OM617 inboard glow plug/relay query
 

Hey there,
I'm new but my Mercedes 617 ain't! OM 617 912, sitting in my 1934 Norwegian ex-fishing ketch, 40ft and 16tons of boat. My engine is fine, but the glow plugs packed up, replaced yes, with the same type- filament type glow plugs. Now the engine before only had a key start with no and I mean no extraneous wiring, so no relay, fuse, ind. light, get the picture? So I figure on putting in a relay so that maybe the plugs will last longer with different people starting the engine... everyone counts different, slower etc. So I have relay, part no. 116 545 00 45. It has the 5 wires for the plugs etc. Now I have filament type and the relay was for the pencil element type. Can I use my plugs with this relay? Just wire them up like they were pencil type.
Also do I need a coolant/temp. sensor or can that be bypassed? Is it in the relay? OK there ye go... Help!
Cheers Conan

No, you cannot use the newer "pencil" style relay with the older "filament" style glow plugs. The reason is the parallel "pencil" style system sends 12 volts to each and every glow plug. The series "filament" design runs 12 volts through ALL the glow plugs in series - so, each filament glow plug is designed to work on 12/5 or about 2.5 volts.

If you use that newer relay with parallel wires to each glow plug, you will burn out those filament style glow plugs almost immediately.

What you can do is buy an adapter kit that converts the larger filament style holes in the head to the smaller pencil diameter glow plug. You screw the adapter into the head and then the smaller pencil glow plug in the adapter.

How did you start your boat engine before? Hold down a switch to send electricity to the glow plugs?

Ken300D

HERE are the glowplugs you need to work with that realy. Since you have the loop style plugs, you will have to convert to pencil type with this kit.

How did you start your boat engine before? Hold down a switch to send electricity to the glow plugs?

Ken300D[/QUOTE]

Yup that was it, I was hoping to get away with the random count and try method, and also as there are times when I might not be starting the boat I thought I'd be clever... maybe not! Is there a relay for these type glow plugs? as the plugs I got are all new and it seems a waste.

Those older style glow plugs are hard to destroy. I bought my 78 with a well used set in place and they were still there 165,000 miles and seven years later when I sold it.
Maybe just use a momentary switch, or get a timer off a pre 1979 MB.

Any 300D/300TD/300CD from 77-79 should have the relay you need.