I've been having tons of problems with my poor car (mostly issues with
getting it started). We changed the oil, using rotella this time (didn't
know we weren't supposed to use the $4 a gallon no-name from the parts
store) and that helped. Replaced the battery and that helped. Now cycle
the glow plugs 2-3 times and that helps. Unfortunately it's still hard to
start, and it looks like the starter is beginning to fail. It will turn
over a few times and then just buzz. After several attempts it usually
turns over long enough to start up. While trying to start I'm giving it
about 1/2 to 3/4 throttle.
I've been told that when I'm trying to get it started it's okay to crank it
for up to a minute - but I only began having problems with the starter since
the cold weather/long cranking. Am I harming the starter?
Also, I notice that the car is much easier to start when it has been started
recently (within 8 hours or so) rather than sitting for a few days. There
are times when I don't need to use the car for up to a week. Is it bad for
the car to be used only once or twice a week? And, is it better or worse to
try to take it out 3-4 times a week but only for a two minute drive across
town? I know very short trips aren't great for the car.
Here are the other issues I know I need to fix or keep an eye on: two
leaking fuel injectors and leaky diesel prime pump, turbo beginning to leak
oil, block heater not functional, possibly replace the glow plugs (they
haven't been individually tested to confirm all working). I don't know how
to prioritize these issues . .
I'd love guidance and suggestions. I've always driven new japanese cars so
the elderly MB diesel is rather baffling to me.
Glow plugs are quite essential for cold starts. If your engine is warm
or warmish after eight hours, it doesn't need the glow plugs, the engine
is warm enough. Check them and replace if necessary. Difficult cold
starts in cold weather usually are to do with glow plug problems, (or,
if it is very cold, with diesel clogging up). Glowing them twice or
thrice helps in cold weather.
You should not need the throttle for starting, it is enough to adjust
the idle using the knob on the dashboard and turning it counterclockwise
all the way before you start. Press the throttle half way before you
turn it though.
Leaking fuel injectors: are the injectors leaking, or are the rubber
hoses leading to and from the injectors leaking?
A leaking diesel pump is not good as in: expensive to replace.
Does the engine run smoothly when it is warm?
Excessive starting is not good and after starting for a minute the
starter should be allowed to cool down. The buzz from the starter is the
starter relais shutting the starter down. The relais can be cleaned or
fixed to solve that problem.
I wouldn't recommend driving short trips around town, however
pleasureable: cold starts are not good for the engine and after 2
minutes your engine isn't warm yet. I use my 1980 200d also
intermittently, but I have no problem getting it started. It should be
no problem for a diesel.
Your turbocharger uses oil from the engine, so if it is bleeding, check
the oil level more regularly and get it fixed, probably some leaking
Hope this helps.
Perhaps MB didn't fit the US version with this knob, but it is located
on the dashboard, behind the steering wheel, on the left. If you turn
it, it produces the same effect as pressing the throttle a little bit.
My (German) manual says to turn this knob fully to the left before a
In another post it was suggested it was bio diesel that damaged the
rubber fuel hoses. That can happen.
Where are you located? What sort of temperatures are you coping with?
Have the glow plugs checked. But even more important, see to it that your
battery is fully charged and has enough capacity to crank the engine at high
speed for as long as it takes to start. Our cold weather (New York City)
failures have always been the result of not enough juice in the battery.
Indeed, when we know it's going to be very cold -- less than 10 F -- we take
the battery out of the car (which is parked on the street) and bring it into
the apartment to keep it warm and charge it fully. We also have a back up
booster pack, which is what the road service guy uses.
1981 300SD "Der Klunker"
I'm in NC. The coldest we've been dealing with is in the 20's overnight,
30's-40's during the day.
Would it work to put a heating pad around the battery a few hours before
starting? I'm guessing this would be totally insufficient for warming the
engine . . any idea how to troubleshoot a non-working block heater?
The starter is crying for power. Charge the battery, either with a
charger or a one hour drive.
When were the engine's valves (intake and exhaust) last adjusted?
(Unadjusted valves leak and that means lower compression and harder
starting of this compression engine.)
Does the glow plug light: Light prior to starting? Blink after starting?
Don't depress the accelerator when starting.
The car can stand for any period with a fully charged battery; it
doesn't need to be driven.
The current use is about the worst you can do to it, IMHO. Either drive
it or store it.
The fuel leaks are not the problem, they just make the car reek like a
If it won't crank over easily something between the battery and starter
is screwed up. You said it was a new battery. Is the battery being
charged? If you only take a very short trip once or twice a week, that
could be the problem. It takes a good deal of energy to start the car
and a short trip of a couple miles will not recharge it. I'd put a
charger on it, make sure it's fully charged then see what happens. It
should crank over easily, as long as we're not talking extreme, sub
zero weather. Other possibilites are corroded cable/terminals from
the battery to the starter or a bad starter. If you have some bad glow
plugs, that could make it more difficult or impossible to start, but it
should still crank easily.
The short trips you asked about are definitely not good for the car.
When you don't allow the engine to reach full temp and run for long
enough, water vapor condenses everywhere from the crankcase to the
exhaust system. If you drive it till it's hot and then run it for
awhile, the water vapor gets driven off. Left inside, it does nasty
city, eh? Let's see if I can convince my husband of that reasoning . .
The battery is new but it sounds like it just isn't being charged enough.
When the battery was replaced the car began to turn over much more quickly
than before, so I assume that the old battery was in fact shagged out. It
still turns over quickly but the cranking can go on for 10-30 seconds before
the engine really catches (or it stops turning over and buzzes). Take some
long drives, replace the glow plugs, and check out the connections between
battery and starter?
I guess I'll have to take a road trip! The most the car is driven is about
30 minutes, wait a couple of hours and then 30 minutes back. Sounds like I
need to drive more!
I purchased the car in July. I know it had a service the previous March but
I don't know if they adjusted the valves. Can I have this done at an
average mechanic's shop or do I need to find a MB specialist?
Glow plug light lights for about 10-15 seconds. The mechanic said he
noticed that after the light goes off, the plugs are still charging for an
additional 10 seconds so I wait through that period until cycling again.
under 30 degrees, if I remember correctly.
that it leaks, I'm hesitant to use bio till I get current leaks fixed!
Thanks for your help,
After reading the various posts I'd say just drive it more. If that
doesn't help have the alternator's output checked. If weak, its diodes
(only) can be replaced for not too much $.
The glow plugs seem to work as designed so that's good.
The block heater is located on the passenger side of the engine, below
the exhaust and ahead of the starter. If it can't be easily repaired I'd
say forget about it for removing it after 20 years may be impossible. If
you can't frequently drive the car to keep the battery charged, buy a
modern (electronic) charger that will keep the battery fully charged.
Then a block heater is moot.
Using Biodiesel is a nice thought but 100% Bio (Bio100) dissolves all
the old deposits in the fuel system and, now we learn, causes leaks in
the old fuel hoses too! Bio20 is supposed not to do these things.
The leaks won't fix themselves. Suggest you replace all the "bleed off
hoses" with new fabric covered "bleed off hose" and replace the hand
primer pump as its rubber seal is gone. Pump costs about $20 on line,
bleed off hose about $15 per meter (you cut to length) on line. Just cut
off the old hose using a utility knife, one segment at a time, cut new
to that length and push onto the barbed fittings. Stub hose at #5
injector contains a small steel plug that should go into a new stub
hose. You can do this, wear gloves so you don't smell of diesel.
Yes the manual suggests stepping on the accelerator when cranking a cold
engine. The contrary thought is that the cold fuel quenches the hot glow
plug and so makes ignition harder. I, myself, don't step on it and my 25
year old engine fires immediately.
Hannah, there are no shortcuts to these cars. Parts and maintenance
sometimes seem horribly expensive BUT afterward the car performs
reliably, as it should. Cheap fixes almost always come back to bite one
- these are false economy.
replace the entire fuel system) but I will try to be more conscientious of
using a blend rather than b100. I don't intend to shortchange this car on
maintenance - I'm just trying to be more informed about what's going on. I
don't want to simply send it off to the mechanic for mysterious repairs. If
there is work I can do myself I'd like to do that, and I want to know why
the car needs what it needs. I took the car for a long drive today so
hopefully that will help with the battery/starter issues. I'm sure I'll be
back with more questions!!
Thanks so much,
Dec 28, 11:30 pm show options
P.S. Fix the bleed off lines - most leaks are from them"
Here's an interesting observation I made regarding these lines. I had
the original fabric covered type that start weeping a few years after
being put on. I knew they were weeping a bit, but wasn't in any hurry
to replace them, as they did not appear to be leaking much at all.
Occasionally I would smell a whiff of diesel when near the car, but
that was about it. No, spots on the garage floor or evidence of any
significant leakage. I assumed the tiny leak didn't amount to much at
Then one day I decided to check my mileage. It had dropped to 20-21
MPG. At first I thought maybe this was a one time thing, but I checked
it for several tanks and it was the same. I replaced the lines and
voila!, back to 25MPG. So, this leak that looks very small can in fact
have a significant effect on mileage. I would think most of the fuel
must vaporize on the engine and disappear, so a lot more is leaking
than you might think.
I replaced mine with the plastic type fuel line. They have been on for
about 4 years now, with no sign of any weeping.
Fuel injectors are made in two halves that screw together. They
sometimes develop seepage at the joint. The repair is very simple,
loosen, don't remove, the high pressure line to the top center then put
a wrench onto the top half of the injector nozzle and tighten it - you
may not even sense movement. Then snug the high pressure line - snug
means only tight enough not to leak, too much and it WILL leak. Like a
firm handshake, no more.
Driving the car for 30 mins a trip should be enough to recharge the
battery, if it starts normally. But if you're having trouble starting
it, then cranking for an extended period may draw more power from the
battery than can be replaced by a 30 min drive. It also depends if
you're driving at night with the headlights on and a 300Watt stereo
In any case, there is apparently an ongoing problem with the car
starting readily. I'd charge the battery fully and see what happens.
If it doesn't crank easily and start readily in NC this time of year,
where a block heater should not be needed, something is wrong. I'd
take it to a good shop with experience with MB diesels. Whatever it is
will have to be addressed one way of the other before long. And it's
better to figure it out than burn a starter out or get stuck with a tow
We had a situation recently where we had to call road service. It was a
rainy day and we were doing a lot of stop and start shopping with
lights, wipers and radio. Started every time except the last one after I
sat in the car with the radio on, the wipers on a bit and the engine not
running. Turned the key. Nothing. The booster was home. Road service
started it at once. I had the mechanic check the battery and it's fine.
It just wasn't getting charged that day. These are not very big
batteries. Diesels take a lot of juice to start. A weak or not fully
charged battery won't have enough oomph on a cold day. Just to contrast,
the car battery weighs about 25 pounds. Almost the same size battery on
the boat weighs 52 pounds. That's the engine starting battery. The house
batteries are two weighing 165 pounbds each.
1981 300SD "Der Klunker"
PS. Spend the money to keep that car ruunning. There is no better.
I intend to keep this car on the road - it's wonderful!! I'm just trying to
learn more about how it works and what the issues are so I can be informed
rather than just signing checks to the mechanic.
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