Author Topic: 1975 450SE Big Service  (Read 7128 times)

brettj

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1975 450SE Big Service
« on: 22 November 2009, 05:23 PM »
Hi All,

After sitting in my mechanic's shop for the last 3 months my 75 450SE is back on the road. In August I thought  I destroyed my transmission when the car stopped shifting and started shooting trans fluid all over the place. I was very lucky  in that the problem was only failure of the high pressure transmission hose. No damage was done to the trans. Now the trans works great!

Since the car was in the shop, I had my mechanic take a look at the warm stall problem that will never go away. I had him replace the fuel pump with a rebuild I purchased at German Star. Turned out all of the braided hoses in the fuel pump area were shot and just about ready to go. All new braided hose was put in as well as a new fuel damper. Unfortunately the change of the fuel pump did nothing to end the warm stall probelm and now I'm stuck with a new fuel pump that makes a humming noise. I've been told that some of the D jet fuel pumps are quiet others make a hum. Is that true? Personally, I can't stand the hum.

My central locking system was going flat just before the trans hose let go. I  replaced the main switch and was getting ready to replace a couple of vacuum elements. I had my mechanic examine this sytem and replace all of the vacuum hoses for the central locking system  as well as all of the vacuum elements. He found that most of my elements had very small leaks and the vacuum lines had fine cracks in very strange places. The central locking system works great now. I'm surprised how fast the locks pop up!

So I'm back to the rough idle and warm stall issue that won't go away, I've decided to replace all of the fuel injectors and replace the intake manifold gaskets. Anyone know a source for new, not rebuilt, injectors at a reasonable cost? MB wants $320.00 a piece for these things!


Thanks,
Brett

oscar

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Re: 1975 450SE Big Service
« Reply #1 on: 24 November 2009, 06:09 PM »
Firstly, I can't hear my pump over a running engine.  There's just the whirrr before starting when ignition is switched to II and that's all I notice.

Secondly, re injectors.  Not sure where to go other than direct from bosch or independants.  Eg, autohaus has got em for $178US each.  However, personally I'd take the injectors in to a FI place to get flow tested and cleaned.  Has to be the cheapest option and I'd only replace any one that was faulty.  It's not worth getting new if you don't need to IMO.

Lastly, intake manifold, whilst I don't reckon there's a leak there it might be worth taking them off to see if there's a build up of carbon inside the manifold and plenum that might be choking the motor.  I know you've done a lot to the car and I can't remember every step you've done but IIRC you haven't had the plenum and intake pulled.  You remember the change in performance when you got your flame gaurd filaments?  Sure there was no cure to the warm stall but it did breathe better.  There's been a number of posts in the past about carbon build up in intakes and it might be worth having the intake inspected to see if that's what is happening.
1973 350SE, my first & fave

brettj

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Re: 1975 450SE Big Service
« Reply #2 on: 25 November 2009, 04:29 PM »
Oscar,

Thanks for the carbon build up info. I never thought of that. I thought about having my injectors flow tested and cleaned. Wouldn't it be better for the motor to have a totally new set of injectors instead of a mix of new and old?

The rough idle issue is getting worse. The other day I drove the car  to work which is about 15 miles. After work I started the car. The motor turned over but started to sputter and chug and then started to shake. It would not go to a normal idle at all! I gave the car some gas by pressing on the accelerator and the car stalled. I restarted the car and the idle immediately returned to normal. I really think that my injectors are on the way out! If some of the injectors quit entirely, will the car run or just stall after starting?
« Last Edit: 25 November 2009, 04:44 PM by brettj »

oscar

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Re: 1975 450SE Big Service
« Reply #3 on: 25 November 2009, 10:41 PM »
Wouldn't it be better for the motor to have a totally new set of injectors instead of a mix of new and old?

Yes I suppose.  I was mainly looking at it from a cost perspective.  From a practical point of view too, if the old injectors are given the thumbs up regarding spray pattern, mechanical and electrical condition,  I'd reuse them and only replace any that were cactus.  However that's just me.  We'll hear or read how durable injectors are, but when you think they are 30+yrs old there's potential for weakened return springs on top of any physical wear to the valve and if one or more are found to be leaking or not performing well, one would think the others aren't too far behind.  8 new injectors will buy you peace of mind and hopefully some general improvement in engine running.   Let's face it, you can't beat new replacements but personally I'd have the old ones looked at first.

The rough idle issue getting worse.....    Not dismissing injectors entirely but I don't think this bit is an injector issue, more of a spark problem I would guess.   

For me, the same situation you describe happened to the 350 towards the end of our winter.  I had too many things on the go and left the crappy idle problem until eventually two cylinders were constantly misfiring at idle and eventually stayed misfiring when warmed up.   
Fouled spark plugs the cause and earlier oil change needed. 
So just a thought.  Although we know it's not the root cause of your warm stall it might pay to pull a few plugs and inspect for fouling and black deposits, clean and/or replace with new.  Because, if we're right about soot and carbon deposits restricting airflow thru your intake, your going to get a comparatively rich mix which will cause an unstable idle plus unburnt fuel will then gradually dilute your oil.  That will lead to more oil and fuel being partially burnt in the future and progressively add deposits to your plugs and eventually some cylinders will start missing all the time.  It's a guess but worth pulling a few plugs to investigate.

As for your car running ok when restarted after chugging to a stall.  I can't explain that.  I had the same too a few times towards the end of winter but even if fouled spark plugs are a problem at the moment,  I'd really be reaching for theories on what is happening there. 

1973 350SE, my first & fave

gordonm

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Re: 1975 450SE Big Service
« Reply #4 on: 26 November 2009, 11:55 AM »
Hi Not pretending to be any kind of expert but my 350SL had a problem with an open decal valve which stabilises the idle speed on decelleration. If this sticks open the engine gets unmeasured air bypassing the air meter and entering the intake further downstream, in my case this led to fouling in the intake chamber downstream of the throttle.
regards
Gordon
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brettj

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Re: 1975 450SE Big Service
« Reply #5 on: 26 November 2009, 02:43 PM »
Oscar, Gordon,

Thanks for the replies. I just had the car tuned up in the big service that was just preformed. The plugs are brand new!  The car has only been driven 150 miles since the plugs were changed. Would carbon build up that fast? I'm not sure what a decal valve is. do you mean the air slide?

I appreciate all of the suggestions  and info on repairing  this car. To tell you the truth, I'm starting to get very frustrated with it. It is a wonderful car and I absolutely love it but I've  spent over 30,000 dollars on it and it still runs like crap. Perhaps I should sell it and buy a new Mercedes.

Thanks,

Brett

oscar

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Re: 1975 450SE Big Service
« Reply #6 on: 26 November 2009, 04:14 PM »
Damn! 
150 miles after new plugs and oil I wouldn't expect the issues I raised to be a problem, unless you had poor compression figures, and although poor compression alone on one or more cylinders would give you a crappy idle and stalling, once again I'm sure that checked out ok along the way.

The decel valve I'm sure is specific to k-jet but I've no idea what it does or if it can be on some emission controlled d-jets if somone wants to ellaborate please?

I feel for you brett, so sorry I'm not sure what else to suggest.  If you do go ahead with injectors and the intake removal etc it would be great to hear results and see some benefit.  Like everyone else I bloody hope so.
1973 350SE, my first & fave

WGB

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Re: 1975 450SE Big Service
« Reply #7 on: 27 November 2009, 05:56 AM »
If the plugs were changed before the prolonged storage they could still be fouled.

We have discussed this before with your car- but have you checked the auxillary air valve.

If it is not closing at operating temperature it will lead erratic hot idling.

There is plenty of discussion about this on this forum.

Bill

TJ 450

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Re: 1975 450SE Big Service
« Reply #8 on: 27 November 2009, 08:01 AM »
If you decide to remove the intake manifold, I wouldn't expect much of a difference unless there are actual vacuum leaks. This is speaking from experience, plus there are a few risks involved. ;)
It can very easily go pear-shaped given the age of these cars.  8) The plus side of it is that you know that all the rubber parts and gaskets are new down there.

Does the car have air injection or EGR? These two systems can cause drivability problems, too. I'm not sure what the US vehicles of this time had.

If the engine is wobbling around, the problem is likely to be something basic, like no spark or out of spec air/fuel ratio in one or more cylinders. Presumably compression is OK. Wet fouling of the plug(s) can easily do it, which is no doubt a symptom of another problem.

Another thing to check is the throttle body. The small vacuum orifices may be blocked due to carbon deposits, and on cars with the D-Jet system it is able to be removed easily for cleaning.

Unless air starvation is part of the problem, or an excessively high idle speed, I wouldn't have thought that the AAV would have such a profound effect.

I would, before touching anything else;

  • 1. Confirm that the AAV is functioning.
  • 2. Have the injectors cleaned and flow tested.
  • 3. Ensure all spark plugs are clean and dry.

Then I would re-evaluate the situation.

BTW, how is the air filter element? A dirty element has a huge effect on the mixture setting and can make any car run like a dog.

Tim
« Last Edit: 27 November 2009, 08:12 AM by TJ 450 »
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

brettj

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Re: 1975 450SE Big Service
« Reply #9 on: 27 November 2009, 05:29 PM »
Great suggestions here, thanks! The air cleaner element is brand new. Replaced it with the tune up. I had the engine compression checked as well. Everything thing was great. I agree with everyone that the intake seals probably are OK and should be left alone. I've decided to go all the way and purchase new injectors. Hopefully that does the trick! Somewhere along the line I read that besides rough idle and loss of power an additional sign of bad injectors is lots of white smoke. My car produces lots and lots of white smoke. Never thought much about it and wrote it off to condensation. How easy is it to change the injectors? Is it a job I could do myself? Do you need any special tools? The idea of gas shooting all over when I take the harness off kind of scares me.

WGB

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Re: 1975 450SE Big Service
« Reply #10 on: 27 November 2009, 06:05 PM »
I thought D-jet injectors were well nigh indestructable.

Failing a little clogging they either work or not.

I don't think changing all of them will fix your problem - I would use injector cleaner first or get your mixture checked and adjusted.

Bill

brettj

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Re: 1975 450SE Big Service
« Reply #11 on: 28 November 2009, 04:11 PM »
Bill,

I've been using injector cleaner on and off for the last two years. I've even been using Heat which is a type of dry gas to prevent freezing of the fuel lines in winter. Heat also contain injector cleaner. No change.

I drove the car today and its definitely getting worse. I started the car after driving 15 miles and the idle was very weak. The motor felt like it was going to die. Put the car in reverse and the motor sputtered but the power came back. I put the car in drive, pressed down on the accelerator and the motor once again lost power and started to sputter again. This time the car would not drive over 20 miles per hour and just sputtered down the road until I took my foot off the gas when all of a sudden the motor went back to normal. I drove the car home without any issues until I parked it. Upon restart the motor stalled and stalled and stalled. It took 4 tries to get the car going again. I'm wondering if my problem is a combination of bad injectors and a bad MPS. The MPS was replaced last year with a new old stock part. Perhaps that part died already. Anyone have any ideas?

Thanks,
Brett

Big_Richard

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Re: 1975 450SE Big Service
« Reply #12 on: 28 November 2009, 05:16 PM »
car produces lots of white smoke ? Are you sure its not condensation - If your in a cold climate this is going to be perfectly normal. The car isn't loosing any coolant is it ?

black smoke is a classic sign of an engine running too rich, and usually because the MPS is leaking internally. Hopefully your NOS unit hasn't been "borrowed" for another customers car. Checking these things is easy, they should hold vacuum, not leak.

Injectors, especially electronic, can be bench tested for performance and flow, I wouldn't replace them without having checked them first - It could be a big fat waste of money otherwise.

If it were my car with such issues, I'd also be performing an engine control unit harness continuity and short circut test. Its possible with the age of the vehicle the harness has chafed somewhere so its shorting to ground even broken internally, perhaps intermittently, so the controller sees false readings from inputs. Its also possible that such things can do permanent damage to controllers and subsequent replacement controllers if the wiring is not corrected.

Its rather strange that this all started happening 150 miles after the big service. Something very strange is going on there indeed.

Is your mechanic an MB specialist, experienced with D-Jet - If not, You should find someone who is, this could be half the problem.

« Last Edit: 28 November 2009, 05:21 PM by Patrick Bateman »

oscar

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Re: 1975 450SE Big Service
« Reply #13 on: 29 November 2009, 12:48 AM »
What Pat said.  Sounds plausible that intermittent electrical issues could be the cause.  Bit of a daunting task to check for continuity for every component but all the info is there in the online manual if your keen, even if all you've got is a multimeter.  Your last post and the way you describe the situation getting worse reminds me of a time when I had a faulty alternator and a so so battery.  But I'm guessing you might have had these bits seen to or replaced over the past couple of years.  Then again it reminds of crapped up spark plugs too. ::)  Owing to what WGB said about the possibility of fouling despite minimal mileage it's worth pulling a couple to check.  What's the chance of you compiling a list of everything you've had done to the engine, particularly what's been replaced?  I know there's a lot but it might help rule things in or out. 

And on the "white smoke" issue, again what Pat said.  You need to determine whether the white smoke is steam or smoke, ie coolant or oil.  You probably have read it before but white smoke usually gets attributed to ATF sucked back thru a faulty AT modulator or engine oil in the combustion chambers from worn valve stems seals/guides or rings.  Head gaskets leaking coolant into combustion chambers gets the blame for white steam.  So is this white stuff there all the time ie when the engine's fully warmed up to?  If it's just whilst it's warming up then I'd double Pat's comment on it being normal.

Re: white smoke from bad injectors.... never heard that one before so I did a bit of googling and found info mainly relating to diesel engines, however there was the odd mention relating to bad injectors in gas/petol engines causing lean F/A mixes and producing grey smoke. Grey, white, might be not much difference. 

So to removing injectors.  Do it the following day after the engine has cooled overnight, disconnect battery, take off air filter, then lossen a few or all connections along the fuel rail.  The fuel will leak out a little but not much.  It will later as it drains from the rails as more joins are undone but still no big deal, I spill more when I fill my mower.   ;D Just make sure there's no spark or ignition source around.  I was just looking at the manual to see what's recommended to relieve any pressure in the line.  They short the cold start valve for 20sec which I didn't realise.  All I did was just wore eyewear (because I wasn't sure what to expect) and loosened connections a bit at a time.  There shouldn't be any air in there and since fuel isn't compressible there's just the minimal flex of any hose that will rebound as pressure is lost.  You might not even notice it.  Anyway, pull the electrical connections off each injector and undo the injector clamp and the injectors just come straight out.  The manual leaves the injectors connected to the rail so a bank of injectors is lifted in one go.  Wish I read that before. :D Sounds easier.
1973 350SE, my first & fave

brettj

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Re: 1975 450SE Big Service
« Reply #14 on: 29 November 2009, 08:54 AM »
The white some goes away after the car is warmed up and the motor doesn't use oil or coolant. I never get gray smoke at any time either. I think the valve stem steals are OK.

I'll make up a list with everything that I've replaced relating to the motor. The list is quite extensive and will take me a while to compile.

It sounds like an easy job to change out the injectors. Patrick does bring up a good point that perhaps it is an electrical problem in the harness. I thought that I had electrical probelms to begin with so I replaced every relay cube I could fine including the elusive hot start relay. New relays really helped the car run better but still didn't solve the problem.

My mechanic is certified by Bosch and has actually owned 3 W116's in his lifetime. He feels that the problem is bad injectors and leaking intake  and throttle body seals. He wants to change out all of these parts. He stated that he called Bosch on this issue and that the Bosch rep felt that it is bad injectors as well. My mechanic feels that if the problem persists after changing the injectors then I have a bad MPS.

I may schedule an appointment with the only Mercedes dealership in my area, Hartford, CT, which is a considerable distance from my home to get a second opinion as well. By the way,  I drove the car to work this morning and it ran fine! No stalling , no sputtering! This is one crazy situation!

Thanks,

Brett