Le "français" 350 SE no start !

[Nutz]

Hi Denis,

While cranking,there should be 12 V at pin # 24 of the ECU.If not,check for 12 V at pin # 24 of the relay.If there is not 12 V present at the relay but the relay clicks,replace the main relay.If there is 12 V at pin # 24 at the relay,repair #24 wire between the relay and ECU.

If the relay fails to click,inspect the wire from the main relay pin # 45 to ground.If there is a good ground and 12 V at relay pin # 38 when the engine is being cranked,replace the main relay.

[Denis]

Hello all you W116 lovers

I finally got my 350SE to sputter and start. 

I assumed that the ECU side was OK as it DID fire injectors when I moved the throttle mechanism and the ECU needs to be alive and processing to do this.

Tested the spark once more : open points with screw driver = one discharge at the coil, and so on every time. The spark looked weak but it is a SUNNY day in cold, wintery "Ile de France " (the name of the Paris region).

More fuel it wishes to see, I said to myself  then, so I clamped the fuel return line after the fuel pressure regulator almost shut and turned on the ignition. The engine sputtered to life with a nice overrich mixture, but would hardly idle for the first 30 seconds so I held the throttle slightly open.

The car spat, cleared its throat, coughed and started signing normally...

So what was this all ABOUT ?


If the car restarts normally tomorrow, I will still be mystified  If not, I will start wondering about the checkball (pressure holder) in the fuel pump or even the fuel pressure regulator. To start quickly, a decent remaining fuel pressure must be available (the checkball's job) but this can be lost if the fuel pressure regulator "leaks".

Does anybody know if the fuel pump MUST be replaced if the checkball goes awry ?
What worries me is that this episode may be an indication of things to come :

BEING STRANDED IN THE MIDDLE OF THE NIGHT BY A BLOODY OLD S-CLASS MERCEDES-BENZ : the ULTIMATE letdown !!!

Men, this is a time of immense strain - if the Mercedes does this to me on my vacation in Biaritz, I will start a TRABANT love board !

* gruesse aus Paris, Frankreich

Denis

[Nutz]

Hi Denis,

Unlike K Jetronic,there is no check valve on D Jetronic that I'm aware of.Pin # 19 and #25 of the ECU are connected to the fuel pump relay.When the ignition switch is turned to the on position,the ECU energizes the fuel pump to ensure that the fuel system is filled to ease starting.If the engine is not cranked,the ECU will shut off the fuel pump in 1 or 2 seconds.

Have you tested the resistance of your spark plug wires and rotor?

[Nutz]

More fuel it wishes to see, I said to myself  then, so I clamped the fuel return line after the fuel pressure regulator almost shut and turned on the ignition. The engine sputtered to life with a nice overrich mixture, but would hardly idle for the first 30 seconds so I held the throttle slightly open.

The car spat, cleared its throat, coughed and started signing normally...

So what was this all ABOUT ?


Denis

Oh,there's your problem!!!!!! If the pressure increases when you pinch off the return line,replace the fuel pressure regulator.Enjoy 

[John Hubertz]

(Raises his glass in sympathetic relief)  I'm so happy you got your car running without significant difficulty Denis -

Despite the obvious Francophobes in our government and elsewhere in the English-speaking world, I love France and hope to visit again someday - and your very Parisian slant on life and priorities is such a fun element here on this forum.

Congratulations and happy motoring!

[michaeld]

Yea for you, Denis.  And yea for my K Jetronic test valve!!!

I'm glad you got your car up and running.  Now you can go to Biaritz in style.  Now you don't have to start your Trabant love forum.  I'm sure we are all just  for you!!!

[Denis]

Thanks fellows

Just an interesting aside, I contacted the "stealership" a few streets from my work for the fuel pressure regulator (likely to be in questionable condition, thanks Nitz for confirming my hunch). The guys were worried as they have NO idea how this "thing" works  so we looked at the FI illustrated parts catalog and I showed them the device. The price is 96â,¬ (tax included) and the part can be had in one day (they have one in stock in the Valenciennes (northern France) parts depot).

How does this compare to where you fellows live ?

Just curious

Denis

Paris, France

[Denis]

Ouais,   

I've started to think "smarter than the parts man". Is my fuel pressure regulator really "defective" or was it stuck open by foreign matter ?

As I said, I had been naughty and did not change the fuel filter for a long time...

Just my 2cts of an â,¬ - these cars often go "wrong" through small neglect because of the owner...

Denis

Paris, France

[Essling]

Hello everyone,

In the same vein, my 280se refuses to start and sounds very similar to Denis' experience with his 350se.

Understanding that these are different engines, is the process the same for mine?

Regards,

Jonathan

[Nutz]

Hello everyone,

In the same vein, my 280se refuses to start and sounds very similar to Denis' experience with his 350se.

Understanding that these are different engines, is the process the same for mine?

Regards,

Jonathan

Hello stranger!  Yes and no. Your 280SE has K Jetronic if it's a 76 or newer but the principal is somewhat the same.Start from the fuel pump and work your way to the front. I would guess that maybe your control pressure regulator may be suspect if adequate fuel delivery is confirmed.Of course verify that the ignition system is up to par as well.

[OzBenzHead]

In the same vein, my 280se refuses to start and sounds very similar to Denis' experience with his 350se.
Understanding that these are different engines, is the process the same for mine?

Welcome, Jonathan   

Just be aware that the Oz-delivered 116s had somewhat different anti-pollution fittings /settings from the North American market versions - and also from the Euro version (which was, I believe, unfettered with any such equipment).

Many Oz 116s are, like mine, private imports that were originally sold in the UK, and so have none of that complicated, power-sapping clutter at all. They might have an AS compliance sticker, but it doesn't mean that much - or anything - has actually been changed.

These differences are not always clear in the workshop manuals (even the genuine M-B ones!), so the first important thing to do is to ascertain where your car was first sold; it will have the equipment mandated by that country. You can, if you have no other means of doing so, ascertain country of first sale by contacting the M-B Classic Center in Germany; you'll need to quote your car's VIN. Contact silvie.kiefer@daimlerchrysler.com

A few months ago, I had similar, if erratic, no-start problems with my '79 280SE (116) (K-Jet). Absolutely everything in the fuel department was checked; all hints, tips, and suggestions offered on this and other forums were followed; nothing made any difference.

I then switched my attention to the ignition system; it turned out that the distributor's mechanical advance was sticking (randomly) in the position it was in when I stopped the engine. On hitting the starter next time, the dizzy advance might, or might not - as it felt like - return to a suitable setting. If it didn't, no start.

I replaced the dizzy with another - used - one of which I knew no history or condition, and the problem disappeared - it would seem permanently. (I have since purchased - but not yet fitted - a brand-new one.)

The sticking of the mechanical advance mechanism was something nobody on this or any other forum had ever encountered or heard of; even my very Benz-savvy mechanic found it a new phenomenon.

If you want to test for this problem, do the following:

1. Loosen the distributor retaining bolt (it has an Allen-key head). (Don't forget to first mark - with a scriber of some kind - the current position so that you can put it back in the right advance position!)

2. Give the dizzy a few firm, swift turns from extreme advance to extreme retard, making sure it collides forcefully with the stop at each end of travel. This should jar the advance mechanism and release the stickiness.

3. Return dizzy to the original setting (your scribed mark), tighten the fixing bolt, and see if car starts.

4. If that does satisfactorily address your problem, replace the dizzy - either with a secondhand one or, if you want to go the whole hog, a new one. Just do not buy it from an M-B Australia stealership - it will cost you over $2300! I paid $110 for mine, and it's the genuine article, not a "Claytons" no-name pretend one.

Good luck.   

[Denis]

Hey follows

As was the original subject of this thread, "Von Humboldt" STILL does not start. Yes, it did quite well for a day ! So I replaced the fuel filter a niggly leaking fuel hosealong with a new fuel filter...still no go..ok must be the FPR...

So last night, while doing a NON-W116 activity (electronics), I thought " doesn't trigger every time" on the scope display, hmmm.." and then ...double-hmm - that W116 has that, that..that trigger point set.

So the distributor is in for R&R..No, I do NOT have THE solution yet, could be the FPR but I want to avoid that blind "change those parts" modern mechanic idea - I want to determine the cause 

The point ? diagnosis of ano start on a D-jet has many , many parameters.These cars are ancient, so oddball problems supersedes the factory manual.

DenisParis, France

[Nutz]

Hey Denis,

A long shot but have you ever cleaned the intank filter?

[Denis]

Considering how well fuel comes out of the fuel tank, it is most unlikely to be an intank filter problem.
I ordered the FPR as it really seems to be high on the list of culprits. The car did start after sitting  24 hours but not after sitting 72 hours.

C'est la vie !

At least the sun is out  maybe winter will go away 

Denis

Paris, France

[Denis]

Follow-up on the mystery (sigh) 

Well "Von Humboldt" has a new FPR, fuel filter and completely new fuel lines. The car still starts rather poorly, and idles poorly (engine speed is unsteady). Even only lukewarm, the car runs beautifully without even a hint of a miss. Once warm, it idles poorly.
Restarting when warm is a gamble : it needs a lot of cranking and responds to pumping the pedal like some "old carburettor whore" car of the past 

In other words, it eventually "catches". Whether it is steady ignition or fuel is hard to tell
but I bet the problem is ignition. The two current limiting resistors are OK, the breaker points impeccable.. I am starting to suspect something thermal and/or intermittent in the electronic ignition unit.

Any revelations for me ? this is getting annoying....maybe I should buy a Trabant after all


Denis

Paris, France