Got a part number for this alleged sensor?

You are right; the light cannot determine anything. But the solid state device that controls the light certainly can.

There is no coolant temp sensor on an 85. There is one on earlier models. Don't know in what year it was deleted. My 79SD had the coolant temp sensor.

__________________
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

That's precisely why I specified "alleged" sensor.

Thanks for your responses guys.

Just got in from testing the glow plugs and found #3 is not working. I took the glow plug out and tested it with the charger.......neg. cable to the threaded part,... then touching the pos. cable to the brass stud the wire attaches to, and it does not light up. I have exhausted all the glow plugs from my spare motor so will have to rob the 1980 300TD. The other plugs were.06-.08 ohms and an audible signal from the meter.

I tested the relay/timer and I get 12v at each side of the strip fuse ...I get twelve volts at the main power stud... and get 12v at each pin from the larger plug that leads to each of the glow plug wires. It seems to be working with the key turned to the glow position detent. I could also hear the clunk that whunter talked about.

Yes... its cold alright....yesterday I had to spray wd-40 into the ignition key to get it to turn. The day before I would take off my mit to turn the key and steam would rise from my hand and I presume to condensate in the igniton making it difficult to turn the next day (yesterday). Or maybe just a warm key into a cold lock was enough to condensate in there?

I changed the diff. a few years ago on the '80 TD in these temps. and my main problem was trying to see what I was doing through the fog of my own breath. The little things you don't think of usually....seem to get you when it is this cold.

I do have a battery blanket on the newer battery that keeps it warm. I also have a magnetic oil pan heater that I have not tried yet. I do have 5w-40 synthetic in there. The block heater quit so I was scared to remove it and put the bottom rad hose unit in. I now think a Real block heater would be much better.

I had used a small propane torch to warm up the hard lines going from the fuel pump to the injectors.

I only have one electrical circuit on that side of the house so I have to choose how many power devices I can use or it will trip the GFI. recepticle.

As it is, I have a battery blanket...a battery charger and the lower coolant rad hose heater plugged in.

To keep the fuel warm I use the propane torch on the hard lines......I read about heating the metal fuel filter so I will try that after the new glow plug is in.

I am warmed up now so...out I go in search of a good glow plug.

I was wondering if having a bad glow plug on #3 would cause #4&5 to not work... essentially trying to start with only #1 & #2 glow plugs working?

Thanks again.

See post #5.

One bad glow plug is more than enough to stop a 617 from starting at those temperatures. I had a thread recently where one bad plug was causing that to happen on a relatively new 617 at around 20 degrees F.

__________________
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

switch, automatic, pre-glow system
MB# 0055450324

Engine application:

OM615.940, 963

OM616.912, 936, 940, 960, 961, 963

OM617.912, 931, 950

OM601.911, 912, 940, 941

OM602.911, 912, 930, 931, 938, 939, 940, 942, 946, 947, 961, 962, 990, 993, 994

OM604.910, 912

OM605.910, 912, 960

OM606.912

.

And which of those applications are applicable to a 1985 300TD?

Not a single one.

You assume it is factory spec?

At best, I can only pray it is still unmolested.

.

O.K... so, got a used working glow plug into #3 cyl. and re-tested the ohms through the large plug from the g.p relay. I got .08 ohms on each pin. I also tested the setting on the meter leads by themselves and got .02 ohms.... so I am figuring .06 ohms from each plug as well as an audible signal.

I plugged everything back in.

I heated up the hard lines, the fuel filter canister and briefly the injector bodies with the propane torch...they were all warm enough to the touch.

I tried to start it and got the same dismal cranking speed after using the two glow method from whunter. I changed his method and just glowed it once until the light went out.... then off .....then again until the light went out then cranked it. The reason I changed his method is I am by myself and can no longer hear the clunk from the relay? I don't think it is glowing as long as before ...but maybe went from glowing for 40 seconds down to 30 seconds. still longer than I am used to I think.

No go.

I put the magnetic oil pan heater on, the battery charger and the lower rad hose heater. It is starting to get cold again as the sun goes down. I'll maybe let the oil warm for abit and recharge the battery and try again later.

I am almost certain that this is the original engine in the car.

The one thing I noticed is that coming from the bottom of the wiring harness for the glow plug relay there is a four or five pin electrical connector, connected to another connector and wrapped with electrical tape. It does'nt look like something from the factory. I will maybe take a picture later.

I reread post 5 and so that question is answered. I have 5 working now.

I did notice that the non-working #3 glow plug that came out of the engine was quite wet looking and smelled of diesel fuel.

Thanks

This 85' engine has two temperature sending units in the cyl. head. My 1980 300TD only has one temp. sensor in the head. The 1980 model has had a turbo motor put in place of the n/a motor that was oem. I bought the car this way so I know nothing about the transplant on that car...so yea The 85 300TD I am trying to get going has two sensors in the head. I wonder why this has two sensors?

One for the gauge, one for the EGR control unit. Neither has anything to do with the preglow timer.

only if the solid state device in the relay is working... I've often found a glow light on, and had all 5 plugs dead. I've had the light flash on for several seconds, then go out, when all plugs are working, but 5 seconds of relay activity is inadequate. best to actually TEST them, not go by the indicator light...

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

If you understood how the system works, that would make perfect sense to you. Unless all five plugs failed at once, there should have been plenty of advance warning that things were going downhill.

The fault detection system works by comparing the current drawn by the #1 GP to the combined current drawn by the remaining GPs. If none of the plugs draw any current, there is no imbalance, therefore no fault indication.

Clearly, the intent of the fault detection system is to warn of a problem that is not otherwise apparent. I pay attention to the light every time i start my car. If you want to test your glow plugs before every start, have at it.