1978 240D won't start...starter? - PeachParts Mercedes-Benz Forum

apsaulters · #1 05-04-2007, 11:39 AM

Folks,

Just when I thought my leaky trunk was my biggest problem, the car refused to start last night. Here's some information on what's going on (apologies for length; trying to be thorough).

Situation: Last night I drove the car for about thirty miles then parked it. I came back to it after fifteen minutes and it wouldn't start. The first time I tried to start it, I ran the starter for about ten seconds and gave it some fuel; no go. The second time the starter went for five seconds; third time, two or so seconds. The fourth time the starter would not move at all. The motor sounded weaker each time. When I tried it again this morning, the engine still wasn't turning.

History: The car's been taking longer than usual to fire of late, but I thought that was the cooler weather we've been having recently (Greensboro, NC). The previous owner says the starter was replaced some time ago, perhaps 10 years ago, before his father handed it down to him. The earliest repair order he has on the car says the mileage was 517,531 on 8 August 2000. The present mileage is 540,198. Engine was rebuilt around 400,000, in case anyone was wondering.

Starter sound: I think the solenoid is clicking, but I can't tell for sure; there's a click-like sound when I try to turn it over, but I can't tell if it's coming from the ignition lock or the solenoid.

Voltage: Took a reading of battery voltage after the first failed crank last night; it was 12.5 volts at that time. I've tried to crank it maybe six times since; my last voltage reading was 12.25 volts. (I'd give a current reading, but my multimeter just died. Alas.) Lights and the lovely 'door ajar' buzzer still work without fail.

Fuel pump/fuel level: I haven't checked this yet; the tank has about 13 gallons in, and, like I said, I drove it for thirty miles without a problem beforehand.

Glow plugs: The glow plug light comes on for the customary length of time when I turn the key. I check the resistance of the glow plug circuit from the relay under the dashboard, and it looks like one glow plug is bad. The car has been starting roughly recently, so I suspect I'll have some work to do on the glow plugs when I figure this out. Don't think that's the culprit, but I figured someone might want to know.

So, I guess my question is...what's up with this? I've read on the forum that one can expect a decent starter to last 7 to 15 years--by that metric, it sounds like the starter could be dead. But at that same time, the car was driven an average of 3,400 a year over the past seven years, which doesn't sound like a very heavy duty usage history (for instance: assuming ten miles driven per crank, a minimum of two cranks per trip, the car would have been driven less than one day out of two each year for the past seven years). Over the past few months I've driven more than the previous owner, on schedule to do about 10,000 a year, but that was mostly on long (out of town) trips.

I haven't tested voltage to the solenoid/starter yet because I am not really sure what to poke down there (any ideas?). I have not yet plunked it with a hammer--does that sound like something that would be useful here? (Again, it sounds as if the solenoid could be working properly.) What's the sound of a starter dying? (I expect it would be the sort of affair where the starter motor just stops, not the slow fading that I experienced.)

I expect to replace the starter, but before I put down the money for a replacement, I'd like to make sure I'm replacing the right things. Interpretations of this information and suggestions on what to inspect are much appreciated.

Thanks,
Andrew

kerry · #2 05-04-2007, 12:13 PM

Sounds to me more like a bad battery than a bad starter. Get your battery checked, usually for free, at an auto parts store like Pep Boys.

Stevo · #3 05-04-2007, 12:24 PM

One bad GP out of 4 will cause serious a starting problem. I would replace them all with the new style, it makes a huge difference.

vstech · #4 05-04-2007, 12:40 PM

get your MM fixed, measure volts at the battery while cranking... you may need a helper here.
I bet it's battery.
John

apsaulters · #5 05-04-2007, 12:47 PM

Kerry Edwards and Stevo: Thanks for your suggestions. I would place a little more suspicion on the battery (looks like 12.25 V at 50 deg. F. is about half charge), except I just replaced it two months ago. The previous battery (a 640 CCA thing the previous owner had put in) seemed to take longer to fail (I was able to get the starter going, albeit without starting the car, for about a week before I jumped it off, and that was in February, ~30 deg. F.). I'm a little leery of bringing batteries into parts stores for voltage checks. The first time I did, the mechanic just came out with this remote-control-looking thing that had two leads on it; he hooked it up to the battery and, sure enough, the readout of that little magic wand said "GOOD BATTERY" and that's it. The second time the mechanic put it on the charger for an hour before he realized he hadn't started the charger (two different shops, I might add). But I'm done with my complaining. I'll get it checked out as soon as I figure a way to strap that 49-1R to my bicycle. In the meantime, as I order new glow plugs, do either of you know any way I can check the starter? I'd like to clear it from my list of suspicions.

kerry · #6 05-04-2007, 02:08 PM

If you want to check the starter, you will need to measure its amperage draw. If you take the whole car to most chain auto parts store, they can check the whole thing, starter and battery together.
Given the information you added about replacing the battery, I would also begin to suspect the alternator or voltage regulator. Did you check the voltage with the engine running to see how much you were getting from the alternator.
Given your symptoms, I believe the liklihood that the starter is bad is very low.

vstech · #7 05-04-2007, 02:48 PM

simple test without starting the car is have someone crank, then someone else measure the voltage at the battery. far from foolproof test, but a good test with limited tools and a non running car.
John

apsaulters · #8 05-04-2007, 03:59 PM

Kerry Edwards: Yeah, I got curious about the alternator back in March. After I replaced the battery I measured 14.5 volts across the terminals with the engine running; is that in the right ballpark? I haven't checked the running voltage since then, though. Also took a look at the voltage regulator back in March; the brushes were about three-eighths of an inch long...somewhere around there; compared it against the pictures on dieselgiant.com, and it seemed that was an acceptable length.

vstech: Good idea; once I get my multimeter fixed I will try that. (Looks like the fuse on the meter blew.)

Seems like everyone thinks it's a downed battery; I'll check out the alternator and voltage regulator again once I get it running (Go-Go-Gadget Optimism!); perhaps they've begun to fail. I suppose I should invest in an ammeter to see what the parasitic loads are. I read somewhere that a shorted alternator diode could drain the battery; I'll look into this as well. Any other ideas as to what would make the car eat up batteries like this? I could understand the car having difficulties with the 640 CCA thing that was in it back in March, but this is an 1100 CCA Battery Of Doom...it seems Hard and From The Streets, as they say in the vernacular.

Seems the rain has stopped; off to RadioShack for a multimeter fuse, ammeter. I'll check the current unloaded voltage, voltage under load, and try to get an idea of parasitic loads with everything off. Thanks for all your suggestions.

Andrew

barry123400 · #9 05-04-2007, 04:43 PM

Check your battery properly or just put a charger on it. It is obviously very low. Fix the glow circuit. That may leave no issues once done.

Bio240D · #10 05-04-2007, 08:12 PM

Hi all,

One question I haven't seen asked is does the 1978 have the parallel pencile type GPs or the older series loop type GPs?

If you have the series GPs with the resistance wires jumping from GP to GP, then one bad plug kills them all just like christmas tree lights!

By the way, it does sound like your battery is weak as well. If your alternator is working, a 30+ mile drive should have the battery fully charged, and it should crank for 20 seconds or so without noticably slowing down.

Good Luck
Chris

apsaulters · #11 05-05-2007, 05:23 AM

Bio240D: Ah, yes. I have those wonderfully quirky serial glow plugs. I think the position of the bad one means that two of the glow plugs are lighting. Will be taken care of soon.

Remeasured my battery voltage earlier today; it's around 12.5 V now, which I guess is down a quarter volt from where it should be. Also inspected the battery cables; they were clean on top, but there was some gunk on the bottom of the positive clamp; also noticed some minor green stuff on the positive cable itself; might that be part of the problem? Looks like I'll be replacing it before I charge the battery.

barry123400 · #12 05-05-2007, 06:50 AM

If you fix your glow plug circuit first all should be well. I really think your senario was the glow plug circuit quit. You tried to start without it and bled off your battery charge with several attempts.
A lot of old indirect injection diesels will not come to life with glow plug problems. Even at seventy degrees ambient.
The thing here is to get used to it and always carry a spare glow plug, something to test them with and tools to change out one with in your trunk. If you own the car long enough another will fail and this type of plug is not commonly stocked everywhere. Always prudent to carry a spare fuel filter and again a wrench to change it as well. Can save a tow truck charge. Or save you wasting a day. A very cheap and cost effective thing to do.

apsaulters · #13 05-05-2007, 03:08 PM

Barry: I'm beginning to see what you mean about the glow plugs...thinking back over the last month, I've noticed some strange behavior with the pre-glow indicator light (like it has come on a few times while I was driving; does that mean I should suspect a faulty relay as well?). In any event methinks I should just go ahead and switch to the parallel plugs, as suggested by Bio240D.

'if I own the car long enough...' I'm beginning to think it's more like the car 'owns' me.

Good ideas on the extra filter/glow plug. I'm thinking that I should pick up a voltage regulator Just In Case, as it's been mentioned that's another part that can leave you stranded. I'll soon have a small parts store in my trunk...sort of satisfying...in a strange way.

apsaulters · #14 05-05-2007, 05:50 PM

Update: put the ignition switch in the pre-glow position to do a voltage test on the plugs for more information about which ones are out, and the relay box under the dash started making the most disheartening buzzing sound. Yikes. Did it again after I took out the key and let it sit for a second. I don't think I'm going to try it again. When I get the time (hopefully Tuesday?) I'll pull the plugs to see what condition they're in firsthand. Don't know what to do about that relay.

barry123400 · #15 05-05-2007, 06:57 PM

One other basic principal is do not spend money on items that are not required. At low voltage the relay may not want to stay engaged and could buzz. In troubleshooting you are always trying to break things down into the smallest possibility.
You need a proccedure to follow. I suggest as you have mentioned is to examine each glow pliug for resistance. Do not bother to take them out of the engine at this point. In fact in your situation do not even remove any wiring. Just read the resistance between the two heavy wires present at each glow plug. Leave the ignition key in the off position. Let us know the results if you wish. You should have an indication of how many glow plugs are burnt out and exactly the one or ones that are. It is probably just one by the way so replace it. Charge or get your batery charged up. Have it tested if you wish. Then when the car is starting again the alternator output can be checked. Doing the above items is within your grasp.
If you do not understand anything as you move along ask questions. We all have to start somewhere and in my day there were absolutly no help sites like this one. If you do not have a good multimeter the same test could be conducted with a 12v test light and a charged battery. Of course you would have to provide voltage to the glow plug string then.
If you have the squiggly wires between some of the glow plugs they are then certainly the series plugs. Exactly like old fashioned christmas tree lights. Where if one is out even the good ones do not operate. Lets get this fixed and you driving. I do not like to see you saving this much fuel with me buying fuel like crazy reciently.

This also starts the learning proccedure by the way. Also you slowly become more confident as you do things over time. You own the right car if not the best to learn from as well.