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Discussion Starter #1
Sorry if this got covered somewhere, I've been searching but haven't found what I think I need yet.

I just got given a 79 300D. It was running fine, then parked and sat for a bit. I bought a new battery for it, and hooked it up. When I turn it to preglow there is no glow plug light, and given that the weather is cold, it cranks but won't start. I have been to the diesel giant site, and I checked the fuse in the engine compartment, and its ok.

What I found was there is no voltage on either side of that fuse. I checked the relay under the steering column that I think is the glow plug relay, and there is voltage going into it when the key is on the preglow setting. If I remember right there are 2 of the seven that show around 12 volts, and some others that are less. Can't remember off the top of my head. I also noticed that the relay has a rattle when I shake it. I've been trying to track down the relay, but I can't find anyone who actually has one.

Is there any way that I can bypass this just to test and see if thats the problem? Can I run a 10 gauge wire from the positive on the battery to the wire leading from the fuse to the plugs for a few seconds to fire them, or would that be bad? Is there something else it could be that I'm missing, and where can I get one of those relays if I need to? I'm trying parts houses, junkyards, anything else I can. I really want to get this car going, its in great shape aside from this issue. Thanks!
 

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2003 Volvo V70 5 Speed
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Yup, I've done that. If you have the original loop style plugs (curly wavy wires connecting them) run the wire from the + battery terminal to the fuse on the firewall. If the plugs have been updated to the pencil style it doesn't matter where you introduce the power. Hold the power to the plugs for about 30seconds (less if it's warm out) an then run inside and try to start it (or have someone start if for you immediately after you take the wire off the glow-plug circuit.
As for finding a new glow-plug relay, the on-line stores are usually stocked in them, but they are rather expensive new. A junk yard a good option.
 

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Discussion Starter #3
I'll give that a shot. Do you think that the relay is definitely the problem then? I'd hate to go through all this to get the relay and then discover its something else.

Oh, and it is the orginal style plugs. I plan on changing them out to pencil at some point, but I need to get it started first.
 

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2003 Volvo V70 5 Speed
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From your description it sounds like the relay. I believe you can actually open the silver can (relay). Might be worth having a look. Maybe just a dirty contact. I don't have a lot of experience with the original relay as mine was replaced with a fast glow unit. I would check the wire between the glow-plugs and and the relay for continuity. I had mine develop a break once, very annoying....
 

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1984 300D
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A new Glow Plug Relay of the type that is near the Steering Colum cost around $250 or more new.

If you have the Loop/Filament type Glow Plugs you can get the Pencil types in a Kit with a Relay for I believe less than the $250.

Or some have used a Ford type Starter Solenoid (mounted in the Engine compartment) to replace the Relay and used a Push Button Switch mounted somewhere. (I did this to my Volvo Diesel that I am still driving around 1993 and have had no problems at all with it. I got the Solenoid at the Junk Yard for less than $5.)
 

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'79 300TD - '74 Triumph Spitfire, '86 Alfa GTV6 & Spider
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RockAuto.com has a Beck-Arnley brand glow plug relay on closeout for $85. I bought one for my '79, works fine. I'll actually be selling mine, as I am upgrading to the newer type with after-glow. Used for < month. Drop me a private message if interested.

-Kevin
 
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