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  #1  
Old 04-14-2012, 05:48 AM
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Pre-glow cycle spin-over

If my car has been sitting for a while, sometimes I like to turn my engine over for a couple seconds before the glow plugs get a chance to heat up (turns over, but won't start), Then I let the glow plugs do a full cycle and start it. Seems to help the oil pressure build a little quicker when the engine begins to run. I know it's more work for the battery, glow plug system, and starter- but does doing this reduce any engine wear (at startup)?
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Old 04-14-2012, 06:30 AM
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I do that sometimes when the car has not been started for a week or more. I have replaced the o-rings on the shaft that goes through the oil filter. The oil pressure came up quicker for a while. Seems like all too soon the delayed oil pressure problem returned.\

I'd say if we bought an ample supply of those o-rings and changed them with each oil change our delayed oil pressure would cease.

Does anyone know if the nitrate o-rings sold by Harbor Freight are suitable for this application?
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Old 04-14-2012, 12:04 PM
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There is a purple/Voilet wire that goes from the Glow Plug Relay to your Starting Circuit. So, your Glow Plugs are actually on during cranking.
One of the reasons that Starting Fluid should not be used as the Glow Plugs will ignite it early on.

On the Turbo Models you can see a White and Purple wire on the Terminal box. The White Wire comes up from the Starter Solenoid and gets Voltage when the Engine is Cranking; that gives the Purple Wire Voltage and activates your Glow Plug Relay.
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Old 04-14-2012, 12:25 PM
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Pre-start

Quote:
Originally Posted by sgnimj96 View Post
If my car has been sitting for a while, sometimes I like to turn my engine over for a couple seconds before the glow plugs get a chance to heat up (turns over, but won't start), Then I let the glow plugs do a full cycle and start it. Seems to help the oil pressure build a little quicker when the engine begins to run. I know it's more work for the battery, glow plug system, and starter- but does doing this reduce any engine wear (at startup)?
So long as you do not rev the engine significantly above idle when first started, there should be no significant wear on the engine in the few seconds before the oil pressure comes up. Even though the oil drains to the pan and other low spots when the engine is stopped, there is still a film of oil adhering to the internal surfaces. This film is enough to provide lubrication for a couple of seconds.

I've read (don't know if it's true) that very large engines have starting systems that bring the oil pressure up before the engine starts. This may be related to the difficulty and expense of overhauling these large engines. Since Mercedes diesel engines last hundreds of thousands of miles without such systems, they must not be necessary.

We would be better off spending our time and dollars keeping the oil in our engines clean through frequent oil and filter changes. Although much less exciting than special starting systems, oil changes are the single most effective way to promote engine longevity.

Jeremy
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Old 04-14-2012, 01:17 PM
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Quote:
Originally Posted by Clemson88 View Post
I do that sometimes when the car has not been started for a week or more. I have replaced the o-rings on the shaft that goes through the oil filter. The oil pressure came up quicker for a while. Seems like all too soon the delayed oil pressure problem returned.\

I'd say if we bought an ample supply of those o-rings and changed them with each oil change our delayed oil pressure would cease.

Does anyone know if the nitrate o-rings sold by Harbor Freight are suitable for this application?

I didn't replace the little o-rings at last oil change and there is a little more delay in oil pressure at startup. I think your right, change 'em every time. There really should be a filter that includes those o-rings. ?
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Old 04-14-2012, 01:20 PM
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Quote:
Originally Posted by Diesel911 View Post
There is a purple/Voilet wire that goes from the Glow Plug Relay to your Starting Circuit. So, your Glow Plugs are actually on during cranking.
One of the reasons that Starting Fluid should not be used as the Glow Plugs will ignite it early on.

On the Turbo Models you can see a White and Purple wire on the Terminal box. The White Wire comes up from the Starter Solenoid and gets Voltage when the Engine is Cranking; that gives the Purple Wire Voltage and activates your Glow Plug Relay.
Are you sure about that (glow plugs on while cranking)? Logically, one would think that Mercedes, by using good design practice, would put a relay in the circuit to cut power to the glow plugs while crranking in order to deliver full power to the starter. I can't do a test on my car since I've modified my glow plug relay to manual operation. Could you run a test on yours (provided it has not been messed with) and report back?
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Old 04-14-2012, 03:10 PM
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Quote:
Originally Posted by funola View Post
Are you sure about that (glow plugs on while cranking)? Logically, one would think that Mercedes, by using good design practice, would put a relay in the circuit to cut power to the glow plugs while crranking in order to deliver full power to the starter. I can't do a test on my car since I've modified my glow plug relay to manual operation. Could you run a test on yours (provided it has not been messed with) and report back?
Actually what Mercedes did is sort of idiot proof the system for the Person who forgets to preglow. By having the Glow Plugs on during Starting you increase the chance of the Engine starting, starting faster and not dumping raw Fuel down on top of the Piston.

You can verify it for yourself by looking up the Wiring Diagram or if you have a Turbo Diesel; or,
locate the Junction/Terminal Box in front of the Battery. On the Rigt side of the Pic is a White Wire (that comes up from the starter Solenoid) and the Purple/Voilet wire under it.

Remove the Screw there and touch the Purple/Voilet Wire to any of the 2 Terminals to the left (they have + voltage) and you will here your Glow Plug Relay click on.

You will also note the Purple/Violet Wire at the Glow Plug Relay connection.

Also note that this is the same place a Remote Starter Switch can be hooked up to (the yellow arrows).

On other non-turbo Diesel 123 models the Purple/Violet Wire is connected at the Starter Solenoid.
Attached Thumbnails
Pre-glow cycle spin-over-ab-wire-junction-bloc-123-qqq.jpg  
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Old 04-14-2012, 03:36 PM
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Originally Posted by Jeremy5848 View Post
So long as you do not rev the engine significantly above idle when first started, there should be no significant wear on the engine in the few seconds before the oil pressure comes up. Even though the oil drains to the pan and other low spots when the engine is stopped, there is still a film of oil adhering to the internal surfaces. This film is enough to provide lubrication for a couple of seconds.

I've read (don't know if it's true) that very large engines have starting systems that bring the oil pressure up before the engine starts. This may be related to the difficulty and expense of overhauling these large engines. Since Mercedes diesel engines last hundreds of thousands of miles without such systems, they must not be necessary.

We would be better off spending our time and dollars keeping the oil in our engines clean through frequent oil and filter changes. Although much less exciting than special starting systems, oil changes are the single most effective way to promote engine longevity.

Jeremy
Search = When does the most engine wear occur?
Comment from one article I found: "This is an important attribute since most of the engine wear occurs during the start-up, primarily due to lubricant starvation."
Chapter 5: Combustion Engine Lubricants

The longer a Engine sits not being used the more time the Oil has to drain out of the Bearings and create that "Lubricant Starvation" the article mentions.
You notice that UPS and the like delivery Vehicles leave the Engines running. That reduces Engine wear from starting and also wear on the Starter.
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Old 04-14-2012, 04:13 PM
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Quote:
Originally Posted by Diesel911 View Post
.........

You can verify it for yourself by looking up the Wiring Diagram or if you have a Turbo Diesel; or,
locate the Junction/Terminal Box in front of the Battery. On the Rigt side of the Pic is a White Wire (that comes up from the starter Solenoid) and the Purple/Voilet wire under it.

Remove the Screw there and touch the Purple/Voilet Wire to any of the 2 Terminals to the left (they have + voltage) and you will here your Glow Plug Relay click on.

You will also note the Purple/Violet Wire at the Glow Plug Relay connection.

Also note that this is the same place a Remote Starter Switch can be hooked up to (the yellow arrows).

On other non-turbo Diesel 123 models the Purple/Violet Wire is connected at the Starter Solenoid.
I thought I already explained that my glow plug relay has been modified and I cannot do a proper test and that is why I asked if you can do a test.

Looking at a wiring diagram tells you nothing as to how the glow plug relay operates in regards to the purple wire.
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  #10  
Old 04-14-2012, 08:35 PM
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Quote:
Originally Posted by funola View Post
I thought I already explained that my glow plug relay has been modified and I cannot do a proper test and that is why I asked if you can do a test.

Looking at a wiring diagram tells you nothing as to how the glow plug relay operates in regards to the purple wire.
You ask if I could run the test mine (Turboed). I had already done that A long time ago just as I had explained it.
Seeing the Wiring diagram is what made me wan to test it.
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Old 04-14-2012, 09:04 PM
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You're spending more on new ignition tumbler/switch, starter, battery, and glow plugs than you will save by reducing any engine wear. If you use a good synthetic oil it will stick to metal parts in the engine and protect them better during long sits between starts.
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  #12  
Old 04-14-2012, 09:06 PM
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Quote:
Originally Posted by funola View Post
Are you sure about that (glow plugs on while cranking)?
Perfectly sure.

Tested and confirmed by several members on here.
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  #13  
Old 04-14-2012, 11:35 PM
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Quote:
Originally Posted by funola View Post
Are you sure about that (glow plugs on while cranking)? Logically, one would think that Mercedes, by using good design practice, would put a relay in the circuit to cut power to the glow plugs while crranking in order to deliver full power to the starter.
One would think that Mercedes, using good design practice, would incorporate a battery perfectly capable of powering the entire start system, which includes the starter and glow plugs.

Quote:
Originally Posted by funola View Post

Looking at a wiring diagram tells you nothing as to how the glow plug relay operates in regards to the purple wire.
The purple wire is hot in the "start" position. The wire goes "cold" when the key is released from the "start" position; that signals "start complete" to the timer, which terminates the glow cycle. In the absence of the hot/cold sequence, the timer "times out" as if no start was attempted. (Not applicable to afterglow systems.)
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Old 04-17-2012, 02:58 AM
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On mine the the glow light goes out as soon as the key goes to START position. I assume the glow plugs are instantly bypassed because the engine just spins over without starting, if I do it quickly.
A remote starter would be a much better way to go- A good remote starter is always really cool,
Great Info! Thanks
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  #15  
Old 04-17-2012, 09:34 AM
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Quote:
Originally Posted by sgnimj96 View Post
I assume the glow plugs are instantly bypassed because the engine just spins over without starting
That would be an incorrect assumption.

The glow plugs are energized during "start".

If you wait sufficient time in "start", the plugs will build sufficient heat to enable combustion.
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