Do I dare ask what next? - PeachParts Mercedes-Benz Forum

psaboic · #1 09-25-2020, 09:52 PM

Boy what a week. Started with a near flat tire due to a 3" sheet metal screw in the tread, then out of the blue the wife's ML350 developed a sudden fuel leak from somewhere in the bowels of the engine bay that required a tow home, then the boys car threw a check engine light for an intermittant cylinder misfire, and now my issue.

The 1983 300D has been running fine. Today I went to leave work after an 8 hour shift, tried to start the car and it cranked but no fire. I looked down and no glow plug light at all. Without tools I checked what I could and then just tried cranking it hoping it was just one plug or two that went out. No dice, it took almost 2 mins of 30 sec crank followed by 30 seconds of starter cooldown until she suddenly fired up. Since it took was so hard to start I concluded I had no glow plugs at all. Let me tell you with an ambient temp of 55 degrees, starting with no glow plugs suck.

Anyway, I got it home, changed clothes and went to mess with it. I turned the key to be greeted by the cheery yellow glow plug light. Turned the key and it started right up. Tried it three more times and same result.

I'm going to troubleshoot the glow plug system tomorrow but what the hell could suddenly cause no glow plugs at all? I'm thinking either the glow plug relay, the 50 Amp metal strip fuse, or wiring. I'm kinda leaning toward a cracked metal strip fuse that made contact once the engine bay got warm. Any tips or suggestions are welcome......With a week like this, I can use all the help I can get!

merc lover · #2 09-25-2020, 11:55 PM

I've had the metal fuse strip blow before, be sure and check it first since it is easiest. Next up check out the glow plug relay. I forgot how to check it properly; just type in "glow plug relay" under the search engine on this forum and you will get plenty of threads on how to do it. By the way, running the starter for as long you did might burn it up. I'd say changing out starters is one of my least favorite jobs so I do everything I can to protect it. Speaking of which, I need to buy a new battery for the car to keep the starter happy.......

To me it sounds like it is one or the other of these two that is causing your problems.

merc lover · #3 09-26-2020, 12:02 AM

If the car wll not start within 20 - 30 seconds, best to turn off the starter and let it cool down. If you try a second time and still no joy, CALL A TOW TRUCK. I know my insurance company provides a 1800 number for free towing, I used it recently and was glad they were there to provide the service. Best to request a flat bed tow truck, BTW.

Better to have the car towed home than burn out a starter.

psaboic · #4 09-26-2020, 12:30 AM

Agree it was probably rough on the starter, but in all honesty it was not a full 30 seconds of non-stop cranking, more like about 10 seconds, wait a five or 10 seconds and try again. As for the tow truck, where I work out in the boonies it is very hard to get a tow truck out there and if you do it is at least an hour wait or more, hence the reason I took a chance. Until I get the other two cars mentioned fixed, I GOTTA drive this one. I will do the full multimeter test of everything and see what I come up with. I still have the old relay that was in the car about 10 years ago that I could use in an emergency if I have to order a replacement. Its problem was that it would intermittanly turn on the glow plugs while driving. I suppose I could use it to start the car, then pull either the power connector or the connector that goes to the glow plugs after it starts

vtmbz · #5 09-26-2020, 08:36 AM

I had one 190 with relay issues that I could make click by pushing down on the relay box cover, meaning that the harness to the glow plugs was not making contact as well as it should.

With cars this old, contacts are my first go to. They get sloppy.

merc lover · #6 09-26-2020, 09:41 AM

Sounds like ordering a new glow plug relay would be a good move. Seems we are all playing the role of 'parts hunter' nowadays.

psaboic · #7 09-27-2020, 01:58 PM

Ok, based on a post a few years back from Diesel911 (see below), I made an emergency jumper and it works great. I just took some 10 gauge wire, cut 5 pieces about 12 inches long, stripped about 2 inches of insulation off one end of each wire, bent the wire over to make a tight loop and ground it a little bit to ensure a tight fit in the glow plug connector. On the other end, I stripped about 3 inches of insulation off each piece of wire, and bundled them all together with zip ties and electric tape. I recommend it to anyone for an emergency.

From Diesel911

There is a thread from long ago on taking the solid copper (#10 not sure of size but that is what I remember) House Hold type Wire from the Hardware store and the Wire size is the size of the pin holes in Connector that goes to the Glow Plug Connector.

Un-plug the Glow Plug Wire Connector from the Glow Plug Relay.

You remove the Insulation on the Wires and shove them into the 5 pin holes on the Connector that goes directly to the Glow Plug Wires and you bunch together the other end and twist it together so that they will not untwist.

At that point you have all those Wires connected to the Connector and with the Twisted End you clip on one of your Jumper Cables leads and clip the other end of said Jumper Cable to the Positive Batter Terminal and that connects up your Glow Plugs.

For emergency use. The above is to the best of my memory.

jt20 · #8 09-28-2020, 01:44 AM

Please check your all your grounds before doing any work.

Specifically the engine ground strap on the bell housing bolt, located at the engine to transmission connection.

psaboic · #9 10-05-2020, 11:04 PM

All grounds look tight and intact. It is definitely an intermittent issue. It worked fine for the last week, and still worked fine when I started it this morning. I drove about 20 miles to a store and was in there for about ten min. I came out and no glow plug light. Engine was hot so it started right up. Drove another 20 miles to work and shut the car off. 8 hours later turn the key, glow plug light came on and car started fine. I ordered a new relay today. Just for grins and giggles, does anyone have a wiring schematic or a pin out of the small 4 pin connector that goes to the relay. Just wondering if I have an intermittent signal from the ignition switch.

Thanks

pawoSD · #10 10-06-2020, 11:37 PM

I wouldn't worry about the starter, the battery will die off before the starter cooks itself. I cranked a loong while plenty of times on my 300SD in cold temps or if there was a glow plug issue....never killed a starter.

I had an intermittent glow like that on mine too, ended up having to replace the whole relay to resolve it.

g300d · #11 10-07-2020, 04:48 AM

^ I killed a starter after a lot of long cranks with dead plugs in cold weather up in the mountains. The reduction gears inside the starter disintegrated soon after that episode.

psaboic · #12 10-07-2020, 09:52 AM

Quote:

Originally Posted by pawoSD

I wouldn't worry about the starter, the battery will die off before the starter cooks itself. I cranked a loong while plenty of times on my 300SD in cold temps or if there was a glow plug issue....never killed a starter.

I had an intermittent glow like that on mine too, ended up having to replace the whole relay to resolve it.

Yeah, I ordered a new relay and plan on swapping it out as soon as it arrives...probably keep the old one as an emergency spare. unless someone wants it to take it apart and screw around with it.

merc lover · #13 10-08-2020, 08:09 PM

I'm sorry it has come to this for us vintage mercedes owners but I believe when ordering any part it is best to order at least TWO. The powers in Stuttgart have become shutting down availability of these parts and having a spare as a backup is a good idea, IMHO.

psaboic · #14 10-09-2020, 09:36 AM

Whelp......new relay is in and seems to be working normally. I'm keeping the old one as an emergence spare.