1991 300CE-24 stalling then immediate re-start

[ray_hennig]

This is an interesting one for the brainy boys.

I bought my 1991 300CE-24 in 1997. And for the last 26 years it has suffered from occasional stalling. The engine starts immediately afterwards.

In the early days, performance was good and has continued that way. Now, the car is even better after renewal of many, many parts.

But occasionally it still stalls. Every 4 months, at a guess.

These stalls have always taken place at very slow speed, always under light braking and sometimes when turning.

The car has aircon, ABS and ASR. No cruise control. Over the years, I have stacked up replacement electronics, including:

• KE jetronic controller,
• MAS box,
• ABS module,
• ASR module,
• EZLs – many.

This stalling condition has not got worse over the years and today is only very occasional.

I am baffled and my thoughts turn to some marginal timing issue that prompts the various electronics to shut down the fuel pumps via the MAS box. Possible?

Almost every electronic box that I have received as a spare has been tested on receipt and left in place if found to be OK. They all seem OK.

But the stalling condition remains.

BUT, the only 2 modules that have not been changed are the ABS and ASR modules.

My plan is to swap these and then continue. Of course, I shall only know if this has fixed the issue when stalling does not happen. This could take years for maximum confidence.

I find it difficult to believe that it is a sensor as this would surely have died in 26 years. As said, baffled.

Has anyone else had anything similar?

Any and all suggestions will be most gratefully received.

Best to all.

RayH

 

[grober]

Ignition switch dry joint?
Only other thing I can think of is some form of external electro magnetic interference--- radar/mobile phone mast et cetera causing a momentary shutdown of electronics [ have you checked that the bonnet has a good earth connection to the rest of the car to act as an electromagnetic screen ?--- does this happen in an urban/motorway/country environment--- it may also be happening at higher speeds but there is enough mechanical/electrical "momentum " in the system at that point that you don't notice a restart? Can you monitor the 12 V supply via some sort of readout to see if you're experiencing total electrical failure momentarily?

 

[ray_hennig]

Ignition switch dry joint?

New one installed a few years ago.

I shall check again any earth connections.

Over the 26 years I've been running this car, most of the active components have been replaced. Some several times, if only to test spares. As said, the only "originals" in place are the ABS and ASR modules; easily replaced.

Invariably, the stalls take place at slow speed, under gentle braking. I cannot recall a stall without braking.

I could try monitoring supply voltage but it is a question of effort versus criticality. In short, "Can I be ****d?"

As always, thanks for the input.

R

 

[grober]

Does this phenomenon occur in wet or dry conditions? There are two electrical connections associated with the brake assembly- the pad wear sensors or the ABS magnetic sensor. Particles can build up on either of those assemblies and in dry conditions one could imagine a light application of the brakes might build up static charge which would then discharge to the vehicle electrical system causing a momentary shutdown?

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[Bellow]

Invariably, the stalls take place at slow speed, under gentle braking. I cannot recall a stall without braking.

My suspicion is a mechanical component being a touch tardy eg, whatever controls idle speed not reacting fast enough or the brake servo momentarily messing up the air: fuel ratio.
Possibly one of those things that have to be left to get worse before a diagnosis is possible. Is it a manual or auto?

 

[grober]

Sorry 2nd video should be

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[optimusprime]

Ray this is not a new problem for you is it ? I can see its come up over the years, on other forums . So it is still a thorn in your side ?

 

[grober]

If its voltage spike related then this OVP explanation may help?

OVP - basic function and test

Mercedes OVP – A Basic Primer and Test Process I am dealing with my second failed OVP and reviewing the various links prompts me to try to consolidate some of the scattered information into this single format. I hope it is useful. See Figure 1. below for a picture of a typical OVP relay...

www.benzworld.org

TAKEN FOM THIS THREAD

OVP - basic function and test

www.benzworld.org

 

[ray_hennig]

So it is still a thorn in your side ?

Hello again all,

It's not a real pain. But I have become a bit fanatical about getting everything right.

I cannot think of anything that hasn't been changed over the years aside from the ABS and ASR modules. And if I change them, I may have to wait 6 months or more for something NOT to happen, if that makes sense.

Frustrating but not the end of the world.

Thanks again to all.

RayH

 

[optimusprime]

Ray what about the ECU ? You can re cap them if you find them bleeding out its the 2 black 220140s

 

[ray_hennig]

Ray what about the ECU ?

Yes, I am considering re-capping any and all electrolytics in all modules.

Good plan.

R

 

[ray_hennig]

Another development. We had the car up on the hoist to detect a coolant leak. It’s the radiator. I have a Nissens replacement in stock having refused to pay 750€ for an MB original. The 200€ Nissens looks identical and feels robust. We shall see.

The car had been on the hoist for a couple of yours and we started the engine. We detected a significant whining noise that seem to come from the area around the fuel pumps. After about a minute, the whining stopped and normal service was resumed.

Until this morning.

I returned home after a 30 Km drive and parked the car for about 30 minutes. We then got in, started and the whining started. I turned out into the road accelerated and the engine cuto out. And immediately restarted. So we returned home and took the Yaris.

I started the engine in the garden and no whining. I left it for about an hour, started it again and heard the whining again. I’m pretty sure that it is from the fuel pump area.

So, I have checked stock and I have 2 pumps, a filter and an accumulator. I’ll get those fitted pretty soon and see where we go from there.
Interesting times.

RayH

 

[optimusprime]

Ray i think you are on the right track . Fuel pumps make a noise just before they stop working for good. I recon you have changed the acumulator , and fuel filter before this .

 

[ray_hennig]

I recon you have changed the acumulator , and fuel filter before this .

The filter was changed in 2017, about 6K Kms ago. But I have another so why not. The accumulator is about 15 years old so that'll be changed too.

I've sent a txt to my son who will order the rubber hangers from MB in Angouleme.

R

 

[optimusprime]

Ray, my next job in line will be the fuel pumps . I replaced everything on my car but the 2 pumps .I had a bit of hot start problems back in 2014 .