I am not sure that I understand the use of the Glow Plugs. I know that they heat the fuel pre-chamber for starting. But do they stay on after that at just a lower power? I am changing my GP's tomorrow and I just went out to put a test light on the main power wire, and both sides of the fuse and all was well with the key turned one click. I had my wife turn it until the GP light came on and started testing the five connectors on the relay and still had power after the dash light had gone out. Is this right??

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1985 300D burning WVO using 26 FPHE, half gallon heated fuel filter,glow plug heater,home made injection line heaters. Home made cold air induction. ALDA full out.
2003 F350 7.3(the last of the great motors)
1987 Paint Horse-non running too, just walks!

Yes, this is normal. Depending upon relay - they will stay energized for approx 30 seconds to 2 minutes.

Turn the key on and listen, you will hear they relay click off when it stops energizing the glow plug circuit.

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83 300d - 390k

I will check that again tomorrow, but I did hear a "click" and still had power to the prongs.
Thank you for your reply.

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1985 300D burning WVO using 26 FPHE, half gallon heated fuel filter,glow plug heater,home made injection line heaters. Home made cold air induction. ALDA full out.
2003 F350 7.3(the last of the great motors)
1987 Paint Horse-non running too, just walks!

The light is just an idiot light, more of a recommendation based on the ambient temp. The relay will run the full cycle no matter if its freezing or a hundred and five, at least on the older models, like non-cdi's. Its only the timing of the light that changes with temperature. I'm assuming you're asking this about your '85, which will not have an afterglow feature built into the stock relay, meaning that as soon as the relay senses the starter engaging, the gp's kick off. I'm not sure if an afterglow relay can be purchased for the 123's or not. The plugs will always be on at full power when they're engaged, no half power setting.

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Seth

1984 300D 225K
1985 300D Donor body
1985 300D Turbo 165K. Totaled. Donor Engine. It runs!!!
1980 300SD 311K My New Baby.
1979 BMW 633csi 62K+++? Dead odo

You can install an afterglow relay in a W123, I have one in my 300D. The stock relays do not have the afterglow feature.

Sorry, but a little too fast. "The relay will run the full cycle ", what is the full cycle process of the GP's? "meaning that as soon as the relay senses the starter engaging", so your saying that the dash light may go off, but the relay is still suppling power to the GP's until the starter is kicked over?
Last, this is a question that may be for the WVO part of my car. "afterglow relay ", this would keep the GP's on after the engine is running?

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1985 300D burning WVO using 26 FPHE, half gallon heated fuel filter,glow plug heater,home made injection line heaters. Home made cold air induction. ALDA full out.
2003 F350 7.3(the last of the great motors)
1987 Paint Horse-non running too, just walks!

Once my glow plugs are activated they stay on for 40 seconds each and every time regardless if it's the first start of the day or if I've been running errands and the car has only been parked for a few minutes in between stops.

I can time it each time by starting the car while leaving the door open. Leaving the door open causes the dome light to stay on. Look at the light as you insert the key into the ignition. The light will be bright. As the key is turned to energize the glow plugs, the dome light will dim due to the current draw. Continue to watch the light. When the glow plugs shut off the light will brighten again.

www.dieselgiant.com has a great test procedure with pics

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Pictures of the MB: http://s230.photobucket.com/albums/ee41/EricandRobyn/1981%20Mercedes/

1981 300 SD with a Goldenrod water block and Injetor line heaters. EGR is missing

1999 F-350 with HP X-over, Dahl 100 Fuel Filter, Coolant by-pass filter, CCV mod, Tymar intake.

Both on single tank WVO blend

After a little more testing this morning, it does cut off power to the GP's about 40 sec after they turn on.
I have four of the five old GP's out now and 4 out of 4 have tested good, they glow. This does not help my hard starts issues of late. The "D" fuse in the fuse box did not look to good and I have changed it as well this morning, is that the fuse for the GP relay? I have lost the paper from the back of the cover with the fuse info on it.

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1985 300D burning WVO using 26 FPHE, half gallon heated fuel filter,glow plug heater,home made injection line heaters. Home made cold air induction. ALDA full out.
2003 F350 7.3(the last of the great motors)
1987 Paint Horse-non running too, just walks!

On a 1985 model, the duration of the glow period varies inversely with ambient temperature. It is not a "fixed" duration.

The fuse for the relay is located on the relay itself, under the cover towards the front/lower end. its about an inch and a half long and is held in place by a visible screw at each end. Even if it appears to be intact, it can have microscopic cracks in it that will impair performance.

The full cycle for the gp's is to engage when you turn the key to the on position and disengage after either the set time, approximately 40 seconds, or the engagement of the starter. The dash light time will vary depending on ambient and engine temps and is really more of a guideline. It wouldn't hurt anything to wait a couple of extra seconds after the light goes out, as the gp's should still be engaged.

Yes, an afterglow relay will keep the plugs energized after the engagement of the starter, whereas a standard relay will cut the plugs out as soon as you turn the engine over.

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Seth

1984 300D 225K
1985 300D Donor body
1985 300D Turbo 165K. Totaled. Donor Engine. It runs!!!
1980 300SD 311K My New Baby.
1979 BMW 633csi 62K+++? Dead odo

Is it really the ambient temp? ...Or water temp via the temp. sensor on the thermostat housing?...or the temp sensor on the cylinder head next to the temp. guage sensor?

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'85 300D Turbo - CA Version

In another thread recently (Craig I think) mentioned that the temperature sensor was in the relay itself and not in the head.

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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

On an '85, yes.

Thanks for all the replys and help, but all of the GP's , relay,and fuse were good. I still changed the GP's with some new Bosch. But my problem was a leak that I had not noticed in a fuel line from my WVO GP heater to the IP. I saw a small amount of oil and touched the hose and got a spray of hot oil all over the engine, windsheild as well as myself. It must have been letting in air and the fuel in the lines flowed back to the tank everytime I stopped and shut down. I know that some do not like the use of the car for WVO, but I am proud of my home built system and would like to post a pic. If offended please turn away.

http://i63.photobucket.com/albums/h145/hotwheelbill/newwvosystem001.jpg

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1985 300D burning WVO using 26 FPHE, half gallon heated fuel filter,glow plug heater,home made injection line heaters. Home made cold air induction. ALDA full out.
2003 F350 7.3(the last of the great motors)
1987 Paint Horse-non running too, just walks!