Don't continue looking for the relay until you figure out whether that spliced wire is putting out current when the key is in the glow position. So far, there's no evidence the relay is bad.
Yes, that is the fuse block and it should be replaced.

__________________
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

I don't have a voltage tester so I placed a jumper between the spliced wire (after doing a new and better splice) and the #4 glow plug. Still, I get no indication that the glow plugs are warming up; no light or heat coming from the plug that I can feel on the outside. Granted, it's hot out and the engine is firing right up now.

I did find the relay and it works but the ground in the 5 pin plug got too hot and bubbled the housing a bit. The relay will still close the circuit but I think there is a break in the ground somewhere. Both the male and female side of the ground pin got hot at sime time in the past and caused the plastic nearby to melt a bit.

That's all I know so far. I'm not sure what other testing I can do without a voltage tester. I'll see if I can get to a parts store today, maybe I can find one.

Phil Forrest

__________________
1972 220D "Trudy," named by a friend.

"The 220D sounds good... I suspect it is the only car that you need a calendar for, rather than a stopwatch, when doing acceleration tests."
Tom Abrahamsson

That test won't work because if there's a burned out plug there's no ground to the circuit. You need a test light or a voltmeter. The electricity flows through all the plugs and to the block via the ground wire at the glow plug nearest the radiator. They are wired in series and any failed plug takes out the series. Using an ohmeter to test the continuity from the first plug to the last will also tell you whether there's a bad plug or not.

__________________
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

All the plugs were replaced 3 days ago with brand new Monark series type glow plugs. I'll see if I can get a meter to test the current.

Phil Forrest

__________________
1972 220D "Trudy," named by a friend.

"The 220D sounds good... I suspect it is the only car that you need a calendar for, rather than a stopwatch, when doing acceleration tests."
Tom Abrahamsson

That's an important piece of information. Have they worked since they were replaced? It's pretty easy to put the wires back on incorrectly with the insulators in the wrong places, causing the plugs not to work. We might be able to tell if things are correct if you post pictures of the wiring. The key feature is that the input wire and the output wire must be separated by the insulator. If they touch, the plug won't work.
If they were wired incorrectly, the ohmeter will show continuity but the plugs won't work.

__________________
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

They worked perfectly up until last night after the instrument panel job. They are indeed wired up correctly even though the previous owner used a different kind of insulator on the #5 glow plug. I have a Bosch on the way and will replace it as soon as it arrives.

Yesterday on a drive the glow plug light came on once for a second while I was driving which led me to believe this was a relay issue (I should have mentioned that earlier but forgot that detail till now.)

I just tested the wire to the #5 plug and it has no current. The relay does click but I'm suspicious of that ground that got hot.

Phil Forrest

__________________
1972 220D "Trudy," named by a friend.

"The 220D sounds good... I suspect it is the only car that you need a calendar for, rather than a stopwatch, when doing acceleration tests."
Tom Abrahamsson

So, after I left the parts store this afternoon and got in the car, the glow plug light came on then went off soon after because the car was warm. That was the last time it came on so I'm thinking there's a relay or wiring gremlin wreaking havoc under my dash.

Phil Forrest

__________________
1972 220D "Trudy," named by a friend.

"The 220D sounds good... I suspect it is the only car that you need a calendar for, rather than a stopwatch, when doing acceleration tests."
Tom Abrahamsson

Any more ideas on what might be causing my glow plugs to not heat up?
I'm out of ideas. Thanks a ton for all your healp already.

Phil Forrest

__________________
1972 220D "Trudy," named by a friend.

"The 220D sounds good... I suspect it is the only car that you need a calendar for, rather than a stopwatch, when doing acceleration tests."
Tom Abrahamsson

you need a multimeter. don't be shy, they cost almost nothing and are good for a lot of uses. if you find that there is no voltage at the glow plug circuit - even sometimes - then that will answer your question. was there voltage on the other side of the glow plug relay? and so on. when the problem occurs, trace the missing voltage back towards (or past) the glow plug relay. now, i'm not saying this is trivial, but i do think it can probably be solved at home, if you don't want to hire a pro.

I now have a multimeter but I'm not sure what to test past what I already have. I don't have any voltage gointgto the plugs but the relay does work as I've both seen and heard the relay close. My suspicion is the ground since the ground pin has bubbling around it and the plug got hot where the female plug side is.

I cleaned all the connections on the instrument panel and re-installed it since that's where the problem started. No joy.

It's gonna get cold soon and starting up the car is going to be hell in the mornings.

Thanks a bunch.

Phil Forrest

__________________
1972 220D "Trudy," named by a friend.

"The 220D sounds good... I suspect it is the only car that you need a calendar for, rather than a stopwatch, when doing acceleration tests."
Tom Abrahamsson

The procedure for checking glow plugs is in the FSM chapter 15-510

If you don't have a copy of the FSM yet don't worry go to www.startekinfo.com and get one for free. (I do say this with reservations as it is sometimes a bit of a tricky site to get working. See this thread for more details Mercedes Startek have done the right thing - to help you do the right thing! )

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

Sorry I wasn't more specific in the use of the word plug in a thread about glow plugs. My suspicion is the ground pin on the relay is either completely cooked off of the circuit or the wire itself has a break. The plastic around the ground pin bubbled up at some time in the past and the heat there made the female side of the connection hot enough to melt a very small amount of plastic on that side of the connection. I'll be back on Friday to test it with the back side or plug cover off of the connector while the relay is connected to the car. If that's not it, I'm completely at a loss to think of what it could be next besides a break in the wiring harness between the relay and the glow plugs. I was also wondering if it could be a connection on the ignition switch but the car turns over very strong and at position 3, the battery, ABS and brake dash lights do come on so there is current running at that position.

Thanks again,
Phil Forrest

__________________
1972 220D "Trudy," named by a friend.

"The 220D sounds good... I suspect it is the only car that you need a calendar for, rather than a stopwatch, when doing acceleration tests."
Tom Abrahamsson

I took out the glow plug relay again and opened it up to find this:



It looks like I've got three melted capacitors.
Like I said in a previous post, the relay will collapse the circuit but I don't think there is current going through the relay because all the other parts of the glow plug system appear to be good.

I'll set the relay back on the car tomorrow and test the connections with the back of the relay plug off to see if there is actually any current flowing, pin for pin.

Phil Forrest

__________________
1972 220D "Trudy," named by a friend.

"The 220D sounds good... I suspect it is the only car that you need a calendar for, rather than a stopwatch, when doing acceleration tests."
Tom Abrahamsson

That brown stuff may just be the glue they used to keep them in place during assembly. If you can plug it back in without the can on it & turn the ignition on, the big relay should click on. You may need to clean the relay contacts with a bit of fine emery paper.
If the big relay clicks down & the contacts are good, you should have power to the GP's.

__________________
Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving

Contacts in the relay gap got cleaned very well. There was a fine layer of corrosion on both sides but it's shiny clean now. The issue is that I still don't have current going to the plugs so I'm wondering if there is a break in the harness somewhere at a junction.

Phil Forrest

__________________
1972 220D "Trudy," named by a friend.

"The 220D sounds good... I suspect it is the only car that you need a calendar for, rather than a stopwatch, when doing acceleration tests."
Tom Abrahamsson