Occasional "No-Start" Issue - PeachParts Mercedes-Benz Forum

diesel don · #1 05-06-2003, 10:58 PM

This is strange but hopefully you guys can teach me (like usual).

My '85 TD has this occasional wierd thing happen. I get in the car, turn the key, wait for the light and go to start it and its dead. Wiggle the wheel, wiggle the shift handle, etc. Still dead but the battery is up and all the power is there.

I typically wait for about an hour and presto.....she fires.

This happened about one year ago but now it has re-occured three times this month.

What gives?

Don

gasman · #2 05-07-2003, 07:26 AM

I've had this happen to me with my 300D (sold) also, just as you have described. Additionally, it happened during hot weather when the engine was hot. After cooling down for about an hour, no problem sttarting. Is it possibly a starter problem?

edge · #3 05-07-2003, 07:58 AM

It happened to me last night, then I remembered that I didn't tighten the negative battery terminal after I did some work a few days ago. I hand tightened it, she started up and I tightened it again when I got home.

diesel don · #4 05-07-2003, 08:24 AM

Keep the suggestions coming as my starter was rebuilt 12 months ago and the battery terminals are good and tight.

Thanks for the suggestions so far....

Don

Alec · #5 05-07-2003, 09:31 AM

Here's the problem I've een having although I am not sure it is that same as yours...it usually occurs after i shut the car down when getting diesel or at the store. When I get back to the car I stick the key in, turn it, the glow plug light comes on and goes out, as expected, then I turn the key to start the car. All that happens is that the car turns over and over then I go through the cycle again. After a couple tries it finally starts.

I suspect that it is due to a bad ignition switch since I also have issues with my HVAC not coming on occasionally (I have to turn the key back slightly while the engine is running until I hear the solenoids (or something) 'click' in the dash then the HVAC works). Basically I think the problem I am having is due to a worn out tumbler/ignition switch. Perhaps you as well?

diesel don · #6 05-07-2003, 09:50 AM

I have wondered about the switch. What function does the HVAC have?

Don

Alec · #7 05-07-2003, 09:57 AM

Sorry...HVAC = Heating, Ventallation, Air Conditioning.

Alec · #8 05-07-2003, 10:07 AM

I have been toying with the idea of replacing the ignition switch with a toggle switch and a starter button...hidden in the ash tray...but then maybe I'll just replace the switch with a new one.

Rick Miley · #9 05-07-2003, 10:13 AM

If you were thinking of eliminating the key, there would still be the minor issue of the steering wheel lock. Don't want to get started and forget about that. Oops.

Alec · #10 05-07-2003, 10:33 AM

steering wheel lock...good point. I havent totally researched this. I have been trying to make sure the electrical part of the equation would work to my liking. I think I'd totally remove the key switch so there would be no steering lock and either replace it with a starter button or just cover the hole with something asthetically acceptable and put the button somewhere else. I found a guy that has an online 'how to' for a conversion in a Miata...not exactly the same but good resource. I keep creating more work for myself as if I didnt already have enough to do.

#11 05-07-2003, 10:57 AM

could be a bad "neutral switch." Try putting it in neutral, then park, a few times and see if it connects.

P.E.Haiges · #12 05-07-2003, 11:17 AM

ALec,

When you turn the key and your car turns over, does it stay on the roof or roll over back on the wheels?

Ignition switch on a Diesel???????????????

LOL

P E H

JimSmith · #13 05-07-2003, 11:20 AM

Guys,

This was a "hot" topic las summer in the warmer weather and there were a number of posts on the subject. It is not clear in my memory whether or not the people reporting the problems fixed them and closed the threads or not. But a search will turn up a bunch of similar experiences.

The power from the battery goes from the battery to the light switch on the dash, and from there to the starter switch, on to the rest of the fuse panel and to the starter solenoid when the key is twisted to the various positions. So, the problem can only be in a few of these areas, and it seems to be more of a problem when the engine is hot, in warmer weather.

Poor contact anywhere along the path is possible, and as someone noted recently, it is not impossible to power all the wimpy loads, like the dash lights, buzzers, etc. with a poor connection as they draw very little current. The higher loads, especially the glow plugs, solenoid and starter, will draw much higher currents and cause the existence of a poor, loose, corroded or otherwise imperfect electrical connection to become apparent. The connection heats up quickly and the resistance across the poor connection increases, dropping the Amperes passing through it substantially or completely. So, check the connections, especially the ground to the battery, the connection at the solenoid, and the starter power (thick wire to the starter), as well as those to the fuse box, key and light switch.

It is feasible the electrical part of the starter switch is dirty and worn. I believe this can be replaced seperately. Detailed instructions on this and other starter switch repairs can be found using the search function.

If all that is ok you should be able to reproduce the problem when it occurs by by-passing the key operated starter switch. If the problem occurs with the solenoid powered directly from the battery, meaning you get no response, no clicking of the solenoid, you probably have a bad solenoid. I would replace the starter with a rebuilt one from FastLane. Get the heavy duty one.

If the solenoid clicks when bypassed, or when the key is used and the car does not start (with good, clean connections), the problem is the starter. In my experience this is a winding insulation failure that shows up at elevated temperatures. All wire insulation materials degrade when exposed to heat over time. After a while this is not recoverable when the windings are cool. It is a symptom of an over used starter, and is something Diesels do more to starters than gas cars, typically. Long cranking episodes will overheat the windings, causing the insulation to degrade in any weather. The damage is cumulative, so it takes time to turn into a problem you notice. This degradation is first noticed when the starter is at a high temperature such as after a long run, and being parked when it is warm outside and the underhood temperatures soar. It gets worse over time until it becomes apparent at lower ambient temperatures. Finally, the starter will be unable to sustain a torque level to keep the engine turning fast enough to get it to start when the engine is hot or warm.

Since the starter is located near the exhaust system, and close to the engine, it gets exposed to a lot of insulation degrading temperatures so this is not someting you can avoid by some activity like letting the turbo cool down. When the problem gets to the point where it influences the functionality of the vehicle, the starter again needs to be replaced with a rebuilt one. I like the FastLane units because they are rebuilt by Bosch, and include new wiring with new insulation. Most rebuilt units have new mechanical stuff but not new windings. They are not as expensive, but they do not address the main problem with a worn out Diesel starter. So you find your "new" starter exhibiting the same old symptoms in short order.

I hope all this helps you. If you do a search on the subject you will find this is not a unique problem you are facing. Good luck, Jim

P.E.Haiges · #14 05-07-2003, 11:27 AM

Alec,

Replacing the key switch with a starter button may not solve your problem because the key switch also controls vacuum to the injection pump (IP) fuel shut off.

Possible your engine won't start because vacuum is still being applied the IP shut off because of a bad key switch. One way to findout if this is the problem is to remove the brown vacuum line going to the IP when the no start problem occurs. If engine then starts, you probably have a vacuum problem in the key switch.

P E H

Alec · #15 05-07-2003, 11:30 AM

I see your humor but what the hell do you call IT if not an ignition switch...the diesel still ignites when it hits the compressed and heated environment of the cylinders??? Starter switch, key hole switch, on switch...you know what I'm talking about...

Its the elecrtrical component attached to the back side of the tubler located to the right of the steering column and is responsible for applying electircal power to the car's systems that are necessary to start and operate the vehicle and at this point in time can only be actuated with the application of a well worn key.

P.S. my wagon always lands right side up...and no it isnt sitting on the driver side doors.