Wiring diagram for Pre-Glow circuit on 300 D early 80's

You need to find a Haynes MBZ diesel/car repair manual, the wiring diagrams are in the back, and the chapter on electrical covers the glow plug system. That is an interesting engine transplant you are doing-- do you think the 2.5 diesel is going to be big enough for an El Camino?

--Geoff '84 300D

Mats wrote:

I don't know how much you know about swedish driving license rules, but in Sweden you are allowd do drive a tractor from the age of 16, ande a car from the age of 18,.

So many young people register cheap cars as tractors, the only thing that is needed is that the vehicle is converted so taht it only can only carry the driver and one passanger, and that it is not capable of doing more than 30 km/h (usually accomplished by doing some modifications to the gearbox so that the car only can be driven on the first and second gear), so the 300 D engine will be more than enough.

The car has had an 240 D engine earlier, and that too did the job Ok, but it later broke down, on that engine the pre-glow was done manually by estimating the outside temp and the engine temp, and a simpel pushbutton.

/Mats

I assume the glow plug relay is part of the installation. It's a black box of about 10 cm x 7 or 8 cm to which all the glow plug wires etc. are attached. It has a 80 amp fusible link which must be intact for the glow plugs to operate.

All input numbers refer to the harness and glow plug relay - '80 300SD pin-type version - yours may be different.

There are two temperature sensors cooling system (green wire in '80 to input #6 /B and another glow plug relay temperature sensor (brown/green wire in '80 to input #8/ (blank)).

Wire to the relay: starter and air conditioner terminal (violet wire in '80 to input #5/50).

Wire to the dashboard indicator light (blue / white in '80 input #1/LA).

A (red wire in '80 input (blank)/30) goes from the 80 amp fusible link to a "terminal block" - Probably the Battery.

Wire (red/black in '80) connects car fuse #15 to input #2/15 on the glow plug relay.

Wire (green in '80 from input 3/B) goes to "connector, combination instrument, terminal 3" which I believe is the engine's temperature gauge. You should know that these green wires appear to have nothing to do with the glow plug system and appear to simply be wired through it's harness as a conduit.

Five wires to the glowplugs 2/G1, 1/G2, 3/G3, 5/G4, and 7/G5

I don't own a scanner so this is the best I can do, hope it helps you.

Its has been found, and it seems fairly intact.

Thanks for the info !

On the pre-glow relay I have found the following connectors:

30, direct to battery 50, to starter 15, to "ignition"

G1-G5, to the glowplugs

31, earth

LA, indication lamp

I don't understand where the temp senors are connected, but I will check the remanins of the wiring harness tomorrow, to see if that will give me some clues.

Best regards

Mats

I don't understand where the temp sensors are connected, but I will check the remains of the wiring harness tomorrow, to see if that will give me some clues.

I believe there are two wires to one engine temperature sensor, look at the engine block in the area behind its injection pump.

Tom

Ok, then I know where to look for that one, I have seen a sensor with a green wire in that neighbourhood.

But I still don't get how the pre-glow rely/unit will get the temp signal, all connectors on it are accounted for as I mentioned in my previous posting, there is no connector left over that this signal can be connected to.

By the way, you don't happen to know where on the engine the oil pressure sensor is located ?

Best regards

/Mats

There are two wires to one temperature sensor cooling system (green wire in '80 to input #6 /B and another wire to temperature sensor for glow plug relay (brown/green wire in '80 to input #8/ (blank)).

Wire (green in '80 from input 3/B) goes to "connector, combination instrument, terminal 3" which I believe is the engine's temperature gauge. You should know that these green wires appear to have nothing to do with the glow plug system and appear to simply be wired through it's harness as a conduit (6/B and 3/B)

So look at #8/ (blank) for the temperature input to the relay.

Oil pressure sender is at the oil filter base - it may be a mechanical pipe to a mechanical gauge rather than an electric pressure sending unit. The engine's actual oil pressure range is between 1 BAR at hot idle and about 6 BAR if you choose to substitute an electric sending unit.

Tom

Well the relay has no input marked #8 (blank), the only connections to the relay is the ones I have mentioned in earlier postings.

30 to Battery (+)

50 to starter

15 to "ignition"

31 to chassi (-)

LA to indication lamp

G1-G5 to glowplugs

I have wired it up today, and it seems to be functioning well, when ignition is on, the indication lamp illuminates for 3-4 seconds (engine temperature about 15 C), and after staring the engine, the glowplugs are shut off.

The only thing I wonder about is if it's supposed to be like that, the glow plugs still engaged even though the indication lamp has gone off, and the glowplugs deactivated first when the key is turned to the start position ?

Can it be so that this relay is newer, and may be checking the engine temp via the glowplugs (the resistance changes with the temperatur ?!)

Ok, I'll check that tomorrow, I think the donor car has a electric oil pressure instrument, but I am not sure, I'll let you know tomorrow how things work out.

Best regards

/Mats

I have wired it up today, and it seems to be functioning well, when ignition is on, the indication lamp illuminates for 3-4 seconds (engine temperature about 15 C), and after staring the engine, the glowplugs are shut off. GOOD, IT WORKS.

The only thing I wonder about is if it's supposed to be like that, the glow plugs still engaged even though the indication lamp has gone off, and the glowplugs deactivated first when the key is turned to the start position ? YES, I BELIEVE THEY GLOW A BIT LONGER

Can it be so that this relay is newer, and may be checking the engine temp via the glowplugs (the resistance changes with the temperatur ?!)

PROBABLY, BUT I REALLY DON'T KNOW.

Beru or Bosch sell a retrofit relay (in case you ever need a replacement) that extends the glow time to improve combustion and so reduce smoke and emissions.

Good job in getting it running.

Tom

I think so too, today I got the pre-glow and starter back to the ignition lock, before it was done with two pushputtons. When they ripped out the Smallblock 350 with it's autotransmission, they didn't get the starter to work, probably because they forgot the Park/Netural switch on the autotransmission, so I put a jumper over it, and it worked fine.

Ok, I probably din't wait enough time, I'll dig into that tomorrow.

Could be a current sensor to, as the glowplugs get hotter the resistance should be bigger, just guessing though.

Well, the guy who owns this tractor/car (its registrered as a tractor so that he can drive it even though he is only 16 years old), doesn't care that much abot that I think, and since the egine has done some

600 000 km, I don't think that it will do any significant change to the smoke and emissions.

Thanks, tomorrow I will start with the turnsignals, the rear lights and the stoplights, and probably some more...

Best regards

/Mats

Elucidation, he cares about the function (pre-glow), but not about the emissions and smoke, tractors can pollute (allmost) all that they want i Sweden.

/Mats

Well, today I just had 1,5 h to spend on the car, that was just enough to get the tail and stoplights working (corroded grounding), and to hook up the stereo.

My work with the car is now finished (unless there is something more that needs fixing that the owner hasn't told me about), but I hope it's all ok now.

/Mats

Re: Wiring diagram for Pre-Glow circuit on 300 D early 80's Beru or Bosch sell a retrofit relay (in case you ever need a replacement) that extends the glow time to improve combustion and so reduce smoke and emissions.

Well, the guy who owns this tractor/car (its registrered as a tractor so that he can drive it even though he is only 16 years old), doesn't care that much abot that I think, and since the egine has done some 600 000 km, I don't think that it will do any significant change to the smoke and emissions.

Elucidation, he cares about the function (pre-glow), but not about the emissions and smoke, tractors can pollute (allmost) all that they want i Sweden. /Mats xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx i take it we now shoot any one who drives a tractor? BANG case