New Thread -- 240D Still Not Running - PeachParts Mercedes-Benz Forum

Redpeople · #1 02-02-2016, 08:49 AM

Many of you followed along and offered advice on my troubles in this thread: <sigh> Another "240D Won't Start Thread". It seems to have died a natural death, but I still don't have a running car. I'm exploring a different line of attack but haven't received any input on it, so I'm going to repeat my last post here (hopefully I'm not violating forum rules):

OK, here's another angle that I hadn't thought of. When I was first trying to figure out the glow plug problem and find the inline fuse, I popped the cover off the plug right above the fuse holder that goes into the dash. (See photo) Anyway, when I popped the cover off, I broke a piece off the bakelite plug itself, so the cover doesn't snap on tightly any more and I had just left it off.

When I was working on it today, I discovered that the glow plug light wasn't lighting and the plugs weren't glowing. I then noticed that the some of the pins in the aforementioned plug were loose. I pushed them in and the glow plugs started working again.

So my question is this: Is there anything in this plug or wiring harness that has to do with the kill function on the engine and is it possible that is keeping my engine from starting? Related question, how exactly does the "ignition" switch work to kill the engine? I understand how gas ignition engines work, but not these diesels.

BTW, I WILL still adjust the valves within the next few days, but I know if I go through that process and still have no luck I will be incredibly frustrated. Just want to cover all my bases.
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Mölyapina · #2 02-02-2016, 09:26 AM

The shutoff in these cars is vacuum-actuated at the ignition switch -- it applies vacuum to what is known as the shut-off valve in the IP that cuts the fuel to the engine.

Mölyapina · #3 02-02-2016, 09:31 AM

And in general, it is preferable to stay in one thread so that it's easy for everyone to follow along, both now and when someone else looks to it for help in the future. I posted in your previous thread with a link to this one so that it can be followed.

You can always bump a thread if it gets missed one evening or something.

(Link to old thread here for future readers: <sigh> Another "240D Won't Start Thread")

Shutoff links for you to read if you want:

How does the W123 shutoff system work

1987 300d shut off lever not resetting

tyl604 · #4 02-02-2016, 09:36 AM

Here is how it works on a 300SD; I would expect the 240D might be the same. There is a stop valve in the engine compartment with a lever actuated by vac. If you put a Mityvac on the nipple and apply vaccum the interior lever pulls back toward the driver's compartment and the engine goes off. This stop valve is inside the back of the ALDA (in the 300SD it is just in front of the oil cannister). There is also a manual stop exterior lever with a clearly marked big red push sticker in case the engine continues to run.

Inside the cabin the ignition switch also has a vacuum nipple and vac hose. When you turn the engine off the vac kicks in and transfers to the stop valve up front. This turns the engine off. If the hose is off that ignition switch nipple or if the ignition mechanism is bad you get no vac and therefore the engine will not shut off without opening the hood and pushing on the manual stop valve.

Guys - this is from a layman's view. If I am not correct or if the 240D does not work this way, please make the correction.

funola · #5 02-02-2016, 10:24 AM

Shut off is by vacuum and unrelated to glow plug starting. I'd suggest taking the glow plug connector off, take each female pin out and whittle a wooden rod to fit the female pins, spray with WD40 and burnish the female contacts clean. Squeeze the gap of the female pins to increase contact tension and reassemble. Use a pencil eraser to clean the male pins. While your at it, take the glow plug strip fuse off and inspect and clean connections. If there is any hint of a crack, replace the fuse. See if this helps to get the engine started. In a diesel, you need fuel with no air bubbles, good compression, a minimum cranking RPM starter motor, and good glow plugs especially in the winter for a successful start.

Quote:

Originally Posted by Redpeople

Many of you followed along and offered advice on my troubles in this thread: <sigh> Another "240D Won't Start Thread". It seems to have died a natural death, but I still don't have a running car. I'm exploring a different line of attack but haven't received any input on it, so I'm going to repeat my last post here (hopefully I'm not violating forum rules):

OK, here's another angle that I hadn't thought of. When I was first trying to figure out the glow plug problem and find the inline fuse, I popped the cover off the plug right above the fuse holder that goes into the dash. (See photo) Anyway, when I popped the cover off, I broke a piece off the bakelite plug itself, so the cover doesn't snap on tightly any more and I had just left it off.

When I was working on it today, I discovered that the glow plug light wasn't lighting and the plugs weren't glowing. I then noticed that the some of the pins in the aforementioned plug were loose. I pushed them in and the glow plugs started working again.

So my question is this: Is there anything in this plug or wiring harness that has to do with the kill function on the engine and is it possible that is keeping my engine from starting? Related question, how exactly does the "ignition" switch work to kill the engine? I understand how gas ignition engines work, but not these diesels.

BTW, I WILL still adjust the valves within the next few days, but I know if I go through that process and still have no luck I will be incredibly frustrated. Just want to cover all my bases.
Attached Thumbnails

Alec300SD · #6 02-02-2016, 10:29 AM

Just a thought, remove the oil cap and then try to start the engine.

Redpeople · #7 02-02-2016, 11:05 AM

Thanks, guys. And sorry for starting a new thread. I should have just bumped the old one.

toomany MBZ · #8 02-02-2016, 11:21 AM

New thread is fine, you're going in a different direction.

As I understand it, the issue you've just reported should not cause an engine non starting condition.

Make sure all pins are properly connected.

The shut off function has been covered.

barry12345 · #9 02-02-2016, 02:16 PM

In fairly low ambient light conditions. Have someone do the glow plug sequence. If enough glow plug current is flowing the squiggly wires between the plugs will visually appear to be very hot. If they do it indicates the glow plugs are probably working well enough.

After this if the wires indeed past the test. You could either spray a little wd40 down the throat of the air filter with the cover off after a glow cycle. Or loosen one of the nuts on an injector to see if fuel is present when cranking.

Redpeople · #10 02-02-2016, 03:12 PM

Quote:

Originally Posted by barry12345

In fairly low ambient light conditions. Have someone do the glow plug sequence. If enough glow plug current is flowing the squiggly wires between the plugs will visually appear to be very hot. If they do it indicates the glow plugs are probably working well enough.

After this if the wires indeed past the test. You could either spray a little wd40 down the throat of the air filter with the cover off after a glow cycle. Or loosen one of the nuts on an injector to see if fuel is present when cranking.

Thanks, Barry. I've already observed the glow plug wires glowing and also used an IR thermometer to measure the temps of the actual glow plugs (between 170-210F), so I'm pretty sure all are working well enough. I've also had all injector nuts loose to bleed the lines in case there was any air. Fuel started flowing immediately at all four.

I think then next inevitable step is valve adjustment. As noted, just wanted to make sure I covered all bases.

Alec300SD · #11 02-02-2016, 04:18 PM

Did you try to start the car with the oil cap off?

One test of engine health is to pinch the breather hose shut while the engine is running and count the seconds util it shuts down. Under 5 seconds is considered poor and over 10 seconds is considered good.

A plugged crankcase breather line could possibly cause a no start situation.

Redpeople · #12 02-02-2016, 04:45 PM

Quote:

Originally Posted by Alec300SD

Did you try to start the car with the oil cap off?

Not yet. Haven't been home since I saw your suggestion this morning. I'll try that when I get home from work.

Redpeople · #13 02-02-2016, 08:30 PM

Tried starting the car with the oil cap off. No luck. Just smoke coming out of the hole.

Tomorrow I'll try to adjust the valves.

barry12345 · #14 02-03-2016, 04:27 PM

Something seems a little strange. Engine was doing well then this after a failed Glow plug?

I would really do a glow plug cycle and shoot some wd 40 down the throat. Or if you have a block heater plug it in for awhile. This car should have come right back on line when you repaired the glow plug circuit.

Redpeople · #15 02-03-2016, 07:04 PM

Quote:

Originally Posted by barry12345

Something seems a little strange. Engine was doing well then this after a failed Glow plug?

I would really do a glow plug cycle and shoot some wd 40 down the throat. Or if you have a block heater plug it in for awhile. This car should have come right back on line when you repaired the glow plug circuit.

I agree it seems strange, Barry, but that's about the size of it. The only thing I would add is that it had two incidents where it wouldn't start when left outside in temps in the low teens. The first time, after it warmed up into the 20s the next day, it started fine. The second time, about a week later, I burned out the glow plug while trying to start it. Since then, glow plugs have all been replaced and are glowing, it's inside my garage where temps have been as warm as mid 40s, but it isn't coming close to starting.

I agree with many that there is probably merit in adjusting the valves, but it seems strange that it would suddenly go straight from running well to not starting at all.

I will try the WD40. It has a block heater, but when I tested it with an ohmmeter, it appears it doesn't work.

Thanks for sticking with me.