Glow Plug Basic Questions

[shertex]

I have a 92 300D. As of late, I have been noticing the following: a few moments after the engine starts, the glow plug light will come on, stay on for about 30 seconds, then go out. But just in the past few days, it has not been coming on when I turn the key, but then does come on for about 30 seconds while driving.

Any thoughts as to what's going on?

Also, above what ambient temperature is the glow plug system unnecessary? As I live in Texas, I'm hoping I won't have to fix whatever's wrong until it gets cooler.

Thanks.

[DieselJim]

As long as you have enough compression in the cylinders glowplugs are unnecessary period. It will just take a a few seconds to crank. My old 300SD takes about 45 seconds of cranking on a warm day if I bypass the plugs. If you have poor compression good luck. If the plugs are not working or you start cold you will feel the weakest compression or coolest cylinders miss for a bit before the engine gets warmed up.

[Habanero]

I always figured glow plugs are cheaper (and usually easier to replace) than starters. To each their own, though.

[Jim H]

Originally Posted by shertex

...But just in the past few days, it has not been coming on when I turn the key, but then does come on for about 30 seconds while driving...

One or more GPs may be bad. Test them with a multimeter, replace the bad one(s).

Originally Posted by shertex

...Also, above what ambient temperature is the glow plug system unnecessary? As I live in Texas, I'm hoping I won't have to fix whatever's wrong until it gets cooler...

Hard to tell, if you are able to start up in about 5-10 revolutions, it is not too bad. With GPs functioning, it takes about 1-2 revolutions.

Best Regards,
Jim

[shertex]

Originally Posted by Habanero

I always figured glow plugs are cheaper (and usually easier to replace) than starters. To each their own, though.

So am I to understand there's a risk of damage to other components if I leave this problem unattended?

Or, to ask the question differently, other than the car not starting in cold weather, is there any downside to not fixing a glow plug problem?

[Habanero]

At least with my SDL, when the plugs weren't working, it took quite a few more revolutions to start than when the plugs were fixed. I figure the starter has only so many revolutions in its lifetime, so those extra revolutions everytime it starts served to shorten its life. Maybe it is flawed logic, but I would rather pay for glow plugs than the starter.

[t walgamuth]

i am with habanero on this. keeping it working as designed is always the best thing.

i think that diesel jim just meant you dont need them to start a diesel engine. i doubt that he meant you should try to run your car that way day in and out.

[farmboyhull]

So am I to understand there's a risk of damage to other components if I leave this problem unattended?

Or, to ask the question differently, other than the car not starting in cold weather, is there any downside to not fixing a glow plug problem?

i've got the same problem on the same car. i'm wondering if you fixed this or let it go.

i'm not too worried about my starter right now, but more about the glowplugs - could they be staying on?

david

[1983/300CD]

Originally Posted by Habanero

I always figured glow plugs are cheaper (and usually easier to replace) than starters. To each their own, though.

Had to laugh at this one. So true.

Cranking for 45 seconds!? You could probably roast marshmallows on it. That starter is going to die a premature death for sure.


BTW, It sounds like the relay might need a looking at. Check out Diesel Giant's site, and follow his DIY on it.