The shut off actuator is powered by the IFI (Engine Computer), so if you do not have 12V from the IFI when the engine is idling, something else is wrong. You can test the valve by applying 12V to its unplugged connector and hear the click. Or measure the resistance of the solenoid (about 8 ohms).

 

Thank you, there's 4 post inside the plug. Are they all live? The HT lead I showed you isn't that the positive? First photograph. If so I bridge the connection an get it going. Does it require energising to work? I've never even know the lines to be shut off when bleeding these with no key in... Two cars like this. Must be ordinarily open surely.

 

Have a look at the diagram. Y1/1 is the actuator with a fuel temp sensor inside designated as b1. The solenoid is activated by pin 43 of the IFI. See the diagnostic info attached for pin 43.

Legend is also attached.

 

Thanks, I have tried to acquire some useful information from these three. Unfortunately wiring diagrams and other information is beyond me. I have the old valve that I had to break to get off. Not my usual MO but tried subtle ways of undoing the screw with the mashed head. Even a strike screwdriver didn't shift it. Cobalt head drilling went south.

I will try connecting that tomorrow and listen for click. No audible clicks today as usual. What has really foxed me is that after decade of having these cars, I have never known the fuel lines to be blocked even when the car is sat without a key in the ignition. You can unusually bleed with a hand primer pump no problem. I've tried energising the ignition and tapping the switch gently to no avail. They shatter and break when struck hard. I've tried placing a screwdriver in the hole underneath to try to open the valve. I have heard clicks randomly at odd times.

I hope like one of the lists implied, the connection has a ground in there so it should still work without being screwed to the car. The ground does not appear to go through the valve or be connected to the screw holes. There are no numbers on the four post within the plug.

 

Use color coding of the wires. brown = ground. Yellow/black is the wire that activates the solenoid from the IFI.

For ground checking, measure resistance between the brown wire pin and the chassis ground. It should be almost short circuit. The resistance between yellow/black and brown wire pins (at the actuator side) should be around 8 ohms.

 

Thank you this could be most useful. There's three boxes with serial ports in the waterproof box. I think the ECU is the metal box with the large levered interface. I am not sure which side to start counting from. It will require a little more attention and caution. I don't mind testing wires but start connecting 12 volts on my ECU with a "I am not sure which way I start counting". Also, I know that the wires in there, the colour codes are repeated but in different stripes such as a white wire with one or two yellow stripes. It really is spaghetti junction. Not for the faint hearted. If I get an audible click from the old valve I know it's valve and I can get another or try to unlock this one and/or both.

Whilst I was in there I changed the serpentine belt and the power steering pump as it was seeping fluid. So all in all it was a productive albeit slightly disappointing day. Also, I reconnected breather hoses at the top of cam case. I am still not sure of there are other breathers elsewhere. Crankcase breathers I would have thought lower down in the crankcase.

Thanks gain for all your help. I hope it is a simple answer. How final the outcome is with a faulty fuel shut off valve. No negotiations or possible fixes.

 

I was talking about wiring at the actuator connector end, not the ECU. Once you disconnect the actuator connector from the harness, and noting the pins corresponding to the color codes of the wiring, you can measure the resistance of the solenoid at the device which is unconnected from the IFI. If you want to apply fuse 12V to the actuator solenoid, (disconnected from the IFI harness), you put - terminal to the brown wired pin and + terminal to the yellow/black wired pin and you should hear a click. The resistance test confirms that the solenoid is electrically OK, the 12V test verifies that the solenoid mechanically moves and clicks. If the actuator is OK, an you do not have 12V on the yellow/block wire (with solenoid connected and engine idling), then the IFI is not activating it for some reason.

Do you have a code like P0215 or P1622 ?

 

Here is SOV connection layout. Pin 2 negative, pin 3 positive from IFI.

 

That's very useful thank you. Something I can understand. The car ran on the old valve Thursday so there is no reason to suspect it is anything but a sticky/faulty valve. The fuel lines had air in them because of the O-ring behind the valve. This image confirms I can plug the old one in and see if it clicks.

 

Thank you, that sounds very doable. The engine will not run. No obvious beeps and error codes. It is a pre 2000 car.

 

What it could be is a fuse. However, there doesn't appear to be a fuse for the valve, just the pump which has its own power supply. Anyone else know if there's a fuse hiding under another name? Any of the wiring diagrams suggest there is please?

 

The valve is powered by the IFI. I would check the IF fuses and power at K40/4 fuse and relay module in the same module box that the IFI is located. Make sure that the fuses have power on them with key in position 2.

When you say the engine does not start, does it crank at least ?

 

Thank you, that might be the problem. It turn over yes. No suspecting the ignition switch at this stage.

 

Further information- I can heard the relay at the ECU box and interestingly I can hear the loud click like a judges gavel when we turn the engine off, however, that noise is not the fuel shut off valve. My car did it when it wasn't plugged in. I took the valve off and it appears to gunged up with fuel and locked shut. I have it in a sonic bath - like the kind jewellers clean engagement rings with - full of diesel. I would have used ethanol albeit prone to ignition. Especially when agitated at the molecular level. I do not think the valve will ever operate again however worth try. I've tried strong magnets on both the old and new and nothing.

 

I tried to operate the valve safely with a cardboard screen and 12 volts. No response. I have a used valve soon to be in transit for 65GBP. No reason to suspect it won't work. I'll keep everyone posted. Thanks again, Chris

 

Hi Guys,
Thought I'd update everyone. The car is now running superbly well. A used shut-off valve did the trick. It no longer sucks in a big gulp of air in so it is now back to being a flying machine. I also reset the gearbox TCM and I've been driving it in anger ever since. Many thanks for all your help, Chris

 

god im in the same situation as you were. fuel shut off valve was leaking so i took it apart replaced the internal seals and pipe seals and it worked but now its stopped the car from starting. i was trying not to have to buy another. but maybe i have to

 

Easier to replace it, cheap insurance.

The damn thing lasted 20 years......pretty good life. Diesels are not exactly a smooth engine to begin with, so that'll be hell on electronics, particularly on solders.

Replace and enjoy....no need to overthink.

 

well after wasting an entire week running around and finding bloody rubber seals im now looking for a new shut off valve. i might pop the right hand cover off though and have a go at replacing the resistor that sits at the right hand end of the shut off valve as viewed when its atttached to the pump. if i can be arsed that is. yesterday she ran fine though so im scratching my head trying to figure out why she wouldnt run today. but its been an entire day spent mucking about with that bloody car for no result! very frustrating. and ofcourse because of this virus crap we're not allowed to wander around more then 10km here in france. its all so bloody maddening

 

Not reviving, just bookmarking.

 

I am seeking an original part for these. If they don't have two mounting bolts, they are the wrong part. Also there's an annoying O-ring at the rear of these they leaks and you'll have to rig an alternative because Mercedes doesn't support these cars anymore. The part you have posted is likely incompatible. However, it is easy to trace a live feed and earth/neutral on any circuit because impedance (ohms) to ground is always negligible on the neutral feed but not on the live. You probably need to mounting bolts to make this part not leak but rig up a cable tie fix if necessary. However, to simply stop your last one leaking, exchange the O-ring and build it up underneath with tape or heat shrink the like so it seals. This is a relatively several 10K fix.

I know this is a dead and burred thread, so no sarcasm please.