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Discussion Starter #1
I'm having an intermittent problem with my '79 300D not completely starting which has increased in the last 2 days.

What's happening is that when I turn my key enough for the glow light to come on, it's not coming on at all. However, I'm waiting a minute or so for the car to "glow" even though the light is not coming on.

In the last two days, this "no glow" problem has happened once on BOTH days and I've had to spray starter fluid in the air intake for the car to completely start.

I have not had to spray starter fluid when the no glow problem has happened before - I just turned the key to the off position a couple of times and turned it back to the glow position, and the light glowed. I checked my glow plug fuse (the silver piece of metal) and it's in tact (I assume). I don't know a lot about that fuse, however.

This starting problem happens when my car has sat overnight for hours in my garage. The weather has NOT been cold here this weekend, just to mention. Also, after having this problem on Saturday, I plugged up my engine block heater Saturday night, while garaged, but this no glow/starting problem still happened on Sunday (today) when I tried starting the car. Again, I had to use starter fluid for it to completely turn over.

When I tried starting it without using starter fluid (and again, when the glow light did NOT come on), the car will make the sound like it wants to turn over and it sounds strong in doing it. It's just not completing some final step in starting.

Once the car HAS started, the engine runs rough & knocks a bit until I drive it awhile. After it's been driven awhile, the engine purrs and the glow light comes on most of the time after turning it off and starting it up again. There has been times that the glow light has NOT come on and the car starts fine, but that's after I've already driven it for that day.

I switched from the old style glow plugs to the new, fast-starting Bosch glow plugs last month. (I was having problems with needing to wait a LONG time for the car to glow and start before getting the new plugs). So, I'm stumped at this point.

Does anyone have any insight on my current starting problem?

Thanks...
 

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Wasn´t the old style glowplugs connected in series?
And the "new" ones parallell. Maybe...


Wasn´t the old style glowplugs connected in series?
And the "new" ones parallell. Maybe thats the problem.
However, be careful using starting fluid in a diesel. With that high compression you might damage something.
 

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I have seen starting fluid kill Mercedes diesels.
If your going to squirt anything at all...


I have seen starting fluid kill Mercedes diesels.
If your going to squirt anything at all use WD40,
it is Kerosene based. Can still damage the engine, but not as likely as starting fluid.

Use a meter, can be had cheap now to see where the
current is lost. Could be the relay fuse if your lucky.

Also the relay itself or anyone of the GLowplugs in a
series system.
John Gregg
 

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Discussion Starter #4
Thanks for the quick help guys.

I have ceased using the starter fluid per your sugges...


Thanks for the quick help guys.

I have ceased using the starter fluid per your suggestions and glad I didn't use a large amount of it (a couple of sprays each time). Out of curiosity, what's in that stuff that makes it start? Can I do anything to clean that out which I've used?

I took the car to my mechanic last night and left it with him overnight. He can experience the problem this morning like I have for the past 3 mornings. I too hope that it's something simple!

Thanks again,

d2e
 

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If the new glow plugs are ment to be connected in parallell they probably need 12 V. If yo...

If the new glow plugs are ment to be connected in parallell they probably need 12 V. If you have an old series system (With short connections between the plugs) you have only 2.4 V on each plug.
The starting fluid contains what we call eter in Sweden. It burns much faster than diesel and in a dieselengine it burns without any pre-heat by glowplugs. The heat caused by the compression is enough to make it burn. But you will have a very early ignition point and the big bangs will cause a great pressure on piston rings and crankshaft bearings
and other things involved. I would never use starting fluid at all. It´s better to find the actual problem. If everything is in order it will start at temperatures at least down to -15 degrees Celsius.
You don`t have to worry about the starting fluid you already have used, because it is gone sense about a minute after you sprayed it in.
 

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Discussion Starter #6
Hi Anders,I appreciate your reply and thanks for answering the starter fluid cleaning ...

Hi Anders,

I appreciate your reply and thanks for answering the starter fluid cleaning question.

Here's an update: I took my car into my mechanic last week and he kept it 3 straight days.

The frustrating thing was, all 3 days he had it, this problem NEVER happened for him. He tested the glow plugs and said that they are all fine.

He said he believes it's the relay switch but didn't want to replace it since it's $100 and because he couldn't duplicate the problem.

Well, this past Friday night (3 days ago), the problem happened yet again for me. I drove the car about 2 hours and let it sit for about 2 hours.

Tried cranking it - wouldn't completely start and the glow light again did not come on prior to trying to start it.

I have noticed now that this no glow light problem happens primarily after I've driven my car for 1.5-2 hours on the highway at high speeds (65 mph) and then it sits overnight or for a few hours.

Could something be coming loose while driving on the highway? Could it be fuel injection related?

Btw, I noticed that my air intake hose has a hole in it. Should it? When I used that starter fluid last weekend, I saw some drip out about a few inches from the mouth of the hose. Was just wondering.

Thanks again for any help/advice...
 

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This happened to me before. For me it was a small fuse that costs about 0.50$. The fuse is...

This happened to me before. For me it was a small fuse that costs about 0.50$. The fuse is located on the fire wall, near the middle in a little black box. What happened to me was, when I was cleaning the engine, the little box was open and I sprayed water at it, causing damaged to the fuse. I'll try to find a pic of the engine bay and post a diagram.
 

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I have had the connections be "loose/corroded" to in/out of the relay. The fuse can also be bad without being completely blown. It is easy to get off and check. You can take the cover off of the relay and see the coil and points. You could still have one bad glow plug and start, it will not start with two bad glowplugs, but sometimes will give a few days even weeks before the second fails completely
John Gregg
 

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Discussion Starter #10
Thanks Tricky and dfw for the tips...

I've checked the glow plug fuse (little metal bar...


Thanks Tricky and dfw for the tips...

I've checked the glow plug fuse (little metal bar under the cover?) on the back of the engine wall, right where you've circled Tricky...seems to be fine.

I had the mechanic check the new Bosch glow plugs last week and he said they all tested out fine.

I'm having him replace the glow plug relay switch today and hope that this does it.

Again though, the one thing that has happened pretty much like clockwork during this starting problem is that I've driven a long distance for a couple of hours, let the car sit a few hours-to-overnight, and experienced the hard starting problem.

But, when I'm just driving around town throughout the week, this problem doesn't appear to happen...

Really strange! [:(]
 

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Discussion Starter #11
Update....

Had my glow relay switch replaced last week ($150) and after driving it out ...


Update....

Had my glow relay switch replaced last week ($150) and after driving it out of town again this past weekend, the same problem surfaced:

The glow plug light did NOT come on after driving about 2 hours and then letting the car sit overnight. As mentioned in my previous postings about this problem, when my glow light doesn't come on, my car won't start, although it sounds like it's trying to start (after letting it glow for a bit, though with no glow light).

I tried multiple times to start it this weekend and it didn't. But, when that starter fluid has been used, it'll start of course, and the glow light DOES work the rest of the day and week, as long as I'm not doing long distance driving (and 2 hours is not really long distance).

The frustrating thing is that it was assumed the relay would most likely solve this issue, but it hasn't, so that was $150 wasted.

I'm almost convinced now that me driving 2 or so hours on the highway then parking the car after such a drive is DIRECTLY related to this problem.

Why?

Well, when I'm driving my car around town during the week, this problem is NOT happening. I've driven out of town every week now for the past 2-3 months, with this problem happening like clockwork EVERY weekend for the past 1 month.

The only other changes my car has undergone in the past 1-2 months is the use of Mobile 1 Synthetic 15W50 oil and the new Bosch fast-start glow plugs. My mechanic tested my glow plugs week before last and said they were NOT the issue.

I will replace the glow fuse.

Are there ANY other suggestions or answers as to why this happens AFTER I've driven the car on the highway for a couple of hours???

Thanks..
 

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Discussion Starter #12
My car is having problems still with this intermittent glow plug light issue and no starti...

My car is having problems still with this intermittent glow plug light issue and no starting when the light doesn't work.

It's even happening now when I don't drive long distances.

I've now been told that it's "probably" the ignition switch, as my mechanic tested the car with a new ignition switch and this problem didn't happen. But, he didn't drive it a long distance of course, which is always when the problem has occurred, plus he tested it for just 2 days.

I don't want to chunk over another $150 like I did for the relay switch and it not fix this problem.

Can a bad ignition switch cause my glow light to NOT come on???

One other thing I know has changed since this problem has been the type of oil I've used. I switched to regular Mobile 1 Synthetic 15w50 oil (grey bottle).

Could that be causing this problem???

thanks.
 

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Hi!

If it´s the ignition switch, no other control lights would light up when you turn...


Hi!

If it´s the ignition switch, no other control lights would light up when you turn the key to glow position.
Why can´t your mechanic test your ignitionswitch by measuring the current to the relay when the light doesn´t come on?

The oil change have no effect on that, but I would never pour synthetic oil in an old engine.
It may cause leaks in old clogged up sealings and in worst case dirt may get loose and stuck in some narrow oil channel, for example to the camshaft.
Use high quality mineral oil like Mobil Delvac and change it and the filter often.

Anders
 

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Discussion Starter #14
Still happens...

I appreciate your help and feedback Anders.

As for the oil, I'll use Delvac now instead of just Mobile 1 Synthetic oil. I've only had 1 oil change with Mobile 1 and thought it would be quality oil to use. (Perhaps that's why my engine runs a little rougher now after using it???)

As for the ignition switch testing, I don't know why my mechanic has not tested the current to the relay, but I'll ask.

The intermittent glow light problem is still occurring, but I haven't taken my car back to the mechanic because we don't seem to be getting anywhere.

I will say though that the problem happened last week where the light didn't come on without driving any distance.

That time though, I tried starting the car anyway although it didn't completely turn over the first few tries.

Well, after turning the key in the ignition off/on about 4-5 times after I tried starting it, the glow light eventually came on. I let it glow and the car started.

I still don't know what to make of this, however.

Thanks...[V]
 

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Although it may not necessarily be related to your problem, I'd check the engine ground ...

Although it may not necessarily be related to your problem, I'd check the engine ground and the battery cables. On my '80 300D the engine ground is located under the car towards the passenger side, and is a thick braided metal cable. Make sure its connections are clean and attached tightly. Then look at the battery cables. Even though it might not look like it, the cables may be bad.

The only time when I've not been able to start my car (aside from a dead battery) was when my battery cables were bad. My engine spun over fine but wouldn't start. They looked fine, but my mechanic switched them out and then the car started fine. I couldn't really tell you what to look for/check, but if there's signs of corrosion or damage or bad connections at the clamps or the strands of wires (if visible) not twisted tightly together, you may want to look into this.

As a matter of fact, my sister's Honda Civic had an intermittent starting problem where the engine would turn over but wouldn't start. I popped the hood and the engine ground cable (which is right in front of your face when you open the hood) looked all scraggly, uncovered close to the connections, and the exposed strands of wire were untwisted a little bit, as the individual strands were all separated. I twisted the cable up tight, and wrapped up the exposed strands of wire, and now she no longer has any starting problems.

Again, this wouldn't be the first thing to come to my mind to check if I had your problem, but you may want to just check it out.
 

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Sorry, I meant the engine ground is towards the driver's side...
...


Sorry, I meant the engine ground is towards the driver's side...
 

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Hello,

I am having the same problem with my '78 240D. I think my glow plug "fuse" is a screw on the firewall shown in the picture in the previous reply.

I am getting 12v to all the plugs (in series). They are new loop style bosh plugs. It had the same problem with the old plugs, but at least the light came on with the pencil style plugs.

Any suggestions? Rewiring methods?

Where is my glow plug fuse and rely located exactly?
 

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Discussion Starter #18
Hi there Doom,

Where that pic is circled is where your glow fuse should be located as well. Find out if it takes the 50A or 80A fuse if you want to change it, not sure which it takes as I'm still learning these cars myself.

I will share for those following this post that I do believe my no glow light issue was resolved today. [8D]

Yesterday, another mechanic I've been dealing with in the last week checked my glow plugs and wouldn't you know, glow plug #1 was bad. So, they replaced it for me and I'll get pay back from my orig mechanic who did the upgrade. The other shop also changed to a new 50A fuse and removed the 80A I had in there for 2 days.

I drove home after that repair (almost 2 hour drive), let the car sit awhile, tried cranking it and guess what? The glow light came on and the car has run fine all day!!! Yes, I am QUITE estatic, as this problem has plagued me for almost 2.5 months.

Thanks everyone for your help and hopefully Doom, you can get yours resolved quickly.
 

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Well... I just replaced the hand pump, at least that helped get the air out of the lines.

But... I still can't get the glow light inside to come on. There is no fuse on the firewall. It must have been "removed" a while ago. The first glow plug is directly connected to the wire coming from the relay. (i.e. - connected but no fuse). The old glow plugs were pencil type connected in series. Are the new filament type I just bought supposed to be in series as well? My manual says they are. Also is there a ground connected to the last glow plug (# 4)? Where is the ground on the engine block?

Picture would help a ton.

Thanks,
Ryan
 
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