Glow plug light & plugs only come on when cold? - PeachParts Mercedes-Benz Forum

Panzer_Man · #1 12-17-2005, 07:46 PM

83 300D turbo in Florida

The last few months the Panzer's glow plug light sometimes comes on, sometimes it doesn't. When it doesn't, the plugs obviously arent' operating because it takes about 8 seconds to crank the car. I put a used, supposedly good glow plug relay in it and it did not resolve the problem. I then had my mechanic replace the glow plugs; no change in symptoms.

Interestingly, when it is really cold, both outside and the engine, the light seems to thankfully always come on and the car cranks right up. But if it is mild outside the light doesn't always come on leading to the long crank (and smoke).

Is there a sensor that says "if engine warm do not turn on glowplugs"? If there is, that may be the problem.

Also the relay may not be good as it is used. Also note that the relay that was in was a new part put in about 2.5 years ago. So perhaps I just need a new relay. (?)

Ideas?

Thanks in advance,
Matt

Hit Man X · #2 12-17-2005, 09:59 PM

My GP light comes on regardless of ambient temps.

Are the connections to your relay tight? What about the fuse?

#3 12-17-2005, 10:05 PM

I agree, mine always comes on for some amount of time, even if it's just a few seconds with a warm engine. It stays on noticeably longer when it's colder. Sounds like a relay issue, or a bad contact (assuming all the GPs are good).

MTUpower · #4 12-17-2005, 10:38 PM

yes check the relay. BTW- the 1972-1989 SL class were called "der Panzerwagon" by the germans...so by your name they might think you know alot about the 107's....

zcc · #5 12-17-2005, 11:52 PM

I have the same problem in my 560SEC 1989.

Jim H · #6 12-18-2005, 10:40 AM

Quote:

Originally Posted by Panzer_Man

...The last few months the Panzer's glow plug light sometimes comes on, sometimes it doesn't... ...Is there a sensor that says "if engine warm do not turn on glowplugs"?

No. Outside temperature in some models will change the time the light stays on, but not the total glow time.

Quote:

Originally Posted by Panzer_Man

...Also the relay may not be good as it is used. Also note that the relay that was in was a new part put in about 2.5 years ago. So perhaps I just need a new relay. (?)

You need to test the resistance of each GP, and check all of the pins on the harness plug for corrosion. Temperature changes can affect corroded connections, sometimes the work, sometimes they don't.

Jim H · #7 12-18-2005, 10:40 AM

Quote:

Originally Posted by zcc

I have the same problem in my 560SEC 1989.

Do you mean you have a Glow Plug lamp?

Panzer_Man · #8 12-18-2005, 02:07 PM

Many thanks for all the replies.

I believe my mechanic has a known good relay that I can use before I buy a new one. The last 5 years I have bought an awful lot of parts I probably didn't need (the last being new injectors) and wish to cut down on unneeded purchases.

I will assume that my mechanic checked the wiring to the GPs themselves when he changed them out but I will confirm with him. I will also look at the wiring to the relay in the meantime. The fuse is present and intact (the thick metal one on the relay itself). I assume that is the fuse mentioned in the thread. Somehow this problem is engine-tempature related, or the least, engine tempature brings out the symptoms. First crank on a cold morning the GPs always come on. Drive around for a bit, let the car sit for 10 minutes, then they don't..... strange.

MTU, I didn't know that about the 107s; I'm a military history fan and this car is built like a tank so Panzer seemed like an appropriate nickname.

Panzer_Man · #9 12-18-2005, 02:08 PM

Quote:

Originally Posted by Jim H

You need to test the resistance of each GP, and check all of the pins on the harness plug for corrosion. Temperature changes can affect corroded connections, sometimes the work, sometimes they don't.

Ah, I re-read this. I can look at the pins for corrosion but resistance testing is over my head. I'll pass this tip on to my mechanic.

Diesel Giant · #10 12-18-2005, 03:08 PM

Maybe the pictorial will help you some.

http://dieselgiant.com/glowplugrepair.htm

Panzer_Man · #11 12-20-2005, 12:24 AM

Quote:

Originally Posted by Diesel Giant

Maybe the pictorial will help you some.

http://dieselgiant.com/glowplugrepair.htm

Hey I COULD do that; and a co-worker has the resistance tool I think. Excellent directions with photographs.

Again. BIG thank you gentlemen!

Matt

Panzer_Man · #12 12-27-2005, 01:26 PM

Checked for corrosion, no problems with connectors or sockets on relay or on the connecting plug between the wires.

Well the car started acting flaky electrically after a 3 hour ride. The last few minutes the radio died etc... One thing I have been noticing is that it has been sounding like the battery has been taking a beating after driving it, even on short trips, as it would turn over slowly (even though the battery is almost new and the car has a 2-3 year old new alternator in it).

Went to start it today and it barely turned over. Ironically the glow plug light did come on.

Could a bad relay be shorting out the system causing a power drain or is this indicative of another problem?

If I am unable to test the relay, I am very tempted simply to buy a new one and gamble the money. Tired of the problem....

Thanks again,
Matt

sailor15015 · #13 12-27-2005, 01:42 PM

This may not make a bit of difference in your case but check all of your grounds. Find out where your engine grounds to the chasis and make sure its intact and corrosion free. I had a really odd electrical issue where my gauges where jumpy then all of a sudden it wouldnt' start. I pulled my instrument cluster and repacled it and had the same problem. I noticed every light in the cluster would turn on when the cluster touched the speedo cable. I was getting a steady 2.97 volts from the cable??? I also got random voltages from engine parts that definately shouldn't have had power. Thanks to Craig for telling me to check my engine grounds. I was in a hurry because I'm out of town on vacation right now so I took a jumper cable, attached one end to the EGR and the other end to the negative post of the battery and it started! Unfortunately I had to leave right after that so when I get back I'm going to find my main engine-chasis ground and clean it. It may not help but its worth a shot.

Panzer_Man · #14 01-02-2006, 10:36 AM

UPDATE:

mechanic said glow plugs were not getting power so he replaced the glow plug relay and it gets a light and starts right up.

But, I drove it for a day and now I'm getting the no-GP light problem again.

It is as if something is destroying my relays. He tested the power at the altenator and said it looked good. I haven't even called him to speak with him about the light not coming on again; I may just take it to the dealership.

Any ideas on what could be killing GP relays?

Thanks,
Matt

Panzer_Man · #15 03-26-2006, 03:32 PM

Months later update-

Relay is fine.

Occassionally the battery warning light will come on (sometimes barely glowing, others brightly). Reving the engine makes it go away.

I'm thinking it's either a short or loose ground as posted by sailor. Gonna let my mechanic try to figure this out. No idea how to even begin to hunt down an electrical problem. It could be my expensive aftermarket stereo (expensive installation too) as it when cut out suddenly.

Regardless, something drains the battery as it is dead now and alternator is fine.