C250 TD - Fuel Shut off Valve Info

[JB1973]

Hi All,

This is my first post on the site, so thanks is advance for any help.

Right then, I have a 1999 C250Td with 105,000 miles on - which was running fine until recently when one cold morning I jumped in and it would not start.
It had done this once or twice before (once for me and a few times for my dad whose car it was, but only found out abut it after he sold it to me ) but always fired after excessive cranking (~20 secs).

However, this latest time it did not fire at all. Closer inspection reveled that all the fuel pipes were dry, so I assumed that I had run it too low as I am aware that the fuel gauges can be a little dicky. I filled the car with twenty five litres and started to turn the engine over, opening the feed line to expel any air. Still nothing. So, I have now removed the inlet manifold, and taken off the fuel stop solenoid.

Here is where I could use some guidance. Whilst the shut valve is plugged in to the electrics, you can turn the ignition on and the internal valve jumps forward then instantly back. I would expect it to remain forward whilst the circuit is engerised, springing back to cut off the fuel when the power is removed. I get a voltage on pins 3 and 4 of 5v and 0.8v respectively.

In theory this seems to be the defective part but I thought I would ask the question before shelling out for the shut off valve in case anyone else has experienced the same only to find it was something else. Are these voltages what you would expect?

Hope it all makes sense and I look forward to your replies

Regards
Julian

 

[luders79]

Hello,

What you have explained is the correct operation for shut off valve when you turn the ignition on it will power up the valve and then take power away! What you need to find out is if the shut off valve gets power to open it when you crank the car! If you do get power there I suspect all your problem will be is air locking in the fuel lines. The plastic fuel pipes all have rubber o-rings on the end also change the fuel filter and the pre fuel filter with it o-ring aswell and it's worth doing the injector leak off pipes whilst your there!

If you don't get any power when cranking let us know and we can look at other options

Hope this is of some help

Lee

 

[Parrot of Doom]

Check the o-ring on the fuel prefilter. A leak there = no fuel.

 

[C250TDSportAuto]

It must be that time of year. My C250td also refused to start first time this morning. Upon first turn of the key it almost started then died again. I gave it a few more cranks but nothing excessive at that point and still nothing. I left it for 10 minutes then gave it another try. After a lot of cranking it finally came to life. I gave it a rev or 2 then it was fine,

The same thing happened when i went to start it to return home from work, Although it did start with less cranks. Does this sound like the same problem.

Where is the pre-filter located? I can't seem to find it in the Haynes. I've replaced the fuel filter around 12 months ago, but not the pre-filter, also there is air in the plastic pipes to the rear of the fuel filter. Do you think i need to replace the o rings on these too.

 

[Parrot of Doom]

Next to the main filter, under a bolt. Part 26:

There should be a small bubble of air behind the pre-filter when the engine is off, thats quite normal. Anything more, or air in all the fuel lines, and you have a leak somewhere in the system.

A new pre-filter does not come supplied with an o-ring for some bizarre reason - you have to buy it separately, although you could probably buy a job lot from Halfords and fine one that fitted.

 

[C250TDSportAuto]

Cheers Parrot I'll Give it a try

 

[JB1973]

Fixed!!!

Thanks Parrot and Luders!

I was convinced it was the fuel shut off valve so the advice from here has saved me a considerable um of money.

As discussed, I replaced all the O-rings including the shut off valve o-ring. The car now starts on the button.

What I did do that may be of some help to anyone else who has the same problem, was create a tank that fed direct into the filter housing.
Basically, I used a fuel filler funnel and forced this into the area of the pre-filter (which was removed obviously) and filled this with fuel before cranking over, as the highest point was now filled with fuel, the head of fuel fed into the system to expel the air - it took a huge amount of time, but I kept cranking it over and filling the filler when near empty.
Once running, I kept the engine ticking over and just added fuel for a short while - about 2 mins, so i was confident all the air gone. I then knocked the engine off and reconnected pre-filter pipe and started it - the amount of air now is only the length of the pipe from the pre-filter to the non return valve, so once started, the engine hiccups a little before demanding fuel from the tank.

Thanks again - You've saved me a packet!