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-   -   Don't always trust your glow plug indicator light! (http://www.peachparts.com/shopforum/diesel-discussion/138347-dont-always-trust-your-glow-plug-indicator-light.html)

Hatterasguy 11-26-2005 05:54 PM

Don't always trust your glow plug indicator light!
 
I have been having trouble getting the SD started in the morning over the last couple of days. Yesterday I noticed the glow plug light wasn't coming on all the time and decided to replace them. This morning the car wouldn't start so my dad gave me a ride to work and told me he would look at it.

Well even though with a meter all the glow plugs tested ok he found something very interesting. When you stick a good glow plug on a battery the tip will glow red in a couple of seconds. Well he stuck all 5 of the old glow plugs on a battery and only ONE glowed red. The other 4 only got a little warm.

So the light was coming on when only one glow plug was actually glowing!:eek:

The point is if you are having trouble starting just spin a new set of glow plugs in. Now the car starts without much trouble. The $50 that a new set cost was worth every penny, I need the car to start.

Brandon314159 11-26-2005 06:48 PM

Quote:

Originally Posted by Hatterasguy
So the light was coming on when only one glow plug was actually glowing!:eek:

Well the light became "sporadic" and didn't come on every time...

After all its measuring a current drop...so that one glow plug SOMETIMES will drop a lot more (cold) than when it is hot.

When the 617 gets down to one glow plug...its hard to start. And yes, the light stops working at that point...or atleast starts not ALWAYS coming on :)

KDHBenz 11-26-2005 07:39 PM

Glowplug/Light
 
Quote:

Originally Posted by Brandon314159
When the 617 gets down to one glow plug...its hard to start. And yes, the light stops working at that point...or at least starts not ALWAYS coming on :)

My light quit working altogether, but the car started fine. As it turned out, my #1 glowplug was bad...very easy to check. I replaced it with a new one (crappy Autolite for now until my new set of Bosch arrive) and everything is cool...:cool:

Lifted from MB Service Manual doc 15-705,
click here or on image for complete PDF file:
http://ken.kdharris.net/kdhbenz/glow...ug-failure.jpg

omegabenz 12-01-2005 01:39 AM

Did you ream the holes when you put the new ones in?

Any special tools required?

KDHBenz 12-01-2005 02:14 AM

I didn't ream the holes as they were pretty clean...

omegabenz 12-01-2005 03:09 AM

Would you recommend doing so?

Hatterasguy 12-01-2005 11:40 AM

I didn't ream the holes and never have. On a 606 I would, but not on the older engines. Carbon really shouldn't be a problem on these unless you idle them around a lot.

sailor15015 12-01-2005 11:45 AM

They make a special reamer that will fit on a socket wrench but if I remember correctly its a tad expensive. I read on here that a drill bit of the same size works and thats what I did. Crank it for a second or two to blast that carbon out of the prechamber. I probably won't do it the next time I need plugs done. I only did it this time because it was my first change and not a lot of carbon came out.

300dster 09-28-2008 12:27 AM

Glow plug light out then instrument panel light now it wont start
 
A couple of months ago I put in a new battery then a few weeks later the glow plug indicator stopped coming on but it continued to start. Roughly a month later I hit the horn and it sounded like my '62 bug, whimpy. Then I lost my instrument panel lights but it continued to start for about a week. Now it wont start. I need help, any suggestions?

ForcedInduction 09-28-2008 12:44 AM

Your alternator or voltage regulator has failed. Search the forum for those topics.

I must ask, why did you continue to drive it knowing it had a significant electrical problem?

argus445 09-28-2008 12:44 AM

Quote:

Originally Posted by Hatterasguy (Post 1024688)
I have been having trouble getting the SD started in the morning over the last couple of days. Yesterday I noticed the glow plug light wasn't coming on all the time and decided to replace them. This morning the car wouldn't start so my dad gave me a ride to work and told me he would look at it.

Well even though with a meter all the glow plugs tested ok he found something very interesting. When you stick a good glow plug on a battery the tip will glow red in a couple of seconds. Well he stuck all 5 of the old glow plugs on a battery and only ONE glowed red. The other 4 only got a little warm.

So the light was coming on when only one glow plug was actually glowing!:eek:

The point is if you are having trouble starting just spin a new set of glow plugs in. Now the car starts without much trouble. The $50 that a new set cost was worth every penny, I need the car to start.

Wow i'm suprized i figured even if 1 was down it wouldn't start on a 4 cylinder vw engine u can tell right off it thumps like crazy the 5 and 6 cylinders smooths out the rough cylinders they're a bit tricker to tell.

chetwesley 09-28-2008 02:28 AM

I use a battery charger to test the plugs to see if they glow. I never knew about using a voltage meter, so I figured the best way to test them was to pop them out the hook up a charger to them to see if they glow.

freeride 12-18-2008 08:29 AM

My 300SD does not light the glow plugs indicator, does it mean I should change glow plugs because I am down to one?

It starts fine but now at around 12-15F it got harder indeed, few more cranks and rough few seconds after starts, then like a dream

http://www.peachparts.com/shopforum/vbpgimage.php?do=full&p=3664&d=1229373678


BTW, BOSCH or BERU?

kerry 12-18-2008 10:02 AM

Check your fuse in the relay and make sure the plugs are getting 12 volts when in the glow position before changing plugs, but it probably means the plugs are bad.

bgkast 12-18-2008 01:32 PM

The light in my SD was taking a second or two to light up after I turned the key to the pre-glow position. I checked my plugs and had one out, now that I have replaced the plug it lights up immediately.


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