603 fuel shut off valve stuck shut??? - PeachParts Mercedes-Benz Forum

odie · #1 11-01-2012, 09:12 AM

My 1987 TD suddenly would start. it's like no fuel flow. cranks strong and the clear inline pre-filter is full. But not even a sputter.

The manual cut-off lever is fully down. With someone else cranking it I can observe the manual cut-off lever rise fully up. Is this normal for the lever? Manually moving the lever in random intermediate positions as well while cranking has no effect either.

It the cut off valve vaccum operated? There is a short vac line on the side of the IP that appear to be rotted. Its on the driver's side, immediately below a little green canister (vaccum filter???). I wish I had a picture but it was late night in a parking lot.

What I believe is the cutoff valve on top of the IP appears to has a wire (it was dark so could have been a vac hose) leading to it. or is this something else?

Does the cut off valve require vaccum to "OPEN" and allow fuel flow?

Most my old diesels the cut off valve has been a solenoid, requiring 12 volts to open.

ah-kay · #2 11-01-2012, 11:35 AM

Quote:

Originally Posted by odie

The manual cut-off lever is fully down. With someone else cranking it I can observe the manual cut-off lever rise fully up. Is this normal for the lever? Manually moving the lever in random intermediate positions as well while cranking has no effect either.

This looks normal. The shut off valve is vacuum operated. When you crank the engine the valve is vented to atmosphere so it goes up and stays up after the engine fires ( key is in position 2). If you turn the key back to 0 and there is residual vacuum then it will go back down. If there is no residual vacuum then it will stay up all the time.

The problem is probably not the shut-off valve. You can try lifting it up by hand and crank but I would look elsewhere. Crack open the injector lines and see where there is fuel coming out. Or crack open the spin on filter outlet ( the out arrow -> line ).

odie · #3 11-01-2012, 12:16 PM

I was thinking the shut off valve is probably fine but the it's not getting the right vaccum signal??? Does it require vacuum to open? and is it spring loaded to close?

ah-kay · #4 11-01-2012, 01:08 PM

I have never taken one apart. It is definitely vacuum operated to close, if you have no vacuum car would not shut off. I would expect it to be spring loaded to open when it is at atmosphere. Hope this help.

uberwasser · #5 11-01-2012, 01:14 PM

The shut off valves on these fail "open" if there is no vacuum. This prevents vacuum problems from disabling your car.

Could be a glow-plug problem.

odie · #6 11-01-2012, 03:56 PM

hmmm....the mystery deepens...

it didn't "get worse" and then stop...it simply started and ran normal every time and then suddenly would not start or even attempt to fire after being parked only a few hours.

not cold enough for glow plugs yet. I'm pretty sure it's no fuel delivery...it seems like fuel is totally cut off... but why?

I would think a plugged filter or a few bubbles of air in the lines it would still sputter or something just to "tease" me.

It's like when you disconnect the fuel supply line or pull the coil wire on a gasser...

odie · #7 11-01-2012, 04:02 PM

the cut-off lever goes up while cranking and then drops back down when you stop. So is the cut-off valve operating correctly? I should look elsewhere i take it?

Is the primary filter before the cut-off valve? Does the lift pump feed into the cut-off valve or comes after the cut-off valve?

whunter · #8 11-01-2012, 04:16 PM

Remove the vacuum line from the white plastic shutoff box (top of injection pump).

Try starting, if it starts, the ignition vacuum valve (attached to steering column lock) has failed = holding vacuum on it at all times.

If it fails to start, it should be one of the following issues.
* If you filled the fuel tank today, possible BAD fuel. 2 stroke oil and/or Diesel911 may cure this.
* Plugged filters. Bad fuel or infestation..
* Massive air leak into the fuel system. The fuel thermostat plastic end O-ring leaking is a common issue.
* Massive vacuum in the fuel tank. A bad vent valve will do this, remove the filler cap and try starting.
* Lift pump failure. Test output volume.
* Injection pump solenoid failure. Hope it is not this, (no longer available) find a good used unit.

.

whunter · #9 11-01-2012, 04:18 PM

Quote:

Originally Posted by odie

the cut-off lever goes up while cranking and then drops back down when you stop. So is the cut-off valve operating correctly? I should look elsewhere i take it?

Is the primary filter before the cut-off valve? Does the lift pump feed into the cut-off valve or comes after the cut-off valve?

Essentially
The shutoff box moves the injection pump rack to a zero fuel delivery position.

.

whunter · #10 11-01-2012, 04:27 PM

whunter · #11 11-01-2012, 04:29 PM

Look through these topics, for more answers
http://www.peachparts.com/shopforum/diy-links-parts-category/142405-diesel-injection.html

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odie · #12 11-06-2012, 09:04 AM

just got back into town last night and went and messed with it some more...

I cracked the fuel filter output line...the big spin on filter....sprays fuel while cranking..so fuel is being delivered to the IP.

I cracked an injector line at the injector....no fuel coming out while cranking...cracking a metal injector line at the IP and still no fuel present....

odie · #13 11-06-2012, 09:07 AM

I was reading my British Haynes....they describe the diesel fuel shut off valve as working this way....turning off the ignition disrupts the vacuum to the shutoff valve...implying that vacuum is required to open the valve and a lack of vacuum closes the valve shutting off fuel supply.

odie · #14 11-06-2012, 09:11 AM

whunter...thanks for the notes...I'll sort thru them and see if I can make any headway...

odie · #15 11-06-2012, 12:46 PM

Quote:

Originally Posted by whunter

If it fails to start, it should be one of the following issues.
* If you filled the fuel tank today, possible BAD fuel. 2 stroke oil and/or Diesel911 may cure this.
* Plugged filters. Bad fuel or infestation..
* Massive air leak into the fuel system. The fuel thermostat plastic end O-ring leaking is a common issue.
* Massive vacuum in the fuel tank. A bad vent valve will do this, remove the filler cap and try starting.
* Lift pump failure. Test output volume.
* Injection pump solenoid failure. Hope it is not this, (no longer available) find a good used unit.

.

what is the "Injection pump solenoid"? and where is it? Is it electrical? or is this another name for the vacuum operated shot off valve on the top of the IP?