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  #1  
Old 06-02-2014, 10:07 PM
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tilly is so hot her glow plugs wont turn off.

ok guys.
bad week for tilly.
fixed all the throttle linkage. super responsive gas pedal now.
but low and behold . the glow plugs wont release ..
im getting around 12v at the actual glow plug this is after minutes...
so they deff arent going off. preglow plug light wont turn off either obviously.
im getting .81v at the preglow time relay. that is having test leads on both end of the fuse. when i unplug the top socket on the relay and plug in my multi meter i get 12v.
so im deff getting juice to the relay.


when i plug in and unplug the glow plug relay i hear it click.

did i do all the tests correctly? is it the fuse or the relay...
im assuming it is bad to drive her with out the glow plugs turning off

1982 300d

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Last edited by minsk; 06-02-2014 at 10:30 PM.
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  #2  
Old 06-02-2014, 10:53 PM
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Originally Posted by minsk View Post
so they deff arent going off. preglow plug light wont turn off either obviously.
There is nothing "obvious" about that. The light is an artificial indication; it is not a direct indication of glow plug operation.

From all indications, your preglow timer has "lost its mind" and needs to be replaced.
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  #3  
Old 06-02-2014, 11:14 PM
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any brands i should stay away from..and is it reallly bad to drive if the glow plugs are not turning off
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  #4  
Old 06-02-2014, 11:24 PM
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Just bad for the plugs. And potentially for the charging ability of the alternator.
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  #5  
Old 06-02-2014, 11:32 PM
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Originally Posted by minsk View Post
...and is it reallly bad to drive if the glow plugs are not turning off
If I had to drive, I would disconnect the plug harness after starting. For a hot start, you might get away with leaving it disconnected.
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  #6  
Old 06-02-2014, 11:50 PM
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Quote:
Originally Posted by minsk View Post
ok guys.
bad week for tilly.
fixed all the throttle linkage. super responsive gas pedal now.
but low and behold . the glow plugs wont release ..
im getting around 12v at the actual glow plug this is after minutes...
so they deff arent going off. preglow plug light wont turn off either obviously.
im getting .81v at the preglow time relay. that is having test leads on both end of the fuse. when i unplug the top socket on the relay and plug in my multi meter i get 12v.
so im deff getting juice to the relay.


when i plug in and unplug the glow plug relay i hear it click.

did i do all the tests correctly? is it the fuse or the relay...
im assuming it is bad to drive her with out the glow plugs turning off

1982 300d
You will always have battery Voltage at that Flat Copper Wire/Nut on the Glow Plug Relay and at either Side of the Strip Fuse.

Your Ignition Key is of and you are always getting 12 Volts at the actual Glow Plug Terminal/End pull off the Smaller Square Electrical Connector.
If the Voltage at the Glow Plug stops you may have an Ignition Switch Problem or somehow you are getting Voltage to the Violet/Purple Wire that goes to the Wire Junction Block in front of the Battery on the Fender Well on turbo modes.
Locate the Terminal Block and unscrew the Screw and remove the Violet/Purple Wire.
Plug the Connector backon if you Glow Plugs are still getting Voltage your Ignition Switch is no good.

If you still have Voltage at the Glow Plugs themselves after pulling that Small Square Electrical Connector (has fuor wires) then your Glow Plug Relay is no good.
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tilly is so hot her glow plugs wont turn off.-glow-plug-relay-jul-14.jpg  
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Last edited by Diesel911; 06-03-2014 at 12:38 AM.
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  #7  
Old 06-03-2014, 12:09 AM
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diesel911 so do i check the voltage of the relay on those bolts.
or do i check them individually using the engine as ground?
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  #8  
Old 06-03-2014, 12:32 AM
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If you move the key from OFF to RUN, does the flow light come on and never go off? Do the plugs never time out? If so, the problem is almost certainly the timer. The violet wire is not a factor if you don't attempt a start.

What happens when you turn the key to OFF?
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Old 06-03-2014, 12:40 AM
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Originally Posted by minsk View Post
diesel911 so do i check the voltage of the relay on those bolts.
or do i check them individually using the engine as ground?
Yes, Positive Probe on the Wire/Nut on the Relay or Fuse and negative Probe to Ground. It should show Battery Voltage even with the Ignition Key off.
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  #10  
Old 06-03-2014, 01:02 AM
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diesel911 so do i check the voltage of the relay on those bolts.
or do i check them individually using the engine as ground?
Your glow plugs won't turn off...and you are checking to see if the relay is getting power?
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  #11  
Old 06-03-2014, 01:05 AM
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12v with engine off at both bolts at preglow relay timer.
i never hear the relay click at all now...waiting 45secs
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  #12  
Old 06-03-2014, 01:11 AM
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Originally Posted by tangofox007 View Post
If you move the key from OFF to RUN, does the flow light come on and never go off? Do the plugs never time out? If so, the problem is almost certainly the timer. The violet wire is not a factor if you don't attempt a start.

What happens when you turn the key to OFF?

the timer never clicks now. it seems as if it has been getting progressively longer to hear the relay click.

when i turn the key off all lights go out.
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  #13  
Old 06-03-2014, 09:34 AM
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The time constant circuit in the relay sounds bad. May be easily repairable by any electronics type. Since you never hear it click off with the key on it is on.

The voltage drop across the fuse shows full current is flowing. I thought for a moment someone may have installed a extended glow type relay. Again since you never have it go off it should not be that.

Although if it were a checked only after a minute may not be enough time for it to drop out. I suspect a leaky or shorted capacitor in the relay. Or really off value resistor. It is not a welded contact issue as you hear the relay drop out when the key is turned off. That alone proves it is the problem.

Junkyards can be your friend. I have never had to service one of these relays or tried to. Just always swapped them out. This is a case or defect where I might look inside the relay box. I assume they use a simple time constant circuit with some type of temperature type thermistor to control glow duration but do not know. It could be far more complex but does not need to be.
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  #14  
Old 06-03-2014, 10:14 AM
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thanx barry.ill get a new one. then open the old one
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  #15  
Old 06-03-2014, 06:23 PM
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so i get the stupid award for the year.
so i power washed tillys engine and engine bay a week or so ago.
sooooooooo
i opened the glow plug relay timer box...there was two inches of water in it.
the board looks fine...not blown caps or resistors...im going to let it dry out for a few hours and see what happens

im sure its fried ....but you never know

question. is there a fuse that leads up to the gp relay box?
is there anything that could have shorted out before the box?

anyone in pittsburgh have a spare?


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Last edited by minsk; 06-03-2014 at 06:37 PM.
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