Having occasional no-crank issues - PeachParts Mercedes-Benz Forum

studjuice · #1 07-16-2012, 11:37 AM

Hi all, I just bought a 1983 300D turbo yesterday, for $900 so it has a couple of problems. The first problem I'd like to figure out is it's starting problem. Sometimes it won't crank. But sometimes it will.

When I go to let the glow plugs warm, the light turns on for about 1 second then turns off. I was under the impression that the light would stay on while the plugs are glowing? I test drove another 300d before buying this one, and on that one the light stayed on for about 3 seconds before turning off. Now, from what I know the glow plugs stuff shouldn't affect the engine's ability to crank, is that right?

The way the car starts is that you have to put the key in and turn it all the way and hope it cranks. If it doesn't, you gotta take the key out and try again. and repeat. Sometimes (if I'm lucky) it will only take about 3 times. Other times it will take around 30 times. My arms getting sore from it, and it's kinda embarrassing to take it to a shop to get it inspected like this.
I read about the neutral safety switch, and that sounds like it's probably my problem. I tried to bypass it with this post (No Crank on 1984 300D - MBWorld.org Forums) and couldn't figure it out. I used some wire to connect the two sides and nothing happened. I thought maybe I need to put the key in and on first, tried that and still nothing. Maybe I'm just jumping it wrong, so I want to get some clarification on that first. Otherwise maybe it's a different problem? I noticed that there is a wire that is cut and goes nowhere. Here is a picture of what I mean: imgur: the simple image sharer It's that wire with that blue tip.
I tested the battery and it had 12.63v so I think that's good. I couldn't read the CCA on the sticker (everything in the engine was/is dirty), so I tried to clean it off and the writing went with it...

vstech · #2 07-16-2012, 12:27 PM

sorry your posts are getting blocked, New members are not allowed to post links.

I fixed it for you.

vstech · #3 07-16-2012, 12:30 PM

when you say the car will not crank, you mean the starter does nothing, or it turns the motor over, but will not fire?

the blue wire was just something somebody installed for constant power, likely a radio or alarm. ignore it.
the factory wires look ok.
I'd get a large copper wire, and jump between one of the big wires, and the small wire, and see if the starter clicks in. if not, you have either a ground/wire problem at the starter, or the starter itself is bad.

vstech · #4 07-16-2012, 12:32 PM

also.
the glow plugs will not keep the starter from cranking, but the NSS will. jumping the terminal block in your pic, bypasses the NSS

the glow light coming on, indicates your glow plugs are either all functioning, or they are all dead.

the light will not stay on more than a few seconds, but the glow plugs will stay on until either 30ish seconds have lapsed, or the starter has engaged and released.

studjuice · #5 07-16-2012, 12:38 PM

Quote:

Originally Posted by vstech

when you say the car will not crank, you mean the starter does nothing, or it turns the motor over, but will not fire?

the blue wire was just something somebody installed for constant power, likely a radio or alarm. ignore it.
the factory wires look ok.
I'd get a large copper wire, and jump between one of the big wires, and the small wire, and see if the starter clicks in. if not, you have either a ground/wire problem at the starter, or the starter itself is bad.

I mean the starter does nothing. Silence.

Okay I'll try that out. Thanks for your help

studjuice · #6 07-16-2012, 01:03 PM

tried it out, and it worked kinda. It wasn't easy. It had to touch and kinda be pushed down on it. Just touching it either did nothing, or provided a spark and a short click sound from I assume the starter. Also depended on where I touched it. some parts I think were too dirty to provide a good connection. I'm going to go clean it.

With pushing it down, the starter started to turn over. But the engine didn't start. Is that right? I let it go for 3 seconds, and then stopped. When I stopped I noticed smoke coming from the positive battery terminal and coming from lower under the engine area (I think that's where the starter is. It's so dirty I can't really identify anything)

studjuice · #7 07-16-2012, 04:05 PM

I'm dumb. I didn't have my key in. It started with my key in the on position.

Next I tried jumping with the purple wires above and to the right of the accelerator pedal, and nothing happened. This means I need a new ignition switch, right?

Diesel911 · #8 07-16-2012, 06:55 PM

It sounds like you need to clean up all of your Battery connections and Cable Connections including the the Chassis to Engine Ground.

If using a remote Starter Switch (safer) or a Jumper Wire acrossed the Wire Terminal/Junction Block in front of the Battery in the Fender dose not get the Starter to move suspect an issue with the Starter or the Starter Cables/Wires.
Doing that bypasses everthing else.

Besides the Netural Safety Switch the bad Shifter Bushings can als cause an issue.

studjuice · #9 07-16-2012, 06:59 PM

Quote:

Originally Posted by Diesel911

It sounds like you need to clean up all of your Battery connections and Cable Connections including the the Chassis to Engine Ground.

If using a remote Starter Switch (safer) or a Jumper Wire acrossed the Wire Terminal/Junction Block in front of the Battery in the Fender dose not get the Starter to move suspect an issue with the Starter or the Starter Cables/Wires.
Doing that bypasses everthing else.

It did work. I just wasn't doing it right. But jumping the place above the accelerator pedal didn't. I got that from this thread: http://www.peachparts.com/shopforum/diesel-discussion/260407-how-bypass-test-your-neutral-safety-switch.html

Diesel911 · #10 07-16-2012, 07:06 PM

When the Glow Plug Relay is working normal there is a Air temp sensor inside of the Relay that determins when the Glow Plug light turns off.
If you keep the Key in the Preglow position even when the Glow Plug Light goes off the Glow Plugs will stay on until the timer in the relay turnis them off.
The whole time the Timer allows the Glow Plugs to be on is about 30 seconds.

If you are someplace really cold after the Glow Plugs have gone through one cycle you can turn the Key back and start again.

Also when your Starter is Cranking the Glow Plugs are on.

The Diesel Giant Site has a good pictorial on Checking the Glow Plugs.

studjuice · #11 07-16-2012, 07:42 PM

Ok thanks. Well I'm just wanting to make sure right now that the ignition switch is what should be bad based on the tests I've done.

I also have a jumpy temp gauge and fuel gauge, if that applies to any of this. Like having a bad ground somewhere?

Diesel911 · #12 07-17-2012, 09:14 PM

If the Ignition Switch is bad it could cause the Gauges to jump.

However, there is a ground in the back of the Instrument Cluster that can cause the Gauges to jump if it is not good.

charmalu · #13 07-18-2012, 02:45 AM

The ground cable from the engine to the body will cause a jumpy gauge.
The ground cable can be seen right below the oil filter housing, and assable from under the car. It connects to one of the bolts at the adaptor plate between the eng and trans. 17mm, and one bolt on the body, 15mm as I remember.

Charlie