Under 10 volts at glowplugs - Page 2 - PeachParts Mercedes-Benz Forum

Zacharias · #16 02-10-2013, 08:34 PM

Quote:

Originally Posted by vstech

what brand plugs did you use?

Bosch

vstech · #17 02-10-2013, 11:11 PM

the problem with cold climate 617's and glow plugs is this...
idling.
limited driving at full operating temp.
under REALLY cold conditions, the engine NEVER gets up to full operating temp...
all this leads to carbon buildup in the PC...
reaming the holes, gives the plugs room to heat the AIR in the PC... without it, you have heat soaking directly into the head... little heats the air, making it hard to start the car.

ream the holes.

Brian Carlton · #18 02-11-2013, 12:26 AM

Quote:

Originally Posted by Zacharias

The plugs were new in October. At this point I have no problem replacing them -- need to change one anyway -- but I would like a solid reason for doing all five rather than thinking that I am throwing parts at the issue (I will have to have a shop do it, I am working outside).

I am leaning more toward the battery as a starting point as the relay shouldn't be showing under 12v, as far as I know.

Now it's becoming ridiculous.

Both Kerry and I have told you, on two different threads, to change the one bad glowplug and see what it does.

You refuse to do that and come back on here with another irrelevant question and now want to replace the battery.

You know the definition of insanity............right???

Zacharias · #19 02-11-2013, 08:46 AM

Gee, Brian? I REFUSE? Really?

Shall we have you screen posts for what is "irrelevant" on this board? If we use your standard, it will be very quiet around here.

To start, I was advised to replace the battery on the earlier threads.

Yes, you and Kerry told me to change the plug. And I could understand your attitude if I was posting a "OH MY GOD MY CAR WON'T START AGAIN" thread. I was not, though apparently that is how you chose to read it.

I started this thread because I mistakenly thought I should be seeing 10v+ at the plugs, which led me to believe I had found new info on the issue. We ended up rehashing some of the earlier info because I had to answer others' input.

Would you like to know WHY I haven't moved on the advice? We are just coming out of a cold snap of around -20 C + wind chills most of the time, for two weeks here. Last weekend the days were colder than that.

I work outside, no garage. No way work is happening at that temp. I have arthritis. Standing still, bent over a motor, for even 20 minutes isn't an option unless I want to spend a day or two immobile in bed after.

From the start of the cold snap, the weather services kept predicting one or two days of cold... then warming. Then one more day. Then two more days. Initially I didn't expect the bad weather to remain as long as it did.

My wrench is in Florida for two weeks to placate his wifey, who hates the Canadian climate. Back today, I believe.

If I call one of the local euro shops for a job this small, I will probably get booked in... in about 3 weeks. All having gone upmarket, they consider anything that produces an invoice under $300 too small to open the bay door. They would be happy if people like me with these old cars just went away.

Brian Carlton · #20 02-11-2013, 09:23 AM

Quote:

Originally Posted by Zacharias

Gee, Brian? I REFUSE? Really?

Shall we have you screen posts for what is "irrelevant" on this board? If we use your standard, it will be very quiet around here.

Would you like to know WHY I haven't moved on the advice? We are just coming out of a cold snap of around -20 C + wind chills most of the time, for two weeks here. Last weekend the days were colder than that.

I work outside, no garage. No way work is happening at that temp. I have arthritis. Standing still, bent over a motor, for even 20 minutes isn't an option unless I want to spend a day or two immobile in bed after.

From the start of the cold snap, the weather services kept predicting one or two days of cold... then warming. Then one more day. Then two more days. Initially I didn't expect the bad weather to remain as long as it did.

It would be very quiet around here. Because most of the advice you receive is, unfortunately, FACTUALLY INCORRECT and not based upon the data presented. What you typically get is someone who cured a different problem, with different symptoms giving you THEIR SOLUTION. Useless.

One of the best individuals on the board with regard to an accurate diagnosis, Tangofox, left the board .

I know all about cold and the inability to work in it. I've got a Dodge van that is now 60 days on a tuneup that I cannot get done due to my knees and my back. But, if it were me, I would take the path of least possible resistance and I would get that single glow plug changed. I might struggle to do it, but I would get it done and see if it improved my situation until warmer weather arrives.

But, that's just me.

You might prefer to spend hundreds of dollars with a mechanic to replace all kinds of things that don't need replacement (you do know how mechanics function..........correct?).

Or you can come on the board and post multiple threads to get hundreds of responses, most of which won't apply to you.

Your choice.

Graham · #21 02-11-2013, 11:15 AM

Quote:

Originally Posted by Zacharias

The plugs were new in October. At this point I have no problem replacing them -- need to change one anyway -- but I would like a solid reason for doing all five rather than thinking that I am throwing parts at the issue (I will have to have a shop do it, I am working outside).

I am leaning more toward the battery as a starting point as the relay shouldn't be showing under 12v, as far as I know.

Hi Zach,
Some of the replies are from owners in warmer climes! In Canada, if I leave my 300D outdoors overnight in winter, it is always hard to start below a certain temperature even with the block heater on. Batteries don't like the cold weather either!

I used to use my 300D as my daily driver. I kept it in an unheated garage overnight usually without block heater. It would sit outdoors at work for 8 hours during the day without a block heater in all Canadian winter conditions. I only once had to call for help!

You have done most of what is needed:
- valves properly adjusted (and good compression)
- New glow plugs
- block heater (make sure it is working!)

I would first jump from a battery on one of your other cars. That should ensure full voltage. If that solves problem, a new battery will no doubt be needed. Nothing like a good battery in a 300D!

I made my own reamer but didn't find much build up. But reaming wouldn't do any harm if you are going to pull the injectors. I wouldn't if they test out - It's a bit of a pain getting by those injector tubes!

If one new glow plug is bad - I would wonder why? Perhaps just a bad connection at plug or at relay? Have you cleaned relay contacts and checked connections? (I have not read complete thread)

Again haven't read complete thread, but some cheap aftermarket glow plugs are apparently prone to failure even when new.

I have not tried this solution, but it looks interesting:
TinyURL.com - shorten that long URL into a tiny URL

Diesel911 · #22 02-11-2013, 11:19 AM

Quote:

Originally Posted by vstech

the problem with cold climate 617's and glow plugs is this...
idling.
limited driving at full operating temp.
under REALLY cold conditions, the engine NEVER gets up to full operating temp...
all this leads to carbon buildup in the PC...
reaming the holes, gives the plugs room to heat the AIR in the PC... without it, you have heat soaking directly into the head... little heats the air, making it hard to start the car.

ream the holes.

X2 on the explination.

In the pic you can see most of the tip of the Glow Plug is well exposed to the Air. While the Tip is supposed to get the hottest the rest of the top also gets hot. However, if Carbon fills up the space between the Head and the most of the tip a good deal of heat will be conducted into the Head making the Tip Cooler.

Another bad effect is that a the cooler the Glow Plug is the more amperage it pulls and for a longer time.

When I tested a single Glow Plug with an Amp Meter connected to it the Meter when up to 60 amps (as high as the Meter would go) and as it got hot settled down to a about 16 amps.

So the Carbon causes heat to be conducted into the Cylinder Head at the same time keeping the Plug Tip cooler and causing it to draw higher amperage from you Batter for a longer period; sapping your Battery faster.

ah-kay · #23 02-11-2013, 11:21 AM

Let me summarize

1) No one is always right
2) OP can do whatever he likes, it is his money
3) OP can post whatever he likes. Keep this forum entertaining.
4) Tango can take a walk for all I care
5) Opinion offered here is only an opinion, some are valid some are not so. Readers use them at their own peril. That is the way I read my responses.

I have not follow the threads closely but I doubt it is the battery. But changing the battery does no harm. If it were me, I would measure the GP resistance and weed out the bad one.

vstech · #24 02-11-2013, 11:34 AM

Quote:

Originally Posted by ah-kay

Let me summarize

1) No one is always right

nuh uh! I'm always right!
2) OP can do whatever he likes, it is his money
3) OP can post whatever he likes. Keep this forum entertaining.

4) Tango can take a walk for all I care ...
5) Opinion offered here is only an opinion, some are valid some are not so. Readers use them at their own peril. That is the way I read my responses.

I have not follow the threads closely but I doubt it is the battery. But changing the battery does no harm. If it were me, I would measure the GP resistance and weed out the bad one.

!!

kerry · #25 02-11-2013, 12:23 PM

You know how to change the glowplug. Find a local healthy young adult and ask that person to swap out your glowplug for $50. You supervise.

whunter · #26 02-11-2013, 12:33 PM

Quote:

Originally Posted by Zacharias

I have had cold start issues for a while, in this thread: Persistent cold start problem - now below -11 C / 12 F

Today I did some checking and rechecking:

1. Redid OHM test with block heater inactive. Four plugs now measure .5-.6, the one that previously gave huge OHM reading now gives infinity.

2. Have power to top right pin in small connector at relay with ignition on.

3. When relay active I have 11.98 volts at all five male pins in relay.

4. HOWEVER, only have 9.75 volts at glowplugs when relay is activated. (I had previously used a test light on the GPs, today I used the multimeter.)

What am I seeing here?

You have one open circuit (bad) glow plug.

Best guess on the voltage issue:
* Weak battery.
* Bad grounds causing resistance voltage drop.
* Damaged glow plug harness.

.

jay_bob · #27 02-11-2013, 01:38 PM

I agree with Whunter, the battery is breaking down under load or you have a bad connection.

Zach, are you measuring the output voltage at the GP relay with the harness plug in place or removed?

I assume you are measuring the voltage with the plug out, therefore you are getting the system voltage with little to no load. Although I would like to see something north of 12 V in this case. 11.99 to me looks like the beginnings of weak battery syndrome.

When you apply the huge load to the battery when hitting the GPs, you will pull down the system voltage. This is because you have internal resistance in the battery. You are setting up a voltage divider between the voltage drop across the internal resistance of the battery and the resistance of the GP system.

A little definition - a "cell" is a single element that produces voltage by chemistry. A "Battery" is a group of cells. An AA is a cell. A 9-V or the big black thing under your hood is a battery. The cell voltage is dependent on the chemistry, I forget what's in an AA but an everyday alkaline one makes 1.5 V, while a NiCd rechargeable makes 1.2 V. The lead-acid cell makes 2 V.

I'm sure you would accept that you cannot take 8 AA's (even though that makes 12 V) and try to start the car. This is because the internal resistance of a AA is much higher than a lead acid cell. All the voltage gets dropped across the internal resistance of the cells and that leaves none to start the car. (Don't actually try this, the AA's will see the load as a dead short and this will probably cause them to explode...)

A car battery is not a single cell, it is six 2-V cells connected in series. A common failure mode for a car battery is that one of the cells fails but the others are still healthy. If one of those cells has failed it brings down the entire battery, since the sum of the cell internal resistance is the total internal resistance of the battery. It is conceivable that you could still have dome lights, or the radio works, or the clock keeps time, because the current draw is low and not enough to where the high internal resistance becomes a factor. But when you hit the battery with a high load you cannot overcome that high internal resistance and the voltage collapses.

The first thing I would try would be to pull the battery and take it to a chain parts store, and have them put a load tester on it.

If that is not feasible for you to get to the store, or your battery checks out okay, try the following, you will need a helper. Be sure both the glow harnesses are plugged in at the relay.

Take your voltmeter and set it to dc volts. (I don't know your level of familiarity with a meter, so forgive me if I over explain things.)
Put the probes on the battery terminals, not the clamps, but the terminals themselves. This should be at least 12 V. Have the helper turn the key to preglow, quickly record the voltage then turn it off.
Have them turn on the headlights and the high beams, check the voltage, turn the lights back off.
If the voltage drops to 10 V at this point you probably have a weak battery and can rule out the rest of the system.

If you get closer to 12 V at the battery posts then let's go hunting for the weak connection. If your meter is inexpensive and has discrete ranges for the dc volts, put the meter on the 2 V scale first. If you get a reading near zero then step down to the 200 mV scale. If it is auto ranging (only one choice for DC volts) then be sure to pay attention to the display as the numbers may be Volts or MilliVolts (1 mV = 0.001 V). I am assuming you are using a digital meter that is auto polarity. If you have an old school analog meter you may have to swap the locations of the probes if the meter swings backwards.

Put one probe on the + terminal and the other on the + terminal clamp. Have the helper hit the glows quickly again, you should have nearly zero volts (looking for bad connection at + post of battery).
Do the same with the - terminal and - clamp (looking for bad connection at -).
Put one probe on the - terminal and the other on a clean spot on the block. Again hit the glows quickly, you should have near zero volts (looking for bad ground straps).
Put one probe on each screw of the glow fuse, hit the glows, should get near zero volts. This will probably be several tens to hundreds of mV, owing to the resistance of the fuse.
Put one probe on the + post of the battery, the other on one of the glow relay fuse screws, hit the glows, should be near zero (looking for bad main wire between battery-starter-glow relay).
Put one probe on the glow fuse screw, the other on the glow plug terminal nut, one at a time, hit the glows, should be near zero (looking for bad individual wire in GP harness from relay to plugs).

Good luck and stay warm, I won't tell you what the weather in SC is today...

Diesel911 · #28 02-11-2013, 02:30 PM

What would be the Voltage of a fully charged Battery with no Electrical load on it at minus 10 degrees F.

My though is if you aready start off with less Volts due to the Cold you are also going to get less Volts when you turn the Glow Plugs on.

Cold Glow Plugs also draw more amperaged till the get hot.
If you combine a minus 10 degree Glow Plug with Carbon that is going to conduct the heat away from the Precombustion Chamber keeping the Glow Plug colder longer you are going to drain you Battery much faster than you would during a nice warm day.

jay_bob · #29 02-11-2013, 02:43 PM

I agree with that theory too. You are correct about the amp draw being inverse to the element temperature. Excess carbon = excess heat transfer to the head = higher current than usual since temperature of the element does not climb as it should = toasted battery.

Ideally he should approach this from both fronts since either could be the cause. Although under his circumstances (weather, his stated physical limits) he might be able to rule out the electrical side easier than pulling out the plugs. If his root problem is the carbon, then changing the battery will only provide a short term fix due to the issue explained above.

jay_bob · #30 02-11-2013, 07:52 PM

I just did some checks on the 1987 300TD (OM603). FWIW, Granted I am at a 73 F ambient in my garage. Not heated, that's SC in the winter...

Car sitting for about 4 hrs so it was pretty much ambient temp.
Standing voltage at battery 12.69 V dc
Key in pre-glow position, voltage dropped to 11.65 V dc.

Just did a quick check, did not wait the full glow time.