Hey all,

I drive my 300D daily. Always reliable, and starts every time. The other day I came home from work and shortly after went out to run some errands. No start. I get a really weird moaning sound coming from the driver's side of the firewall when I turn the key to on, and the sound fluctuates a bit when I turn to start the engine, or turn the lights on.

Unfortunately I've been too busy getting my new-to-me 560SEL road-worthy and haven't spent any time diagnosing the 300D. Hoping this description is of something others have fixed before that'll give me a head start.

FWIW, I have noticed a lag between the time the key is all the way turned and the starter engaging. It's only a second before the engine starts turning, but it's also the only thing I can think of as a culprit.

Thanks in advance,

For the moaning sound, it could be the buzzer for the key, light, seatbelt warning system in a low voltage condition. The starter delay could also be a low voltage, bad connection problem.

I would check the battery condition/voltage and all the cables for solid clean connections.

The warning system buzzer is in an electronics module close to where the steering column goes through the firewall. Not all W123s have the system, mine is a '84 California car.

__________________
____________________
1984 300CD (sold)
1973 220DPK 4 spd (died)
1978 350SL 4 spd gray market
2003 SLK32 AMG
1988 300CE (sold)
1997 E420 (Totaled)
1998 E320 Wagon

have you tried jumping the starter from the junction box on the passenger fender, infront of the battery? get a piece of thick wire and jump the smallest screw to either of the larger ones. this bypasses the key switch and makes it easier to see/hear whats going on in the engine bay..

PS its also great to use for valve adjustments, so you dont have to move the motor by hand

I use needle nosed pliers for this.

__________________

All Diesel Fleet
1985 R107 300SLD TURBODIESEL
2005 E320 CDI (daily)

LOTS of parts for sale!


EGR block kit
http://www.peachparts.com/shopforum/diesel-discussion/355250-sale-egr-delete-block-off-plate-kit.html

1985 CA emissions 617 owners- You Need This!
Sanden style A/C Compressor Mounting Kit for your 616/ 617 For Sale + Install Inst.

Sanden Instalation Guide (post 11):
http://www.peachparts.com/shopforum/diesel-discussion/367883-sanden-retrofit-installation-guide.html

Measure voltage at the battery posts as you try to crank. Place probes on the wire sides since corrosion across the post junction is a common drop (why everyone sells battery brushes). Even better, measure right at the starter to its case. If <8 V there while trying to crank, don't blame your starter. I think you should also hear a clunk from the solenoid (inside starter), though I never noticed on my 300D's.

__________________
1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

Thanks to everyone for the thoughts. I'll play with each of them hopefully by the weekend.

Also, possibly worth mentioning, the key buzzer has never worked since I've owned this car. It doesn't make any chimes or noises at all.

Update!

We finally had a day here not too cold to go outside, and the car wasn't covered in snow anymore either!

I took a picture of the box making these awful tones, and what I assume was the junction box for the starter that was mentioned. With a charger on the battery (it was a little low, sitting for a few weeks in the cold), jumping the small screw on the junction box to either of the larger screws, I only get a groan from the noise box on the other side of the engine. No starter engaging or anything.

So, 2 questions: 1) Am I jumping the correct screws to engage the starter to begin with and 2) if I am, am I looking at a bad starter?

Additional info, I tested to see if it was a faulty NSS by trying to start the car in either park or neutral. I've never gotten other symptoms that the NSS may be bad, but I think I may have ruled it out as a culprit in this scenario.

Something else worth noting is that the glow plug light on the dash is not illuminating. This hasn't been happening before this no-start issue.

Pics:

The screws I jumped in front of the battery


The awful noise box on the driver's side of the engine bay, toward the headlight.

Question 1) You are jumping the correct terminals.

Question 2) Your starter may be okay. You need to check your glowplug relay.

The "awful noise box" contains your glowplug relay. It should only make a single "click" sound when it times out after about a minute or so on cold days.

Try removing the 80 amp strip fuse (under the black plastic cover) and inspecting it. They can develop cracks or have corroded connections that cause poor start conditions.

From your symptoms it is most likely that the relay is sticking (and making noise) from burned contacts and you need to replace it. Swap in a known good used one if you can. New ones are expensive $$$.

Another possible cause of the relay failing is that water may have made its way into the relay, which can cause it to intermittently fail (after drying out it works again).

This happened to my 83 W126 300SD a few years ago. The first junkyard replacement was kaput but the second one is still in service.

Unless you have very good compression, a strong battery and a good starter, it will be very hard to start your car without functional glowplugs.

Don't forget to really clean your battery terminals and where your battery cables connect to the body (negative) and starter (positive). Corrosion causes starting problems as well.

Good luck in getting her up and running again.

__________________
78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

Excellent advice! Thank you! I will go check on this now. If it is the 80amp fuse, I assume eBay or these forums might be the best option for finding a used one?

I'm curious though, even with no glow plugs, wouldn't the starter still engage and the engine just wouldn't ignite?

Update! I just checked the glow plug relay. I assume the smaller of the two plugs under that lid goes to the GPs. I pulled it and checked the dash- no glow plug light. Plugged it back on and the glow plug light on the dash was on, cycled for the correct 7 or 8 seconds or so, and the car fired right up!

Guess maybe there just wasn't great contact there. What is interesting is the the car always has a little bit of a low/rough idle for a few seconds when it's very cold out and the block heater hasn't been plugged in. It started just as quickly and smoothly just now without being plugged in, as it does had it been plugged in. Maybe I've been running off of poor GP performance for a while now?

Congrats on getting her running again!

Glad to hear you only had a poor connection on the glowplug harness.

When the weather is nicer, get a can of electronic contact cleaner (CRC from the auto parts store) or my favorite, a kit of cleaner and conditioner (Deoxit and Deoxit Gold) from Radio Shack.

Take your time and clean (and condition) all your harness, fuse, ground and bulb connections. Remember to disconnect the negative battery cable first.

It is an easy project on a warm spring day that keeps those electric gremlins away.

__________________
78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

I'll pass it along to my dad. He'll actually be getting this car from me sometime in the next few weeks. I'll be replacing her with my 350SDL as my daily, and I don't have room to keep 4 cars (in the garage are an E55 and 560SEL, plus bike).

He'll take good care of her. I've been able to do a decent bit of maintenance in the year I've had it, and I'll just get her back at some point in the future.