Can't start 1979 300d in the cold - Page 2 - PeachParts Mercedes-Benz Forum

ElcapitanKyle · #16 12-30-2012, 10:26 PM

How would I test the voltage to the glow plugs? Would I test the connectors to the glow plugs?

barry12345 · #17 12-30-2012, 10:38 PM

If you have not checked the valves for the proper clearances do this first. For all of these engines the recomended frequency is once ever fifteen thousand miles.

Yet some may not even been touched for many multipals of that. This perhaps is a little understandable as some owners would not even be aware of the need or that mechanical adjustable valves even exist.

Mölyapina · #18 12-30-2012, 11:49 PM

...here is a link to Dieselgiant's valve-adjustment how-to (He does it on a non-turbo OM617, of all things!). It is extremely helpful, though I believe there is some disagreement over the use of the power steering pump bolt to turn the motor.

*EDIT* I added the link...

Mölyapina · #19 12-30-2012, 11:54 PM

Also, is there a reason that no-one has asked him about compression?

kerry · #20 12-31-2012, 12:04 AM

Quote:

Originally Posted by ElcapitanKyle

How would I test the voltage to the glow plugs? Would I test the connectors to the glow plugs?

It depends on whether you have loop plugs or pencil plugs. Which are they? Heavy squiggly bare wires joining them or a single insulated wire to each plug?

whunter · #21 12-31-2012, 02:36 AM

Quote:

Originally Posted by Jooseppi Luna

Also, is there a reason that no-one has asked him about compression?

It is impossible to get an accurate compression reading when the valves are out of adjustment.

.

whunter · #22 12-31-2012, 02:53 AM

Quote:

Originally Posted by Jooseppi Luna

...here is a link to Dieselgiant's valve-adjustment how-to (He does it on a non-turbo OM617, of all things!). It is extremely helpful, though I believe there is some disagreement over the use of the power steering pump bolt to turn the motor.

*EDIT* I added the link...

His procedure is flawed, many years ago we agreed to disagree.
If you are in a warm southern state there is little difference.

I follow the factory procedure, 35+ years experience working on these in the Michigan COLD weather has proven it works better at sub-zero (and lower) temperatures.

The cam lobe must be at this angle for correct adjustment.

Depending upon how much carbon has deposited on the valve face and seat, you may need to adjust the valves up to FIVE times in one day.

The exhaust valves always become tighter = holding the valve open = carbon deposited on the valve face and seat. Each adjustment allows the valve to close a little more + hammer more of the carbon off the valve face and seat.
If you desire more data on the subject, feel free to call me.

Valve adjustment OM615, 616, 617 FYI.

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whunter · #23 12-31-2012, 04:09 AM

Quote:

Originally Posted by ElcapitanKyle

I'm new to owning or working with diesels and Mercedes. I have a 1979 300d. The car will start fine if the temps of 50+ degrees. When it gets colder the engine seems to have a hard time cranking fast enough to get it to start. The only way I've been able to successfully start the car is by hooking up jumper cables from my Suburban and keeping it revved up to around 2k rpm while trying to start the Mercedes.

I have checked the glow plugs. They are new but I checked them still with an ohm meter. They all measured at or just over 1.0. The battery has been checked by two different parts shops (Napa and Autozone) and cycled through 3 different charges just to make sure it was fully charged. Had a mechanic walk through the whole system just to see if anything was obviously wrong. He checked the wiring and said that it all checked out fine.

At this point the mechanic is suggesting swapping out the starter. He doesn't have any specific test to suggest that it is bad. And I'm not sure how to test a starter. I'm looking for any advice on what else I might try to narrow down the issue. I'd love to be able to test a certain part and say for sure that it is bad/good before I just go paying for exploratory repairs.

Change the oil to 0W-40 synthetic.
Your cold start will be easier.

.

kerry · #24 12-31-2012, 09:39 AM

This could be a very simple problem especially if he has loop glow plugs. The first step is to figure what what plugs are there and if they are working. 45 degrees shouldn't require synthetic oils.
It would be very helpful if you posted pictures of the glowplugs and a video on youtube (linked here) of your attempts to start it. The video would immediately tell experienced people if the engine is turning over fast enough.

funola · #25 12-31-2012, 10:14 AM

He said it's pencil type. Does not sound like a glow plug problem at all to me.

vstech · #26 12-31-2012, 10:18 AM

Quote:

Originally Posted by ElcapitanKyle

How would I test the voltage to the glow plugs? Would I test the connectors to the glow plugs?

IF you still have metal lines connecting the plugs, you have loop plugs and checking for intact loops is simple. take a meter set it to volts, and standing at the front of the car, measure at the small braided wire and the outer tip of the glow plug.
if you have voltage there, your loops are intact. if the voltage is not to the last one, move the tip probe to the next tip. keep moving the tip probe towards the firewall until you find voltage.

if you have the updated glow plugs, or if you or someone has updated them with pencil plugs, you will have an insulated wire going to each glow plug. for these style glow plugs, you have to test resistance to ground on each plug to see if they are burned out or not, and if they test ok with resistance, they STILL could be bad... but it's better than not testing them.

kerry · #27 12-31-2012, 10:28 AM

Quote:

Originally Posted by funola

He said it's pencil type. Does not sound like a glow plug problem at all to me.

Sorry missed that.

It does sound like a bad glow plug in low temperatures problem to me. When the engine fails to start in the first few seconds, cold fuel is entering the cylinders, eventually making the engine harder to turn over hence the starter slows down. A single bad glow plug can cause this problem in cold weather in my experience.

If the engine does not start on the first attempt in cold weather, it becomes increasingly harder to start on subsequent attempts. In fact in my experience it becomes virtually impossible to start without a recharged battery, jump or warmer temperatures.
When starting in cold weather, the most reliable way to start a 617 is to plan on a single starting attempt. Keep the starter engaged until it's running on enough cylinders to fire on its own. If it's taking more than about five seconds to start the engine, don't count on any subsequent attempts being successful so keep that engine turning until it runs or the battery dies.

Brian Carlton · #28 12-31-2012, 10:31 AM

Quote:

Originally Posted by ElcapitanKyle

T
-Starting procedure is as follows: Cycle glow plugs twice. Try to start.

Can you please define what you consider a "cycle".

Is a "cycle" the time it takes for the glow plug light to go out?

Quote:

Originally Posted by ElcapitanKyle

-Not sure which type of motor oil is in the car. Sounds like time for a change to make sure I have the right stuff in there.

Of course, the average PO will use the cheapest oil available. This will hopefully be 15W40 diesel rated dino oil, but one cannot be sure. The PO might have used straight 40 weight oil.

These engines benefit by synthetic oil and you can go 5K between oil changes. The best value seems to be Rotella T-6 which is a group III synthetic and is usually available at Wal-Mart. It's a 5W-40 diesel rated oil that will greatly assist in starting in the cold. Much less costly than replacing the starter.

funola · #29 12-31-2012, 10:33 AM

Quote:

Originally Posted by ElcapitanKyle

To answer a few questions:

-The valves have not been adjusted lately as far as I know.
-I live in Utah. Temp yesterday was around 20 degrees F when I as trying to start.
-The sound file for the starter is helpful. My starter does not crank that fast when it is having problems. After I hook up jumper cables from my Suburban and keep it running at around 2k RPM I can eventually get the starter to crank faster which in turn leads to the car starting.
-Starting procedure is as follows: Cycle glow plugs twice. Try to start. If it fails, hook up a portable jump start booster. Cycle glow plugs twice then try to start. If that fails hook up to Suburban with jumper cables. Cycle glow plugs twice. Try to start. Usually have to repeat the Suburban step 4 or 5 times. Seems like it will crank faster if I wait for about 5 mins after hooking up to Suburban.
-Not sure which type of motor oil is in the car. Sounds like time for a change to make sure I have the right stuff in there.
-I have pencil plugs.

-What I'll try out next: Get the oil changes and make sure I'm using the oil suggested here in the forum. Also will make sure the batter terminals are cleaned and wiring to starter is good.

Anyone have a link to a good video about how to do a voltage drop test on a starter?

Thanks for all the advice!

Since your starter is spinning slower than desired, and boosting it for 5 min from your Subburban increases cranking rpm, you really should get the battery checked out better. Take it out, charge it up over night and bring it to Autozone for a load test.

With a good battery and no wiring problems, you should see not less than 11 volts at the glow plugs (make both the +/- DVM lead connections at the glow plug, no where else). If less than 11v, the battery or wiring is suspect.

edit:

Another quick test you can do is connect your DVM at the starter big terminal (not the one from the battery) and measure voltage while you crank. I think you should not see less than 10 V. If less than 10, battery or wiring is suspect.