Engine occasionally stops – fuel injection system

1961-1968: a.k.a "Finnie" or "Heckflosse" models
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einar
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Model you own: w111

Engine occasionally stops – fuel injection system

Post by einar » Sun 11 Oct, 2015 10:08 pm

Hi all, I’ve followed this forum a bit “on and off” as I’ve been looking for a decent w111 220S/SE for a while. Some weeks ago I found the car, a 220SE, sedan, 1964. It has been running very well for around 1000 km, however a couple of days ago it suddenly stopped. There has been a leaking fuel hose from the (electric) fuel pump to the fuel line toward the engine. When it stopped it felt like some fuel problem, so I did not worry that much. It started again after around 5 min. Ran for 5 min and stopped again. Happened a couple of time and I was able to get the car back home to the garage without assistance. Today I changed the fuel hose. It started without any problem, and the engine idled well for around 5-10 min before it stopped. Started again and ran well the same amount of time.

My first thought is a failure on the electric fuel pump., however not sure. I’m a bit worried whether it could be some failure of the fuel injection system.

I’m pretty used to carb engines; however Mercedes fuel injection system is new to me. Any advices of how to continue are appreciated. Is there any decent diagnostic that can be done? I do not find what I’m looking for in the Service manual.

Thanks in advance
Einar
Fintail - w111, 220 SE, limousine, 1964
NORWAY

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Bartman4800
300 SLR
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Model you own: w111
Location: Perth WA

Re: Engine occasionally stops – fuel injection system

Post by Bartman4800 » Mon 12 Oct, 2015 11:25 am

Your fuel pump might be cutting out because it gets too hot.
Check the filter in the fuel tank, make sure the bottom pot is all clean.
Change out any fuel lines if they are only remotely suspect.
Make sure the return lines are free flowing.


Bart
1963 220 Sb Sedan "Kermit" (Australian Assembly)
1960 220 Sb Sedan "Zum Schlachten" (Early German Assembly, with a torsion bar spring for the bonnet) - Stored in Country WA
1981 Subaru Brumby 1.8 with Weber and 5-speed box "little utie" - Sold to another enthusiast!
2006 Ford Focus "daily driver"
2002 VW Passat V6 30V Station Wagon (SOLD - This car into a money pit)
2011 Kia Sportage "Missus commuter Bus"
2002 Mitsubishi Rosa Bus (converting it to a motor home)

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einar
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Model you own: w111

Re: Engine occasionally stops – fuel injection system

Post by einar » Tue 13 Oct, 2015 2:47 am

Thanks. Similar approach was suggested when discussing with car-mates during the weekend. I’ll have a check, and fingers crossed.
Einar
Fintail - w111, 220 SE, limousine, 1964
NORWAY

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Mercmad
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Re: Engine occasionally stops – fuel injection system

Post by Mercmad » Sat 17 Oct, 2015 10:06 pm

Always check the pump for 12 volts at the pump.
then connect a gauge at the cold start valve. you must 14 PSi ,no more- no less . too little and you have blockage ,probably a dirty fuel filter (at the front on the passenger side engine mount. Mahle KX 35 ).
too much pressure and you have blockage at the tank end.

When the car stopped, how much fuel was in the tank?
They have a swirl pot in the tank which the return line flows into. as it flows in it sucks fuel from the main part of the tank, mixing it with the returned fuel cooling it and getting rid of bubbles.

The venturi blocks with debris over time and the swirl pot doesn't fill up. Until you fill the petrol tank right up (80 liters ouch!) then the fuel flows over the top of the swirl pot keeping it full until the level drops and the car stops.
Sometimes enough petrol will slowly leak through the debris so that the engine will restart and then it stop as the pot is emptied out again,usually 5 to minutes later.
There is only one way to fix this,drop the tank, cut itopen above the swirl pot and clean it out then weld it up again.

finnie_am_I
Dernburg Wagon
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Re: Engine occasionally stops – fuel injection system

Post by finnie_am_I » Fri 16 Sep, 2016 4:06 pm

Hi There,

Get your tank cleaned. Our finnie had the same issue. Would start OK and run well for a while (depending on how much fuel was in the tank), then after a while she'd lose power quickly and die. After about 5 minutes it would start again. As the fuel level drops the stalling becomes more frequent.

We found that the tank was full of crud and the strainer on the intake line would slowly clog with all of the debris starving the injector pump of fuel. When we keyed off the suction stopped and the crud would slowly fall off the screen and allow it to start again.

In the end we drained the tank, pulled it out and used a fuel tank reconditioning kit to clean it, etch it and then coat it. There was sooooo much crud that came out of I am surprised that it ran for so long.

Anyway since cleaning the tank we have not had another issue with it, now she outruns most of the Sunday cruisers heading down to Mornington on the weekends.

Hope this helps

Cheers

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Mercmad
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Re: Engine occasionally stops – fuel injection system

Post by Mercmad » Fri 07 Oct, 2016 8:35 pm

onthese early Merc Fuel tanks there is a plastic swirl pot in the tank .To clean them properly you need to cut open the to of the tank and clean this Swirl pot.There are two lies on the fuel tank, the large one is the outlet to the pump and feeds from fuel from the center of the swirl pot. The small line is the return line and feeds from the injection pump. This small line can get rusted up inside.
The small line runs into the swirl pot and creates a venturi flow effect sucking cool fuel from the main part of the tank . over time the venturi becomes blocked. A car owner will fill the fuel tank, the fuel pours into the swirl pot and the car will driven normally for up to 80Km's before the fuel level drops below the edge of the swirl pot.c The car uses the up the 2 liters in the swirl pot then stops. I have seen this so many times i have lost count and there is only one cure unfortunately.

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einar
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Re: Engine occasionally stops – fuel injection system

Post by einar » Mon 28 May, 2018 2:57 am

Refreshing the tread. I’ve not bothered to much about this issue as the car is running fine – apart from this idling-issue. We tested a bit during this weekend and the only issue is that the pump is getting very hot before the car stops. Pressure and delivery rate is according to spec., fuel filters are OK This was the first thing Bart suggested. So, the next question is why is it getting hot? Is it due to some major failure and hence changing the fuel pump is the solution? Any input and advices is appreciated. There is absolutely no problem when I drive the car – FYI.

I’ve also attached a picture of the fuel pump in the car, and someone raised the question whether it is the right fuel pump – any input upon this? The engine is a M127, Engine number: 127-982-10-048412 (M127.III)
You do not have the required permissions to view the files attached to this post.
Einar
Fintail - w111, 220 SE, limousine, 1964
NORWAY

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