87 300D Turbo - 603 Engine.

My Glow light is out and no start with burnt strip fuse on the GP relay. Tried another fuse and it blew also, so must be a dead short some place.

Replaced the GP Relay with a new one and still blowing the strip fuse! I am now out of fuses so I stuck a temp copper wire in there for now!

Just ohm checked all the glow plugs and all seemed good .8 or .9 except for the #1 plug which was .3 The meter tested .3 with the leeds together so subtracting the .3 equals zero for the # 1 plug.

Is this the short? I replaced the #1 and #3 plugs last month with new Bosch plugs and all was well until now.

Any thoughts?

__________________
Gerry

59 Ranchero
83 928 Euro S
84 928 Euro S
87 300D Turbo-Frybrid "WVO, Tastes Great - Less Filling"
90 750 IL
91 560 SEL

Try it with the #1 plug disconnected, it sounds like your short.

I wouldn't run it with copper wire across the fuse connections, could burn up your relay or worse, ... the wiring.

You need to adjust/calibrate/repair your meter.

__________________

Gone to the dark side

- Jeff

I have some extra Bosch plugs so I will just replace the #1 plug. But it is only a month old! How could it short out so soon? Carbon build up in the prechamber?

My meter is an el-cheapo brand and not sure how to zero out the resistance on it.

Where is a good source for these hard to find Strip Fuses besides the Dealer?

__________________
Gerry

59 Ranchero
83 928 Euro S
84 928 Euro S
87 300D Turbo-Frybrid "WVO, Tastes Great - Less Filling"
90 750 IL
91 560 SEL

The "pencil" style glow plugs normally do not short out due to carbon buildup because the heating element is insulated inside the plug.

To blow the strip fuse, you clearly have a hard short. It is either a glow plug gone bad, or the wiring touching somewhere it should not. You did remember to hook up the lead to the glow plug you replaced? If not it could be laying against the block.

There is nothing unusual with a new glow plug going bad if the manufacturing has a defect somehow. Maybe the Bosch glow plugs are coming from India now too.

As was mentioned, you can probably get the car started if you disconnect (and insulate with electrical tape) the lead to the glow plug showing the low resistance ( # 1 ). It is risky to replace the strip fuse with copper wire - I would do that only for starting the car with the hood open and holding the piece of wire. If the wire gets too warm, pull it away. You might be OK if you isolate the short to the one glow plug, but I'd get a fuse back in there ASAP.

Ken300D

__________________
--------------------------
1982 300D at 351K miles
1984 300SD at 217K miles
1987 300D at 370K miles

That's an 80 amp fuse.
You are asking for big trouble, if you subbed in a "slo-blo" copper wire.
Your entire harness feeding the GP relay should be checked for damage.

Jim

__________________
14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles

OK, now I am making some progress, though still have a hard electrical short.

Replaced #1 plug with new Bosch unit then checked all plugs for resistance and no change. Then by chance I looked really hard at everything and noticed that the #1 plug wire terminal was touching the cylinder head!


Freakin Eureka!!!! Thats the short! Bent it away from head and rechecked all the resistance values and all normal including #1 at about .8 each. Done, or so I thought.

Hooked every thing back up and as soon as I turned the key on to preglow, no light and the fuse blows again (home made thin copper wire)

Now what? Rip out and Replace the glo plug wire? Can you even buy them with those terminals?

__________________
Gerry

59 Ranchero
83 928 Euro S
84 928 Euro S
87 300D Turbo-Frybrid "WVO, Tastes Great - Less Filling"
90 750 IL
91 560 SEL

Disconnect the glow plugs and try the relay again. Then test one plug at a time connected, when the fuse blows again, you found your problem. If the fuse does not blow, then reconnect one plug at a time and add a plug each time until the fuse blows.

If the fuse blows with all the plugs disconnected, then you found your problem, an internal short in the relay.

__________________
RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

99 W210 E300 Turbo Diesel, chipped, DPF/Converter Delete. Still needs EGR Delete, 232K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Gone and still missed...1982 w123 300D, 1991 w124 300D

Your home made thin copper wire fuse probably isn't rated at the 80 amps being drawn by a properly functioning glow plug system.

That strip fuse can carry a lot of current. It is a fuse because instead of glowing red when there is too much current, it droops down and melts apart.

You can probably get the car started with a section of regular 12 gauge wire held against the fuse terminals. If the wire gets hot pull it away. This obviously requires a second person to turn over the car while you hold the wire. The more risky alternative is to screw the wire into place, but watch it with the hood up from inside the car. If it starts smoking, hop out and cut it with diagonal cutters.

Ken300D

__________________
--------------------------
1982 300D at 351K miles
1984 300SD at 217K miles
1987 300D at 370K miles

Homemade fuse?

Start by getting the correct fuse installed. You have no way of knowing if your homemade fuse can handle 85A. The relay may be working correctly. Go buy a handful of fuses.

I bought some right here from Phil. I'd get an order in before you do some damage.

__________________
1985 300D Turbo
"Evolution is God's way of giving upgrades" Francis Collins

OK, OK I just ordered 10 - 80 amp and 10 - 30 amp fuses but until they arrive I did some more testing today. Temp fuses are phone wire - very thin copper- they will have to do for now.

Brand new $165 GP Relay, and a few new Bosch Plugs installed. All check at about .8 or .9 ohms minus .3 residual in my ohm meter.

I checked the GP Lamp using the procedure in the CD manual - jump pin 1 and 3 good light check.

I checked continuity between pin 4 and the GP light in dash (black wire) good at about 13 ohms.

Now it gets really interesting. I left the 4 prong plug off the relay and turned the key on to pos 2 and no light - fuse OK. All six glow plugs and wires connected.

Reconnect 4 prong plug and test again- ignition to position 2 and no light and quickly bows fuse.

So now pretty sure problem short is in one of the four wires in the 4 prong plug. During process of elimination I tracked it down to pin #1 by removing each wire from the harness and testing by turning key on individually.

The fuse stayed intact with all except when pin # 1 was connected.


Pin 1 - color rs/rt fuse 7 Terminal 15 ( shorting to ground with test light)

Pin 2 - color vi/ws back up light switch ( normal test)

Pin 3 - color sw pre-glow lamp (normal test)

Pin 4 - color br ground (normal test)



Now I am really tired and have to go make some dinner for the kids.

__________________
Gerry

59 Ranchero
83 928 Euro S
84 928 Euro S
87 300D Turbo-Frybrid "WVO, Tastes Great - Less Filling"
90 750 IL
91 560 SEL

Good troubleshooting. Now hopefully you either have wiring diagram, or someone with the same model car can tell you what wire #1 is on the 4 prong plug in.

__________________
RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

99 W210 E300 Turbo Diesel, chipped, DPF/Converter Delete. Still needs EGR Delete, 232K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Gone and still missed...1982 w123 300D, 1991 w124 300D

The crappy CD "bootleg" manual I have will not spit out the wiring diagram. I don'y know why. Its probably a copy of a copy and so forth.

Anyone have some decent wiring diagrams out there?

__________________
Gerry

59 Ranchero
83 928 Euro S
84 928 Euro S
87 300D Turbo-Frybrid "WVO, Tastes Great - Less Filling"
90 750 IL
91 560 SEL

The 4-prong plug is the electrical circuit that throws the relay. All you have done is prevent the relay from throwing by removing that plug (or pin 1 of that plug).

You need something substantially heavier than phone wire to supply current to the glow plugs. More like hookup wire, 14 gauge or so.

Ken300D

__________________
--------------------------
1982 300D at 351K miles
1984 300SD at 217K miles
1987 300D at 370K miles

I know what you mean, but I don't want to burn anything up using anything too heavy. At first I did use something heavier! The factory 80 amp fuses and blew a bunch of them. Now I am waiting for some more to arrive in the mail.

But what about the wire that goes to pin #1 that appears to be grounded out. I connect my test light to it and sure enough it lights up. The only info I can get from my CD manual is that it goes to "fuse 7 terminal 15" which I assume is the main fuse box.

Fuse 7 protects - Back up lamp, heating watervalve, water pump, engine fan, heating system for water jets, climate control system, rear aux fan term 86, autotrans electrics, blower motor inside temp sensor, and aircond compressor.

These things all work and fuse #7 is intact, so must be between the fuse box and the relay somewhere.

I don't have any more hair to pull out!

__________________
Gerry

59 Ranchero
83 928 Euro S
84 928 Euro S
87 300D Turbo-Frybrid "WVO, Tastes Great - Less Filling"
90 750 IL
91 560 SEL