Ok, I'm still trying to figure out why this one won't start. So far:

Glow plugs check out resistance wise and are getting power
New fuel filters
Fuel flow from main filter
K40 fully functioning
Audible click at SOV (new less than 1 year ago)

I just removed the SOV, and connected a hose to the outlet to the pump. When you turn the ignition on the SOV opens momentarily, then immediately recloses. This is also reflected in the fact that the engine fires a couple of times when you first try, then stops firing. It never fires enough to consider it running.

Previous owner still has slightly leaky SOV he took off less than a year ago, so I'll have that to try tomorrow. To me it seems like it could be the valve, or the signal to the valve. Is there some logic applied that the engine has to be spinning (read from crank signal back by starter) to keep the valve open? Any other thoughts?

Recent history: car ran fine and was daily driver until small front end impact about 3 months ago. Sat unstarted for 2 months, then started immediately and ran fine to pull onto trailer. Started a couple more times moving it around, then gradually ran worse until it wouldn't even start.

When you switch the key on, are you holding the SOV in your hand or having someone else switch the key on?

Reason being is that there's 2 clicks, one for the SOV ("click") and the other is the rack ("tock") cycling. Verify these two sounds.

Also check and make sure the red and green lights on the back of the mirror aren't flashing.

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

Yep - I'm holding the SOV and someone else turning it on. I also hear the deeper, more hollow noise from the rack.

I have never seen the lights on the mirror light up. The keyless does not work either. I've been a little concerned it might be antitheft kicking in. I have both the switchblade key and one with a little plastic end that I guess is a valet. Both would start the car before this.

Thank you Kar

The mirror lights are the alarm/lock state indicators. One or the other should flash when lock and unlocking the car. Here's a crazy thought: To your knowledge, has water or other liquid ever been spilled into the back seat?

The vacuum pump system for the locks is under the right rear seat and it also contains some of the electronics for the alarm system. Over time or in the event of a spill, this PC board can corrode and cause all manner of crazy problems with the car. You might want to pull the pump out and check it. Not a super hard job.

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

I don't know if there's been an spills. I already have the backseat bottom out, so I will check tomorrow. The locks work ok with the dash switch. Thanks for the help!

Here's a shot of the PC board out of a car I worked on a while ago showing the corrosion around the terminals. This car was literally going crazy, the trunk was popping open at random, alarm going off at random, etc...

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

Ok - confirmed that the SOV energizes and immediately shuts back off when you turn turn key to position 2. However, when you engage the starter it comes back on and stays until key is released.

So, it's not the SOV, and I have good fuel flow to it. If I loosen the injector lines at the injectors I am getting a very small amount of fuel. Also, it consistently barely fires every couple of revolutions. I'm thinking the rack is not moving enough to inject enough fuel to start?

I have a friend that is a Mercedes tech and has whatever Mercedes computer is needed to diagnose the security, etc. He seemed to think a 1997 would not give any signal that it had decided to immobilize; said that only happens on later cars with bigger display in dash. He also said something about the lights on the mirror are purely related to the keyless entry/alarm, and would have nothing to do with the key immobilizer. He also thought it immobilizes by not fueling the injection pump as opposed to killing the SOV. Makes sense since hotwiring the SOV would be very easy to do, and getting around the rack motor pretty much impossible.

I did pull my door lock pump, and actually discovered a problem on the circuit board. I attached a pic... There are a couple of resistors burned off the board. I'm thinking this has something to do with the keyless entry not working. PO changed batteries in the remote recently and could not get doorlocks to work - figured it was the fob.

Kartech - it sounds like you know these things well. Does this all sound right? He's going to bring his computer on Sunday and try to figure it out. Good to have friends with the right tools!

Thanks for the help.

Attached Thumbnails

 

I'm not immuned to being wrong about these cars but I would swear that the SOV is the device that immobilizes the fuel system.

There's another test I know of but it starts requiring pulling a lot more stuff off the engine. It involves removing the intake manifold to access the side of the injection pump. From there, you remove the SOV and then the side cover of the pump.

At that point, you will be able to see the fuel rack and observe it's movements. Normal operation is for the rack to cycle full on and then settle into a position that's about 6mm forward of the STOP position. Observe that the rack isn't bottomed out against the back of it's movement range as this is the "off" position.

You can also put the SOV back on and observe the rack while cranking. It's even possible to run the car without the cover on because the flow of oil in that area is very small.

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

What is used to seal that cover? Is there a gasket underneath that will tear upon removal? Since this car was wrecked I have better access - no radiator, etc. I even pulled the 2 bolts out of the ps pump bracket and swung it out of the way. I've been debating pulling that cover to see what the rack is doing, but wasnt sure about the gasket or whether there was fluid in that cavity.

I guess Ill wait and see what this guy finds Sunday before doing that. I'm not sure how many diesels he deals with, so I'm not really betting either way on the immobilizer method. It seems logical to me that the rack control would be more difficult to get around...

Thanks for all the input!

There's a formed rubber gasket under the cover but it hardens over time and is probably leaking. If not, it probably will after you take it off... The first time I took the one off my car, I cleaned everything up very well and used silicon to seal it all back together.

There may be about a teaspoon full of oil behind the cover, if that.

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

Ok, lots more diagnostic work done, still not running:

I've cranked and cranked this thing over both with the injector lines loose and tight to try to purge any air. No change.

This morning a friend with the Mercedes diagnostic computer ran full set of tests on the system. The only faults he found were mostly due to low voltage - and the battery has been run down a few times from all this cranking. The DAS2 is happy, and recognizes both keys that I have. It is not immobilizing...

He also brought up a monitor screen that shows the rack position. WHen trying to crank it's around 13mm, when you stop cranking and let it time out it drops back to 0ish. So, it's back to a mechanical fuel problem... Sure is nice to have access to that kind of diagnostic work, though!

After all that I pulled the SOV back off the inj pump, leaving all the lines connected. Had a friend hit the key, and get lots of fuel out the port to the inj pump. Put finger over the port, and don't have much pressure, though. Not sure if it's even 1 psi...

How much flow and pressure should I have at cranking speed? Is there an inlet screen in the injection pump itself?

In extreme air bubble problems are there any last resorts? Is there any kind of bleed screw to get air out of the pump itself? What next?

Thank you!

OK, i've cranked and craned this thing and can't get more than a couple of weak hits on about one cylinder...

I've since checked the supply (and return) lines from the tank, and they are flowing just fine. I've had the lift pump off, and it is pristine and has good suction. After putting it all back together it primed and went bubbleless quickly. With SOV not mounted to inj pump, I get flow and pressure out the port to the INJ pump when cranking.

I am getting a very, very small amount of fuel from the pump to the injectors, but it just doesn't seem like enough to get it running.

I guess next step is pull cover off inj pump and see what rack is doing. As stated above, the Mercedes diagnostics shows it moving. The one anomoly is that the 2 position readings on that screen were off from each other, and the technician thought that was a little odd. He said it has redundant sensors, and they should be pretty much same reading. Mine were off by almost 2mm from each other.

Any other ideas?
Thank you!

The fuel should kind of burble out. It's pretty low pressure, you can hold it back with your finger, it's only a spring pushing out the fuel. No inlet screen that I know of.

No air bleed screw. Best thing I did for mine was to replace all the O-rings. I'm not sure what else you can do. Generally, if you see bubbles moving through the fuel lines, you can press down on the connections that are upstream of the bubbles and sometimes you can see them quit or at least diminish.

One thought occurred to me today on the way home. Have you verified the glow plug operation? I know these engines really depend on the glow plugs, even when it's warmer outside.

Finally, the next thing I'd do is remove the side cover and visually verify the motion of the rack. You can literally take your finger and hold it wide open (forward) and see if it purges any air out of the injectors while cranking. You can use your finger to keep it running if it starts and once it settles down, you can release the rack and the computer will take over.

The computer sends a square wave signal to the rack electro magnet and that's what pushes the rack forward. A spring pushes it back. If you move it with your finger, you'll feel the computer fighting with you a little but it can't hurt you beyond maybe a little pinch of the finger tip.

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

I've checked the glow plugs as follows:
All 6 measure between 1.5 and 2.0 ohms to ground at connector to relay. Test light confirms power to them all. Also, you can see the interior lights very slightly dim when the relay closes, plus the indicator lights functions normally, indicating no faults.

I am going to pull the intake off, and do the rack check next. While its off I'll pull the glowplugs and check them closer. Hoping that goes uneventfully!

Thank you!

Well, it's time to go back to the basics. I finally pulled off the intake and the cover on the pump. The rack is obviously moving in the correct manner to give it lots of fuel. It starts at one spot, then gradually gives it more when it doesn't start, pretty much gong full rack.

Here is a video I took since I had no assistant:
E300 injection pump rack movement - YouTube

Now that intake is off its time to start over on delivery system since its so accessible now. I guess I've wasted enough time over complicating things!