Hi Group- Want some opinions on an interesting issue that has popped up on my wife's '85 300TDT W123 since a huge go- through- it- all service I just performed at 285K. This included all new filters, NOS nozzles, shim and pop tested, new Bosch glows, valve adjustment, timing chain, tensioner spring and seals, drip timing adjustment, fuel hoses, rack damper bolt, and everything else the car needed. EVERYTHING now works on the car just so.

BUT- the glow light will stay on for 3-5 seconds max, and it has to be glowed at least twice for it to start and stay running- albeit rough- at ambient temps even in the 60s Farenheit when the engine has cooled down through the block.

It glowed and started just great BEFORE I replaced the glow plugs- and the glow plugs in it before were NGKs, which everyone says are junk.

Everything checks out fine on the VOM- no opens to any glows. I unplugged the temp sensor and tried it, but that made no difference.

Suggestions? Comments? Anyone run into this before? I searched on the site and didn't find anything. I found Kent Bergsma's "fix" on YouTube, but I'm sorry- a Ford relay and a push button is a hack- a bandaid for a misdiagnosed system- this car started just perfectly in ALL temps before the glow plug change.

Anyone have any ideas?

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1968 230S Automatic, Elfenbein
1975 O309D Executive Westfalia Camper Bus, Blau/ Weiss
1972 280SEL 4,5 Dunkelrot
1966 VW Type 34 "Grosser" Karmann-Ghia
1963 VW 1500 Variant Pearlweiss
1969 VW Variant Automatic, Perugruen
1971 VW Squareback Automatic, Clementine Orange
2001 E320 4Matic Wagon- Our belated welcome to the 21st century! Polar White
1973 280SEL 4,5 Sliding Roof "The Bomb", Dunkelblau.

Measure the resistance for each glow plug and report same.

How long does the relay remain closed if a start is not attempted?

The temp sensor for your model is inside the timer unit.

First question is confusing. Of course, I don't attempt a start until the light goes OUT.

Temp sensor is inside the timing unit? You mean the relais? How could that possibly sense engine temp? The cylinder head has TWO temp sensors on this. One runs the gauge, and the other should be for glows.

All of the glow plugs ohm out at 0.002 on the Fluke. No variations, and no open loops.

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1968 230S Automatic, Elfenbein
1975 O309D Executive Westfalia Camper Bus, Blau/ Weiss
1972 280SEL 4,5 Dunkelrot
1966 VW Type 34 "Grosser" Karmann-Ghia
1963 VW 1500 Variant Pearlweiss
1969 VW Variant Automatic, Perugruen
1971 VW Squareback Automatic, Clementine Orange
2001 E320 4Matic Wagon- Our belated welcome to the 21st century! Polar White
1973 280SEL 4,5 Sliding Roof "The Bomb", Dunkelblau.

For starters, I am not as dumb as I look. I was not asking how long the light remains on. I was asking how long the relay remains closed. To find out, open the hood and stand next to the timer unit. Have a helper move the start switch to the "Run" position; start your stopwatch concurrently. When you hear a clunk from the timer unit, stop the stopwatch. Report the results.


The temp sensor is in the timer unit and measures ambient air temp. On an '85 model, the "other" sensor in the head is for the EGR.

That is not reasonably possible.

Ok. Lose the 2nd T.......

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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

I thought the glow plugs should measure about 0.6-1.0 Ohms??

__________________
1985 300TDT
2013 E350 Bluetec

For what reason? It's a Touring Diesel with Turbo.

And if I lose the second "T", this fixes the glow issue?

__________________
1968 230S Automatic, Elfenbein
1975 O309D Executive Westfalia Camper Bus, Blau/ Weiss
1972 280SEL 4,5 Dunkelrot
1966 VW Type 34 "Grosser" Karmann-Ghia
1963 VW 1500 Variant Pearlweiss
1969 VW Variant Automatic, Perugruen
1971 VW Squareback Automatic, Clementine Orange
2001 E320 4Matic Wagon- Our belated welcome to the 21st century! Polar White
1973 280SEL 4,5 Sliding Roof "The Bomb", Dunkelblau.

I typically see 0.6 or 0.7 Ohms on brand new GP's straight out of the box.

Thats what I thought. It seems that the .002 that Tram is seeing is nothing more than the inherant resistance found in the meter wiring.

__________________
1985 300TDT
2013 E350 Bluetec

Meter probes are a lot like real estate; it's all about location, location, location...

OK, the box clicks off about 30 sec. after the light.

I've always just used the VOM as an indicator to see which glow plug is open when the light duration started getting short like this. Just checked them again, they're all 0,002 on the Fluke. It's a digital that has started acting crazy on voltage readings and new batteries didn't help, so the readings, while possibly not accurate, are at least consistent.

Since everything was perfectly fine prior to replacing the glow plugs, I'm wondering if it's just five crappy plugs.

__________________
1968 230S Automatic, Elfenbein
1975 O309D Executive Westfalia Camper Bus, Blau/ Weiss
1972 280SEL 4,5 Dunkelrot
1966 VW Type 34 "Grosser" Karmann-Ghia
1963 VW 1500 Variant Pearlweiss
1969 VW Variant Automatic, Perugruen
1971 VW Squareback Automatic, Clementine Orange
2001 E320 4Matic Wagon- Our belated welcome to the 21st century! Polar White
1973 280SEL 4,5 Sliding Roof "The Bomb", Dunkelblau.

No problem there.


What mode was the meter in? Where were you placing the probes?

It was on ohms, and the the red probe went on the harness plug, black probe to ground on the block. While I appreciate the queries on basics, to save time, I'm a VW/ M-B/ Porsche guy with 37 years experience all told (including apprenticeship). Probably 25% of my experience is in diesels. Trust me- this is an unusual problem I've really not run into before. This is why I'm suspecting the new glow plugs... most of the 'WTH' problems I've run into in the last decade across the board have been due to new defective parts straight out of the box that have failed in ways I'd never experienced before.

Oh, and we've owned the car for over ten years, and I serviced it for the previous owner from 1998- on.

__________________
1968 230S Automatic, Elfenbein
1975 O309D Executive Westfalia Camper Bus, Blau/ Weiss
1972 280SEL 4,5 Dunkelrot
1966 VW Type 34 "Grosser" Karmann-Ghia
1963 VW 1500 Variant Pearlweiss
1969 VW Variant Automatic, Perugruen
1971 VW Squareback Automatic, Clementine Orange
2001 E320 4Matic Wagon- Our belated welcome to the 21st century! Polar White
1973 280SEL 4,5 Sliding Roof "The Bomb", Dunkelblau.

Are you getting 12 volts at the plugs with the key in the glow position?

__________________
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

Dark out now- will look tomorrow.

Interesting side note- waiting for 20 seconds or so after the light went out to start made an improvement. It's just weird how the light goes out so fast instantaneously with the new plug install.

__________________
1968 230S Automatic, Elfenbein
1975 O309D Executive Westfalia Camper Bus, Blau/ Weiss
1972 280SEL 4,5 Dunkelrot
1966 VW Type 34 "Grosser" Karmann-Ghia
1963 VW 1500 Variant Pearlweiss
1969 VW Variant Automatic, Perugruen
1971 VW Squareback Automatic, Clementine Orange
2001 E320 4Matic Wagon- Our belated welcome to the 21st century! Polar White
1973 280SEL 4,5 Sliding Roof "The Bomb", Dunkelblau.