Glow Plug Light Basic Question

[shertex]

When I turn the key, the glow plug indicator does not light up. So I wait about the amount of time that it would take for the indicator to go out, start the car and it starts fine. Then, after the engine is running, the indicator comes on, stays on for about 30-45 seconds, then goes out for the duration of my trip. It behaves this way every time without fail.

Two questions:

1. Does this tell me specifically what's wrong? Or is the only thing to be deduced from my description the fact that something is wrong with the glow plug system?

2. Is there any harm to letting it go for a while? After all, the car starts fine.

Thanks.

(And yes, I did a search, but didn't find anything on this exact symptom.)

[t walgamuth]

but i am guessing you have one or more glow plugs burnt out.

tom w

[P.E.Haiges]

Shertex,

You won't hurt any thing. Does the engine seem to missfire for a few seconds then run smooth? This would be an indication of a bad GP.

Do a resistance test on your GP to see if you have any bad GP.

If the GP are all OK, something is wrong with with the dash light circuit in your GP relay.

P E H

[bhanson]

I have EXACTLY the same situation with my 300D. I checked all the glow plugs with an ohmmeter this weekend, and they are all around .2-.6 ohms. When I turn the ignition, I have about 11 volts to the plugs for 10 or 20 seconds. So I'm guessing my dash light is just bad.

Good luck!

Ben

[junqueyardjim]

I was having the same problem with my glow plug lite. Glow plug always worked well, but in the past couple of weeks, the lite would flash on/off, flicker, burn on but very dim, geepers it was a real lite show. Then this morning, on the way to school, it was really dark and the flashing was driving me nuts. I pushed in on the dash on the corner where the lite is, the corner went in about 1/2 inch and the other side popped out. I then pushed in both ends of the instrument section, and it popped into place and my problem is solved. I did have the instrument section out about a month ago and I guess that it just wasn't set in quite right.

[bhanson]

Well, my last post seems premature, after this morning. It was about 48 degrees F, and it took six attempts to start the car, with a puff of smoke. It didn't run terribly rough, but I had to put my foot down on the pedal. No loss of power once started, so it's not fuel restriction ----I'm guessing I have a glow plug problem after all. I noted 11 volts, but memory serves it was really 10.6. Anyone know if that's right, or do I need to clean up some connections while testing. I wonder if it could be a bad thermostat, intermittently failing too. I'll have to check it all more carefully.
Ben

[Jim H]

Originally Posted by P.E.Haiges

...Do a resistance test on your GP to see if you have any bad GP...

Like he said...

Measuring volts is only part of the story, since GPs will still heat with 9-10 volts applied, just not quite as hot.

Look for corrosion in the sockets of the GP harness plug. A little green or white stuff in there can stop the flow of current when the socket tries to make contact, but not show up on the ohmeter since the probe is a point and cuts right through.

Best Regards,
Jim

[bill murrow]

Originally Posted by Jim H

Like he said...

Measuring volts is only part of the story, since GPs will still heat with 9-10 volts applied, just not quite as hot.

Look for corrosion in the sockets of the GP harness plug. A little green or white stuff in there can stop the flow of current when the socket tries to make contact, but not show up on the ohmeter since the probe is a point and cuts right through.

Best Regards,
Jim

Agreed...sounds like a possible corrosion problem.

A friend of mine has a diesel boat and he was having intermittent problems starting from dead cold. A couple of GP's were corroded right at the connection on the plugs. Cleaned them up and its fixed.

Dunno about the light???? Would corrosion cause GP light problems too experts??

Cheers,

Bill

[Old Geek]

Originally Posted by Jim H

Like he said...

Measuring volts is only part of the story, since GPs will still heat with 9-10 volts applied, just not quite as hot.

Look for corrosion in the sockets of the GP harness plug. A little green or white stuff in there can stop the flow of current when the socket tries to make contact, but not show up on the ohmeter since the probe is a point and cuts right through.

Best Regards,
Jim

----------------------------------------------------------------------
If there is no corrosion on the GP harness plug, and you still measure only 9-10 volts being applied (and the resistance checks OK at each of the GP's)
then you are left with looking at your GP relay or the 80 amp fuse on top of the GP relay. Given that you are in RI, I would advise you to resolve this issue before a serious cold snap, else you may find yourself unable to start.

As for the GP dash light coming on well after start up - my vote is for a defective bulb.

[engatwork]

Then, after the engine is running, the indicator comes on, stays on for about 30-45 seconds, then goes out for the duration of my trip

I saw a '79 300SD do this one time and found a loose connection on the grounding cable between the block and the chassis.