My 240D has this problem where the glow plug relay cuts out too soon as evidenced by the audible click and hard cold starting. On the first cycle it usually clicks after 10 seconds. On subsequent cycles it only takes a couple seconds to hear the click. I was just wondering if I need a new relay or if there's something smaller that needs to be replaced.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

Check the current draw of the glowplugs, always rule #1.

Gilly

I checked the plugs a couple months ago and they were fine. I'll check again tonight and will report back.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

Can you check the current consumption of each one? Alway the best test.

Also on some models there is a seperate coolant temp sensor just for the cold start (glow plug) system, that could also cause this problem.

Gilly

Gilly,

But the GP relay should stay on for about 40 seconds regardless of the temperature or until the starter is energized. The length of the time the GP dash light stays on is supposed to vary according to the engine temperature.

There is something with the time delay circuit in the relay if it doesn't stay on long enough.

P E H

"seperate coolant temp sensor"

Look in back of the IP there are two black wires going to sensors, switch the wires if they are long enough. Now if your temp gauge no longer works and your GP light works you found the problem. Drain coolent and replace funky sensor. Not sure if "83"s are rigged with 2 sensors tho. My "79" had a bad sensor affecting the GPs.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

Well I found out my #2 plug is dead. I'll replace that before attempting anything else. I'm hoping that's the only problem.

Stevo, how did your bad coolant sensor affect your GP's?

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

"there is a seperate coolant temp sensor just for the cold start (glow plug) system, that could also cause this problem."

Like Gilly said, but I am not sure your system is set up that way

Steve

Stevo,

I think that sensor only affects how long the dash GP light stays on. The GP relay should energize the GPs for about 40 seconds unless the starter is energized, regardless of the temperature.

P E H

I did a little "light" reading (as in glowplug light ) and it seems this model doesn't have the coolant temp sensor. It uses an internal ambient temp sensor (built right into the relay) to determine glow times.

I would tend to believe what PEH said in regards to the internal timer, or possibly the problem is with the safety shutoff feature. It would seem in either case a new glow plug timer/relay would be required to fix it.

Gilly

The strange thing is that the glow time in my case is inversely proportional not to the coolant temp or ambient temp, but to the glow plug temp. On the first glow cycle I get about 10 seconds of glow time and if I try again immediately I only get about 2 seconds on the second cycle. But if I let the plugs cool down for a minute or so, I can squeeze out another 10 seconds or so.

I'll change that bad plug sometime this weekend and see if it changes the glow time. Somehow I feel that's wishful thinking. But with all the plugs working the glow time might be sufficient.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

P E H

Quite some time ago the relay died (or I THOUGHT it died) on my "79"240D, GPs wouldn't light off so I went to my push button glow system and forgot about a relay. Anyway when I pulled the engine to stick in the rebuilt "80" engine I discovered the sensor was n/g (2 in the head, one for GPs & one for temp gauge) So I have always ASSUMED the relay was OK and my original NO glow problem was caused by a faulty sensor, maybe not....Your saying "the relay shoulda worked regardless of the sensor?
Steve

Stevo,

I'm not sure of the GP relay works same as a 300SD, but on my 3000SDs the time the relay energizes the GP is fixed and does not vary on temp. Only the time the GP dash light stays on varies with temp.

So yes, the relay should have worked regardless of the temp sensor.

P E H

DieselAddict,

My '84 300D had the same problem until I replaced a bad electrolytic capacitor on the relay's circuit board. Possibly, your 240D's relay could be repaired just as easily.

Jerry

I didn't notice the post where you said you had a bad glowplug. I just remember you said they were all good.

Sure, i bet the glowplug will fix it then. If it's shorted out, then the safety feature is shutting down the system early.

Gilly