Starting Issue, 1974 280 SE

Hi Norbert,
Hard to see how they translated reservoir or container to damper cage. Just for fun, I checked this on a German site that has both english and german part names:

www.online-teile.com/mercedes-ersatzteil...tem.html?language=en

(You can change language in top right corner)

On our 107s, there is just an inlet and an outlet. One side of the "can" does appear to be a diaphragm that would act to dampen pressure fluctuations. I believe that some of the later K-jet 107s as well as cars with L-jets have a return line to the device. They then have three nozzles.

I haven't been near the car for a week, I'm feeling better already!

It appears my car is equipped with two "Dampers" though I wonder if we are getting confused between "Damper" and "Pressure regulator." The pressure regulator I have included in the first image.

Hi Carl,
your car is great...

I marked the first picture. The regulator must be situated in the pressure line as I marked.
Ich habe dein erstes Foto markiert. Der Druckregler muss so angeschlossen sein, wie ich es dargestellt habe.



What you call 'damper' is just a reservoirs.
Was Du 'Dämpfer' nennst ist ein Vorratsbehälter.



Regards
Norbert

Hi Carl,

it is correct. Your car has a small black box as damper from tank to fuel pump. And another damper in return line to tank after pressure regulator. It is wasy to differentiate pressure regulator and damper. Pressure reugulator in your car has 3 hose connectors, damper only two. I still do not know why damper in return line has a screw and what you adjust with that.

However there are also pressure regulators with you one connector on top and one on buttom. BTW last year I had a lot of trouble with the fule hose between pressure regulator and damper. In 8-cylinder this is s very short hose that is bent by 90°. It worked well for 5 years, then finally it got weak and closed return line (exactly on the day I wanted to use my car for my 1st D-Jetronic workshop).. Fuel pressure of course went up and my car ran very bad. I replaced that hose by a preformed hose form Baby-Benz W201.

Carl,
If there is any confusion, it is the the translation Mercedes used for the pump suction damper. They call it a "damper cage". Could have been, say "damper/reservoir" indicating it performs two functions ?? It is there to dampen both pressure fluctuation in suction line as well as reduce pump noise and possible vapour formation. There are many patents on such devices. The one below is used on a kjet and some mercedes diesels. It has a more obvious diaphragm and also includes a fuel return port.
www.ecstuning.com/ES1663654/

Hallo again,

'Dämpfer' ist der Begriff, den Mercedes verwendet. Für mich enthält dieser Begriff aber den Hinweis auf ein technisches Element, das dämpfend wirkt.
Ich erkenne auf dem Bild eine Dose, die mit Hartlot verlötet ist. Die dazu nötigen Temperaturen schließen aus, dass da drin eine Membran verbaut sein kann.

Mercedes kann diesen kleinen Tank (Reservoir, Vorratsbehälter) natürlich nennen wie sie wollen - aber für mich ist ein Tank ein Tank und ein Dämpfer ein Dämpfer.

- Mittlerweile habe ich wohl herausgefunden, warum die Dämpfer teilweise einstellbar sind. Sie sollen ja bestimmte schwingungen mildern, die um einen bestimmten Druckbereich herum auftreten.
Für andere Druckbereiche (z.B. L-Jetronic) brauchen die Dämpfer daher eine andere Grund-Vorspannung.

'Damper' is the term used by Mercedes. For me, however, this term includes the reference to a technical element which has a damping effect.
I recognize in the picture a can that is soldered with hard solder. The necessary temperatures rule out that in there a membrane may be installed.

Mercedes can name this small tank (reservoirs) as they want, of course - but for me, a tank is a tank and a damper is a damper.

- Meanwhile, I have probably figured out why the dampers are partly adjustable. They are supposed to alleviate certain vibrations that occur around a certain pressure level.
For other pressure levels (e.g. L-Jetronic), the dampers therefore need another pretension.

Norbert

Hello Carl888,
I just wonder if the problem is due to the fuel pump losing pressure and then having difficulty self priming. I had starting issues and removed the pump, connected power and dipped the suction hose in a pool of fuel and it took a few goes to get it to suck fuel. Once it did the fuel came gushing out. My fuel pressure drops off readily after the engine is stopped which may suggest that the non return valve isn't working. Also, I once changed the fuel line from the tank to the pump and had a struggle getting the car to start and at the time put that down to the pump struggling to prime itself, as once it was going I had no further issues.. This may be due to wear in the pump.
My car also takes quite a few seconds to start when it has been sitting for a while (longer than an hour), but starts almost instantly if I start it within half an hour of stopping. I may have the same problem, but less severe.
And, rather than set it on fire give it to me!
Regards,
Lance.

So, thinking further, the solution might be to install a non-return valve. There is information on the net from Pierburg showing how they should be plumbed in. Look at the following:
www.pierburg-service.de/ximages/pg_si_0044_de_web.pdf

Hi Lance,

it is correct that Pierburg has these non-return valves that I also recommend in article fuel pump as replacement for broken original ones on the pump. However a broken non-return valve would not prevent a car froms starting. It would just take longer to build up pressure on fuel line but finally it would start.

I fear that Carl has lost his motivation on his car. So we better wait until he has forgotten about his frustration.

Hi,
I once found an alternative part for the Pierburg valve.
Produced by Sytec, made of alloy and brass - not plastic. Price is almost the same.
Search for ' Sytec valve ' at ebay platform.

Regards
Norbert

Hello Everyone, a quick update. And thank you all for your replies.

Since my last message I have performed the following:

1. During cranking that the fuel injectors are receiving a signal from the ECU, and that they are flowing correctly.

2. During cranking from cold, the cold start injector is firing.

3. During cranking, the ignition system is firing.

4. The spray pattern from the injectors is lovely!

I decided to make a simple switch box to test some minor functionality from the drivers seat. Sometimes a little distraction is good for the soul. I painted it in grey hammertone in order to have a 1960s feel All it does is allow me to close a circuit remotely. I made up some 3m cables to use with it. I tested the following:

1. Switching the fuel pump on and off before cranking.

2. Remotely shorting out the ignition ballast resistors.

3. Remotely being able to crank the engine from the engine bay (Using the red push button) so I can check the fuel pressure during cranking and warm up phase.

I can tell you that after these tests, I still cannot identify the problem. When the engine finally starts, it runs fine!

I think my next item to look at may the following:

1. I will have a look at the distributor during cranking to check that the firing point and dwell for both the ignition system and fuel injection system is within specification. Whilst I have tested the distributor for play in the shaft I have not done so recently. Additionally, I am curious to plot the ignition curve again and I am wondering if during cranking the timing is OK

2. I am concerned that possibly the starter motor is not turning over as fast as it should be. In fact, I am surprised that the starter still operates after the hell I've been giving it! I have taken the larger battery from my V8 W126 to ensure there are no issues with cranking current.





More later......

Lance, you are 100% correct and the car shows all the systems of low cranking fuel pressure.

However, the pressure tests show otherwise, it is bang on 2.1Bar.

lsmoz schrieb: Hello Carl888,
I just wonder if the problem is due to the fuel pump losing pressure and then having difficulty self priming. I had starting issues and removed the pump, connected power and dipped the suction hose in a pool of fuel and it took a few goes to get it to suck fuel. Once it did the fuel came gushing out. My fuel pressure drops off readily after the engine is stopped which may suggest that the non return valve isn't working. Also, I once changed the fuel line from the tank to the pump and had a struggle getting the car to start and at the time put that down to the pump struggling to prime itself, as once it was going I had no further issues.. This may be due to wear in the pump.
My car also takes quite a few seconds to start when it has been sitting for a while (longer than an hour), but starts almost instantly if I start it within half an hour of stopping. I may have the same problem, but less severe.
And, rather than set it on fire give it to me!
Regards,
Lance.

Hello All,

This afternoon I made further tests on the W116. I have reconnected the pressure gauge to the system and I have made two short videos of the car cranking and finally starting.

The first one is here.

vid115.photobucket.com/albums/n281/carl3...0020_zps1lwzwb0h.mp4

I have taped the pressure gauge to the windscreen. The slight fluctuation you see on the gauge is the pump priming the system. I note this effect only when using a long extension on the pressure gauge, if it's connected without the extension the gauge does not fluctuate. At about 1:09 the car finally starts however it does not run on all 6 cylinders and takes some seconds to fire on all 6, you can see the revs settling down at just over 1,000 rpm cold idle. You will need to turn the sound up. The "Clicking" noise is the ignition key being turned.



The second video is here:

vid115.photobucket.com/albums/n281/carl3...0021_zpsdxcmmshh.mp4

This is simply the engine being started AFTER it has run for about 30 seconds and switched off, then restarted almost immediately. You see there is no issue with it once it has been running provided it is re-started within 30 minutes, hot or cold.

The pressure gauge in connected to the cold start circuit:

Hi Carl,

that reminds me of a 350SLC I once cured fur a friend. When it was cold it would start badly and run incredibly bad. In winter you would not be able to go faster than 40 km/h before it would warm up. After I had fixed some problems with vacuum hose leakage I finally found the main mistake: It was a hanging rpm governor in ignition timer. When it was cold, it would not change properly. When it was warm, it looked okay. I only found that mistake when I put the car in my workshop and let it stay there over night. Next morning I attached it to my Bosch Compac Tester and saw horrible firings on the ignition oscilloscope. That all had looked okay when the engine was warm.

Maybe you have a spare igintion distributor to test. It is a bit tricky to test ignition timing with just the starter running.

According to your videos you have no problem with fuel pressure. And for your motivation: I like the work you are doing, precise and analytic. Good to see that.

Update as of this evening, a nice 24 degrees here in Melbourne at 8:30pm. I have made a VERY slight adjustment to the fuel pressure, 1Psi increase to bring it up to exactly 2.1Bar. Of course, I expect this to make no difference. Incidentally, at junior school, I was the last year where imperial measurements were taught, so you will notice in my posts I mix imperial and metric

I have left the pressure gauge connected, after two hours, the residual pressure is still very good:



Volker, thanks for your message, the more I work on this car, the more I am coming to the conclusion that the starting issues are probably not related to the fuel injection system

The reason I wish to test the distributor at cranking speed is because I want to make sure there is a reliable well times spark at this low speed. I use this handy Australian made distributor tester, it's very good. But these items, like D-Jetronic testers, are very difficult to find working as they have usually had a very hard life and no one knows how to fix them any more.

I drove the 280 SE again today and this morning the starting procedure was particularly tiresome. None the less I drove for some 20kms and parked the car. After 45 minutes standing I re-started the car. I made a short video of re-starting it. After the engine started I then switched it off and re-started it. It's interesting how the car always re-starts hot or cold immediately after running, but if you leave it for more than 30 minutes, it gives trouble. Ambient temperature is about 23 degrees today, good driving weather.

Unfortunately, following up from yesterday, I cannot fault the ignition distributor nor the timing during cranking.

The engine temperature after 45 minutes standing:




And here is the video:

vid115.photobucket.com/albums/n281/carl3...0031_zps6gxtvcro.mp4

Hi Carl,

soory it might be that I ask the question again: Did you do the spray and leakage test on your injectors and cold start valve? I they were leaking, they would fill a cylinder with fuel and that would not be able to start then.

Hi Volker,

It's certainly a mystery! Yes, I have checked the spray pattern of the injectors and that of the cold start valve. They do not leak.

I have to admit, after the recent tests, I have no option but to start pulling things off and replacing them. I think I will start with the fuel pump. I have some other commitments with vehicles that I must attend to so I will put the W116 at the back of the factory and perhaps revisit it during our winter. I cannot express how frustrating the exercise has been. I really dislike the car very much because of its behavior and I admit I have lost motivation to work on it at present. Thanks to you and the forum for all your help and suggestions. It is very much appreciated.

Regards,

Carl.

Hi Carl,
I must admit I did not see the video before... have been quite ill the day you posted it.
We have a game called 'Bosseln' here in Lower Saxony, and it is very tiring to practice this sport intensively.

One last question before the winter takes the car to the end of your factory:

Did you measure the voltage at the ignition and the injection system when starting?
Take care to measure at the same point / directly at the component, taking the ground from the same point the unit does.

Maybe the whole problem isn't related to the D-Jetronic at all, the ignition switch is faulty or the mains coming from the starter are badly connecting, a ground-wire doesn't give contact...

D-Jet-cars are starting immediately within a maximum of 2 seconds. Your car isn't a D-Jet-car

Regards
Norbert

.

Hello again,
I just remembered a small car (Renault R4), which accompanied me through my whole study.

It started always very bad whe cold, and I did not get it under control. Much like your car.
The engine got so hot that I had to drive in midsummer with heating. I had to refill coolant from time to time - but not daily or so..
Nevertheless I made a CO² - leak test without results. The car drove - so I left it as it was.
So I drove this little car more than 200,000 km, until it was completely destroyed overnight in the parking lot by an accident fugitive.

I disassembled the engine and found several cracks in the cylinder head.

If cooling water runs through cracks in the combustion chambers, the following happens:
- The very cold engine starts badly because the combustion chambers and the spark plugs are wet
- The hot engine starts well because the seeping water evaporates quickly.
- The further cooled down engine starts again bad because the infiltrating water does not evaporate.

Regards
Norbert