As Bobby and Brian have said, the plugs will continue to get power for about 15-seconds after the light in the dash goes out. This is normal.
Your car originally came with series-wired plugs. This is indicated by heavy, flat "loop wires" with no insulation on them connecting from one plug to the next, the end of the circuit at the frontmost cylinder grounded to the head using a small, braided strap. In the dark, these heavy wires give off a faint, orange glow when the plugs are getting powered. Many of these cars have been converted to the parallel plugs over the years. These will have 16-ish guage, insulated wires going from the outside threaded connector tip of one plug to the next, with the ground wire disconnected or removed at the end of the circuit (these plugs are internally grounded). If this is what you have, and you are checking resistance without disconnecting the wire from each plug in turn so as to remove it from the circuit, you could be getting a false indication. Just one good plug out of five will give a low resistance reading for the entire circuit if all remain connected.
Resistance is about 2 to 5-ohms, depending on the sensitivity of the ohmmeter. In general, 0 ohms, or close to it, is good; infinite ohms are bad (open). I've yet to find any plug that was in-between (certainly possible, though), so, from what I've seen, it's one or the other.
Mark in Lakewood, CO
From: "rkitt2002" <rkitt@netscape.com>
To: "diesel mercedes" <diesel_mercedes@yahoogroups.com>
Sent: Sunday, September 18, 2011 10:47:00 AM
Subject: [diesel_mercedes] When do glow plugs go off?
Your car originally came with series-wired plugs. This is indicated by heavy, flat "loop wires" with no insulation on them connecting from one plug to the next, the end of the circuit at the frontmost cylinder grounded to the head using a small, braided strap. In the dark, these heavy wires give off a faint, orange glow when the plugs are getting powered. Many of these cars have been converted to the parallel plugs over the years. These will have 16-ish guage, insulated wires going from the outside threaded connector tip of one plug to the next, with the ground wire disconnected or removed at the end of the circuit (these plugs are internally grounded). If this is what you have, and you are checking resistance without disconnecting the wire from each plug in turn so as to remove it from the circuit, you could be getting a false indication. Just one good plug out of five will give a low resistance reading for the entire circuit if all remain connected.
Resistance is about 2 to 5-ohms, depending on the sensitivity of the ohmmeter. In general, 0 ohms, or close to it, is good; infinite ohms are bad (open). I've yet to find any plug that was in-between (certainly possible, though), so, from what I've seen, it's one or the other.
Mark in Lakewood, CO
From: "rkitt2002" <rkitt@netscape.com>
To: "diesel mercedes" <diesel_mercedes@yahoogroups.com>
Sent: Sunday, September 18, 2011 10:47:00 AM
Subject: [diesel_mercedes] When do glow plugs go off?
Hello All
In my 1978 300D the glow plugs are powered after the light goes off.
I think they are in parallel a circuit so they may be the faster plugs.
How long should they stay on?
If I am using my ohm meter correctly there are zero ohms resistance on the plugs. I will have a friend check the resistance. in case I am wrong.
Could the plugs staying on cause the plugs to burn out and have no resistance? (the car will not start)
Where is the glow plug relay? I looked at pictures on ebay but can not find it.
thank you
Rodger
__._,_.___
MARKETPLACE
.
__,_._,___
