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  #1  
Old 10-16-2008, 10:03 PM
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glo plug question

my 83, 300 D that im starting to work on, the rusty one from wisconsin, has a few of the glo plug wires disconnected at the glo plug. P/O took them off for some reason. needless to say, the car starts really hard.

tonite i hooked my ohm meter to one of them thats off, and it has a complete circuit to ground. . . . key off, button hot pushed, etc. is this normal ? i would assume that all the wires are connected to the relay somewhere under the hood, but i thought they would not be hooked to ground.

can someone explain this ?

and, i think the P/O connected the gloplug circuit to a push button on the dash so they need to be operated manually. the little coiley looking light in the instrument panel does not light, nor does the buzzer buzz.

what the heck kind of a problem am i looking at here ?

and another thing, it runs a bit ruff after its warm, and if you pull off to the side of the road and let it idle, it will idle ruff and then smooth out for a bit then idle ruff again. what the heck ? ? ?

these dang cars sure have lots of little gremlins running around in them !

thanks for any input you can add.

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83 300D Alabama Beauty (Son's)
83 300D West Coast Rust Free that been abused
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  #2  
Old 10-16-2008, 11:35 PM
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Dead short, bad plug. You may be getting air into your fuel system causing the poor running. Bad primer pump is a typical culprit.
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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13
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  #3  
Old 10-17-2008, 06:07 AM
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Quote:
Originally Posted by kerry View Post
Dead short, bad plug. You may be getting air into your fuel system causing the poor running. Bad primer pump is a typical culprit.
but, im checking this with the wire totaly disconnected from the glo plug. .
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83 300D Alabama Beauty (Son's)
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  #4  
Old 10-17-2008, 06:15 AM
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sorry about the mileage, its 177k. the car was well taken care of by the first owner, but after about 120k it seemed to stop. i think we all know what happens then.

i did the valve adjustment, that made it much better when its cold, have run diesel purge stuff thru it and that also helped.

your dead on about lack of mtce. the fuel lines are stiff as a . . . so im sure they could easily pull some air in... and the motor mounts, i had the back one out when i fixed the transmission. it seemed to be not terribly wobbley.

i cannot even see the front ones. aarrrgggggg.

and of couurse it has numerous other problems, vacuum stuff mostly im sure. temp control is either wide open or closed. doors do not lock automatically like my sons does. and onand on and on. sounds like a long winter project.

i was going to pull the running gear and put it in a 1947 hudson that needs an engine, etc. that would really be unique me thinks. but the hudson needs as much body work as the benz.

thanks for the replys,

davidh
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  #5  
Old 10-17-2008, 09:24 AM
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Quote:
Originally Posted by davidh View Post
but, im checking this with the wire totaly disconnected from the glo plug. .
Makes no difference. Still a bad plug. Resistance on the plug should be less than 1ohm.
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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13
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  #6  
Old 10-17-2008, 11:35 AM
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kerry, im not checking the plug, im checking the wire back to the relay. but im thinking the relay attaches all the wires together so im reading feedback from the wire to the relay back to one or more of the plugs that are still hooked up
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  #7  
Old 10-17-2008, 03:02 PM
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I suspect that you are checking your glow Plugs from a different view than most of us would.
This site has a step by step pictorial you need to scroll down the page to see it:
http://www.dieselgiant.com/glowplugrepair.htm

For more stuff:
http://www.dieselgiant.com/mercedes_diesel_maintenance_tips.htm

I think the Mercedes Engine might be to heavy for a Hudson.

When I was 10 years old I crossed the street with out looking (I was involved in a rock fight with another kid) and was hit by a Hudson. I still have a slight crease on my left hip where the bumper hit me. The Doc said it separated a muscle in that area.
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Last edited by Diesel911; 10-17-2008 at 03:08 PM.
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  #8  
Old 10-27-2008, 07:52 AM
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i think i checked the weight of the 5 cyl turbo with transmission against the straight 8 hudson with overdrive and it was soooooo close, even in h.p.

the hudson engine is mounted completely behind the front axel centerline so it helps balaance the weight.

but this is just another pipe dream maybe. . . . .

the old hudson is far more comfortable than my m.b. so that could be a plus.

if i decide to do this, a complete documentary would need to be kept for all to view. and i know ive done dumber things in my life, so , , , , ,
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  #9  
Old 10-27-2008, 10:03 AM
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Sounds like you've got a mess to straighten out in the glow plug circuit. I think you need to examine it from head to toe and correct any and all 'fixes' by the PO AND correct the original malfunction. A wiring diagram will be priceless, but if you have a second car to look at you can probably sort it out.

As to the idle problem, you may need the upgraded gold rack damper bolt. A loping idle is usually the presenting symptom, but if you've also got motor mount issues and possibly injector issues, the loping could combine with roughness.

To get a smooth idle, you need new motor mounts (all three) and you need to have the injectors tested and balanced. Balanced means adjusted so that the opening pressures fall within a 5 bar range (3 bars to get really smooth).
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'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
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  #10  
Old 10-27-2008, 01:21 PM
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If the PO has rigged a manual button to power the glow plugs, then he probably eliminated the relay all together. Since there's custom wiring involved, you're going to have to trace it all out to see what you're dealing with.

But its probably a momentary push button that powers a (simple) relay (hopefully rated for continuous duty at 80 Amps or so) which sends powers all 5 plugs. In which case, if you checked ground at one wire (disconnected from its plug) it would be connected to all 4 other plugs which are grounded, so that's probably why you're seeing ground.

Try this, have someone push the glow button while you check each wire individually for +12v. If you've got that, then check each plug for resistance (< 1 Ohm or whatever). Replace the bad ones, connect all the wires and you should be golden.
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  #11  
Old 10-27-2008, 11:11 PM
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When you push on the Glow Plug button do you hear a relay making a click or thunk sound or does it look like the Push Button is made to handle the 80 amps?
On my Volvo I got rid off my Glow Plug relay and used a Ford type starter slenoid to act as my glow plug relay ($20-$30 new and less at the junk yard). I put a push button to activate it. If you do not use a relay the Push Button Switch has to be able to pull the 80 amps (in your case maybe the switch is shot).
It might be easier and faster to put in your own setup.

The Green wires at the top go the push button switch; also at the top is the (+) wires from the battery. On the bottom is the (+) wire going to the Glow Plugs which split off into 6 wires to each glow plug down the line further.
Also I have no fuse on my system; you might want to add one.

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