very smoothly and was quite regular, but smoked a fair bit as it burnt quite alot of very old, oily muck off the exhaust manifolds. Once it started to warm up idle became pretty rough, but engine responded well to a few seconds at about 2000 rpm, and settled down to a (too fast) smoother idle, and blowing plenty of exhaust smoke. I adjusted the idle back successfully, and things seem pretty "encouraging" now. I think a good "Italian Tune" once I get it off the blocks, may reveal more realistic evidence of how it will settle down.

Time will tell. It will be a few weeks (or longer?) before I get the car down on its wheels and out of the shed - still a few "tidy up" things to do before hand. I will make further comments as I know more.

[Mercmad]

Yes it is, the idea being that the pump builds up pressure, but if the engine doesn't fire, the relay shuts it off. Sometimes if i am restarting one that hasn't yet been run ,i work the starter on and off 1/2 dozen times to get the pressure up before giving it a good crank to fire it. With a pressure gauge hooked up at the cold start valve you get a good idea about what is happening ,Just in case the fuel lines and so on have a blockage . it goves you a chance to do a once over to make sure no fuel lines have sprung leaks while the car has been sleeping.

[iank]

Thanks for your comments, Emad. I have purchased a Fuel Pressure gauge and had that connected as suggested for a few months, while playing with getting the engine running. Fuel pressure is fine (as I understand it) at 30 psi. Having just recently (last week) re-installed the reconditioned injectors, I have now removed the fuel pressure gauge, having confirmed the pressure is ok.

I have now run the engine a few times for about 15 minutes a time, and it is now "ticking over" fairly will, but I still think a good "test run" on-the-road will do it the world of good (??) [At least all the crap has now burnt off the exhaust manifolds].

[Mercmad]

great news! .. Dont forget to do the tappets and check the chain and it's guides , change your trans fluid and filter and check the diff oil .Did you know there is a filter in the power steering reservoir?.

[iank]

I haven't checked the tappet clearances or guides yet, but have changed trans filter and fluid, as well as diff oil. And, yes, I now know there is a filter in the bottom of the power steer reservoir, thanks to Chris at MB Spares.

Now tidying up a few "dodgy" wiring problems - on more familiar ground in the electrics/electronics areas!!

New windscreen should go in next week. Progress is sweet!! :dance:

[iank]

Restoration - well "tidy up" - is progressing. New windscreen now installed with no problems. Wiring all seems Ok at this stage. I must admit I had forgotten how to make the windscreen washers work (derrr!) Forgot all about the foot switch - now I have that problem solved, although had to perform a little "magic" on the washer pump to free it up.

My current concern is that while the engine starts easily and runs quite well as it is warming up, once it gets close to "normal" operating temp it starts to run very rough, is not happy idling, and attempting to adjust the idle, seems to have little / no affect!! Any clues would be appreciated. :think:

[AMG]

clean the trigger points on the dizzy. then a new rotor and cap, check the coil wiring and the 2 ballast resistors.
then check the warm up regulator.
Then check the TPS contacts on the throttle body and the connector.
Wiring is old, so make sure you test conductivity and make sure the resistance is low.
Most of this is covered in the D-Jet manual info and other associated information in the reference library.
Also Alastair covered a fair bit of d-Jet troubleshooting with his 3.5 w108. Although he did a pertronix conversion and megasquirt eventually.

Bottom line with D-jet is that if something has been stuffed around with, it needs to be returned to it's original setting before any troubleshooting commences.
For your sake, I hope noone's messed with the MAF, or bashed the warm up reg (aav) to bits.

If you do find that you have an issue with wiring, then the absolute best thing to do about it is NOT to touch anything until you understand the wiring diagram fully. Then carefully rejuvenate it.
The connectors are often aged and crumbly, the crimp terminals often connected to sulphated copper or not connected at all, broken wiring from excessive 'abuse' trying to move/remove components without first removing the injector harness etc.

It really is straightforward stuff, but it just takes simple attention to detail and a bit of care - it's not overly complicated - especially if you can read and follow a schematic diagram - you don't have to have an in-depth knowledge of electronics - just the basics and some basic tools if you wish to tackle anything serious.

But first, Look for obvious areas of filth and then go clean all the connectors in that area with a proper contact cleaner and then spray with switchlube (lightly). If you believe that there is a wiring issue, then now is the time to get the multimeter out and test the wiring in accordance with the ETM wiring diagram.

In my experience, the main things that cause rich running are poor adjustment on the throtle body linkages, dirty trigger points in the distributor, along with a loose trigger point harness connector - that can catch you out, but it's super easy to check. then the electrical connector for the TPS, and internally there is occasionally corrosion or pitting on contacts - in wich case you need to take the TPS apart and clean the same way as you clean electrical connections. the AAV (aux air valve) also known as warm up regulator. This can be thoroughly cleaned by removal and soaking in kerosene / parts cleaner / upper engine foaming intake cleaner etc. to remove all the shellac and oily sooty buildup from the body. the MAP should never be touched. Unless it is diagnosed as faulty or the diaphragm is punctured, in which case the only solution is a s/h one or send away to bosch for refurb, and that's $$$$. so don't touch it.

Brad Cushman, a good friend of a few of us here lives over in Alberquerque and has an early 107. He undertook a mighty task of rewiring the entire engine bay harness, and he found all the CORRECT parts..

Brad covered this epic build over on his native forum D-Jet Engine Harness
It's a solid read. I think it's worth everyone's while - because it shows that you can find what you need and how being resourceful is a necessary thing with these early efi cars.

[iank]

Hi AMG. Many thanks for your detailed, obviously well informed reply to my call for "help". The time you have devoted in compiling such a comprehensive run-down is sincerely appreciated.

I have recently checked the distributor points, including the trigger points which were clean (like new), but I have not replaced the cap or rotor. The ignition wiring all traces out ok, but I could not accurately confirm the values of the Ballast Resistors, as my multimeters do not really read such low Ohms values accurately. I will recheck the Trigger Point connector.

As far as becoming familiar with the general vehicle wiring, and reading a schematic circuit diagram, I am (now at least) pretty conversant with it all on the R107. I am a (retired and aging!) Electronics TechO, so pretty much at home with such wiring, and reading schematics . I have also "fiddled" most of my life with cars, buses, trucks and tractors, although have no formal mechanicing qualifications!

I visited our sponsor in Canberra about a month ago, where, as well as re-sealing the power steering box, Chris also had my 8 injectors refurbished, and I brought back another Cold Start Injector. I had already replaced all the fuel delivery hoses and clamps, etc. and checked the fuel delivery pressure - approx 30 psi.

I have done nothing to the Warm Up Regulator, so will certainly check that next. I also have done nothing more to the TPS other than checking the wiring connections to the connector. Will have a further look into that!

Many thanks for the couple of further reading references in your post. I will get them soon.

As the 350SL was my "daily drive" some 20 years ago when I lived in Sydney, proving to be quite trouble-free (and alot of fun), I am confident that no one will have "messed" with any part of it as it has been in my possession ever since, albeit on "blocks" in my shed for the best part of the past 15 years. So really any failures should pretty well be down to it sitting around unused for so long, while I did much rust removing and welding of new steel, particularly around the rear end suspension.

You have provided me with a number of things on which to focus, and for that again, many thanks. In due course I will add further progress comments to this thread.

[berntd]

Bernt here,

I am doing a major restoration on a 1973 450SL.
These cars are unfortunately total rustbuickets and I am still getting surprises.

Regards
Bernt

[AMG]

Bernt here,

I am doing a major restoration on a 1973 450SL.
These cars are unfortunately total rustbuickets and I am still getting surprises.

Regards
Bernt

Yes, they can catch you out if you don't take a LOT of time and look for the stuff. Then there is the hidden rust in the firewall which is always hard to find, but there are always signs that indicate rust. Just have to be very thorough when inspecting any promising candidate.